Compression question

[CUBuffs]

May have the solution

Hey Gents,

I took the tank cap off and apart. On my cap the vent hole doesn't line up with the hole on the back side. There was a bunch of black powder or something covering the backside hole.

I took the cap off my xs750 and put it on the xs11, knowing that it was a good cap, then drove around town putting on about 10 miles. It didn't crap out once. So I'm cleaning up the old cap vent and going to see what happens. If that doesn't work I'll probably buy a new cap.

Did develop a new problem though. My rear brakes are apparently sticking. When I pulled into my driveway the rotor, pads, & calipers were smokin'. Wasn't more than 2 weeks ago I changed the brake fluid on both front and back.

[John]

Check the adjustment of the rear brake push rod. It may be too long, holding pressure in the system.

[CUBuffs]

Thanks for the tip John. What is the push rod?

[TopCatGr58]

Follow the foot brake lever, into the shaft holder, on the other end is the pushrod attached to the lever, it pushes up into the MC which pumps and actuates the brakes, similar to the piston screw on the handlebar MC lever! THere is a threaded nut and shaft, and you can adjust the length to lessen it's pressure. But you'll want to take the foot lever apart, pull the shaft out, and clean and regrease it. Sometimes, it gets rusty, and after depressing, it won't necessarily return to it's original NO PRESSURE position, too much resistance from rust, and the spring isn't strong enough to fight that resistance!
T.C.

[CUBuffs]

Thanks TC,

That must be what the Clymer book calls the Brake rod. If that checks out ok I guess I'll be ordering a caliper rebuild kit.

[prometheus578]

"Nothing worse than having to qoute oneself'

mine has started acting the same way. Shall unlock the gas cap and ride to work like that tomorrow and see if that cures it.

Plugged cap vent, me arse!
It seems that I had forgotten that I had rejetted in December and had then parked the bike until a week ago. Seems that I had also forgotten that by installing larger jets, my fuel consumption would increase. And, as I'm one that watches the trip odometer to determine when I need to get fuel, I just couldn't believe that that I was out of gas. Well, Duh! My bike was running like crap 'cause I was running out of fuel. Switched it to reserve, problem solved.
Actually, the only thing worse than quoting oneself, is to put down in print the many stupid things that one does!
What a "fuel" I've been.

[CUBuffs]

New compression check

It's been a couple weeks and 88 miles since I had to put Deep Creep in the #2 cylinder. Initially #2 only had 60 psi and then I checked again at about 50 miles with the psi showing about 98. Today's comp check showed another gain in #2 which shows 125 psi. Here is the entire lineup:

#1 --- 160
#2 --- 125
#3 --- 150
#4 --- 160

Clymer's says if there is more than a 10% difference between cylinders that I should check the valves.

Should I just continue on as is? Opinions are welcomed.

[DiverRay]

If you have not checked valve clearance, do so. If the valve clearance is within spec, then on to plan B.
pour about 1 teaspoon of oil in #2, turn over 1 revolution by hand, and then retest. If this does not bring up the compression, then you will probably have to pull the head to see what is going on.
Ray

[CUBuffs]

Ray,

I did that test back when it only had 60 psi and it brought the psi up to 75.

[DiverRay]

Then you probably have a problem in that hole. My guess would be a score in the liner, or a broken ring, #2. I would try it again, just to see how much more you can get now. You can also have someone follow you, and look for blue smoke out of the left pipe. If it's the piston, you should see it when you accelerate. If it shows mostly when you slow down, it's probably a bad valve seal.
My guess is on the #2 compressin ring...
Ray

[randy]

If it's the piston, you should see it when you accelerate. If it shows mostly when you slow down, it's probably a bad valve seal.

Gee,

I learned it the other way 'round:

When accellerating, high pressures in the combustion chamber keep oil from getting past the rings, so oil must be coming from the valve seals.

When decellerating, high vacuum in the cumbustion chamber sucks oil in past the rings.

[DiverRay]

Yeah Randy, I'm getting old. (CRS disease)
Just rub it in. I still think he may have a problem with the #2 ring, because of the readings he's had.
Ray

[randy]

Diverray,

No rub intended. Wanted to double-check my info, too! Like you said, valve clearance should be checked, that may do a lot for him.

CUBuffs,

When you do the compression test, do it warm, all plugs out and throttle wide open.