Valve clearances way out

[cbfb]

Checked valve clearances recently, some were a wee bit off. So I took off the cams and fitted replacement shims where necessary (this is a GSF250, the old version, so it's got tappets and shims).

Now, all clearances were within 0.01mm of the middle of the range which I was happy about. However the 1st intake valve on No 4 cylinder now has a clearance of 0.42mm (range is 0.17-0.27mm).

Once I can escape from gibstopping this arvo I will take the intake cam off and investigate. I am certain I did everything right but will look for obvious stuff, like if I forgot to put a shim in, checking tappet & shim size with a micrometer etc. Numbered the tappets when I removed them so didn't get ex/in tappets mixed up.

But, this seems very odd as it has gone from being 0.07mm out to 0.20mm out. I have double checked my calculations and am sure it's all right. Even if I got the wrong shim, I don't have any shims small enough to cause this problem.

Can anyone suggest anything I should be looking for while I've got the cam out? Beginning to regret buying a 16v bike it takes so bloody long to do this sort of thing, don't want to have to do it all over again. Advice much appreciated.

[Motu]

I'd be looking for a bent valve - do a leak down test.

[Drew]

Dunno about a bent valve, but it certainly sounds like it aint seating properly.

[cbfb]

Cheers guys.


I'd be looking for a bent valve - do a leak down test.

Did initially think about it being a bent valve, but it was fine before I took the cam off and haven't done anything too it apart from that, so can't figure how the valve would have got bent. I did crank the engine a few times, but that was by hand and I would certainly think I'd notice if there was a valve getting in the way of things somewhere???

Unfortunately I don't have a leak down tester. I do have a compression tester though would that tell me anything useful? I am guessing I would expect compression to be quite a bit lower on that cylinder if the valve is jamming open?


Dunno about a bent valve, but it certainly sounds like it aint seating properly.

When you say it ain't seating properly do you mean the valve or the shim?

[bsasuper]

Are the cam caps seated properly with no shit between the mating faces?

[cbfb]

Are the cam caps seated properly with no shit between the mating faces?

Will check that out, seemed pretty good but yeah maybe something has got down the gap where the tappet sits, that would do it.

[_STAIN_]

have you removed plugs while doing valve clearances ?
carbon has dropped onto open valve and is now holding valve slightly open...

[cbfb]

have you removed plugs while doing valve clearances ?
carbon has dropped onto open valve and is now holding valve slightly open...

Yep, plugs are out, but I did stick some rag inside the hole to stop anything getting down there. And I checked the tolerances before removing the cam (after removing plugs) and was all fine.

[Drew]

Yep, plugs are out, but I did stick some rag inside the hole to stop anything getting down there. And I checked the tolerances before removing the cam (after removing plugs) and was all fine.

Stuffing the rag down there could well have got crap in the combustion chamber that has taken up residence between the valve and the head.

The cam not sitting in the bearings properly would cause issue on more than one valve.

[cbfb]

Stuffing the rag down there could well have got crap in the combustion chamber that has taken up residence between the valve and the head.

The cam not sitting in the bearings properly would cause issue on more than one valve.

Well re-seating the shims (after giving the area a blow with compressed air) and refitting the intake cam didn't help.

So I decided to do a compression test - zero compression and could hear the air leaking out of the suspect valve. As I was cranking the engine, all of a sudden I got compression and the leak stopped. Carried on doing this, all fine - it appears whatever bit of crud was in there has moved on.

[_STAIN_]

trap for young players, never remove plugs untill after valve adjustment is finished

[White trash]

trap for young players, never remove plugs untill after valve adjustment is finished

We bow down to your superior knowledge and general awesomeness Bryce :D Now come buy a fuggin bike off me.......

[cbfb]

trap for young players, never remove plugs untill after valve adjustment is finished

The manual made me do it :innocent:

Point taken tho, cheers will leave them be in future.

Thanks everyone :)

[Paul in NZ]

trap for young players, never remove plugs untill after valve adjustment is finished

Hmm... Thinks to himself.... Um - would you like loosen em off to allow compression to blow past when turning the engine over to get various cams into position?

[cbfb]

Hmm... Thinks to himself.... Um - would you like loosen em off to allow compression to blow past when turning the engine over to get various cams into position?

I was wondering that myself, I've always pulled the plugs out when cranking by hand so not sure how hard it would be to turn over with the plugs in?

[_STAIN_]

shouldn't tell you too much of you will be setting up shop and taking my customers :)
1. don't touch plugs, or 2. loosen plugs 2 turns, tighten plugs, carbon has broken free, run motor to crush any carbon that may have fallen on open valves. Plugs in modern motor open across the plug area. Now plugs can likely be safely removed avoiding squids mistake. Best is method 1.

[cbfb]

shouldn't tell you too much of you will be setting up shop and taking my customers :)

Nah I think you're safe there! Thanks for the help tho.

[Paul in NZ]

Nah - definately safe. Besides, I prefer my valve adjustments to have proper tappet adjusters :msn-wink:

[cbfb]

Besides, I prefer my valve adjustments to have proper tappet adjusters :msn-wink:

Yup, next time I'll be going for a single cylinder, 2 valve bike with tappet adjusters. :niceone:

[Paul in NZ]

Yup, next time I'll be going for a single cylinder, 2 valve bike with tappet adjusters. :niceone:

God yes... Takes me 15mins to do the trumpy.... Mind you - given the on road performance I need the extra time for a head start...

[cbfb]

God yes... Takes me 15mins to do the trumpy.... Mind you - given the on road performance I need the extra time for a head start...

It's my on road performance I worry about not the bike's! :scooter: