This was my first bike. I put 33,000 miles on mine and rode it all over (Maryland, Tennessee, Ohio, New York, Connecticut, etc.). It was my sole vehicle for 10 years and I rode it in snow, hail, rain, mud, dirt roads, mountain trails, interstate highways, etc. I did all the maintenance on it and never took it to a garage. I changed the rings in the rain in front of a motorcycle shop. I rebuilt the carbs in the rain under an umbrella at night by flashlight. I loved this bike and sorely miss
I had one just like this one. At 18k, I put a 350 top end on it. REALLY BROUGHT IT TO LIFE!!!! Mildly ported, gold anodized heads, fiberglass reeds and expansion chambers. Hang on tight.... she is definitely gonna wheelie.
My 23 year old daughter is sitting here asking me about my 1st bike and so I searched for images of this Yamaha and bingo! Here it is! That was the color I had and everything! Brought back many memories. It was fun to drive with 6 speeds and it was pretty quick (leaving a trail of blue 2 stroke smoke behind it)! But it was very unreliable and I could never get the thing to consistently run well. Two strokes suck......Four strokes truck!
Kyle to tell you the truth. The only parts that I can’t even think of that wear out inside an RD 28 mm carburetor, is the needle and seat. There’s probably tens of thousands of them carburetors sitting around, I know I have six of them. The needle and seat are the same in the RD 250 and in the RD 350, and I would not be surprised if the R5 and the DS7 have the same needle and seat.Those carburetors do not have constant velocity vacuum diaphragm’s, they do not have Excelerator pump diaphragms, so really isn’t anything in there that needs replaced except for the needle and seat. It is tough to clean the pilot jets, sometimes it’s even tough to get the pilot jets out. But I can’t think of any other parts except maybe the floats that would need to be replaced, but you don’t get new floats in a rebuild kit.. what makes you think you need to have the carburetors rebuilt? Not running correctly? Not starting? If the machine will start but you have to have it spinning quickly like pushing it in gear or kicking it fast to get it to start, it’s probably the crank seals that need replaced, or your pistons/ bores could be wore out.. you could have broken piston rings if the end gap was not set correctly... I hope no one disconnected the oil pump with the auto lube injection system. Those things are perfect. Pre-mixing the oil is not a good thing when there is an oil pump available. Adding oil to gasoline lowers the octane of the gas. Oil does not burn, that’s why you see it coming out the exhaust pipe. Do you need 14 to 1 or higher compression to burn oil. That already has probably about 6/1 or 7/1 compression ratio like most two strokes. If the air cleaner and the airbox are not intact, the machine will not run correctly. It may start, but it is turned at the factory to run correctly with an air cleaner and the air box with the lid on, otherwise, the jetting will be out the window way off.. I do not know what the Jets required to run at your elevation would be without an air cleaner or with using those individual foam or guys screen oiled air cleaners. They do not work as well as the airbox.. why? Because the science in designing and airbox involves velocity stack effect, and air traveling at a speed that requires the same science applied to it as it does when designing airplane wings. Trust me so split the cases, throw in a new set of crank seals, and don’t forget to oil the inner seal area with grease before you put the seals on the crankshaft slashing into the cases. put the air cleaner housing back on and a standard paper air filter. Use the auto oil injection system, and never use Champion spark plugs, not even in your lawnmower. Don’t advance your timing. One exception, if you are at sea level, you will have to increase your Jet size up from 102.5 jets to at least 110 jets there’s more air in the air at sea level. You don’t want to seize..
