Compression question

[CUBuffs]

I need a little help with the results of my compression test please.

#1---160
#2---60
#3---130
#4---150

I also put a little oil (about a teaspoon) in #2 and checked again, it went up to 75 psi.

The bike only has 14K miles on it. I don't know the status of the valves. How do I troubleshoot the #2 cylinder? Thanks.

[TopCatGr58]

Hey CUBuffs,

Have you checked your valve clearances?? I'd start there. IF they are within spec, then could be corrosion/carbon built up between the valve and seat, but could also be a partially stuck piston ring?! You could squirt a touch of MMO into # 2 and let it sit for a day, then turn the engine over a few times to pump out remaining MMO although hopefully you didn't put that much in. What little that would have leaked past the rings into the oil shouldn't cause any problems either. You may need to run the engine on the highway at full operating temps to help unstick that RING, and may also help to burn off the carbon from around the valve. Put a bit of SeaFoam in the gas tank prior to running it!

Then, after running 50-100 miles on it, recheck the COMPRESSION with the engine WARM! Good Luck!

T.C.

[CUBuffs]

Thanks Top Cat,

Is that Marvel Mystery Oil (MMO) and is there a posted procedure for checking valve clearances? I have not done that before.

[CUBuffs]

Hey TopCat or anybody else who knows,

I got some MMO. How much should I squirt down the #2 cylinder?

[DiverRay]

You should only need about three teaspoons of MMO. Just squirt it in, and as TC said, let it set for about 24 hours, or more. Then put some seafoam or berryman's B12 into the tank, and ride.
I would check the valve clearance on #2 before starting.
Ray

[TopCatGr58]

Valve Clearance check technique!

Hey CUBuffs,

Well, I was surprised to not see a tech tip on how to check the valve clearances!?

Main thing is to take the valve cover off. Then you'll see the cams and the lifter/buckets with the shims on them. Rotate the engine several times first, to compress any residual oil that may be under the shims. Then align the cams so that the pointy end of the cam lobe is pointing straight away from the bucket. Then use a good quality feeler gauge and measure the gap. Have a pad with 8 circles drawn, 4 intake, 4 exhaust, labelled, and then write down the clearances. Hopefully they will be within spec.!?

IF NOT, then the fun begins. Hopefully you have the required Motion Pro valve lifter compressor tool, possibly modified since some don't work properly straight from the factory!? You rotate the engine so that the cam is now compressing the lifter fully, then you position the lifter hold down tool, and then you can rotate "JUST A LITTLE" the cam so that it's not pressing on the shim. Then remove the shim, record the thickness value etched on it's underside, and then put it back in, and continue until you have ALL of your Out Of Spec valves shims sizes recorded, but since you're in there, might as well record them all.

Now, IF you have more than one shim out of spec, review the shim sizes for the ones out of spec, and see if you could obtain the correct spec by swapping any of them with the others that are out of spec!? This way, you can possibly cut down on the total number of shims you would need to replace.

Then with any of the shims you still need to replace, find a local Shop, dealer, even IIRC Kaw shop, our shims are similar/standard sizes, and you may be able to swap them out with the shop for the sizes you need!? IF not, then they are still available from Yamaha! Replace shims, and then rotate and remeasure clearances again for thoroughness! Viola, you're done! Uh, well, except for putting the valve cover back on!
T.C.

[CUBuffs]

Thanks TC,

Should I expect to replace the valve cover gasket when I do this?

[TopCatGr58]

Probably,

Lots of heat up there, cooks the gasket nicely, and it usually doesn't survive the separation technique. It's made of a bit more stiffer material than the other gaskets, and is a bit more complex shape, so it's more difficult(but not impossible) to cut out your own, vs. buying a premade one from PNM or Local Dealer!? Have been suggestions of using Pam, or non hardening gasket sealer on at least one side of new gasket to make removal and reinstall easier the next time with a better chance of re-using the old gasket!? Inspect your rubber halfmoons, cause if they look like they are hardened and cracking, you can get replacements from PNM as well as the gasket, and Yamabond #4, might find enough things to order to meet the $35.00 minimum Free SHipping limit!?
T.C.

[CUBuffs]

Here are my clearances,

Exhaust

#1 .178mm
#2 .305mm
#3 .178mm
#4 .152mm

Intake

#1 .102mm
#2 .102mm
#3 .102mm
#4 .102mm

Does this account for the problem with the #2 cylinder?

[trbig]

It's a tough call. If the valve isn't seating all the way, you could burn a valve by running it. If it's the sticky rings, running it is the answer. Leakdown test would be my starting point if you have the valve cover off already.

Tod

[CUBuffs]

Pardon my ignorance but what is a leakdown test and how is it done?

[randy]

cubuffs,

I agree with Tod, while a ring will loosen itself up over time, a burnt valve only gets worse with wear. Looks like the E valve on #2 is burnt or crusty, on the rest of the valves, you need shims anyway. you may be looking at a valve re-grind to clean everything up and at least get the valves back to spec. So, pull the head and go for it.

Remember, there's always plenty of help here. just ask. if you really want a leakdown test, any competent (?) shop can do it.

[John]

A leak down test is done by applying low pressure air to the cylinder, with the piston at the bottom of it's travel. If you hear air escaping, either through the airbox, exhaust or the oil filler hole, that will locate the compression loss. You can do this with a compression gauge that has a detachable end, and use an air compressor. The air coupler is usually the same on both items, the air hose and the tester hose. Use low pressure to perform the test. There may be a tech tip here on the subject.

[CUBuffs]

OK, if I did this right I rotated the cam so the lobe was forcing the lifter down as far as it will travel. It sounded like a little air was escaping through the muffler. I decided to try the 1 and 3 valves also and I got the same noise (through the muffler) from them but the compression on them was 160 and 130 respectively. Any thoughts?

[TopCatGr58]

Hey CUBuffs,

What's supposed to be at the bottom is the PISTON, not the cam lobe! And the piston should be on the POWER stroke, with both lobes for that cylinder pointing up, to try to close the valves as much as possible, that way the cylinder is essentially sealed.

Then when you add air thru the spark plug hole, you may hear it out of the intake or exhaust, which would be leaky valves, or out of the oil filler tube, which could mean worn rings.

Sorry, you need to do it again!
T.C.