50cc to 100cc no compression assistance

[mpdano]

Hello all,

I just bought a 50cc scooter off Craigslist.  The previous owner put a 100cc kit on it but couldn't get it to start.

I dissembled the cylinder head to start from scratch.  First thing I noticed is the piston was on backwards.  The IN was facing the exhaust.  I removed the piston and removed all the rings to verify they we're installed correctly.  I found a great image to show the gap orientation on all rings.  Made sure the black one was on top with the writing facing upwards and chrome on 2nd ring down.  Reassembled and verified cam timing with the "T" and lines up sprocket marks to the top of cylinder.  Cam lobes facing down.

I set the valve lash to .05mm and put it back together, no start with a fresh charged battery.

I got spark as I also had to find the pinout as the cdi harness was hacked.  A lot of the scooter was apart so I had to put it back as I think is correct.  Carb is new as is the intake.  Hooked the intake vac line to the fuel petcock vac line.  Fuel flows fine as I put clear fuel tubing.  
I am not noticing any fuel on the spark plug.

I tried to do a compression test with the throttle wide open but I am not getting a reading.

Any thought would be greatly appreciated.

Thanks,
Leo

[jackrides]

The cam turns half as fast as the flywheel. Be sure the cam is timed correctly.

[mpdano]

Jun 27, 2017 15:04:41 GMT -5 jackrides said:

The cam turns half as fast as the flywheel. Be sure the cam is timed correctly.

I thought by putting the flywheel to the "T" mark and lining up the cam gear correctly is sufficient. What would be the next step in making sure it's timed correctly.



Thanks for the reply.

[tortoise2]

What would be the next step in making sure it's timed correctly.

Sometimes the crankshaft-flywheel woodruff key will shear, which throws off timing. Insert a probe into sparkplug hole and turn flywheel to position piston at top, then observe if flywheel T-mark is aligned with case point.

[mpdano]

Found the issue. Due to the piston in backwards, the intake valve was bent. I could see daylight through the intake.

[humanshield]

Jun 27, 2017 18:21:56 GMT -5 mpdano said:

Found the issue. Due to the piston in backwards, the intake valve was bent. I could see daylight through the intake.

Yep.  That'll do it every time.

[Elektrey]

Glad you found the issue. After all the work you've done, I hope you get it running soon!

[mpdano]

Ughhhh. Got the new head today. Started it up and started the ring break in. My CDI is just open wires as it was hacked by the previous owner and the cdi fell and heard a slight electrical pop and it stopped. I no longer have spark. Only one fuse that I can find and it's good.

I hooked up the spare new one that it came with and the led blinks but no spark on the plug. Tried a different new plug and no spark. Tried a different coil, same results.

Can't find anymore fuses. Any suggestions? FYI, compression is still good.

[mpdano]

Short lived first run.

[mpdano]

Removed the stator and cleaned it up a bit. Ordered a new one as well as a stock cdi. Got the cdi first and she fired up. Took her for a few spins around the pool and she runs perfect now. I guess I now will have a spare stator for it.

[scott7]

I thought the black ring was the middle and the silver ring went on top unless it's marked differently

[mpdano]

She's all done!



Used this paint for all the trim plastics.