Thejeepdoctor Sorry about your bike seizing. But I can’t imagine Champion spark plugs causing that to happen, or any spark plugs causing that to happen. The usual cars for seizures is, too lean jetting, timing too far advanced, did you check to make sure that your timing marks were aligned properly after the rebuild? You can put the stater cover on during reassembly a little advanced or retarded on the timing. Check your timing with a dial-in Decatur. Don’t trust the marks after a rebuild. The factory spec is 2 mm before top dead center. A bad crank seal can cause a lean mixture, but usually only on the left side. The right side crank seal would suck oil out of the transmission and one pipe would be spewing a lot more oil than the other one. A very very common seizure problem on the 73 and 74 models is, the pin on the oil pump that the ramp climbs to advance the oil pump stroke falls out. When this happens, as you open the carburetors, you’re supposed to be increasing the stroke on the oil pump also, without the pin for the ramp to climb, the oil pump never increases. These oil pump pins had guards on them in 1975. It is nothing more than a bent piece of metal, that looks like something made out of an old soup can lid, but it works.. another thing that can cause a seizure is an air leak at the intake manifold’s, or even the idol adjustments that hold the slide up on the size of the carburetors. They are the screws with the springs on them sticking in the slide bore,One on each carburetor on the outside. Another thing that could cause a lien seizure is, there is a rubber air tube connecting the carburetors, only one carburetor has a choke/enriching circuit for cold start up, the other carburetor enriching circuit is activated through that tube that connects the carburetors.. your float levels could also be too low. If for some reason you changed your main jet, or lowered the needle in the slide, and you are at sea level, this could cause you to be too lean and seize.. at least 10% of the racers that go to Daytona, or went to Daytona back when they used to race there, would C‘s in the first practice session if they did not fat and the jet up. A guy I know broke both wrists and one ankle for me too lean seizure at Daytona because he did not account for sea level air which Means, there’s more air in the air, so you have to give more gas to the air by going fat on the jetting.. what kind of a seizure did you have? Was it a hole in the piston top? Or was the piston stuck in the bore?? A hole in the piston is a timing/lean problem.. A piston that ceases in the boar, is a lubrication problem.. after a rebuild. Go to the oil pump. There is a bleeder screw/Phillips head on the side of the oil pump. It has a red sealing washer under the head of the screw. Remove that screw and turn the white wheel/fly wheel with teeth in it that rotates the oil pump when the engine is running..If you had the oil lines off of the carburetors, or the oil pump off, or the oil line from the tank to the oil pump while you were rebuilding the engine. That line gets air in it and you have to bleed that air out by removing that air bleed screw on the oil pump, and turning that white plastic wheel until you get all the air out.. I hate Champion spark plugs. They do not recover from a heat cycle. They are one time use spark plugs. They’re like fire crackers. They only work once. After that, they will misfire. If your engine makes 30 hp, and the spark plugs misfire once every 30 RPM, you lose more than 1hp.. use the oil pump as opposed to pre-mix. Those oil pumps are practically bulletproof. I have never heard of one failing. if by some chance you blocked off the oil pump and went with pre-mix. That could also cause a seizure very easily by using too much oil mixed with the gas. look at it this way let’s say that a drop of gasoline is sucked into the engine each stroke. When you pre-mix the oil into the gas. And you are still using the same jetting that you were using when you were using the oil pump. You have leaned the hell out of your mixture because that single drop of gas that you were using with every stroke, has been reduced from 100% gasoline, down to 90 or 80% gasoline,Because that pure drop of gasoline that you had when you were using the oil pump, is leaned down because that drop is now contaminated by oil taking the place of gasoline. What you’ve done is leaned out your jetting when you add oil to the gas. This will cause a seizure just as fast as an air leak.. it’s amazing how many people think by putting more oil in their gas they are helping their engine by giving it more lubrication. When in fact, they are leaning out the jetting... don’t run pre-mix if you can help it. There are several reasons not to pre-mix. It’s stratifies overnight. Do you have to shake it up in your gas tank every time you start the bike because the oil is at the bottom mostly. And when you turn on the petcock, and start your bike, it’s getting a higher percentage of oil and a lower percentage of gasoline another reason to not run pre-mix is, when you pre-mix gas with oil, that gas oil mix should be used quickly. Within a few days. I don’t know when it happens to it, I’ve heard that it denatures. That was a very big problem when people were using castor base oil mixed with gasoline. You had to use that stuff within a