Flywheel turns backwards By gy6fandan (Read 3,090 times)

[gy6fandan]

Just popped in a cylinder head.

Flywheel turns backwards <---- backwards ? I though it was only supposed to turn forward.

My re-install process "in order" - best as I can remember :

1.) installed 2 hollow metal guides on two of the four stud bolts that the cylinder head slides onto.
2.) put on head gasket.
3.) put on the cylinder head. bolted snugly the 2 side bolts.
4.) put on 2 hollows metal guides that cam holder goes on.
5.) Installed camshaft and made sure marks (holes) were lined up & down.
6.) Installed rocker assymbly.
7.) set valve lash .004 in and .oo5 out.
8.) installed cam chain tensioner.

Stoped at this point because I was re-turning the flywheel to re-check that valve lash was correct and noticed
that the fly wheel turned backwards (due to back pressure ?) about 1/2". I turned gently backwards and it move 3/4 - 1".

What could it be now ?

[Bashan]

Do you have your plug out? It makes it easier. ALSO...the rockers push on the cam lobes hard enough to rotate the crank back and forth a little until the rocker paddle is off of the lobe.

[Alleyoop]

I answered this on ITSTHERIDE for the same dude, oh well no more.
Alleyoop

[gy6fandan]

Bashan & Alleyoop --> Thank you.


Bashan , I can grab the flywheel with my hands and turn it backwards. I do not know if I can turn all the way around or not. I just turned it about 1" or so. it was not really hard - very little resistance.

[FACE PLANT FOR LIFE]

That's normal.

[Bashan]

Yeah, I'm just saying if your doing that kind of work take the plug out. THAT will cause resistance and may exacerbate some cam rotation. But it is the pressure on the cam lobes that makes the flywheel drift. Don't worry about it, get the timing set right and button it up. I'm sure Alley already went over this with you. There's nothing wrong. You don't see that in a multi cylinder engine because all the lobes cancel each other out. But you've only got two in a GY6 so each one has an effect. Do you see now? See the paddle pushing down on the lobe? It turns the cam which turns the crank:

[Alleyoop]

ALSO WARNING WARNING!! DO NOT TURN THE FLYWHEEL BACKWARD(COUNTER CLOCKWISE)or the VARIATOR (CLOCKWISE). IF your cam has a CAM STOPPER BY THE LEFT ROCKER EXHAUST VALVE LIKE IN RICHS PICTURE you will mess up the CAM STOPPER. That is there for a purpose and that is so when the motor starts it does not start backwards. AND if you rotate the crank whether from the flywheel side(COUNTER CLOCKWISE)or the Variator(CLOCKWISE)you may break the CAM STOPPER and if a piece breaks off your in a world of hurt.
Alleyoop

CAM SHAFT STOPPER:

[gy6fandan]

Thank you Alleyoop.

Because of "Alleyoops" warning, I googled the camshaft stopper
and found a discusion in an old "scootdawg" forums dated May 07, 2008.

The direct link and title is :

OEM Valve Adjustment : scootdawg.proboards.com/thread/8313?80264=undefined

It is suggested / stated in the above post that ;
"This stopper is not on any of the high performance cams with the exception of the c6 cam".

I haven't researched / verified this concerning any changes in performance camshafts since that
thread dated in 2008 (six years since then).

It seems to me that if it (camshaft stopper) was installed on stock camshafts - and - that everyone states not to turn the
flywheel counter clockwise during valve adjustment or in any other circumstances that the camshaft stopper surely plays an important role.

I will have to remove my new "A9" cam and look for variance btween my the A9 camshatf my stock camshaft.

I could not find a "rebuild" or "maintenance" thread / video on rocker arm assymbly. - Just saying it may good for future reference purposses / general maintenence / troubleshooting.

[jct842]

Try rotating an engine backwards on a yp400....you get big surprise, they will jump timing!

no 4 stroke engine is made to turn backwards, a 2 stroke on the other hand if it uses reed valve induction can be started and ran backwards if the ign timing is reversed.

[Bashan]

Read this, the rockers come apart one way, and they go back together one way. Just disassemble them and take pix as you do. The parts go back together one way and they can't be assembled any other way. You may want to read the whole thread on that link I provided from the memorable posts board on this site. Here's a video from Youtube that I Googled:

[gy6fandan]

Bashan ---> Thank you for the info.

The video on the top end rebuild is pretty good.

Your post "GY6 Project By Bashan" is AWSOME. Lots of really good pictures and information of the whole process.

I plan on doing some photo uploads of my original camshaft and the part is has that the A9 camshaft does not have. It seems that the performance camshafts do not have this - excluding the c6 camshaft which supposedly does.

I really need to find out if a woodruff key / spline is available for it - just more to research on this particular thing.

Hopefully I will be creating a new small post with pictures to explain what my whole issue has been with this new head and camshaft install.

Thanks again.

[Bashan]

We look forward to any small, or large, posts you feel like contributing. The woodruff key is just on the crankshaft on the stator side, nowhere else. Just make sure you have one from any parts dealer and the flywheel will fit fine. Leave the old one alone if it is there and you'll be cool. As far as the rotation limiter, all you have to do if you don't use it is use a spacer, a washer. I've never heard of it being associated with performance cams or anything in particular. It's there to prevent reverse rotation, the cam lift or duration shouldn't matter. Leave it there regardless of the cam, it'll make a good spacer. Or take it out and put a washer in that is that width. Alley? Guys? Am I wrong here? I just think this is a non issue. Assemble the thing, don't rotate backwards, button it up, fire it up. Rich

[cyborg]

it be a non issue