Clearance issues! Tricky question! Need some help.

[BigDaddyD]

So I finally tore into my top-end to check my valve-tappet clearances.
Here are the measurements I got... but there's a catch!

Cylinder 1 Exhaust: Feeler gauge= 0.038mm / Tappet 2.90
Cylinder 1 Intake: Feeler gauge= 0.051mm / Tappet 2.80

Cylinder 2 Exhaust: Feeler gauge= 0.038mm / Tappet 2.90
Cylinder 2 Intake: Feeler gauge= 0.063mm / Tappet 2.85

Cylinder 3 Exhaust: Feeler gauge= 0.038mm / Tappet 2.85
Cylinder 3 Intake: Feeler gauge= 0.051mm / Tappet 2.90

Cylinder 4 Exhaust: Feeler gauge= 0.038mm / Tappet 2.80
Cylinder 4 Intake: Feeler gauge= 0.038mm / Tappet 2.85

So... the catch is... my feeler gauges only went down to a .038mm
I looked all over town for smaller ones and couldn't find any.
BUT! The .038mm wouldn't fit, the clearance was too small. This mainly occurred with the exhaust valves, the intake valves clearances were between .038 and .063, so I should be ok there.
So if it says .038mm on my exhaust measurement, that means that the feeler gauge wouldn't fit.

So since the .038mm is close to being out of spec, should I replace those exhaust tappets with thinner ones to open up the clearance a little or am I safe??

I measured all the clearances twice, once at 90degrees and once parallel to the cylinder, just to be sure. I also measured the tappets with a digital caliper gauge since most of the numbers were wore off.

Thanks!
D.

[twr1776]

Bikemaster sells a feeler guage set with the .010 increments. Maybe a local bike shop or dealer carries them. Maybe someone else can also chime in but I would change all of the exhaust shims and re-measure. Maybe change the #4 intake shim and re-measure and if it ends up over tolerance change it back unless you can get some of the half shim sizes. Looser is better than tighter, especially on the exhaust side.

[BigDaddyD]

Yeah, I checked around my area, went to autozone, sears, the suzuki dealership, and a few other local bike shops and NOBODY carried feeler gauges smaller then .03mm... it was ridiculous!

[Nessism]

.03mm is .001", or half the thickness of a human hair. You won't find feeler gauges thinner than this and if you were to, they would tear in very short order.

Sounds like you need a thin "checking shim"; install the thin shim and then measure the clearance. After this you can calculate the proper shim thickness for your engine.

Regarding your checking method, the proper procedure is listed in the Factory service manual. If you do not follow the proper procedure the adjacent valve will be pushing up on the cam and skewing it in the journal clearance, thus leading to inaccurate readings. This is not a critical detail but worth paying attention to to assure the best results.

[BigDaddyD]

I used a Clymer's manual for the procedure, plus the GS750 manual found on Basscliff's website.

[Nessism]

I used a Clymer's manual for the procedure, plus the GS750 manual found on Basscliff's website.

Did you check the valves in adjacent pairs or one at a time?

[DMorris]

I ran into the same problem finding a proper feeler guage when I had my GS1000. I don't remember the clearance spec. (.001" sounds familiar) but I do remember that I acquired some machine shop shim stock of .001" and used it as a feeler guage. I would just cut another piece when the one I was using got beat up.

.038mm = .00149" .001" = .0254mm

I believe I could find some shim stock(free) and mail it to you if you would like.

Don

[BassCliff]

Hi Mr. BidDaddyD,

My feeler gauge goes down to .04mm. It that one doesn't fit, I pop in a smaller shim and re-measure. Simple as that. I got my feeler gauge at my local Pep Boys. You can also find them online very easily. I would get way too confused if I used an SAE feeler gauge.

I'm sorry you missed my "garage day" last month. Mr. Gixxer Dan got a lesson on valve adjustments.

Thank you for your indulgence,

BassCliff

[BigDaddyD]

Did you check the valves in adjacent pairs or one at a time?

Both. I checked and re-checked them each a few times.
The manual on Basscliff's site explained how to check 2 at a time. And my Clymer's manual explained 1 at a time. So I checked both ways and got the same measurements.

So weather or not my feeler gauges go small enough, wouldn't putting a smaller shim in where it wouldn't fit bring it closer to spec with the intake valves?

I guess that's my question... even though my gauges only go down to 0.038mm the spec range is 0.03mm thru 0.08mm, so I'm at the tail-end of the spec range anyway.
So since my .038mm gauges won't fit the exhaust valves, putting in a shim the next size down will bring the clearance into the spec range, right?

[BassCliff]

I guess that's my question... even though my gauges only go down to 0.038mm the spec range is 0.03mm thru 0.08mm, so I'm at the tail-end of the spec range anyway.
So since my .038mm gauges won't fit the exhaust valves, putting in a shim the next size down will bring the clearance into the spec range, right?

Hi,

Yes, that's the principle. Your .038mm feeler is near the tight end of the spec. The .051 and .063 are about in the middle. I even run a little looser than spec sometimes, up to 0.10mm, because I'd rather run loose than right at the bottom of the spec.

It sounds like you've just about got your valve check licked. Nice work.


Thank you for your indulgence,

BassCliff

[zathros]

Sometimes the valve seating further into the valve seat will require you to use a smaller shim. It depends what wears. Ideally, the shim wears and everything else stays the same.

[Nessism]

You may have to go down two sizes, no way to know until you can get a thinner shim in there and measure again.

[BigDaddyD]

You may have to go down two sizes, no way to know until you can get a thinner shim in there and measure again.

Would using the method Basscliff explained help, popping in one of my smaller shims to get a measurement?

[Killer2600]

Would using the method Basscliff explained help, popping in one of my smaller shims to get a measurement?

Without smaller feeler gauges that's the way it has to be done (to be done right)...Whenever your smallest gauge doesn't fit, there's no telling what the clearance is--could be .03mm or 0mm or even -2mm.

[BigDaddyD]

Do the clearances need to be the same between all the valves or just with in spec?