Thanks to you, I'm starting to understand the complicated process of porting. I'm planning on modifying early 70's kawasaki g4tr 100cc 11hp to G31M specs at 18.5hp at over 10,000 rpm.The Centurian was the fastest 100cc by far on the flat track. Your the man!
Oh yeah, the Green Streaks, I remember them well, ran against several when I was riding a Hodaka Super Rat on flat tracks in Oklahoma back in the day. They were indeed fast. That sounds like a great project, much like I'm doing on the Yamaha AT-2 MX build. I like this because it's not a restoration, it's a anything goes fun project, my only rule is only to use period parts. You will have to keep me up to speed on your project. It sure sounds fun. I do have a 71 F7 and a 70 F5 Kawasaki that I will get to in the future, I actually have done a couple videos on the F5 already. Thanks again for hanging out in the shop with me.
Wow, so cool you raced flat track back in the day! That was a little before my time. I did a little motocross as a teenager in the early 80's. Would love to own a Big Horn!
What a cool video, Dale! Using a piston ring to determine height was brilliant. Significant changes, so totally agree with your conservative approach. Really looking forward to seeing an hearing it work!
Thanks Jim, yeah you can make a door stop out of a cylinder pretty fast if you dont know what you are doing. I like factory specifications. The best way to go.
Is that a dentist's drill you have laying there?? Holy crap, THAT brings back some traumatic childhood memories! Made me want to sit down and cross my legs REAL tight
I did this to an old 73 125 enduro probably 15 years ago. I have an old yamaha manual that had port maps in it. I noticed the boost port being wider but raised the ports and matched the mx cylinder specs. I couldn't get my dremel to hit the correct angles so the ports looked pretty crude. I also had an old hooker expansion chamber and a head from a trimoto 125 that I shaved and enlarged the bolt holes to fit. The midrange hit this bike gained was very impressive and made me wish the chassis handled better (I did add a 21" front wheel). Pretty sure the yamaha would out accelerate my 72 cz125 but I wouldn't want to go too fast on a rough track with it.
Hey Nathan, yes, it's been a while since I did this, but it seems the enduro boost port is wider than the factory MX cylinder. But so far, I don't see or feel any problems with the way the engine runs. But I don't have an MX cylinder to compare to. You are spot on when talking about the handling of the Yamaha chassis, it needs a lot of help. Thanks for spending time with me in the shop.
Dale, it may be that the MX has a narrower inlet boost port area to create crisper low down power, to get you off the line and out of tight turns faster. I too have a limited understanding of the subject. The expansion chamber on the header allows for a higher revving engine by producing a pressure wave which acts as a sonic barrier, preventing the fresh charge from being scavenged out of the exhaust port at higher rpm. This was invented by Walter Kaaden at MZ in the 1950s and stolen by the Japanese in the 1960s after a defection by an MZ works rider. Kaaden controversially gained his thermodynamics expertise whilst he was a rocket scientist in the German V2 programme during WW2. Great work as usual, I always look forward to spending time in the shop with you. Best wishes, Dean.
Indeed he did. It was that pressure wave which opened and closed the reed valves on the pulse jet engine of the V1. Kaaden himself did not work on the V weapons though. He was mainly concerned with the Henschel radio guided missile.
Wow Dean...the school system in the UK must actually teach something. You and your brother are very learned. Got to be careful, don't want anyone's head to explode from all that really great information. I say this in jest, but you would have to see some of the younger generation here in this country....it worries me. I enjoy all that theory and have read some of it. However, it is just a little over my head, that's why I gave a disclaimer about my limited knowledge of the subject. Wish I had more room in my head for it, but it just doesn't fit. Thanks for hanging out with me in the shop!
Carl...I am indeed impressed, you guys are just a walking encyclopedia. Thanks for your support and all that stuff you know. Now I know were to go for everything I dont know. Thanks for hanging out in the shop with me.
@@montana2strokeracer Dale, it's getting that way here too. I only really know because I have been involved with building and tuning MZ and Simson bikes over the years. My understanding of the gasflow process is pretty limited, you really need a flow test bench and in-depth knowledge to do it properly. I'm very much like you, I can follow a map created by someone with all the gear and some idea!! Always great talking to you my friend. Dean.
