Burtnt valve? Valve clearances? Shim trade anyone?

Looking for someone who has valve shims to trade - mine are very tight (and I may have a burnt valve).

In mm.......1......2.....3........4
Exhaust /0.13/ 0.22/ 0.15/ 0.13
Installed /250/ 250/ 260/ 260
Intake /0.08 /0.105 /0.08 /0.13
Installed /275 /270 /265 /270

According to these calculations, I should replace them with:
Needed 1........2.....3......4
Exhaust /245 /255 /255 /255
Intake /270 /265 /260 /ok

Which means I can move a few shims, but will need:
245, 255, 255, 255

In addition, I will have to trade:
250, 250, 260, 275

One thing that came to mind is if it is safe to roll the cams over with no shims in the buckets? I did it once with no problems, but that does not make it a wise choice.

Additionally, what are the diagnostic procedures of a burnt valve? I did the best job I could to scour the net for a video or description, but the consensus was "you don't want this to happen to you".

I experienced something very similar to what you see in this car video:Burnt Valve

The strange thing is, I put my valve in-spec about 2500 miles ago (or did to the best of my abilities). Very evidently that is not the case.

What surprises me, is that the bike would idle great, and even run up to 5k RPM on choke very smoothly, but when just the throttle was used even in neutral, I would get the terrible rattle sound as in the video, and eventually engine died.

Assuming it is a burnt valve and not the throttle shaft seals (which I am rebuilding shortly), how do I diagnose which valve/s and what should I prepare to repair them?

 

If you are checking for a burnt valve, just do a compression test.

 

Hello,

Please check calculations carefully to choose the right shim --- but --- having said that --- this is a case where I don't know what I would do regarding number 2 Intake?

Don't know how he measures to the thousandths on number two at 0.105mm, but, round it up to .11 as shown and it's out, and rounding it down to .10 puts it in spec for the 265

http://www.xjbikes.com/Forums/viewtopic/t=35302.html

...

 

But he put up his calculations and at first glance they seem spot on?

 

I have two sets of feeler guages - metric and standard. One of the standard guages is something like .025 mm, pairing this with a .08mm metric, I determined that it was at .105.
That being said, I would rather be on the loose end, right? Because it will do nothing but tighten if anything.

 

Thanks I see ... What does the manual say about valve-to-valve gap differences?

I'm sorry I'm of no help on whether or not you have a burnt valve.

 

Run compression test with all plugs out. If there is a low cylinder add a little oil to it . If it comes up it is rings. If it stays the same , it is a bad valve. Use the five count as you spin the engine over for test. They cylinders should basically within about 14 PSI of one another to be OK. Pretty easy test & straight forward. Any questions just message me.

 

-rolling the cams over with no shims is taking a chance on the edge of the bucket chewing up/getting chewed by the edge of the lobe, be very careful.

-use metric feelers and metric numbers, and don't get too "minute." There is only one shim and one shim alone that will put any particular valve IN SPEC; that's the one you go with.

-If using metric feelers and working with metric numbers, choosing new shims is simple enough to do in your head, no auto-calculating spreadsheet required.

-GET THE VALVES IN SPEC then do your compression test lest you freak yourself out unnecessarily.

 

Yes .... and no ... you do a compression test first on any unknown condition to get a general idea where the problems (if any) might be ... worn or broken rings, holed pistons, glazed cylinders, burnt or leaking valves, or valves that are "riding" because of insufficient clearance in the valve train.

The wet and dry compression test sequence will tell you if you have a valve problem ... if so, set your clearances and then see if that problem goes away ... you then know whether you have a leaking valve or just an out of spec condition.

Draw your conclusions logically at each step from what you find and proceed from there with that knowledge in hand.

 

I was more worried about the "lest you freak yourself out unnecessarily" part. Calm, logical troubleshooting is not the forte of most neophyte mechanics in a panic about their new charge. Valves as tight as OPs will throw off a compression test.

You are correct of course, repeated tests after each step will give a better understanding of what's going on. People tend to treat valve adjustment as such a big deal, that we've had more than one member ready to pull a motor apart for a couple of soft readings when he'd never gotten the valves in spec.

 

In addition - The throttle is held open and the battery should be on a charger, or boosted from a (non-running) car.

I caught a valve going tight on my Seca 750. I noticed a loss of performance, found a CYL at 100 PSI, and a valve at 0.038 MM.

I didn't burn a valve. "Splazoid's" tightest spec is more than double that.

No freaking out needed 8)

 

And of course therein lies the trouble. Most who sit on the sidelines see only wrench twiddling and think that is all there is to this mechanical repair caper. But watch any skilled mechanic at work and you will see most of what he is doing is thinking ... testing one hypothesis after another, till he finds the culprit ... this is detective work

 

I would suppose that means I need to reassemble and reinstall my carbs to get good compression numbers :wink:

Thanks for the help guys - I was not looking forward to removing the head to diagnose the issue - Carb parts on their way from Chacal, and a compression tester ready to go.

 

no no no.

You can run a compression test with no carbs on the motor; saves having to hold the throttle open. CARBS don't affect compression numbers unless you don't hold the throttle WFO.

 

Oh, then in that case I'll have compression numbers for you guys to help me analyze tomorrow night. Besides having the plugs out, battery being boosted and a 5 second crank over, what else do I need to do?
I read somewhere that I should unplug the coils so that there is NO spark power anywhere?

 

Unplug the TCI, that'll take care of your coil/spark when compression testing

 

Alrighty - Compression numbers, with valves still out of spec for the time being (Shims on order from Chacal - what a great guy!).

Cylinders 1,2,3 at 120PSI after 5 cranks.
Cylinder 4 came to 130 PSI - not very concerning?

I just bought an inline spark plug tester which I'm going to try after a beer break yet today.

Could deteriorated throttle shaft seals + mega out of spec valves cause the performance issue I described?

What I found intersting was that the bike would rev up to 5k RPM's using the choke very smoothly, but stumbled when I used the throttle, which is what clued me to re-do the throttle shaft seals (vacuum leak?).

 

Sync and float levels could have caused it too. The Mikunis reward precision.

Your difference between cylinders was less than 10%, you're fine. Those numbers are right on the money for a healthy 550, but I'll bet getting the valves in spec brings them up closer to 130. ("Standard" is 121 for the 550s.)

Check 'em again after the valves are in spec; I think you'll be surprised.

No freaking out required. Proceed.

 

Thanks again for your marvelous expertise, fitz - Most appreciated.

Yeah, the compression numbers are very comforting, but on the other hand, it would have been nice to have a confirmed diagnosis. Lets hope the valve shims and carbs will make things right - updates to come next week once I get the parts from Chacal.

 

You can leave the Coils Plugged-in.
Un-plug the Igniter (TCI/Blackbox).

A Remote Starter Switch from the +12V (HOT) side of the Battery to the Power Lug on the Starter will let you not have to reach for the Starter Button while doing the Test.

Especially on Sale!

http://www.sears.com/shc/s/p_10153_1260 ... ockType=G2