Compression Low in a 84 Yam FJ600l

alan

I am new to engine teardowns. Used to have to change the head gasket on my old '66 Mercedes 160 and have done other minor stuff.

The guy who owned it previously said it was diagnosed with poor compression in the right cylinder. My guess is that there is a ring, piston, cylinder or valve issue. The valve cover seems to be leaking on that side also.

What is the most likely or is it likely something else?

Russell · Posted: Sat Apr 10, 2010 7:01 pm Post subject:

You need to tell us a bit more about how it runs, or not. Does it start well hot or cold? Oil consumption?Does it idle smoothly?
Any visible blue smoke from the pipe(s) when you accelerate again after a period of running against closed throttle?Any reliable indication of mileage done and whether or not the motor is still original or already freshened?Any mis-firing or back-firing?

fasterspider · Posted: Sat Apr 10, 2010 8:30 pm Post subject:

Do a compression test so you can know for yourself when it is.
Chances are it is a burned valve if it is just one cylinder down on compression.

Steve Searles · Posted: Mon Apr 12, 2010 10:49 am Post subject: Low compression

When you do the compression test, check all four cylinders. Then compare against each other. Usually 10-15% or more of a difference means there is a problem. Have you checked valve clearances yet?

Russell · Posted: Mon Apr 12, 2010 2:09 pm Post subject:

Valve clearances? Spot on Steve. Is the FJ600 a bucket shim valve train?I'm guessing it will be. There are many many bikes around with that sort of valve gear that have NEVER had the clearances checked since they left the factory!

Steve Searles · Posted: Mon Apr 12, 2010 7:46 pm Post subject:

Just checked microfiche, shim over bucket. Pain in the butt. Many bikes have never had valves adjusted due to the difficulty of this necessary maintenance item. And... some of the shims are no longer available from Yamaha. That's bull sh.... Cool, I finally have someplace to vent after all these years of swearing at Jap engineers. I knew this site would be good for something.

Russell · Posted: Mon Apr 12, 2010 8:19 pm Post subject:

For shims for any bike go to this Australian site.If they don't have it on the shelf they'll make it. Very helpful and fast responding to queries and ship immediately worldwide.

www.precisionshims.com.au/

pd · Posted: Tue Apr 13, 2010 10:13 am Post subject:

That FJ takes 29mm shims . Here's a shim kit :

http://cgi.ebay.com/ebaymotors/BMW-YAMAHA-KAWASAKI-29MM-VALVE-SHIM-KIT-/110508890982

Or , you might be able to do a shim exchange at a Yamaha or Kawasaki dealership . The K bikes from BMW also use the 29 mm shims .

alan · Posted: Thu Apr 15, 2010 4:14 pm Post subject:

Thanks for all the suggestions. I have learned a lot from the info.

After I started to disassemle it I discovered that it doesn't seem to be a 1984 but it is a 1989. My manual is for a 1984 and when I took off the crankcase cover (left side) the gear inside is not the same. Does anyone have a suggestion for where to get a shop manual?

alan · Posted: Fri Jun 11, 2010 7:09 pm Post subject:

Can the shims be swapped without taking off the camshaft?

bobbyjim · Posted: Mon Jun 14, 2010 5:20 am Post subject: Get a Service Manual

I have an FJ600 service manual that I would be willing to part with. If you need one just email or PM me.