Utter shimming confusion

[JTP obsession]

Hey guys,

I'm currently swapping out shims and I've hit a wall less than 1\4 of the way through the job.

The trouble began on intake 2. I failed to double check my calculations from about a week ago before I swapped a 265 for a 240. When I checked the valve clearance, I could squeeze in a .012 feeler gage in. Retracing my steps, I re-installed the 265 and when I rechecked the clearance on that I could barely fit a .003!! I went back and forth a couple of times scratching my head without new enlightenment.

Finally, when I went back to intake 1 to double check, the clearance with the new 240 shim just exceeds my .010 gage. However, when I first checked the clearance after I first popped it in there, it was right on the button at .005!

I'm prepared to get embarrassed here. There must be something staring right at me that I'm missing. Any advice would be greatly appreciated!

Cheers

[Bonz]

Hey guys,

I'm currently swapping out shims and I've hit a wall less than 1\4 of the way through the job.

The trouble began on intake 2. I failed to double check my calculations from about a week ago before I swapped a 265 for a 240. When I checked the valve clearance, I could squeeze in a .012 feeler gage in. Retracing my steps, I re-installed the 265 and when I rechecked the clearance on that I could barely fit a .003!! I went back and forth a couple of times scratching my head without new enlightenment.

Finally, when I went back to intake 1 to double check, the clearance with the new 240 shim just exceeds my .010 gage. However, when I first checked the clearance after I first popped it in there, it was right on the button at .005!

I'm prepared to get embarrassed here. There must be something staring right at me that I'm missing. Any advice would be greatly appreciated!

Cheers

Double checking is for sure a good thing! I gather you are changing shims with "the tool" and cams are in place? If you loosened the cams to do the swap after initial measurement, possibly the cams are slightly different in "tightness" in the saddles based on re-torquing the cam caps and gave the error? Just taking a stab at that. However, if the cams weren't removed then disregard.

"When I checked the valve clearance, I could squeeze in a .012 feeler gage in." -This was the initial measurement before swapping, yes? Just to be sure I read you right. Not sure what to say on that one, maybe the cam wasn't quite on the base circle quite yet on the re-check (if you rotated the engine after shim swap, before re-check) and it is showing tight for that reason. But based on what you say below, appears the engine was not rotated.

"Finally, when I went back to intake 1 to double check, the clearance with the new 240 shim just exceeds my .010 gage. However, when I first checked the clearance after I first popped it in there, it was right on the button at .005!" - This sounds like the shim wasn't seated fully in the bucket. It is needed to rotate the engine a few times, with oil manually slathered on the shim/bucket/cam lobe, IMO before a re-check.

In any case, my thought is oil things up, rotate the engine a few times with shims in place as they are, and re-measure everything. Then begin from there.


On my ZRX1200, I have had cams in and out changing to a ZZR1200 cam. I checked them initially after rotating the engine with the original shims from the previous cams, rotated the engine a few times and checked again. Then I swap the shims that need it, oil things up good, rotate the engine and check again. Being methodical and consistent is the key. Not that you weren't, but start again and see what you get is my thought.

Any other folks care to weigh in?

[JTP obsession]

Thanks Howard.

The first measurement I took with the 265 was .004, so I ordered some 240s (amongst others). The .012 gage is what I measured after putting in the 240. Then when I got the 265 back in, it was much tighter than the original measurement. I took the cams off while removing my head and jugs, however I did not remove them after measuring my clearances. Hope these details make more sense.

Justin

[Bonz]

I am not sure you could call when re-installing the 265 and "barely getting a .003" in there" (which means it did fit, so a bit looser than .003") a much tighter clearance than the .004" initial measurement you just said you had. That margin of error is explained in checking from one time to the next, IMO and in my experience.

Going from a 265 to a 240 is a pretty good jump. .005mm is basically .002" so you went up 5 shim sizes, which would would take you well above the top end of spec for intake. Even from barely getting a .003" feeler in, 2 shim sizes would get you in the middle or slightly above middle of spec for intake.

Intake spec: .006-.008"
Exhaust spec: .008-.010"

Start from where you are, re-check and use that as a fresh start, IMO.

[Radioguylogs]

Dirt &Oil

Dirt and/or pooled oil under the shim are probably the only things that would cause erratic measurements, assuming your shims are not mutilated.

I would wipe the shims and the top of the bucket under the suspect shims and keep measuring them until you are satisfied they are consistent.

I've experienced erratic measurements and I keep putzing with them until I am satisfied they are tweaked.

BTW the step between a 265 and a 240 should move a 0.004" clearance near to the 0.012" you measured. Each shim step is roughly the range of the spec. (0.002").

[Bonz]

My thought is he wants to check them after turning the engine over a few times after putting clean oil on the new size shim/bucket/cam lobe. That will squish out any excess and simulate the thin film that would be there during operation. Then check and re-check, should give a consistent measurement. When you first check shims after taking the valve cover off there is oil on, around and in between everything. You want that consistency when you recheck after installing a shim, IMO.

I don't believe moving five shim sizes at .019685" each (2mm) moves the measurement from .004" to near .012". It would be much closer to .014" (.01384" for precision sake). .002" is a full shim size difference. Not trying to split hairs, just to be clear on the math.

In any case, my thought is what Radioguylogs is saying too. Measure everything and re-check to verify consistent readings. When you are satisfied, make adjustments from there.

For me, many times walking away and coming back later everything seems to work better after I've been staring at it for way too long in a stretch of time trying to make sense of something that doesn't make sense.

[LoHo]

Bonz, .005mm is close to .002in?

[Bonz]

Holy crud, I have no idea what I have been typing for numbers the past few posts...

Each step in shim size of .05 mm is .001985".

Really sorry, thanks for the check.

Double check me, as I apparently am not doing so well on my own!

[JTP obsession]

Thanks guys. My valves aren't too far off for the most part. This is also, i should mention, after putting in new rings and lapping my valves. I think I'll just run it a few times then do a proper valve adjustment.

HOWEVER, now that I've fired her up for the first time I've got another problem. RPMs are running high. I'll get it idling at 1100, then when I give it gas rpms go up as they should but either slowly drop down or sit at 3000 and start to increase from there without any throttle. I've checked my throttle cable, and I've checked for vacuum leaks. I found a leak at the front of my carbs and corrected it. It fixed the backfiring but not the racing rpms. Scratching my head once again! Vacuum advance maybe???

Justin

[Bonz]

The throttle cable itself may be fine however verify there isn't something keeping the throttle linkage from returning properly. On another bike of mine, the intake manifold clamp that holds the boot on to the front of the carb had rotated. The clamp screw was pointing at a different angle and impeded the throttle linkage.

[LoHo]

Check for a vacuum leak...it starts, then revs up waaaay high? I chased that around for a long while.

[LoHo]

Dry, crusty rubber caps or a cracked vac hose are good suspects.

[Bonz]

Could deteriorating enrichener plungers cause an issue like this?

[3Phase]

... Scratching my head once again! Vacuum advance maybe???

Could be, unplug the vacuum line from #2 carburetor.

If the idle drops, the throttle plate is open too far and the carbs are out of synch or something else is wrong.

If the master idle screw has to open all four carbs too far to get the engine to idle because, for example, the pilot circuits are not working, the engine will try to run using the transition ports. That's not a stable situation, it's hard to get it to idle without stalling or running away and will probably kick in the vacuum advance too.

[Radioguylogs]

Did you work on the carbs?

By any chance, did you install K&L pilot jets in the carbs?