Head gasket/Timing chain

[Bryan322]

Any info on pulling the heads and in the process not messing up the timing would b e greatly appreciated. How do we do this?

Thank you very much.

Bryan

[rgierer]

Bryan,

I just went through this. The markings on the chain and cam are such that it ends up pretty simple. (I of course did it wrong and had to do it again but that is another story).

I don't have the manual open but the marks are straight forward when you need to reassemble.

I woule encourage you to have the engine at TDC with the marks showing on the cams when you pull off the head.

[bwringer]

Any shop manual will have clear, detailed instructions about resetting timing after removing the cams and/or head.

Two excellent sources:

http://repairmanuals.com

http://ebay.com

Basically, you pull it apart without worrying about marking things and such, and then set everything right when you reinstall the camshafts using the timing marks under the points/ignition cover.

If you have a manual but still have specific questions, it would be a great help to know what kind of bike you're working on and/or what parts of the procedure seem unclear.

I have replaced cams in OHV cars before and avoided the reset procedure by marking the cam sprocket and chain with a dab of fingernail polish (after cleaning the oil off, of course.) This also requires plenty of notes and a good understanding of how the cam drive system works.

However, on a motorcycle it's impossible to remove the head without moving the crankshaft. Remember, you have to remove the block and replace the base gasket when you remove the head or it will leak.

[Bryan322]

Head gasket replacement/Timing Chain removal

Sorry about that! The bike we are wroking on is a 1982 GS650E. I had forgotten to mention that.. I take it there is a master link on the timing chain?. I have the cover off but have not moved anything as of yet.

Thanks,

Bryan

[flyingace]

The manual is an absolute necessity when doing this. There are multiple markings on the cams that work in concert with the TCD mark on the ignition rotor. They also have you count #links on the chain between the marks - a great idea.

It may sound obvious, but once reassembled ALWAYS turn the engine over by hand (with plugs removed) to make sure it doesn't bind. People have trashed their valves forgetting this simple step.

[bwringer]

There is not a master link or a marking on the chain -- you use the markings on the ignition rotor to set the crank to the correct position, then you install the cams without the chain idler pulley or tensioner so you can rotate them to the correct position using the marks on the cam chain sprockets (these are dashes and/or "T" shaped marks stamped intot the spockets on the cams). There's a bit of finagling involved because you need to hold the chain out of the way while you rotate each cam to the correct position with a wrench.

After the front cam and the crank are in the correct positions, you install the cam chain on the front sprocket. Then you'll count a certain number of links or pins to install the chain on the rear sprocket. Because of the tension of the valve springs, the rear cam will be a bit out of position until you install the idler and/or tensioner -- the important thing is to have the correct number of links between the marks on the front and rear sprockets.

That's sort of the overview, but you MUST ABSOLUTELY have the diagrams and instructions in the shop manual to do it correctly. A Haynes or Clymer manual will be fine, but you definitely need to have or borrow the specific procedure for your model. It's not at all difficult, but you do have to follow the procedure exactly or face rather grim consequences. As noted above, rotate the engine by hand to verify there's no binding and to make sure the markings still make sense after rotating the crank twice.

You have to attach something to the cam chain to keep it from falling into the tunnel in the engine while removing and replacing the head. When you rotate the crankshaft after the cams are off, you need to be careful to feed the chain by hand so that it doesn't bunch up and wreck the chain guides.