week.. One more thing to check. Since you said you did an engine rebuild, and you had cables off and hoses off. Make sure that your oil pump cable is actually connected to the oil pump, and that it actually rotates the stroke advance cam.. I hope you left this stock airbox, paper air filter inside that air box, and the lid on top of the airbox intact. Read valves require intake resistance to close completely at high rpm‘s. RDs run better with the stock airbox. That intake bellows that comes from the airbox to the carburetors has a velocity stack effect.. velocity stacks/velocity stack effect is, when you have a large opening that funnels down into a smaller opening, the air actually picks up speed... you say you rebuilt the engine? Are you sure that the piston clearance was within spec? I forget with the clearances I think it’s under 2 thousands.. The way I broke my engines in when I had a new board job. A very very light coating of oil on the back of the piston skirt. You do not drowned a freshly rebuilt bore with oil. You have to scratch the rings into the shape of the cylinder. I know it’s not a hard to do but make sure you have the rings in correct side up. The writing on the rings is the top of the ring. Make sure that the gap pins/that locate the gaps on the pistons to prevent the ends of the rings from expanding into one of the ports is correct. In other words. There are little metal locators on the ring landings.. The gap on the rings is held in place by those pins. ring and gap is critical also. You check ring and gap by pushing the rings into the boar and measuring the end gap with a feeler gauge. You push the rings into the boar using the piston to make sure the ring is square in the boar. To get a correct reading on the end gap. are you sure there is not a piece of the base gasket missing from one of the cylinders?? possibly the base gaskets were forgotten and not reinstalled? Just saying. anytime you install a paper gasket. You go to the hardware store and you buy a small can of rust oleum silver paint. You do not shake the can. You open the can and dig the bottom of the can with a screwdriver to get that fixed gooey silver paint from the bottom of the can. You work that into the gasket/paper gasket, completely both sides. And you put it on the surface to be sealed with a gasket still wet with the silver paint. Not only will that gasket never leak, but that gasket will come off when you want it to, and you will be able to reuse that gasket over and over. I also prefer to use used head gaskets over and over and over on RDs because they do not have a problem of needing to be retorqued that a new gasket has. that trick with the paper gaskets/silver rust oleum paint was a Honda service bulletin to all service department when I was a mechanic in the early 70s. I still have the same quart can of rust oleum aluminum color paint that I bought in the early 70s. And I use it on every paper gasket I ever use. And I have never had a leak, and when I take an engine apart, the gaskets come off without a problem and they never stick so the way I broke in my race RD engines after a fresh bore. A very light coating of oil on the back of the piston skirt. I would assemble the freshly rebuilt engine, put it back in the frame of the bike. I didn’t stall the kick starter. With the spark plugs removed, I would kick the engine over for about five minutes using the kick starter only. This will help the rings to see it in. Then I would install the spark plugs, and run the engine for about two or three minutes just enough to get it warm. No higher revs.. then I would shut the engine off, remove the spark plugs, and using the kick starter, I would kick the engine over using the kick starter only as the engine cold. For about a minute at a time, over the next half hour. I would start the machine to get it warm, run it for a few minutes, shut it off, pull the spark plugs, and kick it over as it called. This allows the piston to conform to the cylinder bore..
too bad it’s not a 1973 or a 1974. the 1975 RD 250 was the slowest, and I mean by about 10 miles an hour on top end, and by about a second on acceleration in the quarter mile ..The reason, - the disc brake up front how do I know this? I won 6 Championships Roadracing a 1974 RD 250 with a drum front brake .. it was legal for me to use a disc brake front end because the machines were produced with a disc brake like on the RD 350.. So I tried one. Not only was I about 5 miles an hour slower than other riders are used to be dead even with on acceleration, but that front disc is a gyroscope that does not like to change directions quickly. If you have ever held a gyroscope ,You know what I’m talking about. And road race tracks that required quick left right left right turning. My machine would not turn as quickly as it did with the drum break, and I would often run off the track interns I never did before with the drum break, because the bike would not turn fast enough. The disc is also unsprung weight. That is so critical over bumps, which all road race tracks have from the cars twisting the hot asphalt in the hot summer sun and of course it’s online on exit from turns, that the suspension would absorb the weight of that unsprung weight into the springs of the front forks, and the oil in the front fork tubes would have to slow down