Dale your right on the pipe.they really effect preformance. my raceing Suzuki TS-250 had a sweet low expansion chamber and we would saw off the stinger a little at a time, it was like Goldie locks and the 3 bears had to be just right to much and you lowered preformance. think its a back pressure thing. any who! it did sound fantactic. remember starting it up at a car wash once after a race and the spectators ran out, scared the hell out of them. by the way wish i had a recording of my 1974 Kawasaki H2 with 3 chambers.
Yes, the pipe does a lot, there are many videos on TH-cam with running 3-cylinder Kawasaki's. They are nasty sounding; I can just smell the Castrol R too.
need to get perfume in that smell! have to admit pure caster bean is the best, although you have to drain out after one heat cycle.@@montana2strokeracer
Hi Dale, I am just about to do some cleaning up of casting slag /polishing of all the ports and removing some larger casting bumps that appear to be inherent in the TS250 Exhaust Port, I have a spare Barrel and that is exactly the same, I watched another guy doing the same thing in another video with this same casting flaw, I intend to work very slowly but surely and with confidence, I am on a budget so I am going to have a go with my Dremel, got to say a little nervous, but looking forward to it, then I will get this Barrel 0.05 Rebored. I know this is a porting video, But wondering will you be playing around with the Jetting, to complement the Port work done, think I will when I get it back together, I will post again and let all know how I get on, and any performance gains if any. Just want to say Dale thanks for your excellent quality videos, which are an inspiration to me and I'm sure to other classic two strokers out there. Malc U.K.
Hey thanks Malcolm, I think you are approaching that job in the right way. You will do just fine, take it slow and check your work regularly. Your Dremel will work just fine. Yes, I plan to do some plug readings and jet changes I'm sure will follow. I still need to revisit this project because it will not rev past about 2000 rpm. I have gotten another CDI box and will try that. Pretty sure it is in the ignition, remember this is the one I put a YZ CDI set up on. I'm sure we will get it figured out. Thanks for spending time in the shop with me, and good luck on your port work.
Nice videos you make! One question about the transfers, since I cant see much of it in the video. Did you raise the complete roof of the transfers, or just remove material in the port openings to make them higher? It's supposed to be really important with the upwards angle of the transfers, so the whole roof should be lifted maintaining the same upwards angle (since no change seems to be specified). This affects scavenging of the cylinder, and affects both throttle response and power output. Maybe you had an MX cylinder as reference?
Hi there, I used the factory porting specs from the time. I am not a pro at this, but I believe the conception of rasing the roof of the transfers is a more recent procedure. Therefore, it was not mentioned in the factory porting specs from 1972. I do have a factory GYT kit cylinder that needs to be sleeved, and the roof of its transfers seem to be the same as a Enduro cylinder. It certainly makes since what you're saying, and I have read some about it. But this 125 MX project was about only using period parts and data that was used in about a 4-year window of 1972. For the most part I have been able to stay in that time frame. This was all announced at the beginning of the project. Still have some work, mostly painting before this one is complete. Thanks very much for your comment, and for spending time in the shop with me.
Hey Taylor, yes, I will be chamfering after I bore and hone, I always port before I bore so if I slip, it's not on a fresh bore. Thanks for hanging out with me in the shop. Hope all is good out west.
Nice work as usual. (vid and mechanics) Those early cylinders have some thick liners. My 77 is about a third of that one. Probably bean counters thinning them out saving weight and materials. Have you seen people drilling a hole in the intake into the first transfer on each side? All the new bikes have them I guess and I hear it soups them up pretty good. I think it came from the blaster riders as those engines are basically an updated version of these old yammies. Also what brand grinder are you using? Thanks again. Kevin
Hey Kevin, no I haven't run on to any like that. Back in the day we used to run diaphragm carbs from a chainsaw on some of the Hodaka Super Rats, we ran a copper line and fittings to a transfer to pull a pulse signal to operate the carb. Man, those were the days, some of those Rats were unbeatable on the flat tracks. I have two grinders actually, one is a Foredom, the other a CC Specialty tools. The CC uses a Foredom motor, it's the 90 degree one that I use. You can just buy the grinder head from them and use it on your Foredom, that saves some cash. Thanks for hanging out with me.
