Finally someone on TH-cam who actually knows what they're talking about and where I can actually learn something. Brilliant thanks M8. Love your videos thanks for sharing.
The actual measurement of piston clearance I did was 0.6 mm at the top. The 3 mm is only at the bottom in relation to the port. I suspect they used the piston that came with that cylinder to ensure it has small enough clearance at the top suffice to have a reasonable compression ratio.
From the looks of this engine, I'll be reconsidering what engine I'll be using in my project minibike. Although I'd like to use a 4-stroke engine, I need something that I can lay flat, and would run reliably in any position. So an engine like this one, but with better quality would be ideal.
Yes I would look around for others, this was the cheapest I could find (TDPRO brand) There are some with removable heads which would be a better option.
Yes the rings are pretty chunky which is going to limit of peak RPM of this thing. I did a video previously measuring ex timing with a degree wheel and its 154 Ex and 104 Transfer which is pretty low for power but for a chainsaw type engine its not uncommon since they are tuned for low emissions and low noise. Ill be measuring the timing again using the port to deck height method in the next videos to double check those timings.
i've seen many a rebuilt 2 stroke outboard were someone put those style wrist pin bearings in the new aftermarket pistons they got, and the thing was all beat to hell. the best ones , in my opinion, take the 28 loose needle bearings and those 2 cupped washers you spoke of. way better design than stock, and no way of beating itself up!
You are right on that, what you refer to is a "crowded" roller bearing arrangement (no cage) and that is the best for very high RPM engines such as some Kart engines. The bearing cage is the weak point.
@@AuMechanic interesting. never knew the terminology. these days, it's hard to find anyone that works on older 2 stroke stuff. everyone wants a new fancy computerized 4 stroke with warranty. breaks after a few years of no oil changes? no problem. just throw it away lol. i miss the 80's.
@@ct1762 Yeah I liked the 80's, I was road racing bikes back then (350 2 stroke and 1000 superbikes) and it was hey days of road racing, we used to get huge grids (sometimes 30+ starters) and decent spectator numbers too, it was good times. Sadly the end of 2 strokes made road racing even farther out of reach to many as they were the cheapest class to race in.
I opened up my mates cheap 2 stroke generator that was running poorly due to running the wrong ratio oil. The motor was all coked up and after cleaning it up I noticed the ports weren't uncovering like yours. I think with a 5mm spacer at the base of the cylinder and then 5mm machining off the top should sort it out (luckily the head is separate) but would that be worth doing on a generator? I might take it a part again to check the little end, good spot that one.
Yes if the head was removable I could just take 3 mm off the deck and raise the barrel by 3 mm. There are some top end kits for theses engines on Ebay that show a removable head.
I Knew it! I knew these often come out of the box with incorrect pistons installed!! I'm concerned with the 66cc motorized bicycle engines though but, I believe they are very similar perhaps even many manufactured in the same places.
Same thing I noticed while measuring my engine's port after watching your previous videos my exaust port does not opens totally the 2 to 3 mm of piston stays above the lower end of the port, Does it decrease the power of the engine??
@@sumedhovhal8156 The solution is to raise the cylinder the then remove the same amount of the top deck of the cylinder however if the cylinder head is not removable like the one in the video then this is not an option. In short the problem is that the cylinder possibly belongs to and engine with a longer stroke.
When I got a $15 piston amd ring kit for my vento I just reused my factory bearing because there was nothing wrong with it,just bearings were wore down some.
if the bearings were worn, why re-use? the kits with the loose needle bearings and the 2 cupped washers are awesome. i'm sure your fine, but why chance it for $15?
@@ct1762 mine weren't wore out,it was the rings that were wore out and instead of using the cheap junk new one I just soaked the old one in oil and reused it.
