Tuning Carbs

Ok so first things first:

I have measured my valve clearances and here is what I have:

(when veiwing the engine from the front of the bike)

Intake
.007 - .003 - .006 - .007
270 - 275 - 270 - 275

Exhaust
.009 - .006 - .007 - .007
265 - 265 - 265 - 265

Am I safe to assume that based on these measurements and the valve shim chart found here:
http://xjbikes.com/Forums/viewtopic/t=1 ... chart.html

I would be putting the following shims in their place:

Intake
275 - 285 - 275 - 280

Exhaust
275 - 275 - 275 - 275


Someone please correct me if I am wrong

Thanks

 

OK, sorry but you're wrong.

You don't install THICKER shims, you install THINNER ones to increase the clearances. I suspect you're reading the chart wrong.

Are those "American" (Imperial) measurements, or metric? Clarify, and I'll help you figure out the correct ones.

 

Sorry I did not include that those are in (inches)These are the numbers on the feeler gauges, Mine includes Standard and those odd ball Metric values

Intake
.007 - .003 - .006 - .007 - inches
.178 - .076 - .152 - .178 - MM
Shims installed
270 - 275 - 270 - 275

Exhaust
.009 - .006 - .007 - .007 - inches
.229 - .152 - .178 - .178 - MM
Shims installed
265 - 265 - 265 - 265

How is the chart read?

 

Fitz - I think you have our friend Libertas confused now because those measurements are in inches and that being the case - the only one he really needs to change is the second intake shim. The rest of them I would leave alone - IF - those measurements are accurate. The thing that has me doubting their accuracy is that they seem to good to be true unless someone has just completed an airhead check on that bike recently.

Granted, the gap on the first and fourth intake and the first exhaust are a bit on the loose side but not so much that I would bother changing them - better a bit loose than a bit tight.

Libertas - please verify that those measurements that you have stated are in inches. If so then only the second intake needs your attention.

 

Libertas - you need a 267 (or whatever is closest) on the second intake.

 

I agree, but only to a point. And since those are Imperial measurements, you were reading the chart correctly.

However, there is only one size shim, and one size alone, that will put a valve truly in spec.

Intakes 1, 3 and 4 need attention as well; although I agree that #3 is probably OK, 1 and 4 are loose. Intake #2 is too tight.

Exhaust #1 is loose, and exhaust #2 is too tight.

I'd put them all IN SPEC. And I too agree that somebody must have done it recently, although not 100% correctly.

 

Libertas, I apologize for stealing your thread. rather than starting another valve clearance thread thought I'd post my results and see what others think. thanks in advance!

EXHAUST going from left to right (1-4) in metric (mm)
.203 .152 .178 .203
260 260 245 260


INTAKE going from left to right (1-4) in metric (mm)
.178 .152 .178 .152
260 260 270 275



this is what I think needs replaced.
#2 exhaust with a 255
#1 intake with a 265
#3 intake with a 275

whaddya think about #1 & 4 on exhaust? they look to be right on the verge of either switching with 265 but I'm afraid if I do then the clearance will be too tight. anyone got extras they'd like to swap with me? I have a few bigger ones (270's thru 285's). where's that shim pool?

 

Bigfitz

So in the instance of the valve being too loose, you would put in a THICKER shim?

To get everything in spec I have

In
275 - 265 - 270 - 280

Ex
270 - 260 - 265 - 265

Already have: 275, 265, 270, 270, 265, 265

Need: 260, 280

Anyone want to trade my 265,275 for their 260,280?

 

yes, in the case of too loose, you do put in a thicker shim. Usually, they're too tight, necessitating a thinner shim.

XJ4Ever carries aftermarket shims for less than half of what Yamaha gets; and then you don't have to chance running used shims.

moellear, I'd leave exhausts #1 and #4 and keep an eye on them. They should only get tighter.

It appears as though you guys are both using American feelers with metric equivalents rather than a "true" metric feeler gauge, which adds to the "conversion confusion."

This is much easier with a METRIC metric feeler.

 

Libertas - The valve clearance specs in my book for the 650's are .006-.008" for both the intake and exhaust. That being the case, only the number two intake and the number one exhaust are out of spec. So you need a 265 for intake number two and 270 for exhaust number one. That will put you at .007" for both of them. The rest of them are IN spec.

 

Libertas - I have the following extra shims on hand: 255, 285, 270, 260, 285, 270, 285

I need a 265 and 275. If you and anyone else is interested for swapping with what I need let me know!

 

moellear - where're you at in Ohio? I'm in LaGrange 44050. Based on your numbers and what shims are available at this time - I wouldn't change a thing. You're golden.

 

That is because your book (factory OR Haynes) contains a MISPRINT.

INTAKE SPEC IS .11mm~.15mm (.004"-006" "equivalent".) That misprint is a well-known mistake.

Oh, and .004" is actually .0102mm which is tight. Again, another reason to use a true metric feeler.

 

Hmmm - how do we know of this "well-known" misprint? Fitz YOU KNOW I think you should be awarded a Phd in xj technology! You have been more help to me and the many xjers on this site than you will probably ever know in your lifetime!! Thank you.

I'm just tryin to be helpful and keep guys out of trouble. Measuring stuff is what I do for a living. It absolutely does not matter if we measure in mm or inches. As long as we do it accurately. I do it all the time every day - inches to mm and mm to inches. And btw, .004" is not .0102mm -it's .1016mm. No zero to the right of the decimal. At this time of day our eyes get weary.

Please take no offense from me. I am in your debt and in constant need of your help and advice.

 

Fitz, are exhaust measurements correct in the Haynes manual? Going to be doing this soon, want to make sure I get everything right the first time.

 

Celina. its right next to one of the largest man-made lakes in the country and has had algae problems for a year or so now. last year at this time the blue aglae was so concentrated fish were dying and people got sick from breathing the surrounding air nearby. gross stuff

anyhow; anyone have spare shims they'd like to trade?? my spares are listed in my previous response. (I plan to be gone for the wknd so I won't respond til sunday sometime)

 

Yep. The error occurred in one of the factory 650 books, (the 650 Seca supplement, the "base" book is correct) and got picked up by the Haynes. It was simply a matter of listing the exhaust specs for both intake and exhaust; a typo.

Specs are .11mm~.15mm for intake; and .16mm~.20mm for exhaust.

 

ahem..

anyone have spare shims or know of someone else to swap?? I'd like to get a 265 nonetheless...