4:17 I guess a good start would be to measure the width of the boost port on the Enduro cylinder first, that should help you work out whether the info on that port has been transposed.
in the olden days, if memory serves me correctly, my hop up guy would insert the piston and remove material from the skirt that would be blocking a port. like 4mm off the intake side of the piston. also does polishing the ports work on 2strokes like it did on 4 strokers?
In the good ole days, some folks removed material from the top of the piston to control the intake and exhaust events, you can also use a spacer plate under the cylinder, that also raises the port timing. More than one way to skin the cat so to speak.
@@montana2strokeracer hope you dont mind all the questions, as with time you will become a big time TH-camr and have so many question you wont be able to answer. you can hire me and Cain to be your personal assistant to answer your mail. LOL
Oh geez, between you and the UK boys, I feel so inadequate, you guys have me going to the dictionary. Guess I'm going to have to look up ole Erv now. Thanks buddy
Looking forward Dale, to the knowledgeable video. Are the abestos exuast string as bad as people make them out to be? I figured with a good facial mask and clothes installation should be fine
Thanks to you, I'm starting to understand the complicated process of porting. I'm planning on modifying early 70's kawasaki g4tr 100cc 11hp to G31M specs at 18.5hp at over 10,000 rpm.The Centurian was the fastest 100cc by far on the flat track. Your the man!
Oh yeah, the Green Streaks, I remember them well, ran against several when I was riding a Hodaka Super Rat on flat tracks in Oklahoma back in the day. They were indeed fast. That sounds like a great project, much like I'm doing on the Yamaha AT-2 MX build. I like this because it's not a restoration, it's a anything goes fun project, my only rule is only to use period parts. You will have to keep me up to speed on your project. It sure sounds fun. I do have a 71 F7 and a 70 F5 Kawasaki that I will get to in the future, I actually have done a couple videos on the F5 already. Thanks again for hanging out in the shop with me.
Wow, so cool you raced flat track back in the day! That was a little before my time. I did a little motocross as a teenager in the early 80's. Would love to own a Big Horn!
What a cool video, Dale! Using a piston ring to determine height was brilliant. Significant changes, so totally agree with your conservative approach. Really looking forward to seeing an hearing it work!
Thanks Jim, yeah you can make a door stop out of a cylinder pretty fast if you dont know what you are doing. I like factory specifications. The best way to go.
Excellent work as always. Really enjoy your thought process on these jobs.
Thanks Carl, just winging it as usual. I really do enjoy the process though...it's fun.
Is that a dentist's drill you have laying there?? Holy crap, THAT brings back some traumatic childhood memories! Made me want to sit down and cross my legs REAL tight
Relax, it isnt a dental drill, it is a grinder made for porting. But it looks like one. Thanks for following the channel
I did this to an old 73 125 enduro probably 15 years ago. I have an old yamaha manual that had port maps in it. I noticed the boost port being wider but raised the ports and matched the mx cylinder specs. I couldn't get my dremel to hit the correct angles so the ports looked pretty crude. I also had an old hooker expansion chamber and a head from a trimoto 125 that I shaved and enlarged the bolt holes to fit. The midrange hit this bike gained was very impressive and made me wish the chassis handled better (I did add a 21" front wheel). Pretty sure the yamaha would out accelerate my 72 cz125 but I wouldn't want to go too fast on a rough track with it.
Hey Nathan, yes, it's been a while since I did this, but it seems the enduro boost port is wider than the factory MX cylinder. But so far, I don't see or feel any problems with the way the engine runs. But I don't have an MX cylinder to compare to. You are spot on when talking about the handling of the Yamaha chassis, it needs a lot of help. Thanks for spending time with me in the shop.
