Yamaha TRX850 Enthusiasts Forum

I've got the rocker cover and cams out, and now im trying to remove the buckets to get at the shims, ive removed all 5 of the left hand side ones (both inlet and exhaust) without so much as a wee bit of hassle however all 5 of the right hand side buckets wont lift out.

Does anyone know why or what im doing wrong? I've never had SUB's and only SOB's so i've always been able to remove the shims easily.

It seems strange that one side would be stuck so severely where the other is fine.

I might point out the bike is fine and runs perfectly so it's not bent valves or warped head or anything silly like that!

Thom

Yes, a problem quite a few have experienced Thom. Just how `stuck` do they seem to be?
Obviously they couldn`t be seized or the bike wouldn`t run!

I used a powerful mechanics magnet to get some of my buckets out when I last adjusted my valves. They all came out in the end, I reckon it is just the oil creating a seal so as you try to pull the valves out you are pulling against a vacuum????? AS mincehead says its doubtful they are seized as you would not be able to turn the engine

After a search online the TRX off road bikes and quads have a problem with the camshaft seats wearing and causing a bur or lip which overlaps the buckets, i had this problem on 4 of 5 buckets on the RHS cylinder.

30mins with a small file and a hammer and chissel (not reccomended!) and theyre all smooth again, but im a little disheartened by yamahas build quality as i considered them to be the best!

Saying this my bike has 28000miles.

I'll be on the lookout for a new cylinder head but i feel this head has at least another 10k+ miles anyway so no real worries!

Thom

As thom says, a lip forms on the side of the cam bearing surface and wont allow the bucket to come out. I cut a disk of very thin plastic to protect the top surface of the bucket. Using a small half round file with the end ground flat work around the bore of the bucket hole where it meets the cam bearing to remove the bur. Using a good light and Q-tips moistened with oil to remove all filings. A respected race engine builder told me not to use a magnet on shim buckets as it can leave some residual magnetism in the bucket which although weak can hold steel particles just where you don't need them. I use a small valve lapping tool. For really stubborn buckets I made a tool from a washer slightly smaller diameter than the bucket brazed to a piece of tube connected by hose to a vacuum pump. Using an o-ring as a gasket this will stick to the top of the bucket and allow some force to be used. Old fridge compressors you can find for free are good vacuum sources.

I agree Lenny, magnetising any of the cylinder head components is not a good idea.
And I also agree over the valve lapping tool being utilised, good tip on the vacuum pump by the way.

........always thought TRX off road bikes and quads were Honda