Valve clearance waaay out of spec :(

So today I thought I would do my first compression & valve clearance check on my 86 xj900n - i've had it for 3 years but never done the clearance check :/

As you can imagine from the results below, its not running all that well - poor mileage and trouble starting etc... Other than that, the power seems to be okay.

Cyl 1 2 3 4

Compression
Dry 160 150 60 65
Wet 1 65 160 130 125

Clearance
Intak 0.063 0.102 0.076 0.102
Exhaust 0.140 0.152 0.152 0.152

Another thing, i've never taken my valve cover off before, and noticed that one of the bolt holes has been snapped inside, with the broken alloy no where to be seen.

I haven't got the tool to take out the shims but will get one soon and then start getting the valves back into spec.

Any suggestions on what i can do about the bolt hole?

 

Is the bolt in the hole?? If it is you can try and walk it out with a pick.

 

so the broken bolt is on one of the inner rocker clamps; No idea if thats an expensive fix or a get out of jail free card... Pic shows front left clamp, but it's front the right one..

 

how to adjust valves with zip ties or 12 ga insulated wire

AIRHEAD VALVE ADJUSTMENT with Pics


AIRHEAD VALVE ADJUSTMENT Part 2: The Tool vs. ZipTie -w/pics


you do need to fix the bolt

 

If you can back it out with a pic then if you remove the other bolt the top part of the cam bearing should come off leaving the bole exposed. If so, a vice grip wrench should do the trick.

 

This is the part that is broken, I'll head to the wrecker tomorrow to see if i can find a replacement..

I measured all the shims today as well using the zip tie method - super easy.

 

Ugly. Hope you can find a replacement. Chacal may have one.

 

fwiw, if the cam bearing caps are anything like on cars, it must fit precisely, and not all are the same. If Yamaha was really good, they'd all be the same, so others should chime in. I just know that the bearing caps must match the head as those are bored out together.

 

Just finished my annual valve adjust and 5 of 8 out. Must have been a little rough on the old girl this summer.
Yikes after midnight ... Go to bed now
Ps no broken bolts

 

Yes they are made as a set at factory
But any used one and some plastic gauge will tell you if it will work. Soon as you torque down the cap you will find out if it will work.
Failing that a replacement cap could be line bored to spec.
But good luck finding one that doesn't have a head with it , no wrecker is going to sell you just one cap unless he has a junk head laying around.

 

Only if it was too small/not enuf clearance to begin with........

 

I don't know about the 900 motor but on the 650 the cap near the chain sprockets does not hold the cam in place and is simply for the valve cover bolt. It's hard to tell from the pic of you holding it in place but it kind of looks like its not really a cam cap and could be replaced with one from another head without worrying about it damaging the cam.

 

As with any bearing cap, they can be cut down at mating surface and then resized.

 

so after closer inspection when I had stopped cursing the bike, I figured it was just a bracket to bolt the cam cover on.

I spoke with a few wreckers who weren't keen on parting out a cylinder head so I just improvised a bit and ground a bit of the thread off the top of the bracket to give me enough clearance to put a spring loaded nut on the inside of the cam cover. So far it seems to be fine...

 

i have a few of those i can send to you. I bought a xj750 head for parts. I have two of those caps. and @jayrodoh is right. It doesnt touch the cam. so no bearing issues.

Message me with you address. i'll ship it out to you in two weeks. Along with the package i owe Jay!

 

All the cam journals were ground to the same dimension, and all the cam bearings were machined to the same dimension (the cams run directly on the head casting, no shells). The only thing that will prevent swapping parts is excessive wear. SOP for (most) motorcycles.

 

Thanks mate, I'm in Melbourne so that will be a fair effort. It's okay for the moment but appreciate the offer.