the spring rebound. This took extra time between bumps because of the extra weight and the extra weight of the disc in the caliper. The third disadvantage the disc hampered my race bike or any bike with a disc is, it is also a fly wheel, like the little matchbox cars we had when we were little kids, you had to run them across the ground to get this fly wheel spinning, and then they would want to keep spinning. Well a fly wheel Hass to be accelerated, and that takes horsepower. so those are the three major disadvantages of the disc brake front end over that very light RD 250 that did not need a disk. The top speed on an RD with 16-40 Gearing at 1000 feet above sea level, with the airbox in tact with an air filter in the box and the lid on the airbox, was about 105 miles an hour on an 80° day, that was on the first lap. On the 15th lap, I would be very lucky if the machine even reached 95 miles an hour. Air cooled machines slow down that much when they got hot.. there was also one more factor that the disc brake front end catch did that slowed the machines down, and that was brake puck drag. I agree that the disc brake would slow the machine down much quicker than the drum brake especially after the fifth or six lap. But the handling, the quicker steering, the acceleration, and the ability to reach top end quicker, more than made up for the deficiency in the braking of the drum brake, which could be adjusted to have zero drag. A new brake cable for the front brake helped every fifth or sixth race. The inner cable doesn’t stretch, it’s the outer cable that collapses over itself and makes it seem like the inner cable got longer. The machine in this video is beautiful. But the two prior years would leave it in the dust. The one thing that the 1975RD 250s and 350s head that the 73 and 74 machines did not have, what is the metal guard over the oil pump stroke advance pin.. If you can ever find a set of cylinders for the RD 250 that has only three full cooling fins above the reed block instead of four fins above the reed block,Those three fin cylinders are faster than the cylinders that have four complete cooling fins above the reed block.. how do I know these things? Like I said I rode raised a brown drum brake RD 250, I won six championships on it, and two national championships on that machine. With a drum brake, and you must leave the complete airbox in tact, with the stock paper air filter , and the lid on the airbox, otherwise, the reeds do not close correctly .. been there, done that.. Harry lime is not my real name, it’s Jody
This was my first bike. I put 33,000 miles on mine and rode it all over (Maryland, Tennessee, Ohio, New York, Connecticut, etc.). It was my sole vehicle for 10 years and I rode it in snow, hail, rain, mud, dirt roads, mountain trails, interstate highways, etc. I did all the maintenance on it and never took it to a garage. I changed the rings in the rain in front of a motorcycle shop. I rebuilt the carbs in the rain under an umbrella at night by flashlight. I loved this bike and sorely miss
I have one of these, same exact paint job. Hoping to get of storage this year and try to get it running again. My first bike I bought when I was 18.
It looks likes mine from 1977.I worked so hard to save up for it.Happy days.
I had a Yamaha RD250C in 1976,great fast bike.Huge fun!
Beautiful !!😍😍
I had one just like this one. At 18k, I put a 350 top end on it. REALLY BROUGHT IT TO LIFE!!!!
Mildly ported, gold anodized heads, fiberglass reeds and expansion chambers.
Hang on tight.... she is definitely gonna wheelie.
I am looking to purchase one of these as a first bike. Im coming from 2T mopeds and want a small 250 2T. Any thoughts?
if you ever get another one can you tell me....well wishes!
very very nice
I had the same exact bike and I had to replace the rings about every 3000 or so miles
I had one in 1980
My first. rpm sweet spot almost threw me off it.
My 23 year old daughter is sitting here asking me about my 1st bike and so I searched for images of this Yamaha and bingo! Here it is! That was the color I had and everything! Brought back many memories. It was fun to drive with 6 speeds and it was pretty quick (leaving a trail of blue 2 stroke smoke behind it)! But it was very unreliable and I could never get the thing to consistently run well. Two strokes suck......Four strokes truck!
Please help I have one and am in need of a rebuild kit for the carb cannot find parts anywhere please help
Have you checked on eBay
Google Yamaha RD parts and vendors will come up
Kyle to tell you the truth. The only parts that I can’t even think of that wear out inside an RD 28 mm carburetor, is the needle and seat. There’s probably tens of thousands of them carburetors sitting around, I know I have six of them. The needle and seat are the same in the RD 250 and in the RD 350, and I would not be surprised if the R5 and the DS7 have the same needle and seat.Those carburetors do not have constant velocity vacuum diaphragm’s, they do not have Excelerator pump diaphragms, so really isn’t anything in there that needs replaced except for the needle and seat. It is tough to clean the pilot jets, sometimes it’s even tough to get the pilot jets out. But I can’t think of any other parts except maybe the floats that would need to be replaced, but you don’t get new floats in a rebuild kit..
