Valve clearances waaaayy out of spec..

We finnaly got a day here that it didnt rain, So I measured my clearances today, and found 5 out of the 8 valves way out of spec. they were all between .002 and .003 inches. Now I am waiting for my valve shim tool to come in so I can see what shims I need, Then I gotta wait for the shims to come in. What a tedious process.

 

Just to make sure things go well, the correct clearance for intake and exhaust on the XJ650RJ are both 0.16-0.20mm or 0.0063-0.0079 in. Some have been using the clearance in the base manual and not the service supplement. That is if you have the XJCD.

 

Blue....I'm not so sure that those clearances for the 650 Seca are correct....I know that's what is quoted in the Haynes manual but for the life of me I cannot figure out why the US XJ650 Seca should have different valve clearances than every other XJ engine, which are:

Intake: 0.11mm - 0.15mm ( = 0.004" - 0.006")
Exhaust: 0.16mm - 0.20mm (= 0.006" - 0.008")


I believe this Yamaha Service Supplement clears up the issue, since this supplement supercedes previous supplements, with a "triangle" figure denoting what items have changed from the previous information, and the triangle is on the valve clearance specs.

 

According to service data in Yamaha parts fiche:

Intake 0.11~0.15mm
Exhaust 0.16~0.20mm

 

I just measured my valve clearances today and also found that they measured about .002 on both intake and exhaust sides. Do I need to adjust these clearances? What causes the gap to get smaller (assuming the engine was built to the suggested specifications)?? I was assuming that the gaps would be wider... Any insight to help me out here?

 

Dpathill....are you sure that's .002 (and is that inches or millimeters)? I mean, that's AWFUL small, as in basically "not there".

Also, what kind of bike do you have?

As valvetrain components wear, the valve clearances can become larger or smaller than specified (original) due to which items are wearing faster. In any case, too tight (too small of a clearance, as you indicate) is a far worse situation that too loose, as valves that are too tight---especially on the exhaust side----not only lead to a lack of performance, but you also run a real risk of burning the valve (the valves are always held a bit "open", off the valve seat, when the valves are much too tight, and the valve-to-valve-seat contact during the valve's "closed" phase is what conducts the heat awat from the valve).

 

general rule of thumb is bucket and shim valvetrain get tighter as they wear,rocker arm valvetrain gets looser as they wear

 

MiCarl and Chacal, I don't want to steer anyone wrong. My specs are from the XJCD which has the base service manual that applies to the 650 Maxim. It also has the service supplement for the XJ650RJ Seca. It gives the intake and exhaust clearances I posted. The clearances you guys posted agree with the base service manual which applies to the Maxim. I don't know if it is a typo on Yamaha's part or is in fact the correct clearance.

 

Forget waiting for the silly "tool' Just pull the cams and then do the shims.

 

Blue....I believe that the specs in the 650 Seca "supplement" manual are INCORRECT........they were later corrected by a Technical Service Bulletin that noted an error in the service manual specs. All of the side cover decals (the "tune up/emissions decal" that is pasted inside of the side covers) from 650 Seca models shows the clearances should be :

Intake: 0.11mm - 0.15mm ( = 0.004" - 0.006")
Exhaust: 0.16mm - 0.20mm (= 0.006" - 0.008")

I think this is a case that the factory service manual was simply wrong, and like so many things that are "wrong at first", that info keeps getting repeated over and over again in other venues, such as the Haynes manual, etc. ONLY if you look at the TSB (which updates and corrects the service manual) or the side cover decal do you find the correct clearances listed.

 

this link above is for a 2 stroke yamaha 2 cyl motor...

 

BlueMaxim; chacal and Carl are correct; the .16~.20 for intake spec was a simple typo in only one book but it got picked up and run with. IT'S WRONG. Yes, it got "propogated" on the XJCD too-- it's still wrong.

Intake specs for the 650 non-YICS motor (and every other airhead XJ) are .11mm~.15mm for the intakes, and .16~.20mm for the exhaust.

 

as a mnemonic device (if anyone cares) I remember "fifteen over and out"
to remind myself that .15mm UP (over) to .2 (the next feeler in my .05 set) is for exhaust (out)
as such intake is "under".