ME THINKS THE PARTS BIN'S GOT MIXED UP ? WOULD GRINDING THE TOP OF THE PISTON ALL ROUND .OR JUST ON THE MARKED OUT 3mm SECTION OF THE PISTON BE VIABLE ?. OR WOULD THAT CAUSE A REALLY BAD IMBALANCE . OR MAYBE USE A THICKER GASKET . THATS IF YOU COULDNT FOR ANY REASON PUT ANOTHER PISTON IN.? BASICALLY , WHATS THE BEST BODGE? THANKYOU
I'd say they probably couldn't source the right barrel and pistons for it anymore so used these ones. Removing part of the piston by 3 mm would leave it a bit thin at the crown for one thing and the other problem would be a loss of compression ratio as it would add to the volume at TDC by quite a bit. If I had to resolve it I think the simplest would be just to accept the piston doesn't go all the way down at the exhaust and just raise the exhaust and transfer ports by the same 3 mm and just accept a little less trapped comp ratio. That would recover some lost port area and timing as well. You will see in the next video coming that the transfers have no bottom of the port they are slots all the way down the cylinder.
@@choco107 TA MATE JUST WON A £10 OF THE LAD NEXT DOOR WHO THINKS TUNING IS BLOWING THE THE CRAP OUT OF SOMETHING .THEN SAYING IT WAS THE BEST IT EVER WENT FOR THOSE 2 MIN BEFORE IT LETS GO. THE TWIT AINT EVEN GOT A £10 TO LOSE , BUT THE VICTORY IS ENOUGH IN THAT HE MIGHT ACTUALLY MIGHT REMEMBER 10% OF WHY HES WRONG
Nice to see your face! Does it really matter that much if the port does not open completely? If there is not enough duration or port area just make the port higher. If we are talking crap chinese engines like the motorized bike I race...
Cheers.That would be the simplest as I mentioned in another comment here to GAZGIT by just raising the ports to recover some timing and port area and just accepting the overlap at BDC and a little less trapped CR.
Yes you could but I probably wouldn't use stainless simply due to weight. 2 stroke engines that use a "crowded" roller arrangement at the small end that has no cage use Aluminium washers at each end of the rollers. Same could be used for this. They would need to be high grade Al like 6061 Also would need a fair amount of side clearance in them to ensure lubrication can still get to the rollers.
If the bearing cage moves enough so the rollers can hang out either end like that when the piston is centre to the rod then yes Id be using some spacers to keep it centred enough to at least ensure the rollers don't hang out either end of the small end of the con rod.
@@AuMechanic so i recently rebuilt my engine (new seals) and also tried putting in spacers they went into bits only by reving it a bit after the first start and fucked my piston completely (stuck ring and scuffed up skirt) the washers were gone completely so from my experience i would not recommend that
One thing comes to mind that if the piston end spacer clearance was less than the big end side clearance was then the side load would then be taken up by the piston end and not the big end and in that case the spacer up top are not designed for that load.
You could do....but The trench left in the piston top would mean that area doesn't come close enough to the squish region. Although in an engine like this the CR is pretty low so it wouldn't matter much. OTH there is probably not much to be gained by doing it anyway. It just highlights the fact that this engine basically has the wrong cylinder on it for the stroke among other flaws with it.
On 4:30min, can we do something to solve this? Or just change the bearings for example every 5000km? O already bought the cylinder kit, there is no way back 😁 thank you!
Hi, sorry i missed this comment. You could machine up spacers to fit in each side but you need to be careful to make sure there is plenty of clearance each side. Someone has already tried it and it failed but I think they made the spacers too tight. They only need to be big enough to stop the rollers hanging out the side of the small end of the con rod and no tighter than that otherwise it might rob the small end bearing of lubrication too. If you do them an Ali it needs to be 6061 at least nothing softer.
Yes if you can get one that has the same OD and ID that would do it, if you could get one to suit which might be a challenge as they don't usually sell them with sizes like OD and ID and width specified.
The short answer is no, but that said there are gains to be had be cleaning up the surface of the ports and removing any irregularities. Polishing the port alone does not improve flow. There is a theory that polishing the port can help to reduce the build up of carbon however my experience is that is not the case and what causes build of up carbon inside the ports is actual depressions that create turbulent flow over the surface at the point carbon deposit is present.. The there is a carbon build up on one part of the otherwise clean port can be a sign that there is a depression at that are in the port that is significant enough to warrant blending it out to improve laminar flow across that region of the port.. Ill go into this topic more in future videos on porting.
