XT600 E 3TB 1992 camshaft clearance
 

Hi, I'm doing a topend rebuild on my XT600E. It had a blown head gasget where oil was going to the cylinder trough the head. When opening up the motor I saw that the bearing surface was not good anymore on the rocker cover, so I replaced it with a good second hand one. Seen in the pictures. I also inspected the camshaft journals and these are now out of spec.

Therefore my question. Should I run with this just out of spec cam shaft or should I buy a new after marked (new Yamaha is like 300euro) cam shaft to make sure bearing clearances will be ok?

I measured the journals of the camshaft:
Journal close to camchain: 22.962 mm
Journal in middle (3 locations): 22.966 22.975, 22.958 mm
Journal at oil inlet: 22.970 mm

Spec according to service manual is: 22.967 - 22.980 mm

For photo's of camshaft, rocker cover bearing faces and head bearing faces. see link below.

Camshaft
https://i.postimg.cc/MZMPNDs6/Camshaft.avif

Cylinder head:
https://i.postimg.cc/L5k2TMw5/head.avif

New rocker cover:
https://i.postimg.cc/FzXh3KPw/rocker-cover.avif

Old rocker cover (I did sand 600grid and polish the bearing faces but then realised that does not make much sense):
https://i.postimg.cc/fLCjGVGh/202503...8491-i-OS.avif

Hi, if i understand correct you only replaced one part of top? Its machined togheter and must be replaced as one part.

I see your point but they do assemble ok. I have already tried to bolt all together and then the crankshaft does turn nicely and free (with some oil off course).

I guess it will be ok?

You quess, you dont know how it looks inside after torque down. You will soon know if its not correct, turning around its not the same as correct journal measurements. Good luck!

post a pic also of the bad rocker cover....


sorry to tell you, but regardless of dimensions, camshaft journals surfaces look like low oil supply already made them rough, they should be should be smooth like the cam lobes.... pass you fingernail over those grooves and you will see what i mean. so your problem is not just the clearance.....


Then, to have an idea if the cam tolerance is ok (with your new cover), use plastigauge, like you do in car crank journals. should be in the 0.02-0.07mm range,



the fact that crank turns free is not telling much....

Yes agree cam journals do not look to great. I'm considering now to buy a new camshaft.

Thinking about ordering this non original one (new Yamaha is ~350euro):
https://www.ebay.com/itm/176834810299

Thanks for the guidance on the clearance. I have ordered bore dual gage and will measure the clearances today and share measurements.

Buy new head and rocker cover, didnt see pictures..Find a complete set from original.

measurements
 

I have done the measurements. Please see below.

Findings:
- clearances about 0.1, thus to high.
- small misalignment of rocker cover and head at location D (probably because I have new rocker cover, seems not to bad to me. Rest alignment perfect)
- Bearing faces are oval. about 0.05 more in vertical direction. I'm thinking about sanding the mating faces to correct. Please let me know your thoughts.

https://i.postimg.cc/gjT0Lxcv/New.png

Service manual specs:

https://i.postimg.cc/pdJXYGXV/Service-manual.png

You mean new original Yamaha? Is that still for sale?

No, i mean original from day 1 so you know its never been swapped rocker cover. Personally i would never buy new cam and do some sandpaper save to maybe get this right, but you must do whats right for you, good luck.Btw buy the 96 up you get the rocker that dont break on the frame mounting. Good buy https://www.ebay.de/itm/276196230131...3ABFBMnMHcgqtl

interesting. I actually ordered a new rocker cover from a 1994 that had a crack in it. Well, I agree it would be best to find better top end, but also hard to find i think. Can be as bad as I have now. My plan is now to order new camshaft. Then sand down the mating faces of the rocker cover and head to make the oval shape of the baring faces less oval end get them in spec. This is not a pretty fix but I should get the oil pressure to ok level I would think. Maybe worth a try before ordering whole new top end?

Ye mine cracked to, think about the one i sent, ask for pict of cam out. Buy a cam set you back 1/3 of the price here and cam looks good. If you have a keeper that you are riding for years to come i would recomend to buy this.

Looking into it. Not sure what to do yet. He says it is from a 1995 to 2002 model. Would 1995 and up be ok with regards to cracking of the rocker cover? I asked hem for photo's of the bearing faces. Let's see. Still very hard to judge if this one will have ok clearances or be close to what I now have. That is the risk only.

Yes its the upgrade JYADJ021.4PT Dont think anyone would sell something like yours, never seen anyone like it on ebay.

good luck sanding down your rocker cover while keeping a straight sealing surface.....


mechanic friend used to salvage worn cam bearing areas with a ball milling tool pass on head an cover and then a lick with the surface mill toll, but all done on a bridgeport machine.... not on a piece of emery cloth