Checking valve clearance - Caution

This may be covered in the owners manual, I haven't checked yet, but the buckets over the valve spring and shims are color coded and different thicknesses. I noticed a little dab of paint on the inside of the buckets, mine were green and yellow. I know that on multicylinder engines Honda color codes (or used to when I was racing 20 years ago) connecting rods according to their weight. When replacing a rod in a 4 cylinder street bike you have to check the color and order the same to keep the engine balanced. I checked the thickness of the buckets, where they sit on the shim, with a micrometer and sure enough the yellow dot buckets were thicker than the green dot buckets.

The manual does say to keep the buckets in their original position and it's always a good idea anyway since things break in and wear a certain way. If you accidently mixed up your buckets after your shim calculation, you could throw off your clearance. Of course you're going to recheck the clearance after assembly if you did change shims so you'd catch a problem, but if you reassemble without changing shims you might not check. If the buckets get crossed you could have trouble.

If this is common knowledge or it's been covered before feel free to point that out. :cry:

you're spot on with that frosty, not sure if it's been covered here before.

I'd consider it to be common knoledge to the more alert engine builders on here. It can actually be used to your advantage. By mixing and matching shims and bucket thicknesses sometimes you can get your clearances closer, or avoid having to buy as many shims.

I thought about mixing and matching since 4 valves are now a bit snug with the new cams and it'll take 3 weeks for shims to reach me but I didn't want to take a chance and I couldn't get 'em all in spec without new shims anyway. The buckets are very snug in their cylinders and I wasn't comfortable swapping them.

I also had a hard time getting the buckets out of their bores (this is the first time they've been out, my clearances have never gone out of spec even after break in). There was a tiny lip mushroomed out from the cam bearing surface and I had to very carefully remove/chamfer it with a utility knife before the bucket would slide out. Have you run into this Hamish?

no.. havent heard of that before frosty. Thats something I'd keep an eye on if I were you. Maybe it was an oversight by Yamahas QA dept? :cry:

The buckets are always tight to come out, but thats due to the oil between the bucket and the head. Put them in dry and you'll see how loose they really are. If your buckets dont come out with a small magnet (i use the magent you get on the back of pin vice drill set) attention is required. I'd like to see a close up pic of where you chamfered the bucket bore if it's not too much trouble?

As far as swaping buckets goes, the OD of all the buckets should be the same (as should the bucket bores). A quick check with a micrometer will verify this. I'm of the opinion that yamaha (and the rest of 'em I guess) use different thickness buckets in an attempt to keep the shims fitted from factory about the same size. As you could imagine, no 2 castings come out exactly the same.

My buckets would slide up their bore fairly easily until they reached the edge of the cam bearing surface and then would stop dead. It’s like the cam bearing surface wore and produced a little lip. If you think of the actual bearing surface as horizontal and the bucket bore as vertical, the lip was at the 90 degree angle where the two surfaces meet. It reminded me of trying to get pistons out of an 8 cylinder chevy. They slide up and down in the bore easily but you need a ridge reamer to remove the lip at the top of the bore before they will slide out. In my case the ridge was at the cam bearing. The cam surface in the head is a U shape. The bucket would slide up until it reached the bottom of the U. I scraped away the lip at the bottom of the U and then it would slide up a bit farther so I had to scrape all of both sides of the U.

If you look at this picture, the plain bearing surfaces(not the ball bearings at the ends), kind of have an hourglass shape, and I had to scrape the curved sides of the hourglass. The exhaust buckets and outside intake buckets only hooked on 1 side each, but the center intake bucket was the worst since it is between 2 bearing surfaces. I think that the bearing surface mushroomed out a bit as it wore and produced the lip.

There were only 2 matching shims in my head so I don’t think that’s the reason for using the different color codings, and most were odd numbers like .179 and .168, but you can only buy in increments of .005. Us privateers can only adjust our valves to a general range, they save the .001 shims for the factory riders to give them an edge.

I agree with you on the castings. I think they mass produce them within certain tolerances and then measure them and mark them accordingly for finer tolerances. Easier to do that than to run them back through the machine shop until they are to an exact spec. On 4 cylinder street bikes the connecting rods are color coded by weight(for internal balance) for the same casting reason. They whack them out fast and then color them by weight rather than trying to get them all the same weight. The colors had a range, something like blue was something.010 to .020 grams, yellow was .020 to .030 grams etc. It didn’t matter what color rods were in an engine, as long as they were all the same color.

I used to race 600’s and spent one winter building an engine, I guess what they call balancing and blueprinting, that was legal for the production class. Production racing is brutally competitive and everybody is looking for an edge. I did everything legal that I could including balancing each rod, piston, pin ring and circlip assembly to within a ten thousandth of a gram of each other using a scale I borrowed from a chemistry lab. The engine was noticeably smoother and seemed to rev quicker. Racers would go so far as to cut the seals out of the sealed wheel bearings so they’d spin freer and lube them before each race. If they got caught in a tech inspection they’d say the seals must’ve tore.