I was a little nervous about getting an engine like that just because the head top end isn't removable and might be 38 cc ..is it really 38 cc ? the reason why I got the bicycle engine is it's 60 cc but the ignition cdi is odd unreliable cheesaneeze. Only now figured the flywheel magnet got too weak on that and I was thinking ignition coils were coming in the mail dead on arrival ... the race version of the one you got. the head bolts extend up to the top end with the head removable ? That would probably make things easier if and when you Deck the cylinder and correct that exaust port . And compression I don't think that the Piston wrist pin being loose is much a problem so long as the cylinder hold the Piston right center. My nephew had a tiny scooter with the same engine it was no way near as fast As a tomos A35! moped.
Hi Dan Note in the video I mention at 4:35 even with the piston held centre of the rod small end the bearing still hangs our quite a bit. This engine also has no squish band over the full area of the head which limits compression ratio so the removable head type one may improve on that also. With the coils you need top ensure the coils are as close to the flywheel as you can possible get them with them touching it, that air gap can make a lot of difference to not just the spark voltage but the timing as well I did a video some time ago on that topic using an oscilloscope and timing light.
@@AuMechanic yeah that's what I was thinking I use a business card for the flywheel magnet 1000 s of 1" works for the bike engine as well and that stater better be screwed tight but I'ma try this engine for the smaller scooter side project I'm welding together for a friend
@@capchassuck Business card is very thick. Use a feeler gauge, just be sure not to use it when the magnet is near the coil pickups or use a brass feeler gauge which is designed for that purpose.
@@AuMechanic I didn't know if there was a tool for that. I know thousands of an inch was the standard of lawn mower engines but thanks. learn something new every day. this one guy does a tutorial for bicycle mount engine but screwed up everything and had a commercial for every screw up like he must be smoking crack cus it almost seems like he did it on purpose. I subscribed to your channel cus you know more about what you are doing. how does a Dino work ?. more power compared to rpm speed I'll have to review the one that two stroke stuffing made. I'm thinking a flange and metal bar Bell whaight and dc electric motor attached to a pen graph machine that makes a chart on paper or something like that nothing. fancy like a computer . I'll see what I can get on eBay and thrift store may have to go get machine work at the local machineist.
@@capchassuck The simplest Dyno is like Alex has at twostrokestuffing which is an inertial dyno. You need to measure how long it takes to get a weight to spin up to maximum speed. In theory you could just use a timer and a tacho to see how long it takes to get the weight to spin up to a given speed but that will only give you peak power to compare between runs which may be enough to compare after mods. What a computer allows is to graph that time over speed over the whole period and then calculate power over the curve since based on the moment of inertia which is put into the computer as well as roller rpm.
i dont think the ports being fully open is important, unless you are trying to get the most rpm out of the engine, i.e a horrible tuned up racer, i prefer standar and quiet reserved 2 strokes, a bit of restriction is good. i mean, are you going to remove the whole expansion chamber and exhaust to make it breathe even easier? no. you want small ports.
Finally a real tuner I can learn from. Thanks
Thank's for the comment, hope you find the videos useful.
same tought , this guy knows how to explain , and he is old school mechanic , not a ''tuner' or ricer boy ;)
Finally someone on TH-cam who actually knows what they're talking about and where I can actually learn something. Brilliant thanks M8. Love your videos thanks for sharing.
Thank's for the comment
Cheers.
34+3+3=40 stroke. 3mm at top 3mm at bottom . Great content .
Exhaust calculation very enjoyable and rare to see in such a clear way.
The actual measurement of piston clearance I did was 0.6 mm at the top.
The 3 mm is only at the bottom in relation to the port.
I suspect they used the piston that came with that cylinder to ensure it has small enough clearance at the top suffice to have a reasonable compression ratio.
Learn something new from your channel always. Thx
Cheers Bob
From the looks of this engine, I'll be reconsidering what engine I'll be using in my project minibike. Although I'd like to use a 4-stroke engine, I need something that I can lay flat, and would run reliably in any position. So an engine like this one, but with better quality would be ideal.
Yes I would look around for others, this was the cheapest I could find (TDPRO brand)
There are some with removable heads which would be a better option.
great video! I'm interested to see the port duration's on this. Those piston rings look thick .
Yes the rings are pretty chunky which is going to limit of peak RPM of this thing.
