Re: 50cc four stroke scooter

Also, being off a few thousands on valve lash will not give you zero compression.

Re: 50cc four stroke scooter

Guess I’ll be taking the whole top end off and put all new on it.

Re: 50cc four stroke scooter

> Brian Terrell Wrote:

> -------------------------------------------------------

> Guess I’ll be taking the whole top end off and put all new on it.

Dont just be a parts changer.

Squirt some motor oil into plug hole, rotate motor a couple times and compression test again. You will get a compression reading of some sort if rings are worn. The oil will act as a temporary seal around piston to substantiate theory.

Re: 50cc four stroke scooter

Do I have to put the valve cover back on ? I’ll check it later tonight when I’m home. Thanks bud

Re: 50cc four stroke scooter

I'm gripped by this.

Re: 50cc four stroke scooter

Well put some two stroke oil in the plug hole and still nothing !!!! I did it with the valve cover off. Piston is moving and valves too.

Re: 50cc four stroke scooter

Well did the oil thing ( used 2 stroke ) left valve cover off and still got nothing for compression. Going to take the whole top end of this Saturday. Just don’t have a freakin clue what went wrong. Adjusting 2 valves to all this shit. Drove it in let it sit over night removed valve cover adjust the valves 3 times and all three times no compression. Just blows my mind. Scooter just turned 1100 miles and it did sit for 5 years before I got it. The owner pasted away.

Re: 50cc four stroke scooter

Is the cam chain loose on either side???

Re: 50cc four stroke scooter

No it’s tight. This is a mystery

Re: 50cc four stroke scooter

When the "T" mark is lined up on case have you verified that piston is indeed at tdc looking through plug hole? Use a plastic drinking straw as a probe if needed.

Re: 50cc four stroke scooter

I’ll check again but the way I did it when the intake was going down and starting to head back up I stopped at the T and the three holes were lined up as well. I’ll check with a straw as well. I added the oil in the plug hole and still no compression. Piston is going up and down. Do I need to put the valve cover back on to check the compression? Didn’t think it would matter. It’s nuts that it has zero compression..... what the hell would cause that by adjusting the valves. Ran decent but hard start and didn’t idle good. I put air into the plug hole and it seems like it’s holding since I have to push hard on the nozzle to keep it in the plug hole.

Re: 50cc four stroke scooter

Valve cover has nothing to do with it.

2 stroke oil is kind of thin. 10w30 would have been better. And btw how's tge oil level in the crank case? Loosen the valves back up to .008 and see if it starts.

Re: 50cc four stroke scooter

Well got fed up so here it is now. Besides carbon buildup everything looks ok

B1D758B9-C943-4D76-ABE7-0ECF23BF88C8.jpeg
3DEF21E9-BE15-401C-B388-10CEBBF12396.jpeg
3DEEE123-6F91-4314-AC39-C0AA79ED8B1C.jpeg

Re: 50cc four stroke scooter

Was the piston at TDC when lined up with "T" on flywheel?

Re: 50cc four stroke scooter

Yes. As far as I could tell. It was using the straw. Did you get my pics ? Let’s say it wasn’t at TDC it should still have some compression right ?

Re: 50cc four stroke scooter

Yes I did.

Pics show nothing out of the ordinary.

I wish you hadnt taken it all apart already.

I cant believe you had NO compression. No resistance turning over motor with spark plug in place??

Re: 50cc four stroke scooter

Sorry I’m just frustrated with it. Yeah had spark but try compression tester and just my finger over the hole and nothing at all. I’ll really flip my lid if I buy this and put it all back together and still no compression. I’m going to put a spark plug in the head and put some two stroke oil upside down and see if o seep through

EBB8FD67-E37B-4C67-8DA4-96142BDE7355.png

Re: 50cc four stroke scooter

Lay the old head on table and shine a strong light into intake and exhaust ports while looking around valve seats in combustion chamber to see if light is shining through.

Better pics of rings too from side.(edited)

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