Re: 50cc four stroke scooter

Did use a real tester and it doesn’t move at all. He’s been driving it for almost 2 months with the noise ( it sounded more like valve lash. I’ll try the other test. When I shot air into the plug hole the air was pushing my air gun back at me. Just all blows my mind. Also if those wholes are lined up on the gear and the timing mark and T line up could it still be off one rotation?

Re: 50cc four stroke scooter

Ok, after reading from beginning to end it sounds like you adjusted the valves when the motor was on exhaust stroke instead of compression stroke.

Forget everything you know about 2 strokes for a minute.

On a four stroke the cam turns half as fast as the crank. So it takes two full revolutions of the crank to complete all four strokes. What this means is that the piston comes to "tdc" (next to the "f" mark) twice in one combustion cycle.

If you did not have it on the compression stroke when you adjusted your valves then they are way too loose because they were partially open during exhaust stroke when you set the gaps.

To tell where you need to be remove plug and place finger over hole while rotating engine. When the piston comes to "tdc" on the compression stroke you will feel it push your finger off. Thats where the engine needs to be to adjust the valves with it lined up at "tdc"

Remember, that an engine fires a few degrees before "tdc". So any "tdc" marks will come after the "f".

Also be damn sure you're rotating the engine in the correct direction.(edited)

Re: 50cc four stroke scooter

There is no compression so I don’t feel any air. Also what happens if you do turn the engine over in the wrong direction ? I know my buddy did do that a few turns by hand. So will lose valves cause no compression?? Like I said it did run before all this

Re: 50cc four stroke scooter

If the valves are so loose that you have no compression then another way to find "tdc" on compression stroke is to rotate engine and watch for intake valve to open and as its closing is when you will be coming up to "tdc" on compression stroke.

Intake not exhaust look carefully(edited)

Re: 50cc four stroke scooter

Nothing will happen to motor turning it backwards except you might be a little off on measurements because of any cam chain slop from normal wear.(edited)

Re: 50cc four stroke scooter

You wont be able to see the valve open per se, but rather the rocker arms moving. Looking at the one photo you have the intake valve is at top of head and the rocker arm that opens it is to the top where you show a feeler guage inserted. Thats the intake valve. Rotate the motor and watch that rocker when it depresses inward and starts to come back is the revolution on the crank you need to check valves lined up at "t".

Re: 50cc four stroke scooter

Turned over the engine until top valve went down and when it started coming up I stopped right there and everything is way off. The timing T and the holes in the gear/ timing sprocket

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Re: 50cc four stroke scooter

I’m watching the valve move area where I check the .004 gap is that the wrong spot ?

Re: 50cc four stroke scooter

> Brian Terrell Wrote:

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

> Turned over the engine until top valve went down and when it started

> coming up I stopped right there and everything is way off. The timing T

> and the holes in the gear/ timing sprocket

Because you're not supposed to stop where you did. You're simply on the correct stroke and continue to rotate to the "t" mark.

Re: 50cc four stroke scooter

Ok I’ll check it tomorrow and see how it is. But do you think even if the adjustment is way off it would cause zero compression?

Re: 50cc four stroke scooter

> Brian Terrell Wrote:

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

> Ok I’ll check it tomorrow and see how it is. But do you think even if

> the adjustment is way off it would cause zero compression?

Zero on a compression guage?

Never seen that on any motor ever. Car, truck, motorcycle, moped, lawnmower

Re: 50cc four stroke scooter

Well did what you said and it goes right to where I did check it and there both at .004. Just blows my mind. Maybe I should go up to .006 or go down to .003.

Re: 50cc four stroke scooter

Yeah me either. The thing drove in. I even put my finger over the hole and feel nothing. The exhaust valve was way the hell off probably around .009 when I adjusted it back to .004

Re: 50cc four stroke scooter

> Brian Terrell Wrote:

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

> Well did what you said and it goes right to where I did check it and

> there both at .004. Just blows my mind. Maybe I should go up to .006

> or go down to .003.

So that means you adjusted correctly the first time.

Four or five thousands difference wouldn't give you zero compression.

As you rotate motor you are seeing both rocker arms move in and out correct??

Obviously not at the same time.(edited)

Re: 50cc four stroke scooter

Yes both moving fine.

Re: 50cc four stroke scooter

I’m ready to just buy the whole top end. Ugggg

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Re: 50cc four stroke scooter

Do me a favor and get me a pic of the I.d. tag that shows the name of manufacturer, model and engine info please.

Re: 50cc four stroke scooter

All I can find

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Re: 50cc four stroke scooter

I think the very first time I might of did it wrong. I just lined up the T mark and the

Re: 50cc four stroke scooter

> Brian Terrell Wrote:

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

> I think the very first time I might of did it wrong. I just lined up

> the T mark and the

Remember the t mark will line up on two different occasions, on exhaust stroke and on compression stroke. You need to check valve lash on compression stroke.

Re: 50cc four stroke scooter

Yes did do that

Re: 50cc four stroke scooter

I'm painting right now, but will look up that motor and see where the manufacturer wants the valves adjusted at.

The point of which measurements are taken is not as important as taking them on the "base circle" of the respective cam lobe.

Re: 50cc four stroke scooter

Overpriced Parts /

After you get it all figured out and get your bike all tuned out, let me know!

When you hit a 3 inch chuckle hole or railroad tracks that aren’t as good as it seems post about it,ha ha!

I flew over Rr.tracks most my life in 75 to 250 ccc Enduro bikes because being living next to Rail road tracks most of my life‘! And sometimes it was cool and sometimes not so! Haha !

Re: 50cc four stroke scooter

How many miles are on this motor?

Re: 50cc four stroke scooter

1160 miles

Re: 50cc four stroke scooter

Squirt a about a tablespoon of motor oil into the spark plug hole. Compression test again and see if you get a reading.(edited)

Re: 50cc four stroke scooter

I was debating on just buying a top end rebuild kit. This thing is driving me nuts.

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Re: 50cc four stroke scooter

> Brian Terrell Wrote:

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

> I was debating on just buying a top end rebuild kit. This thing is

> driving me nuts.

You may have to.

You did the valve adjustment correctly.

What I'm asking you to do will show if the rings are worn out

I doubt you damaged the valves but anythings possible.(edited)

Re: 50cc four stroke scooter

First time I adjusted the valves to .004 I was not on the right stroke so I redid it to the correct spot with everything lined up. When I did do the adjustment the intake was at about .002/.003 and the exhaust was around .007-.008 which was way the hell off. Maybe I bent the valve ? Just don’t know. But I figured if I’m this far in I might as well go the whole nine yards. Just sucks because should of been a easy job and I got two moped engines stripped down for rebuilds and I’m screwing with this. Never again I will work on a scooter.

Re: 50cc four stroke scooter

> Brian Terrell Wrote:

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

> First time I adjusted the valves to .004 I was not on the right stroke

> so I redid it to the correct spot with everything lined up. When I did

> do the adjustment the intake was at about .002/.003 and the exhaust was

> around .007-.008 which was way the hell off. Maybe I bent the valve ?

> Just don’t know. But I figured if I’m this far in I might as well go the

> whole nine yards. Just sucks because should of been a easy job and I

> got two moped engines stripped down for rebuilds and I’m screwing with

> this. Never again I will work on a scooter.

You cannot bend a vavle unless you had adjustments so tight that the valves could not close completely, which I doubt.

That would mean you could not have inserted a feeler guage at any point in your adjustments.(edited)

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