I did a video previously measuring ex timing with a degree wheel and its 154 Ex and 104 Transfer which is pretty low for power but for a chainsaw type engine its not uncommon since they are tuned for low emissions and low noise.
Ill be measuring the timing again using the port to deck height method in the next videos to double check those timings.
i've seen many a rebuilt 2 stroke outboard were someone put those style wrist pin bearings in the new aftermarket pistons they got, and the thing was all beat to hell. the best ones , in my opinion, take the 28 loose needle bearings and those 2 cupped washers you spoke of. way better design than stock, and no way of beating itself up!
You are right on that, what you refer to is a "crowded" roller bearing arrangement (no cage) and that is the best for very high RPM engines such as some Kart engines. The bearing cage is the weak point.
@@AuMechanic interesting. never knew the terminology. these days, it's hard to find anyone that works on older 2 stroke stuff. everyone wants a new fancy computerized 4 stroke with warranty. breaks after a few years of no oil changes? no problem. just throw it away lol. i miss the 80's.
@@ct1762 Yeah I liked the 80's, I was road racing bikes back then (350 2 stroke and 1000 superbikes) and it was hey days of road racing, we used to get huge grids (sometimes 30+ starters) and decent spectator numbers too, it was good times.
Sadly the end of 2 strokes made road racing even farther out of reach to many as they were the cheapest class to race in.
Man true 2stroke guru tricks here man !!
I opened up my mates cheap 2 stroke generator that was running poorly due to running the wrong ratio oil.
The motor was all coked up and after cleaning it up I noticed the ports weren't uncovering like yours.
I think with a 5mm spacer at the base of the cylinder and then 5mm machining off the top should sort it out (luckily the head is separate) but would that be worth doing on a generator?
I might take it a part again to check the little end, good spot that one.
Yes if the head was removable I could just take 3 mm off the deck and raise the barrel by 3 mm.
There are some top end kits for theses engines on Ebay that show a removable head.
I Knew it! I knew these often come out of the box with incorrect pistons installed!! I'm concerned with the 66cc motorized bicycle engines though but, I believe they are very similar perhaps even many manufactured in the same places.
There are a lot of copy or knock off versions of these engines produced.
Same thing I noticed while measuring my engine's port after watching your previous videos my exaust port does not opens totally the 2 to 3 mm of piston stays above the lower end of the port, Does it decrease the power of the engine??
Potentially yes it does reduce power, if the engine has a reasonable amount of BMEP eg flow through ports it will limit power.
@@AuMechanic so .. what should I do now?? Should I raise the ports by 2 to 3 mm or is there any other way??
@@sumedhovhal8156
The solution is to raise the cylinder the then remove the same amount of the top deck of the cylinder however if the cylinder head is not removable like the one in the video then this is not an option.
In short the problem is that the cylinder possibly belongs to and engine with a longer stroke.
When I got a $15 piston amd ring kit for my vento I just reused my factory bearing because there was nothing wrong with it,just bearings were wore down some.
if the bearings were worn, why re-use? the kits with the loose needle bearings and the 2 cupped washers are awesome. i'm sure your fine, but why chance it for $15?
@@ct1762 mine weren't wore out,it was the rings that were wore out and instead of using the cheap junk new one I just soaked the old one in oil and reused it.
@@ct1762 I meant to put rings where wore down some,not bearings.
@@ct1762 If the bearings were wore there's no way I would of reassembled it without getting new ones.
ME THINKS THE PARTS BIN'S GOT MIXED UP ? WOULD GRINDING THE TOP OF THE PISTON ALL ROUND .OR JUST ON THE MARKED OUT 3mm SECTION OF THE PISTON BE VIABLE ?. OR WOULD THAT CAUSE A REALLY BAD IMBALANCE . OR MAYBE USE A THICKER GASKET . THATS IF YOU COULDNT FOR ANY REASON PUT ANOTHER PISTON IN.? BASICALLY , WHATS THE BEST BODGE? THANKYOU
I'd say they probably couldn't source the right barrel and pistons for it anymore so used these ones.
Removing part of the piston by 3 mm would leave it a bit thin at the crown for one thing and the other problem would be a loss of compression ratio as it would add to the volume at TDC by quite a bit.
