compession test results

[audijunky]

the results are in , my compressions are as follows
#1 137.5,
#2 150,
#3 155,
#4 110.
Am I wrong to assume that #4 is the only low value? Are the rest decent? How long do I wait after putting oil in the cylinder before I try again? And if the oil doesnt increase the compression what is the next step?
Thanks in advance

[mro]

And if the oil doesnt increase the compression what is the next step?

Oil will increase pressure if rings are leaking, otherwise it's valves.

Sorry, don't remember.......are you just getting this bike running from it sitting for awhile? If so would ride it for about 500 miles and check it agin.

If valves leaking, off with the head, lap valves, new seals etc.....


mro

[DiverRay]

Audijunky,
I would put a little Berryman's B12 Chemtool in #4, about 3 oz. and then let it set for 30 minutes. after that put a little oil in #4, and then do a compression test on it. If it brings it up to 135 or 140, the rings are leaking. You can put a little ATF into the #4 cyl, let it set for a day, and then crank the engine over. The ATF has a LOT of anti foam and anti rust additives, and may help out.
As mro, our new GURU said, drive it for about 500 miles and then retest BEFORE you decide what to do. Sometimes the rings can be stuck, and once the bike is running again, they free up.
Ray

[audijunky]

thanks fellas,
I know the rings aren't stuck cause I had the head off already to do a paint job. What is ATF? Where can I get berrymans B12? Is it possible to have reinstalled the head with the ring notches(for lack of a better term) lined up with each other ? could this cause low compression? I am not sure how they were aligned , I didnt spin them or anything, just squezzed them to fit them back into the cylinder. Allright, so as of right now when I get home I am going to do another compression test with oil in #4, and #1. See if the compression increases. If it does I have bad rings? Or should I ride it for a while first? It has only run about 30 minutes in the last ten years. But like I said I already have taken the head off and cleaned out the cylinders, cleaned out the combustion chamber, and the top of the pistons. Which route should I take?
Thanks

[randy]

audijunky;

it IS possible to have lined up the ring gaps, and, yes, that would cause poor compression. if that is what happened, riding it won't fix it, you'll have to re-index the gaps (remove cyl's). the gaps should be 120 degrees apart.

BTW,

You wrote that you "cleaned out" the cylinders, by what method? What did you find that had to be cleaned out? Did you use abraisives?

[strom]

Tested compression on my 1.1 the other day:

1: 9.5
2: 9.3
3: 9.7
4: 8.0

Same thing... it sat for a while.... sprayed it a few times with WD40, turned it over a bit, repeat... left it to soak in WD for a few days while doing the above. That was the result. Will start it and ride for a few days and see.

LP

[79XS11F]

A more important issue is the difference between cylinders. Check you manul. It stats the min and max readings and the max difference between them.
Spec = 142 PSI
Min = 128 PSI
Max = 156 PSI
Max difference between and number = 14 PSI.

This test is done with the enging warm and the throttle WIDE open.
Rob

[audijunky]

hey Randy,
I didn't use chemicals, but htere was a ton of cabon build up in the cmbustion chamber, on the valves, and on the piston heads. Not sure if it was a good Idea or not but I used a wire brush on a drill to clean off the carbon. The brush was a softer type and didn't seem to scar the metal.

[randy]

audijunky;


I asked because you wrote that you cleaned out the CYLINDERS and I was wondering if maybe you scored the walls causing your sealing problem.

[mro]

Took cylinders off to paint em?????

that's XSive



mro

[audijunky]

Let me clarify(and possibly use the right terminology) I pulled off the top end of the motor. Seperating the head from the cylinder housing(whatever that is called) Only thing that I put in the cylinders was oil. they were in really good shape, nice and smooth. The top of the piston heads and the combustion chamber were covered with carbon so that is what I cleaned off.Around the valves also. I didnt paint the cylinders while this stuff was apart I CLEANED and CLEANED and CLEANed then painted the outside of the head and Cylinder housing.

When I did the first compression test I didnt hold the throttle open. Has anyone else not done this and has it made much of a difference?
Heres a pic of what I did while the top end was off

[TopCatGr58]

Hey Steve,

Just having put the jugs back on, the rings may not have reseated properly, so you'll probably need to put a few hundred miles on it first. ATF is Automatic Transmission Fluid! And yes, folks have done a Comp test with throttle closed, and got low or irregular readings, repeated with WOT and got much better and even readings, so it DOES make a difference!!

You've got it rebuilt, get on it and ride it and enjoy it for a while first, and then when winter really hits, then do your diagnostics!
T.C.

[79XS11F]

Originally posted by audijunky
hey Randy,
I didn't use chemicals, but htere was a ton of cabon build up in the cmbustion chamber, on the valves, and on the piston heads. Not sure if it was a good Idea or not but I used a wire brush on a drill to clean off the carbon. The brush was a softer type and didn't seem to scar the metal.

Did you remove the carbon ring at the top of the cylinders? If so that could be part of your issues and the bike is going to burn oil even if compression is good. That carbon ring that develops at the very top of the cylinders is not to be removed, as per manuals, unless new rings and a hone is carried out.
Rob

[audijunky]

Hey Fellas,
I did not remuve the carbon rings from the top of the jugs. For the first time in my life I actually read something before I started to do something. Thanks for the heads up any way. I think I'll take TCs advice. SWtill got some fabricating to do though, not going to be riding to much except around the neighborhood. I actually took it out for a spin for the first time yesterday. I need to do some carb tuning.
How does 145 main jets and 45 pilot jets sound for pod filters and open header(no muffler) but I do have 1 and 3/4 pipe going back to the rear axle? I saw the jetting gude and it looks like I should be running 147.5 mains w/45 pilots but I think I'll try the 145s first(cause they are already in)
Thanks for the replys guys I would be no where close to this with out the expert advice found on this site. Ill post some pics of the bobber pretty soon.

[mro]

straight pipes?

Should you have trouble tunning carbs, (can be difficult w/o back pressure) trikenel?? had a good mod.

Weld a washer to a 1/4 inch dia. bolt, drill hole in bottom of pipe, and install. Washer can be turned allowing more or less restriction for back pressure


mro