Uh...oops. By FACE PLANT FOR LIFE (Read 519 times)

[FACE PLANT FOR LIFE]

So we tore down my brothers engine today because he needed a new head, turns out he had a big bore kit installed that we didn't know about (that's why it's so fast..) and we couldn't use the rebuild kit. So we got the old head helicoiled at the local shop (they're fast!) so we arnt having trouble with the head anymore. The head is on fine, but I feel we may have messed up bad, because I put the camshaft back on one tooth off and kicked it over (key off) to make sure everything felt fine. Things did NOT feel fine, and I took off the tensioner and everything AGAIN and found that I had put it one tooth off, YIKES. I tried to get it to top dead center again but the chain slipped off the camshaft and now I have no clue where top dead center is anymore. Did I just blow it?

[cyborg]

pull the plug get a 1/4 inch dowel SLOWLY rotate the engine and watch the dowel and when you get to the top of the stroke thats it ,,,orient the cam in the correct position put the chain on it and you be done,,,

[FACE PLANT FOR LIFE]

Doh, this makes sense. How didn't I think of that. Thanks Cyborg!

[Bashan]

Agreed, just be aware that when the piston is at the top you get a lot of movement of the crank because the journal is moving essentially horizontally, while the piston doesn't move vertically as much until the journal is headed south:

So you'll feel the crank "slop" back and forth a little but you'll be able to feel when it's at TDC. Now all of this crank movement/piston movement is why the T and F marks are so imprecise. So you get TDC determined and then put your cam sprocket on like this, let the flywheel drift a bit off of T or F if it wants to when you put the chain on:

And I'll say it again, if you jump a tooth from there your flywheel marks are not going to be close at all! So keep the cam sprocket oriented like that and use TDC and you should be cool.

[Alleyoop]

First line up the FLYWHEEL like in the picture RICH put up THEN set the cam like in the picture and make sure the FLYWHEEL does not move when you put the CHAIN on. Also when you put the chain on MAKE SURE the SLACK is on the top of the chain, the bottom should be tight then put in the Chain Tensioner and release the plunger to push down on the chain guide to take up the slack on the top of the chain. Then if its a 50cc set both valves to .003 inchs if its a 150 set them both to .004 inchs DONE.
Alleyoop

[Bashan]

Yes, that is actually an ironclad way to do it. Do it like that and there will be no mistakes. Rich

[FACE PLANT FOR LIFE]

I got it done today. I took a plastic straw and put it into the spark plug hole and got perfect TDC, and then tried like 4x to get the camshaft on perfectly. Needless to say I got it eventually. Got the rocker arms on and assembled everything except the exhaust. Just to make sure it ran I started it without the exhaust and muffler (sounds like a giant bubble maker!), sure enough, it ran! Tada! Thanks you guys!

[FACE PLANT FOR LIFE]

Uh, I really don't want to say that it has an issue, but I think it does. What would cause a sputtering sound while riding that comes and goes? It sounds like a steady "thump" and does it regardless of RPM.

[tvnacman]

Did you use a torque wrench ?
You should not have started it with no exhaust .

John

[FACE PLANT FOR LIFE]

I did use a torque wrench and torqued everything to specifications. The thump goes away when warmed up. It sounds like it's missing.

[Alleyoop]

Video with sound of it making the noise would help.

[FACE PLANT FOR LIFE]

I'll get that tomorrow. I'm quite busy right now. Our family is getting together tonight.

[Bashan]

So!?.....what Sue? It's the plant guy's family, it's just a bunch of ferns and deciduous growth. OW! OK! I'm sorry Plant, we'll wait till tomorrow...sheesh! Did you put an exhaust gasket in chlorophyll breath? HUH!?