If I had to resolve it I think the simplest would be just to accept the piston doesn't go all the way down at the exhaust and just raise the exhaust and transfer ports by the same 3 mm and just accept a little less trapped comp ratio.
That would recover some lost port area and timing as well.
You will see in the next video coming that the transfers have no bottom of the port they are slots all the way down the cylinder.
@@AuMechanic you could also reshape the inlet port, weld and shape or just epoxy it. That step left from the piston would seriously mess up airflow.
Maybe the piston is blocking the port to stop the engine making enough power to rip itself to pieces, the small end bearing looks doomed already.
@@dreddwailing6395 YA NOT WRONG THERE MATE .EVEN WITH RESTRICTIONS THEY FALL APART
@@choco107 TA MATE JUST WON A £10 OF THE LAD NEXT DOOR WHO THINKS TUNING IS BLOWING THE THE CRAP OUT OF SOMETHING .THEN SAYING IT WAS THE BEST IT EVER WENT FOR THOSE 2 MIN BEFORE IT LETS GO. THE TWIT AINT EVEN GOT A £10 TO LOSE , BUT THE VICTORY IS ENOUGH IN THAT HE MIGHT ACTUALLY MIGHT REMEMBER 10% OF WHY HES WRONG
Nice to see your face!
Does it really matter that much if the port does not open completely? If there is not enough duration or port area just make the port higher. If we are talking crap chinese engines like the motorized bike I race...
Cheers.That would be the simplest as I mentioned in another comment here to GAZGIT by just raising the ports to recover some timing and port area and just accepting the overlap at BDC and a little less trapped CR.
To solve the problem at minute 4:30, stainless steel washers with a hole equal to the diameter of the piston pin may be enough
Yes you could but I probably wouldn't use stainless simply due to weight.
2 stroke engines that use a "crowded" roller arrangement at the small end that has no cage use Aluminium washers at each end of the rollers.
Same could be used for this.
They would need to be high grade Al like 6061
Also would need a fair amount of side clearance in them to ensure lubrication can still get to the rollers.
Great videos and content by the way...
Thank's for the comment
Again even a polini has those insane gaps between the piston and the rod
So youd recommend making aluminium washers to put in between?
If the bearing cage moves enough so the rollers can hang out either end like that when the piston is centre to the rod then yes Id be using some spacers to keep it centred enough to at least ensure the rollers don't hang out either end of the small end of the con rod.
@@AuMechanic so i recently rebuilt my engine (new seals) and also tried putting in spacers they went into bits only by reving it a bit after the first start and fucked my piston completely (stuck ring and scuffed up skirt)
the washers were gone completely
so from my experience i would not recommend that
@@schelmean16
A few questions, how long did they last, what grade aluminum did you use and how much clearance did you have ?
rollers
One thing comes to mind that if the piston end spacer clearance was less than the big end side clearance was then the side load would then be taken up by the piston end and not the big end and in that case the spacer up top are not designed for that load.
Is it okay to just grind off the part of the piston that doesn't clear the exhaust port?
The ring wud still be okay, so I think it'll be okay
You could do....but
The trench left in the piston top would mean that area doesn't come close enough to the squish region. Although in an engine like this the CR is pretty low so it wouldn't matter much.
OTH there is probably not much to be gained by doing it anyway.
It just highlights the fact that this engine basically has the wrong cylinder on it for the stroke among other flaws with it.
Was thinking of putting alumi-rod /filler for that, but true @@AuMechanic :)
On 4:30min, can we do something to solve this? Or just change the bearings for example every 5000km? O already bought the cylinder kit, there is no way back 😁 thank you!
I'm curious on this also
Hi, sorry i missed this comment.
You could machine up spacers to fit in each side but you need to be careful to make sure there is plenty of clearance each side.
Someone has already tried it and it failed but I think they made the spacers too tight.
They only need to be big enough to stop the rollers hanging out the side of the small end of the con rod and no tighter than that otherwise it might rob the small end bearing of lubrication too.
If you do them an Ali it needs to be 6061 at least nothing softer.
Could you use a wider pin bearing so it can't walk out the end?
