Shimming my valves. Please confirm.

[Incubus]

Because of troublesome low rpm stumble, I pulled the valve cover to check the valves clearances on Succubus, the almost runner who hasn't really been a runner since I rebuilt it a few years back. With several project bikes since, I am better at this stuff than I was when I did Succubus, which is helpful.

It appears that back then I set the valves according to that the clearances should be on a XS11F. However, Succubus has the head from an XJ, so with the bigger valves I guess I should have set the intake clearances tighter. The intake clearances I found, No.1 to No. 4 four, were .012 (.3048MM), .012 (.3048mm), .008 (.2032mm) and .010 (.2540mm).

To get the desired clearances (.004 to .006), by my calculations I need to reshim as such: 1: up four shims sizes; 2: up four shim sizes, three: up two shims sizes; four: up three shim sizes.

I don't know what is in there yet, but am I calculating this right?

Thanks.

Patrick

[natemoen]

God I dread the day I have to figure this out. Unfortunately it is going to happen late this week or next week when I get things put back together....

[jmnjrpa]

Make it simple-

1st- If you need more clearance then reduce shim size and vise versa.

2nd- Each 5 division =.002" - (example 265 is .002 bigger than 260)

3rd -Go with a larger (smaller size) clearance shim rather than a closer as the clearance is reduced over time.

4th- Most shims are marked in 5 division (260,265,270,275, etc...)

5th- Shims that are not marked can be measured with micrometers.

6th -1MM = .03937" (.04 for roundoff)

7th- The shims should be marked 2.65MM but usually just have 265 on them (265 is example)

That help??

[WMarshy]

Save yourself the headache and download the clymer manual with the table from Catatonicbug. It will tell you exactly what clearance you should run and the size shim you should change to to get the correct clearances based on the shim you have in now. No calculations necessary. Or you could do a little searching and you will find a nifty rule of thumb someone made for standard measurements that will tell you how many shims to move up or down.

[DiverRay]

Here is a link to a "tip in progress". I'm not sure if you can view this, so please let me know if you cannot and I'll copy past the important part.
http://www.xs11.com/forum/showthread...lve+shim+guide

[prometheus578]

Jmnjrpa is correct.

Your shim change calculations are also correct.

[WMarshy]

Did not open for me...

Here is a link to a "tip in progress". I'm not sure if you can view this, so please let me know if you cannot and I'll copy past the important part.
http://www.xs11.com/forum/showthread...lve+shim+guide

[planedick]

Confused

Where is it found that the gap in the valve clearance decreases with time? It has been my experience that the opposite is true on my bikes. Each time I have had to do the adjustment I have had to increase the thickness of the shims.

[Incubus]

1. Ray, it doesn't open for me either. Says I don't have enough clearance.

2. Prom! Where have you been. It's been a long time since you commented on one of my posts.

Patrick

[DiverRay]

Sorry, I tried. I know someone had the Yamaha chart on here at one time. As I have a manual or two at home, I just use the chart they have. And yes, I have found that the valve on my bike close up over time, and I need to put in smaller shims.

[bikerphil]

Valve Shim Chart

80 + up intake


exhaust (all years)


78-79 intake

[DiverRay]

Thanks bikerphil! you got me out of a tight spot!
I have these here at home, in my Yamaha manuals. Just didn't have the books with me at work. I'm supposed to be going through five years of particle beam test data, not trying to help with the site!

[prometheus578]

Prom! Where have you been. It's been a long time since you commented on one of my posts.

Hell... not my fault, Incubus. Look how long it's taken you to actually write something interesting!

Truthfully, the way it's been the last few years... by the time I see a thread, several others have already posted good advice and there's very little that I can add.

Where is it found that the gap in the valve clearance decreases with time?

Planedick... the general consensus is that over time, due to the up and down movement of the valves, (valves 'slamming' closed, wear on valve faces and seats, etc) they tend to seat themselves further up in the head. This would have the effect of reducing the gap between shim and cam lobe surface. Now, on other types of valve train mechanisms I've seen increased clearances (due to wear on tappets or adjusting screws), but on "bucket and shim" types, decreased clearances are the norm.

And to further expound upon what Jmnjrpa wrote:
You may occasionally run across shims that say Y265 or 270A, etc. (Just manufacturer's numbers)

Rarely, you might find "half-size" shims... 2.625 which would be a shim between a 260 and a 265. Probably used by racers or other anal-retentive people who really feel that they need their clearance exactly perfect, etc.

The shims that we use have a diameter of 29mm. If you find a local shop that will swap your shims for free make sure that you compare your old ones with the ones that they give you. Some older Suzuki's use 29.5mm shims and you may get one by mistake. They won't fit.