buellistic
Well-known member
Is it at all rideable?
2 stroke Puzzle
- Thread starter FastCletus552
- Start date
FastCletus552
Well-known member
Yes. Rebuilding rear brake caliper today, and then plan on trying to ride it around.
FastCletus552
Well-known member
It acts like a governor would. I can pin the throttle and hold it there and it will just sit there at whatever RPM that is until I release the throttle.
FastCletus552
Well-known member
Its been one hell of a mind F*ck. I asked for a project bike and I damn sure got one. Today I went in and made sure piston was installed correctly. I did notice that the cap of the head was put on wrong. I fixed that. I put the original throttle cable back on. So throttle cable is solid. Maybe I am chasing an issue that doesnt exist. maybe this is as high as it revs? Im new to trials bikes. Tomorrow I will ride on the street and go through gears and see what happens
kpke
Veteran
Do them trials bikes have a tach with a redline? Probably not. Sounds weird but it's a trials bike and not a motocross racer. Can you make a video and post it here?
Sorry, not to threadjack but someone asked...
Inside a different 2 stroke
power valves open can be seen at the top of the exhaust port
power valves
more inside
Sorry, not to threadjack but someone asked...
Inside a different 2 stroke
power valves open can be seen at the top of the exhaust port
power valves
more inside
FastCletus552
Well-known member
I cant post a video on here as far as I can tell. I am trying to post one on you tube, and then link it here. Was speaking with some folks in the UK, and they are mentioning that maybe the stator was wound wrong. Anyone in the bay area who can thoroughly test a stator? I know the readings its supposed to have but the stator has some kind of clear coat sealant on it (assume to protect it) dont know how to penetrate the clear coat and where to get a proper reading
FastCletus552
Well-known member
buellistic
Well-known member
Clogged spark arrestor or muffler...
ST Guy
Well-known member
Try removing and see if it revs.
FastCletus552
Well-known member
Tired it after removing muffler and even adjust carb settings same issue. Again chatting with some UK folks in FB in Beta group and I got a message from a guy who asked who did the rewind? He said the company he used didnt do a good job in rewinding his stator. He said he was having same problem as me. I told him who the previous owner sent the stator to and he said that was the same company that did a bad job for him. So now I am thinking this is a stator issue. Found a guy in Socal that does stator rewinds. Anyone know of anyone in Norcal or just a recommendation? Im going test my stator now and see what it says. But in the puzzle its the last piece... or so I think
puckles
Well-known member
For people asking redline/tach related questions, modern 2 stroke ignition is typically handled by what is called a CDI. It is a small electronics box that takes an rpm signal from the stator and then based on how it is programmed/mapped, drives the coil with the correct ignition timing/cut needed.
A bad cdi could be the issue, or it could be an exhaust restriction as mentioned. For what it is worth, the video doesn't sound like ignition cut to me as much as it sounds like the engine is running out of fuel. I'd check the floats and main jet circuit in the carb.
A bad cdi could be the issue, or it could be an exhaust restriction as mentioned. For what it is worth, the video doesn't sound like ignition cut to me as much as it sounds like the engine is running out of fuel. I'd check the floats and main jet circuit in the carb.
FastCletus552
Well-known member
Swapped CDI. Previous owner gave me a box of goodies and CDI was one of the goodies. Same issue.
Ive used a brand new carb on it and same issue, and tried different jets and needle positions and nothing changed
Thanks everyone for your help!
FastCletus552
Well-known member
Just tested my Stator. Vendor in UK says if I test the red/ black wire the OHMs should be 5, mine tests at 8. the other test is a green and white wire and vendor says that should be 7, mine says 10. I am no electrician so I don't know if the my higher numbers are a good thing or bad
Z3n
Squid.
This screams ignition problem to me. I’d check your grounds, but it sounds like the stator is the likely culprit. I wouldn’t check it statically - good stators can fail static checks and bad ones can pass them. Try to check it while it’s running to see if it’s putting out consistent AC between wires. Not sure if those bikes ran a DC converter but that crapping out could also cause ignition problems.
Check that your ignition coils, wire attachment points, and engine grounds are good as well.
Dark horse option: check that your expansion chamber isn’t caked full of shit and only letting a tiny amount of air through.
Check that your ignition coils, wire attachment points, and engine grounds are good as well.
Dark horse option: check that your expansion chamber isn’t caked full of shit and only letting a tiny amount of air through.
Demoni
Well-known member
Only two stroke I have seen that did anything similar to that was a 50cc bike with a aftermarket Chinese CDI. One of the CDI wires enabled an 5000 RPM limiter to cap the top speed.
Looks like you have had the top end and related components off, how deep into this motor have you gone? Crank seals on motors that have sat around can dry out and cause gremlins. Small leaks normally cause issues with tuning carb jetting but could prevent a motor from building RPM? Leak down testers are expensive but can be invaluable when troubleshooting problems.
If you are handy it is possible to make a DIY tester
Few suggestions for additional tests you could run on the electrical system:
Test 1
Measure the resistance between each of the coils and ground. You should see a OL, indicating there is no continuity. If you get a ohm reading it means that you have a wire with damage that is causing voltage to leak from the circuit to ground.
Test 2
Get the bike up to temp and then give it full throttle for a bit. Is there any difference in how the bike revs now that it is hot? The stators coil resistances will go up when it gets hotter. Remeasure the wires with everything hot. At ~100c expect to see a resistance measurement 1.5x higher than at ambien.
Looks like you have had the top end and related components off, how deep into this motor have you gone? Crank seals on motors that have sat around can dry out and cause gremlins. Small leaks normally cause issues with tuning carb jetting but could prevent a motor from building RPM? Leak down testers are expensive but can be invaluable when troubleshooting problems.
If you are handy it is possible to make a DIY tester
Few suggestions for additional tests you could run on the electrical system:
Test 1
Measure the resistance between each of the coils and ground. You should see a OL, indicating there is no continuity. If you get a ohm reading it means that you have a wire with damage that is causing voltage to leak from the circuit to ground.
Test 2
Get the bike up to temp and then give it full throttle for a bit. Is there any difference in how the bike revs now that it is hot? The stators coil resistances will go up when it gets hotter. Remeasure the wires with everything hot. At ~100c expect to see a resistance measurement 1.5x higher than at ambien.