compression

[donebysunday]

Checking my parts bike I get 150 lb compression on 2,3,4 but 180 lb on 1 ?
I noticed the wires are switched, 1 is on 4 and 4 on 1 ?

[jetmechmarty]

Done,
Perhaps a valve adjustment is due?

It's a waste spark system, just like the XS650. It should run fine with #1 & #4 swapped.

[donebysunday]

OK, so if I'm understanding right (?) the valves are closing sooner on that cylinder so they are capturing more air to create the 180 lb of compression.
If those valves wore into the head further they would be opening for a longer period of time ? I'll check and see if it needs more or less thick shims ?
I was thinking carbon ?

[MPittma100]

Compression

When doing a compression test, you should verify that you have a very good battery. It is a good idea to have a battery charger hooked up. There is a possibility that the battery went down some causing the compression to show lower on the latter cylinders. All of your numbers are higher than normal. It is very unusual to have too much compression. It does not appear that you have a problem at all.

A valve adjustment is routine maintenance.

Mike

[TopCatGr58]

Hey Done,

You also didn't specify HOW you did the comp.test, cold or warm...suspecting cold only because you were concerned about the 1-4 plug wires, if you had tried to fire it up you would have found that it would have still fired properly. Did you try a squirt of oil in the cylinder and repeat....if increases can indicate worn rings...but again if cold, would not be as accurate. Yeah, aside from valve clearances being different, it could be carbon build up.....the #1 cylinder and carbs can get more clogged due to bikes being parked on sidestand.

But like has been stated, check/adjust the clearance, clean the carbs and the electrical connectors and fire it up. How long has it been since it has been run? Could also have partially stuck/gummed/varnished rings....a dose of Marvel mystery Oil in the engine prior to the oil/filter change...even if it has old oil in it now...as long as there is enough, the MMO will clean things nicely....NO hard full throttle revs, NO riding the bike, NO stress on the engine, just idle till warmed up, then run the clutch through the gears on the center stand to help clean the clutch plates. Let it run in the engine for about 5-10 minutes with a fan blowing across it, then kill it, drain and continue with the rebuild! And then while it's warm recheck the compression, but if still a little different, don't worry about it, just ride it a few hundred miles and then retest, will probably find it more evened out after engine has reseated and the rings have gotten unstuck.

T.C.

[Radioguylogs]

Probably doubtful that your parts bike has gas in the tank, but if it does, any gas leaking past the petcocks and floats will likely make #1 higher.

I had it on one of my triples when I bought it.

Easy to pull the plug and see if the gas blows out.

[donebysunday]

Yes this was done cold, Slick 50 ONE lube used in testing, battery was at full charge and the high compression cylinder was the last one to be checked. Tank is off being soaked inside with a can of Berryman cleaner and fresh fuel, carbs will be next, can't wait to see what they look like inside ? I was told the bike ran fine last year but by it's looks I doubt that.
Will follow all your advice ! Thank You All !

[BA80]

XSive carbon buildup can cause differences in readings also or even a little more lube in that particular cylinder sitting on top of the piston.