Dale, it may be that the MX has a narrower inlet boost port area to create crisper low down power, to get you off the line and out of tight turns faster. I too have a limited understanding of the subject. The expansion chamber on the header allows for a higher revving engine by producing a pressure wave which acts as a sonic barrier, preventing the fresh charge from being scavenged out of the exhaust port at higher rpm. This was invented by Walter Kaaden at MZ in the 1950s and stolen by the Japanese in the 1960s after a defection by an MZ works rider. Kaaden controversially gained his thermodynamics expertise whilst he was a rocket scientist in the German V2 programme during WW2.
Great work as usual, I always look forward to spending time in the shop with you.
Best wishes, Dean.
Indeed he did. It was that pressure wave which opened and closed the reed valves on the pulse jet engine of the V1. Kaaden himself did not work on the V weapons though. He was mainly concerned with the Henschel radio guided missile.
Wow Dean...the school system in the UK must actually teach something. You and your brother are very learned. Got to be careful, don't want anyone's head to explode from all that really great information. I say this in jest, but you would have to see some of the younger generation here in this country....it worries me. I enjoy all that theory and have read some of it. However, it is just a little over my head, that's why I gave a disclaimer about my limited knowledge of the subject. Wish I had more room in my head for it, but it just doesn't fit. Thanks for hanging out with me in the shop!
Carl...I am indeed impressed, you guys are just a walking encyclopedia. Thanks for your support and all that stuff you know. Now I know were to go for everything I dont know. Thanks for hanging out in the shop with me.
@@montana2strokeracer Dale, it's getting that way here too. I only really know because I have been involved with building and tuning MZ and Simson bikes over the years. My understanding of the gasflow process is pretty limited, you really need a flow test bench and in-depth knowledge to do it properly. I'm very much like you, I can follow a map created by someone with all the gear and some idea!!
Always great talking to you my friend.
Dean.
Dale your right on the pipe.they really effect preformance. my raceing Suzuki TS-250 had a sweet low expansion chamber and we would saw off the stinger a little at a time, it was like Goldie locks and the 3 bears had to be just right to much and you lowered preformance. think its a back pressure thing. any who! it did sound fantactic. remember starting it up at a car wash once after a race and the spectators ran out, scared the hell out of them. by the way wish i had a recording of my 1974 Kawasaki H2 with 3 chambers.
Yes, the pipe does a lot, there are many videos on TH-cam with running 3-cylinder Kawasaki's. They are nasty sounding; I can just smell the Castrol R too.
need to get perfume in that smell! have to admit pure caster bean is the best, although you have to drain out after one heat cycle.@@montana2strokeracer
Hi Dale, I am just about to do some cleaning up of casting slag /polishing of all the ports and removing some larger casting bumps that appear to be inherent in the TS250 Exhaust Port, I have a spare Barrel and that is exactly the same, I watched another guy doing the same thing in another video with this same casting flaw, I intend to work very slowly but surely and with confidence, I am on a budget so I am going to have a go with my Dremel, got to say a little nervous, but looking forward to it, then I will get this Barrel 0.05 Rebored. I know this is a porting video, But wondering will you be playing around with the Jetting, to complement the Port work done, think I will when I get it back together, I will post again and let all know how I get on, and any performance gains if any. Just want to say Dale thanks for your excellent quality videos, which are an inspiration to me and I'm sure to other classic two strokers out there. Malc U.K.
Hey thanks Malcolm, I think you are approaching that job in the right way. You will do just fine, take it slow and check your work regularly. Your Dremel will work just fine. Yes, I plan to do some plug readings and jet changes I'm sure will follow. I still need to revisit this project because it will not rev past about 2000 rpm. I have gotten another CDI box and will try that. Pretty sure it is in the ignition, remember this is the one I put a YZ CDI set up on. I'm sure we will get it figured out. Thanks for spending time in the shop with me, and good luck on your port work.
Nice Work Brother!
Thanks Philip, I sure appreciate you hanging out in the shop with me.
Is there nothing you won't try Dale. Not for me but goodonyou. Well done and thanks
Nice videos you make!
One question about the transfers, since I cant see much of it in the video. Did you raise the complete roof of the transfers, or just remove material in the port openings to make them higher? It's supposed to be really important with the upwards angle of the transfers, so the whole roof should be lifted maintaining the same upwards angle (since no change seems to be specified). This affects scavenging of the cylinder, and affects both throttle response and power output. Maybe you had an MX cylinder as reference?
