My valve clearance numbers - how they look?

I just pulled my valve cover off - glad I did, these donuts look horrible. Looks like the po just used excees amounts of blue gasket sealer on this thing.. Uggg.. Luckily I have new replacements from Chacal I got a while back and just never got to using.

I had to take a break from trying to get the shims out because the shim tool I have doesnt seem to want to work on #3 I/E and #4 I/E, so I am taking a break before my frustration breaks something. (UPDATE and FYI for those that might care: I've been reading how people have been having problems with the motion pro valve shim tool, and it seems I had the same issue - I didn't just have to file out some spacing for the screwhole, I actually had to shave down the curve of the tool as it was not allowing it to wrap around the cam and actually get into position. I had to do a fair bit of filing to get the curve just right so it would wrap and get into position.)

The bike is a 1981 XJ750RH (Seca) - is running lean so I wanted to get valve clearances checked before I tore out the carbs and fix them up and replaced all of the rubber bits

So here are my (updated) numbers:

#1 I - .003"/.076mm - had a 280 shim in it
(per the shim chart I changed out this shim with a 275 that I had from
my parts bike and is now showing a clearance of .007"/.178mm)
#2 I - .006"/.152mm - with a 275 shim in there
#3 I - .007"/.178mm - no idea, shim not marked and my digital caliper is dead
#4 I - .003"/.076mm - no idea, shim not marked and my digital caliper is dead

#1 E - .006"/.152mm - with a 265 shim in there
#2 E - .008"/.203mm - with a 265 shim in there
#3 E - .008"/.203mm - with a 275 shim in there
#4 E - .006"/.152mm - with a 275 shim in there

For my novice eyes, the exhaust looks good - at least they are in spec (.006"/.16mm - .008"/.20mm) but the intake is having some problems. The interesting thing is on #1 Intake, where I changed the shim based on the shim chart it Fitz's write up, it is still out of spec - is it better to have more clearance instead of less?

For the shims that are not marked, I will be buying a new digital caliper tomorrow and will update then with numbers.

So, that being said, I would appreciate any experience and advice from those of you that are more versed on this then I am ;-)

Thanks in advance!!!

--josh

 

The used 275 shim from your parts bike might be worn and actually have a thickness less than 2.75mm. This would explain the unexpected increase in clearance there.

 

That's true, I have a digital caliper but it doesn't seem to want to turn on today, lol.

That does make sense, as the .006 feeler gauge was somewhat snug, and the .007 gauge just barely fit - so I would put that as borderline.

So that still begs the question, if I am out of spec, is it better to be loose or tight on the clearance?

--josh

 

That's easy-- Don't be out of spec.

Only one size shim and one size alone puts you in spec. IN.

Anything else is OUT. Put them in spec.

If you want it to make more sense, get a true metric feeler gauge. The K-D Tools #2274 is commonly available and usually for under $10.

Personally, I don't re-use shims. So I can't say I've had a similar experience.

 

Bigfitz: understood, to phrase differently, I'm going to order the shims I need - per the shim chart so I can put everything into spec. The question is more for, between now and then (I figure at least a week), if possible I'd like to 'not' have my bike holed up in my garage, so I was curious what end of the 'out of spec' spectrum was....safer/less concerning. On the flip side, since I have my girl all torn down, I'm probably going to have her off the road for a week either way so I can do the carbs and a few other odds/ends I've been postponing -- so the question is mostly academic at the moment for my curiosity ;-)

Re: The feeler gauges I have are metric and I have a set of non-metric ones. I used both to check just to play it safe and cover all bases ;-)

--josh

 

Gotcha. Loose is better than tight. Tight means a valve that isn't spending enough time on its seat, and therefore getting too hot.

TOO loose and you spit a shim, and frag the upper end. Expensive.

 

Sabre: you hit the Nail on the head, the shim I used to replace was out of spec just a tiny bit - which would account for it going to .007 instead of .006. Good catch!

--josh

 

Ok, so all checked out and reshimmed. Would be interested in expert opinion on these numbers to see if they are good enough. They are in spec, but 'just'.... Not sure if I should strive for 'middle' of the spec, or if it doesn't matter and that would just be a big ole waste of time.

1I - .006"/.152mm
1E - .006"/.152mm
2I - .006"/.152mm
2E - .008"/.203mm
3I - .004"/.102mm
3E - .008"/.203mm
4I - .006"/.152mm
4E - .006/.152mm

Thanks!!!

--josh

 

There is ONE and only one shim that will put each valve in-spec, so you can't get them in the middle of spec. It's in or out. In is fine, out is not.

 

Fantastic, works for me

Now I can button her up and rip the carbs off and get her tuned.

Thanks!

--josh

 

Did you measure in metric, or did you measure in US and convert to metric? I ask because a few of your valves are slightly out on the tight side. #1 and #4 exhaust, for example. Spec is .16mm, minimum. Yours are .152mm. Granted, that's only .008mm too tight, and that's a miniscule amount (I'm not even sure how you'd measure something so small with a feeler gauge), but they get tighter with time.

 

I mainly used/documented a US gauge and converted - also compared to published US standard ( intake is .004- .006 and exhaust is .006 - .008)