what makes you think you need to have the carburetors rebuilt? Not running correctly? Not starting? If the machine will start but you have to have it spinning quickly like pushing it in gear or kicking it fast to get it to start, it’s probably the crank seals that need replaced, or your pistons/ bores could be wore out.. you could have broken piston rings if the end gap was not set correctly... I hope no one disconnected the oil pump with the auto lube injection system. Those things are perfect. Pre-mixing the oil is not a good thing when there is an oil pump available. Adding oil to gasoline lowers the octane of the gas. Oil does not burn, that’s why you see it coming out the exhaust pipe. Do you need 14 to 1 or higher compression to burn oil. That already has probably about 6/1 or 7/1 compression ratio like most two strokes. If the air cleaner and the airbox are not intact, the machine will not run correctly. It may start, but it is turned at the factory to run correctly with an air cleaner and the air box with the lid on, otherwise, the jetting will be out the window way off.. I do not know what the Jets required to run at your elevation would be without an air cleaner or with using those individual foam or guys screen oiled air cleaners. They do not work as well as the airbox.. why? Because the science in designing and airbox involves velocity stack effect, and air traveling at a speed that requires the same science applied to it as it does when designing airplane wings. Trust me
so split the cases, throw in a new set of crank seals, and don’t forget to oil the inner seal area with grease before you put the seals on the crankshaft slashing into the cases. put the air cleaner housing back on and a standard paper air filter. Use the auto oil injection system, and never use Champion spark plugs, not even in your lawnmower. Don’t advance your timing. One exception, if you are at sea level, you will have to increase your Jet size up from 102.5 jets to at least 110 jets there’s more air in the air at sea level. You don’t want to seize..
Harry Lime couldn’t agree more about effin Champion plugs. Caused my fresh rebuild to seize. I’ve had a hard on for Crapion plugs ever since.
Thejeepdoctor
Sorry about your bike seizing. But I can’t imagine Champion spark plugs causing that to happen, or any spark plugs causing that to happen.
The usual cars for seizures is, too lean jetting, timing too far advanced, did you check to make sure that your timing marks were aligned properly after the rebuild? You can put the stater cover on during reassembly a little advanced or retarded on the timing. Check your timing with a dial-in Decatur. Don’t trust the marks after a rebuild. The factory spec is 2 mm before top dead center.
A bad crank seal can cause a lean mixture, but usually only on the left side. The right side crank seal would suck oil out of the transmission and one pipe would be spewing a lot more oil than the other one.
A very very common seizure problem on the 73 and 74 models is, the pin on the oil pump that the ramp climbs to advance the oil pump stroke falls out. When this happens, as you open the carburetors, you’re supposed to be increasing the stroke on the oil pump also, without the pin for the ramp to climb, the oil pump never increases. These oil pump pins had guards on them in 1975. It is nothing more than a bent piece of metal, that looks like something made out of an old soup can lid, but it works..
another thing that can cause a seizure is an air leak at the intake manifold’s, or even the idol adjustments that hold the slide up on the size of the carburetors. They are the screws with the springs on them sticking in the slide bore,One on each carburetor on the outside. Another thing that could cause a lien seizure is, there is a rubber air tube connecting the carburetors, only one carburetor has a choke/enriching circuit for cold start up, the other carburetor enriching circuit is activated through that tube that connects the carburetors..
your float levels could also be too low.
If for some reason you changed your main jet, or lowered the needle in the slide, and you are at sea level, this could cause you to be too lean and seize.. at least 10% of the racers that go to Daytona, or went to Daytona back when they used to race there, would C‘s in the first practice session if they did not fat and the jet up. A guy I know broke both wrists and one ankle for me too lean seizure at Daytona because he did not account for sea level air which Means, there’s more air in the air, so you have to give more gas to the air by going fat on the jetting..
what kind of a seizure did you have? Was it a hole in the piston top? Or was the piston stuck in the bore??
A hole in the piston is a timing/lean problem.. A piston that ceases in the boar, is a lubrication problem..
after a rebuild. Go to the oil pump. There is a bleeder screw/Phillips head on the side of the oil pump. It has a red sealing washer under the head of the screw. Remove that screw and turn the white wheel/fly wheel with teeth in it that rotates the oil pump when the engine is running..If you had the oil lines off of the carburetors, or the oil pump off, or the oil line from the tank to the oil pump while you were rebuilding the engine. That line gets air in it and you have to bleed that air out by removing that air bleed screw on the oil pump, and turning that white plastic wheel until you get all the air out..
I hate Champion spark plugs. They do not recover from a heat cycle. They are one time use spark plugs. They’re like fire crackers. They only work once. After that, they will misfire. If your engine makes 30 hp, and the spark plugs misfire once every 30 RPM, you lose more than 1hp..
use the oil pump as opposed to pre-mix. Those oil pumps are practically bulletproof. I have never heard of one failing.
if by some chance you blocked off the oil pump and went with pre-mix. That could also cause a seizure very easily by using too much oil mixed with the gas.
look at it this way
let’s say that a drop of gasoline is sucked into the engine each stroke. When you pre-mix the oil into the gas. And you are still using the same jetting that you were using when you were using the oil pump. You have leaned the hell out of your mixture because that single drop of gas that you were using with every stroke, has been reduced from 100% gasoline, down to 90 or 80% gasoline,Because that pure drop of gasoline that you had when you were using the oil pump, is leaned down because that drop is now contaminated by oil taking the place of gasoline. What you’ve done is leaned out your jetting when you add oil to the gas. This will cause a seizure just as fast as an air leak.. it’s amazing how many people think by putting more oil in their gas they are helping their engine by giving it more lubrication. When in fact, they are leaning out the jetting...
don’t run pre-mix if you can help it. There are several reasons not to pre-mix. It’s stratifies overnight. Do you have to shake it up in your gas tank every time you start the bike because the oil is at the bottom mostly. And when you turn on the petcock, and start your bike, it’s getting a higher percentage of oil and a lower percentage of gasoline
another reason to not run pre-mix is, when you pre-mix gas with oil, that gas oil mix should be used quickly. Within a few days. I don’t know when it happens to it, I’ve heard that it denatures. That was a very big problem when people were using castor base oil mixed with gasoline. You had to use that stuff within a week..
One more thing to check. Since you said you did an engine rebuild, and you had cables off and hoses off. Make sure that your oil pump cable is actually connected to the oil pump, and that it actually rotates the stroke advance cam..
I hope you left this stock airbox, paper air filter inside that air box, and the lid on top of the airbox intact. Read valves require intake resistance to close completely at high rpm‘s. RDs run better with the stock airbox. That intake bellows that comes from the airbox to the carburetors has a velocity stack effect.. velocity stacks/velocity stack effect is, when you have a large opening that funnels down into a smaller opening, the air actually picks up speed...
you say you rebuilt the engine? Are you sure that the piston clearance was within spec? I forget with the clearances I think it’s under 2 thousands..
The way I broke my engines in when I had a new board job. A very very light coating of oil on the back of the piston skirt. You do not drowned a freshly rebuilt bore with oil. You have to scratch the rings into the shape of the cylinder. I know it’s not a hard to do but make sure you have the rings in correct side up. The writing on the rings is the top of the ring. Make sure that the gap pins/that locate the gaps on the pistons to prevent the ends of the rings from expanding into one of the ports is correct. In other words. There are little metal locators on the ring landings.. The gap on the rings is held in place by those pins. ring and gap is critical also. You check ring and gap by pushing the rings into the boar and measuring the end gap with a feeler gauge. You push the rings into the boar using the piston to make sure the ring is square in the boar. To get a correct reading on the end gap.
are you sure there is not a piece of the base gasket missing from one of the cylinders?? possibly the base gaskets were forgotten and not reinstalled? Just saying. anytime you install a paper gasket. You go to the hardware store and you buy a small can of rust oleum silver paint. You do not shake the can. You open the can and dig the bottom of the can with a screwdriver to get that fixed gooey silver paint from the bottom of the can. You work that into the gasket/paper gasket, completely both sides. And you put it on the surface to be sealed with a gasket still wet with the silver paint. Not only will that gasket never leak, but that gasket will come off when you want it to, and you will be able to reuse that gasket over and over. I also prefer to use used head gaskets over and over and over on RDs because they do not have a problem of needing to be retorqued that a new gasket has.