Yes if you can get one that has the same OD and ID that would do it, if you could get one to suit which might be a challenge as they don't usually sell them with sizes like OD and ID and width specified.
How to remove this crankshaft and their center bearing take out
Using a hydraulic press, but I probably wont be doing a video on that, there are plenty of other videos showing how to replace crank bearings.
@@AuMechanic thank you for responding
Is polishing the exhaust port worth it?
The short answer is no, but that said there are gains to be had be cleaning up the surface of the ports and removing any irregularities.
Polishing the port alone does not improve flow.
There is a theory that polishing the port can help to reduce the build up of carbon however my experience is that is not the case and what causes build of up carbon inside the ports is actual depressions that create turbulent flow over the surface at the point carbon deposit is present..
The there is a carbon build up on one part of the otherwise clean port can be a sign that there is a depression at that are in the port that is significant enough to warrant blending it out to improve laminar flow across that region of the port..
Ill go into this topic more in future videos on porting.
@@AuMechanic Thank you for replying! I can tell you really want to educate people on the subject and that is a rare thing nowadays. thanks!
I was a little nervous about getting an engine like that just because the head top end isn't removable and might be 38 cc ..is it really 38 cc ? the reason why I got the bicycle engine is it's 60 cc but the ignition cdi is odd unreliable cheesaneeze. Only now figured the flywheel magnet got too weak on that and I was thinking ignition coils were coming in the mail dead on arrival ... the race version of the one you got. the head bolts extend up to the top end with the head removable ? That would probably make things easier if and when you Deck the cylinder and correct that exaust port . And compression I don't think that the Piston wrist pin being loose is much a problem so long as the cylinder hold the Piston right center. My nephew had a tiny scooter with the same engine it was no way near as fast As a tomos A35! moped.
Hi Dan
Note in the video I mention at 4:35 even with the piston held centre of the rod small end the bearing still hangs our quite a bit.
This engine also has no squish band over the full area of the head which limits compression ratio so the removable head type one may improve on that also.
With the coils you need top ensure the coils are as close to the flywheel as you can possible get them with them touching it, that air gap can make a lot of difference to not just the spark voltage but the timing as well
I did a video some time ago on that topic using an oscilloscope and timing light.
@@AuMechanic yeah that's what I was thinking I use a business card for the flywheel magnet 1000 s of 1" works for the bike engine as well and that stater better be screwed tight but I'ma try this engine for the smaller scooter side project I'm welding together for a friend
@@capchassuck
Business card is very thick.
Use a feeler gauge, just be sure not to use it when the magnet is near the coil pickups or use a brass feeler gauge which is designed for that purpose.
@@AuMechanic I didn't know if there was a tool for that. I know thousands of an inch was the standard of lawn mower engines but thanks. learn something new every day. this one guy does a tutorial for bicycle mount engine but screwed up everything and had a commercial for every screw up like he must be smoking crack cus it almost seems like he did it on purpose. I subscribed to your channel cus you know more about what you are doing. how does a Dino work ?. more power compared to rpm speed I'll have to review the one that two stroke stuffing made. I'm thinking a flange and metal bar Bell whaight and dc electric motor attached to a pen graph machine that makes a chart on paper or something like that nothing. fancy like a computer . I'll see what I can get on eBay and thrift store may have to go get machine work at the local machineist.
@@capchassuck
The simplest Dyno is like Alex has at twostrokestuffing which is an inertial dyno.
You need to measure how long it takes to get a weight to spin up to maximum speed.
In theory you could just use a timer and a tacho to see how long it takes to get the weight to spin up to a given speed but that will only give you peak power to compare between runs which may be enough to compare after mods.
What a computer allows is to graph that time over speed over the whole period and then calculate power over the curve since based on the moment of inertia which is put into the computer as well as roller rpm.
Do you have a email where one could contact you besides your TH-cam channel
Click on the "about" tab on the main channel page to see Email
It's ausmecham @ gmail
i dont think the ports being fully open is important, unless you are trying to get the most rpm out of the engine, i.e a horrible tuned up racer, i prefer standar and quiet reserved 2 strokes, a bit of restriction is good. i mean, are you going to remove the whole expansion chamber and exhaust to make it breathe even easier? no. you want small ports.