So, you've been riding your bike a lot, but you've started to notice some odd things happening. It could be that your bike is backfiring, or popping out through the carbs. Or, you may be hearing valve clatter. Either occurrence means that it's time to check, and reset your valve clearance, also known as Valve Lash. Today, I’ll be providing information on changing your valve clearance for under-bucket shim equipped engines like the 550 through the 750’s. On larger bikes, the engine uses an over bucket shim. On these engines, you can use a bucket compressor tool to press the bucket down, and remove the shims without removing the camshafts.
The method I describe below is the same method I have used on my 750 4 with great results. It avoids the need to re-time the cams, and that minimizes the chance that you can end up doing bad things to the engine.
- HAND Impact driver and assorted bits
- Wrenches / Ratchets
- Torque wrench
- Suction cup about ¾ of an inch in diameter. A valve lapping tool works great.
- Digital calipers (Can be bought from any auto supply store for about $20)
- Gasket scraper or high quality sharp wood chisels.
- Exact-o knife
- Hole punch
- Red fingernail polish
- Diagram from below
- Empty egg carton
- Sheet of paper gasket material
- New shims
- Gasket in a tube.
- Remove: Gas tank, Coils, Fresh air system.
- If you have an automatic cam-chain tensioner, make sure it is locked or removed before continuing.
- Using the impact driver when possible, and a correctly sized screw driver attachment on your ratchet, remove all of the screws holding the cam cover in place.
- Pull off the cam cover, and pull the reed valves and covers off of the top, and set them aside.
- Take the points cover off, and using a 17mm ratchet rotate the engine in the direction of normal rotation until the first cam lobe is pointed exactly away from the cam bucket. Measure the gap. If it falls outside of the .08 to .18 mm, write down the gap you measured (90% chance the gap will be smaller), and continue for all of the cams. If there is no gap, we’ll cover what to do in a few lines.
- Using the fingernail polish, paint a small line from the cam gear to the chain, make sure none gets on a rivet in the chain, and that the mark is easy to see. This is going to be your reference mark. Do this to both cam gears.
- Take the cam holders off of one of the cam shafts. Once they are off, ‘roll’ the camshaft toward the other. Keep it engaged on the chain and the chain taught. (If you don’t you can be in for one hell of a ride, and not a good one.)
- Using the suction cup, pull the buckets out, one at a time. Use the digital caliper to measure the thickness of the shim. (It may be printed on the shim.) Use the thickness of the shim, and the gap you measured to find out what shim you need to buy. If there is no clearance, buy a shim about .2 to .25mm thinner than what is in the engine right now. Roll the first camshaft back into its cradle, and repeat the process with the other camshaft. You can leave the buckets out of the head, but make sure that you make note of which valve they came out of. Use the empty egg carton to hold both
- Go to your Kaw dealer, or other bike dealer. BRING YOUR CALIPERS and old shims! Buy the correct thickness shims to finish the job, and before paying, use the calipers to make sure that you are buying the right thickness. (Dealer may have jumbled the shims up a bit, and this will save you a trip back) Also, see if they will give you a discount if you give them you old shims.
- Go back home, and put all the shims into the holders. Put the buckets back on. Make sure that you carefully slide the buckets in PERFECTLY STRAIGHT! Any angle, and the bucket may jam in place, and become very difficult to get back out. As long as the cam gears have not been disengaged from the cam chain, the cams should still be in perfect timing. Make sure the dots of nail polish still line up. CAREFULLY reinstall the camshaft holders, making sure they go in the right place (They are numbered), and in the right direction.(The arrow points forward). DON’T STRIP THE SCREWS! Torque them to the specs in your service manual.
- After both cam shafts are installed, re-test the valve clearances to make sure they are all within specs. Pay special attention to any cam that had no clearance. If the clearance is not correct, repeat the relevant steps, and smack yourself for doing something wrong.
- Scrape the gasket off of both the cam cover, and the engine, making sure that you don’t gouge the aluminum, and don’t let anything fall into the engine. DON’T use a razor scraper. (I had a blade break, and almost make it down into the engine. Damn near had a heart attack.)
- Using the cam cover as a guide, trace its outline onto the gasket paper, and cut it out. I found that scissors allow less room for screwing it up. Next, apply a small amount of oil to the cover, and press it onto the gasket. This will give you the position of all of the bolt holes, and the thickness the gasket should be. Use the hole punch to make the bolt holes. Finish cutting out the gasket.
- Pop out the cam plugs, and clean them off with a de-greaser. Make sure you get all of the cleaner off, and the coat the curved side of the plug with a thin coating of the gasket-in-a-tube stuff.
- Reinstall the cam cover, and assorted other goodies you took off. Start up the bike, and listen for any cam chatter. You shouldn’t hear any.
- Take your bike for a spin. You deserve the wind-down after all of that work. See below for the lash chart.