that trick with the paper gaskets/silver rust oleum paint was a Honda service bulletin to all service department when I was a mechanic in the early 70s. I still have the same quart can of rust oleum aluminum color paint that I bought in the early 70s. And I use it on every paper gasket I ever use. And I have never had a leak, and when I take an engine apart, the gaskets come off without a problem and they never stick
so the way I broke in my race RD engines after a fresh bore. A very light coating of oil on the back of the piston skirt. I would assemble the freshly rebuilt engine, put it back in the frame of the bike. I didn’t stall the kick starter. With the spark plugs removed, I would kick the engine over for about five minutes using the kick starter only. This will help the rings to see it in. Then I would install the spark plugs, and run the engine for about two or three minutes just enough to get it warm. No higher revs.. then I would shut the engine off, remove the spark plugs, and using the kick starter, I would kick the engine over using the kick starter only as the engine cold. For about a minute at a time, over the next half hour. I would start the machine to get it warm, run it for a few minutes, shut it off, pull the spark plugs, and kick it over as it called. This allows the piston to conform to the cylinder bore..
What would you estimate this bike is worth?
jack jones thanks! I have a '75 and love it.
Tengo una en mi provincia esta dañada por el plato y la volanta y los Coit , en Rep Dom no eh dado en singun Respuesto con estas Piesa
Plzz sir I want this bike plzz give me..sir
sri maharshilab Is everything ok with you man??
Yo he looks normal
too bad it’s not a 1973 or a 1974. the 1975 RD 250 was the slowest, and I mean by about 10 miles an hour on top end, and by about a second on acceleration in the quarter mile ..The reason, - the disc brake up front
how do I know this?
I won 6 Championships Roadracing a 1974 RD 250 with a drum front brake .. it was legal for me to use a disc brake front end because the machines were produced with a disc brake like on the RD 350.. So I tried one. Not only was I about 5 miles an hour slower than other riders are used to be dead even with on acceleration, but that front disc is a gyroscope that does not like to change directions quickly. If you have ever held a gyroscope ,You know what I’m talking about. And road race tracks that required quick left right left right turning. My machine would not turn as quickly as it did with the drum break, and I would often run off the track interns I never did before with the drum break, because the bike would not turn fast enough.
The disc is also unsprung weight. That is so critical over bumps, which all road race tracks have from the cars twisting the hot asphalt in the hot summer sun and of course it’s online on exit from turns, that the suspension would absorb the weight of that unsprung weight into the springs of the front forks, and the oil in the front fork tubes would have to slow down the spring rebound. This took extra time between bumps because of the extra weight and the extra weight of the disc in the caliper.
The third disadvantage the disc hampered my race bike or any bike with a disc is, it is also a fly wheel, like the little matchbox cars we had when we were little kids, you had to run them across the ground to get this fly wheel spinning, and then they would want to keep spinning. Well a fly wheel Hass to be accelerated, and that takes horsepower. so those are the three major disadvantages of the disc brake front end over that very light RD 250 that did not need a disk. The top speed on an RD with 16-40 Gearing at 1000 feet above sea level, with the airbox in tact with an air filter in the box and the lid on the airbox, was about 105 miles an hour on an 80° day, that was on the first lap. On the 15th lap, I would be very lucky if the machine even reached 95 miles an hour. Air cooled machines slow down that much when they got hot..
there was also one more factor that the disc brake front end catch did that slowed the machines down, and that was brake puck drag.
I agree that the disc brake would slow the machine down much quicker than the drum brake especially after the fifth or six lap. But the handling, the quicker steering, the acceleration, and the ability to reach top end quicker, more than made up for the deficiency in the braking of the drum brake, which could be adjusted to have zero drag. A new brake cable for the front brake helped every fifth or sixth race. The inner cable doesn’t stretch, it’s the outer cable that collapses over itself and makes it seem like the inner cable got longer.
The machine in this video is beautiful. But the two prior years would leave it in the dust. The one thing that the 1975RD 250s and 350s head that the 73 and 74 machines did not have, what is the metal guard over the oil pump stroke advance pin..
If you can ever find a set of cylinders for the RD 250 that has only three full cooling fins above the reed block instead of four fins above the reed block,Those three fin cylinders are faster than the cylinders that have four complete cooling fins above the reed block..
how do I know these things? Like I said I rode raised a brown drum brake RD 250, I won six championships on it, and two national championships on that machine. With a drum brake, and you must leave the complete airbox in tact, with the stock paper air filter , and the lid on the airbox, otherwise, the reeds do not close correctly ..
been there, done that..
Harry lime is not my real name, it’s Jody
Red blinkers are dangerous orange better on back of bike