Hi there, I used the factory porting specs from the time. I am not a pro at this, but I believe the conception of rasing the roof of the transfers is a more recent procedure. Therefore, it was not mentioned in the factory porting specs from 1972. I do have a factory GYT kit cylinder that needs to be sleeved, and the roof of its transfers seem to be the same as a Enduro cylinder. It certainly makes since what you're saying, and I have read some about it. But this 125 MX project was about only using period parts and data that was used in about a 4-year window of 1972. For the most part I have been able to stay in that time frame. This was all announced at the beginning of the project. Still have some work, mostly painting before this one is complete. Thanks very much for your comment, and for spending time in the shop with me.
Nice job Dale... looks good! Your exactly right about porting and catching a ring, I am assuming you will be chamfering all your port edges?
Hey Taylor, yes, I will be chamfering after I bore and hone, I always port before I bore so if I slip, it's not on a fresh bore. Thanks for hanging out with me in the shop. Hope all is good out west.
Nice work as usual. (vid and mechanics) Those early cylinders have some thick liners. My 77 is about a third of that one. Probably bean counters thinning them out saving weight and materials. Have you seen people drilling a hole in the intake into the first transfer on each side? All the new bikes have them I guess and I hear it soups them up pretty good. I think it came from the blaster riders as those engines are basically an updated version of these old yammies. Also what brand grinder are you using? Thanks again. Kevin
Hey Kevin, no I haven't run on to any like that. Back in the day we used to run diaphragm carbs from a chainsaw on some of the Hodaka Super Rats, we ran a copper line and fittings to a transfer to pull a pulse signal to operate the carb. Man, those were the days, some of those Rats were unbeatable on the flat tracks. I have two grinders actually, one is a Foredom, the other a CC Specialty tools. The CC uses a Foredom motor, it's the 90 degree one that I use. You can just buy the grinder head from them and use it on your Foredom, that saves some cash. Thanks for hanging out with me.
4:17 I guess a good start would be to measure the width of the boost port on the Enduro cylinder first, that should help you work out whether the info on that port has been transposed.
in the olden days, if memory serves me correctly, my hop up guy would insert the piston and remove material from the skirt that would be blocking a port. like 4mm off the intake side of the piston. also does polishing the ports work on 2strokes like it did on 4 strokers?
In the good ole days, some folks removed material from the top of the piston to control the intake and exhaust events, you can also use a spacer plate under the cylinder, that also raises the port timing. More than one way to skin the cat so to speak.
@@montana2strokeracer hope you dont mind all the questions, as with time you will become a big time TH-camr and have so many question you wont be able to answer. you can hire me and Cain to be your personal assistant to answer your mail. LOL
Dale can a small 2 stroker be Dyno tested so you can verify the HP and Torque inprovement or not?
Sure, they can.... just not where I live, we are lucky to have grocery stores here.
Looks good brother. A lot of work is the payoff worth it?
Thanks Cain, I think it will be, its sure a lot of fun.
.. Good vid,.. Who makes those 90 degree grinders, may I inquire ?..
Hi thanks for watching my videos. The 90-degree grinders are made by CC Specialty tools.
@@montana2strokeracer .. Hi there, Dale,.. Thanks for the swift reply,.. Keep-up the good work ,... :o)
Dale your going to make Erv Kanemoto jelous. LOL
Oh geez, between you and the UK boys, I feel so inadequate, you guys have me going to the dictionary. Guess I'm going to have to look up ole Erv now. Thanks buddy
nice job dale should rev now
Thinking you are right Mark, it has been a long time since I rode a AT2 MX. I remember them screaming. Of course the smell of Castrol R.....priceless.
Looking forward Dale, to the knowledgeable video. Are the abestos exuast string as bad as people make them out to be? I figured with a good facial mask and clothes installation should be fine
Hi Larry, Im sure as long as you gear up you should be fine. Just use common sense and be careful.
i give up ,quick draw Cain got me again.
Poor Frank, just can't get a break...thanks for hanging with me buddy!
Well I made it before Frank
Small miracles, thanks Cain for hanging out with me.