compresion problems

[tony7914]

hey there!
i need some feedback on a problem i'm having with my 79 xs1100 special....when i got the bike it had been sitting for 4-5 years, it had been kept in a garage, and the p.o. at least drained the oil and fuel from the tank (he missed the carb bowls tho.....) after much cleaning on the carbs and doing several of the fixes i have found on this site the one problem i have found that worries me is a problem i'm having with compresion....as i said the bike had sat for some time, before i tryed to turn the moter over i had soaked each cylinder with a good penetrating oil (zep 45) for several days then after some pleading and creative swearing she turned over fine....to make a long story short the number 3 cylinder has some pitting as far as i can see without pulling the head the other cylinders are fine the bike was well maintained as near as i can tell (head in good shape, new cam chain, valves don't leak or stick) i ran a compresion test with the bike cold and the carbs and exaust removed these are the results i got: #1) 160 psi #2) 148 psi #3) 120 psi #4) 160 psi these were the max. presure they would reach i got 155 psi on number 3 after i added some oil to the cylinder and retested......given the price of the big bore kit, what else can i do for this problem? anyone else have this kind of problem?? any tips and ideas would be great!! if i can i would like to get it running as best as i can without having to refinance my house to do it....thanks in advance!!

[TopCatGr58]

Hey there Tony,

Well, increased comp. measurements with added oil points to the rings. But you say you just got the bike and have done this work, but possibly not have ridden it much. Due to the wet clutch, we're kinda limited as to what we could add to the oil to try to help the rings seal better......like Restore and such... which I wouldn't add, but others on the Forum might have and might not have had any trouble with their clutches?!

You may need to drive the bike for a while, like a nice highway trip, not too much intown stuff, and take it easy, easy revs and such, and see if it may be a matter of reseating the rings after you apparently had to break a partial sieze...possibly due to rust in that cylinder.... due to the valves being open during storage!?

After riding it for a few hours, then recheck the compression and see if #3 comes up or not!? If not, then I'll leave it to the REAL GURU's here to provide some more thoughts!

[mitch]

HI!!

Hey Tony , how long have you run the bike now that it is going ?I would put a few 200 or more miles on it then retest the compression. before i got too worried about the compression.It might just suprize you and not need a rebuild. Some people on here swear bye a product called seafoam you might wanna try it . If that doesnt work then i would try a rebuild. Just a thought ,good luck .............MITCH

[sixtysix]

First I would do the compression test correctly as outlined in the manual, engine warm, plugs removed, WOT...that low compression may not look so bad with the engine hot. Even before this I would check valve clearences and make sure they are in spec. Then if you still have a cylinder that is 30 psi lower than the rest, I would.......just forgrtabout it and run it. My #2 cylinder is 120 psi to 150 in the other 3. I have put over 30K miles on it like this so if money is a problem, just forget about for a while and enjoy the ride.

[tony7914]

hey there!!
thanks for all the advice!!! seems like i've got a lot to try yet before i start getting to worried!! i did put sea foam in the oil and the fuel to help break up any deposits in the moter....i haven't riden the bike more that a couple of miles yet due to some irritating carb problems and spooge in the rear master cylinder.......had the cam cover off today to inspect the chain and valve shims, the exaust side shims seemed to be fine, the intake side is tight, my feeler guage only goes as small as .152 mm ( my clymers says intake= .16 to .20 and exaust .21 to .24 ).....i belive the valves are all seating correctly, from what little i can see of them through the spark plug hole, and based on a rather crude leak down test ( i hooked up compressed air to each cylinder at TDC and listened real close to the intake and exaust ports, then timed how long it took for 40 psi to leak out of the cylinder....about 3-4 second each) the carbs on the other hand are giving me fits!!! i've had them apart 3 times now and i'm thinking i got some bad parts ( k&l kits) at this point i'm soaking all the original jets in gunk parts cleaner to remove all the nastys that the P.O. left me with, once they shine again i'm going to reinstall them and see how that goes...( BTW the carbs themselves are clean enough to eat off of, inside and out) i would more than welcome any ideas or sugestions! my old mechanics teacher used to tell me that a good mechanic is one who knows when to ask for help!! thanks again!!

[sixtysix]

The pilot jets in the K&L kits are not right they are too big and the bike will not idle properly. Used the originals or go buy new from Mikuni.