I also heard of guys who would cut their transmission gears to reduce drag. Synchromesh transmissions produce a lot of drag, just spin your sprocket by hand with your bike in neutral and imagine the drag at high RPM. Racers would have a machine shop bevel the edges of the gears at a 45 degree angle and reduce the contact area of the teeth to ½ of original. Then they would get the gears shot peened to increase strength since the teeth were smaller and weaker. I’ve heard that shot peening can up to double the strength of a gear. With only ½ the surface area of the teeth meshing there is a lot less drag. I’m pretty sure that’s illegal. I’ve seen lots of teardowns after races due to protests, right down to the crank, but I’ve never seen or heard of someone opening a transmission, and that cuts drag a lot more than cutting bearing seals.


Keep a close eye on those intake cam journals. My head ended up in this same condition on me rather quickly. I was pretty good about checking/adjusting the valves on my 98 WR400. I had everything in spec prior to a 300+ two day ride, after that ride I found all three intake valves were tight. I pulled the cam out to make the adjustments and discovered similar wear on my cam journals. Engine Dynamics re-machined the journals for me for $90. Head is now good as new. I suspect that I may have gotten interrupted and did not finish cross torquing the cam bolts when doing the valve adjustment prior to the 300 mile ride. It’s the only thing that makes sense except that I didn't notice that any of the cam bolts were loose when I discovered the problem. After doing some research on this site, I have found that this has been a somewhat common problem with earlier WRs. Good luck.


you can just see it on the LH ex valve, but the bucket bore is undercut at the very top, obviously to prevent this problem. Being such an old bike, I assume you've had the buckets out many times before so you can discard the 'from the factory' theory. If the cam bearing surfaces have mushroomed enough to interfere with the bucket removal, I'd put $$$ on the fact that you'll have cam bearing clearance problems. Get out the inside micrometer and check it out if I were you. As for the gearbox, all bikes run a dog clutch gearbox (same as nascars, pro stock cars etc) as opposed to a scyncromesh type tranny that is used in production cars.

As for your 600, I went down a similar path building a 791cc ZX7R. From balancing the bottom to marking out and calculating piston flycuts, to making gsxr1100w valve springs fit in the head :cry: . This is where I got my engine building experience from. The ol' thumper is a walk in the park after doing 4 cyl slipper bearing engines!

Thanks Scott, I'll order some plastigauge and check my cam bearing clearances.

Hamish, I've never had the buckets out. My clearances have never gone out of spec from brand fire new, even after break-in. I used to check them every couple of months but the stayed consistant so I slacked off.

They were on the snug side of spec when I took them out last weekend and the new Hotcams pushed some just over the snug limit which is why I took the buckets out.

On the tranny comment, I'm not sure if you agree with agree with the drag reduction or not. If you look at the specs of most bikes they list the transmission as synchromesh, and all the gears turn and mesh all of the time, although power is only transmitted through the set of the gears selected. With all the gears meshing there is a lot of drag. If you ever have your tranny apart, slide on only one pair of gears and feel the difference in drag at the countershaft. The reason they all spin together and mesh is for smooth shifting. I used to drive a 5 ton truck without a synchromesh transmission and if you missed a gear you almost had to pull off the road and start over in 1st.

As always, of course, I could be wrong.

just different termanology re the tranny, no big deal anyway.

I spoke to a very knoledgeable man (taught me almost everything I know)tonight regarding your cam bearing problem. As soon as I told him what happened , and the climate you are from he reckons it's caused by running an oil that is too thick at startup when the engine is cold. Might be something to look at.

just different termanology re the tranny, no big deal anyway.

I spoke to a very knoledgeable man (taught me almost everything I know)tonight regarding your cam bearing problem. As soon as I told him what happened , and the climate you are from he reckons it's caused by running an oil that is too thick at startup when the engine is cold. Might be something to look at.

That could be it Hamish. I was running what I thought was a light engine oil in the bike the first year here. One cold morning I needed a bit of oil to top my truck up with. There was a quart of bike oil in the truck so I was going to dump that in. It had been sitting in the truck overnight at about –35C and the oil wouldn’t pour out of the bottle. When I squeezed the bottle the oil came out like toothpaste, scary. :cry:

I bought a couple of different brands of oil and left them in the truck that night. The following morning the only one that would pour was Polaris synthetic 0W40 so that’s what I use now. The ridge probably formed that first winter. Thank you and your pal for the tip. :cry:

Yes Frosty, thoose cam bearings are very tight (.0008")and a few of us have had them sieze or in my case semi-sieze up. I was removing the cam cap to change shims and the cam came out with the cap. Had to kind of pull it apart.

When I put the cam back in I noticed the intake cam was much harder to turn by hand than the exhaust cam.

I sent it to EDco and had Mike resurface the cam journals. I think I damaged it by riding the bike on the highway in the cold weather w/o warming it up quite enough.....and since your name is Frosty I figure you ride in the cold too.

The good news is it can be fixed.

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