Valve clearences

[daniel3640]

Recently bought a 1998 xj600n with 35k miles on clock. Just went and check the valve clearences and found all 4 intake valves were at 0.002", 1 was even less, that is half of what they should be. Just wondering what would have caused that? All the exhaust valves were sitting at 0.008" which is correct. Also would i be better sourcing a yamaha tool for removing shims or would a universal one do?

[bobh]

Clearances do close up gradually on modern bikes as the valve seats bed in - wear on the cams and followers is negligible.

I've only ever used the Yamaha tool and it's quite fiddly even with that. You may be able to borrow one from a kind local member if you ask ever so nicely. But if you're just doing all four inlets I'd venture to suggest that it might be easier to take the camshaft out to do them, which would save you having to get a tool at all at all.

Be ultra-careful with the oil cooler connections - always back-hold the hexagonal bosses when you're turning the banjo bolts to avoid stressing the (weak) joint between the bosses and the body of the cooler itself.

[daniel3640]

Oil cooler removed on my bike when I got it bought a second hand one from trev on here will fit it once I know all the valves are ok. Will maybe look at removing camshaft. Also where would the best place to get replacement shims?

[daniel3640]

Any thing to watch out for when removing camshaft?

[bobh]

Actually I don't think you'd have to take the camshaft right out, just displace it far enough to allow room to work.

Buy or borrow a Haynes manual if you haven't already got one. This will show pix and give tightening torques etc.

The main thing is not to turn the crank once you've started, and make sure it's all marked so you can get it back together with the timing correct. Ideally if you can keep the chain in mesh with the sprocket downstairs on the crank it will be easier to get it all back together with the timing right. And double check it to the book afterwards, turning the engine gingerly in case it's slipped and a valve is trying to make contact with a piston!

Also cover the camchain tunnel while you're taking the bearing bolts off or changing shims so you don't drop anything down into the crankcase, and watch out for the hollow dowels on the bearing caps.

Other than that it should be fairly straightforward. Just take it steady and remember to undo and redo the bearing cap bolts evenly and a little at a time.

You'll have to take out the camchain tensioner before you lift the camshaft. This is not a bad thing as it's a good opportunity to check it's still free and working properly.

All Yamaha dealers, and many independents, will either have or be able to get shims. Some do them on an exchange basis. And you can always try posting a "Wanted" ad on here.

[daniel3640]

Ok got shims out it was only 3 intake shims that needed to be removed did it without removing camshaft completly just be slackening of bearing caps enough so hopefully timing will be ok. Chain tensioner seems to be working good. So this is the clearences measured cylinder 1 0.002", cylinder 2 less than 0.0015" ( did not have small enough feeler blade to fit) and cylinder 3 0.002". These are the sizes of shims removed cylinder 1 and 2 both had 272 shim and cylinder 3 had a 275 shim. Could anyone help me with selecting right shim size i have a table in my haynes but im confused.

Thanks

Daniel

[bobh]

Cylinder 1 clearance is 0.002" = 0.05 mm. Therefore its clearance need to increase by 0.05 mm so it needs a 267 shim. Normally they are only available in steps of 0.05 mm so you would use a 265, but as it happens I have a 268 you can have if you want to try it.

Cylinder 2 clearance is (say) 0.001" = 0.025 mm, so needs to increase by about 0.075 mm and thus needs a 265 shim, though as you haven't been able to measure it accurately this needs to be checked when you have a smaller shim in place.

Cylinder 3 needs the same increase as cylinder 1, but it's probable that the 272 shim from 1 will open up the clearance enough to be in spec. If it's not enough I also have a 270 which should do the trick.

So with any luck you just need to buy a 265 shim and if you p.m. me your address I'll send you the 268, and the 270 if you want it, for £1 each including 1st class postage.

Bob

[daniel3640]

Ok got new shims in all clearences sare withing spec now:) Thanks bob

Another question though after checking timing it seems to be slightly out when piston 1 is at tdc i can only see the slight edge of the centre punch through the bearing case. I think it must have been like this before as i never took the camshaft out of mesh. Would this need to be sorted or would it be ok?

Another thing while turning crank at certain points the chain seems to go slack between the 2 camshafts and the tightens straight up again it did this before and just wanted to make sure this is normal?

Thanks Daniel

[bobh]

Not sure about the timing - as far as I know it's not adjustable. Sorry, don't have a Haynes any more, so can't be more definite.

I suspect the reason the chain goes slack then tight is because the cams are being turned by the valve spring pressures.

Bob

[daniel3640]

Would I be able to remove the chain tensioner and then set the camshafts and lift the chain around the sprocket a bit?

[bobh]

It should be possible to slip the chain round the sprockets if the tensioner is backed right off.

Is it possible that the chain became disengaged from the sprocket down below on the crankshaft at some point?

[daniel3640]

Could have been possible when I took the tensioner out but most of the slack seemed to be between the camshafts

[daniel3640]

I took the tensioner back out today but there was not enough slack in the chain to move it another tooth. I put timing marks on the sprocket and chain before i removed the first time and they are all lined up so it must have been like this before.
Anyway rechecked timing hadn't moved and rechecked all valve clearences and they are all within spec. It turn over by hand free enoguh although i could hear a slight knocking sound or cluncking sound every couple of turns coming from crankshaft area what could that be? Hopefully get it up and running next weekend

Thanks Daniel

[bobh]

Help! I'm at the limit of my knowledge here, and don't have any manuals now to help this guy.

My gut feeling is that the chain may have slipped one tooth round the crank sprocket so although the chain and both camshaft sprockets are still aligned, the timing of the whole assembly may be out. But without knowing what the timing marks are or what the valve timings should be I can't suggest how to check it.

Can anyone else step in and suggest what he should do next?

Thanks - Bob

[daniel3640]

Well i have a haynes and looking at my timing marks there is one on the pulley at the crank to mark tdc and a punch mark on each camshaft that lines up with a hole in bearing cap number 2.

It is just when it is at tdc the exhaust camshaft mark is bang on and the intake one i can just see the edge of the punch, so i dont think i could have moved around the crank if the exhaust camshaft is alright could it?

Another thing was with the rocker cover of there was no compression when turning it just wondering if that is normal? By no compression i mean i could hear it escaping down in the crank area. I have since put the rocker cover back on but never got a chance to try it will have a look tomorrow.

Also there was that slight clunking sound i could hear now and again when turning it which i have never noticed before again i will check again tomorrow now the rocker cover is on.

Thanks

[daniel3640]

Ok turning it over now it does feel like the is compression but you can still hear the hissing sound like it is leaking must be coming out the breather at the top. Just wondering if that is normal the bike was running before i started?

Also that clunking sound doesnt seem to happen at a certain point seems to be a little random and there is no resistence turning it when the clunk happens.

[bobh]

The 600 engine is pretty easy to turn over, and you don't feel a lot of compression doing it slowly. The pistons depend on having a film of oil to help them seal, and as your engine hasn't run for a while the bores will be fairly dry and you will get the leak that you describe.

If the clunk is random it's probably in the transmission somewhere, so nothing to worry about.

Fingers crossed that you're good to go now!

[daniel3640]

Ok thanks going to give it an oil change, some fresh fuel and a new fuel filter tomorrow and hopefully take it for my first run. Thanks bob for everything will post how I get on.

[bobh]

Might be best to take it for a little run before you do the oil change. That way the old oil should pick up any dust or dirt etc. that might have got into the motor while the top was off, plus the oil will be warm so it'll drain easier.

And unless you know that the oil filter is fairly new I'd change that as well.

Good luck - Bob

[daniel3640]

Ok so got it to start on choke today and when i let the choke out the revs slowly dropped down to around 1200 which was fine and it sat there for about 5 mins but everytime i touched the throttle the thing would just splutter and die, after doing this a couple of times it wouldn't start without full choke on and then even with the choke off the revs wont drop below 3000.

Would i be right in sayin i have a blocked pilot jet?

Apart from this it sounded alright when it was sitting at idle just abit of a chain rattle and a slight knocking noise. Also when pulled in the clutch it made a loud rattle would this be the noise everyone talks about?

When i had the carbs off doing the valve clearences i did try to clean them out but the float bowl bolts were solid and just started to round off, so i just sprayed what i could with carb cleaner and gave it a blow with compressed air.

Thanks

[newell]

Yes that's the classic symptoms of blocked pilot jets. Go easy with the float chamber screws, they're known for chewing up.

Get them in a solid base like a vice and using a good fitting screwdriver tap them with a hammer gentlyish as you turn the driver. But go easy or you'll end up mullering them.

Good luck

[daniel3640]

Ok thanks for the advice i think i will start a new thread as this is a little off the original topic