Poor compression

[Guest]

Bike model - '83 Katana 750, mileage at 35K.

Sat in outside storage for 4 years. I did a compression test to reveal the following:

1. 65 lbs
2. 35 lbs
3. 70 lbs
4. 40 lbs

It has no mechanical history but was terribly dirty from grease and road dust so I doubt anyone has even undertaken a valve adjustment.

Any ideas why such low numbers?

If I can get it to start, what are the chances that things will free up?

[rustybronco]

I doubt anyone has even undertaken a valve adjustment.

Any ideas why such low numbers?

If I can get it to start, what are the chances that things will free up?

1. Valve adjustment, stuck rings, rusty bore ect.

2. Very good

2 T's are vent lines...

don't part it!

[bobthebiker88]

valves are likely. free to check those, and an easy fix if indeed the culprit of such sickly numbers. pull the plugs and put some ATF/Acetone mixed at 50/50 into each cylinder, it might help dissolve whatever may be keeping th rings from sealing.

[spyug]

I would agree with the guys. Pour the ATF/Acetone to it for a day or two and while waiting check the valves.

Once you know the valves are right change the oil and plugs and see if it will fire up. If you can get it to run for a while and warm up I'm sure your numbers will come up.

My GS had sat for 7 years before I got it and the"cold" compression numbers were in the 60/70s. Once it started and ran for a while the numbers jumped into the 150+ and its been running well for 4 years now.

I think it will come back to life, these are tough bikes.

Good luck and let us know how it goes.

cheers,
Spyug

[rapidray]

Put in an 1100 or 1150 motor & be done with it! Much more fun with the bigger motor & you lose the plain bearing failure issues! I have MANY motors if you need one. Ray.

[nastyjones]

I've used the ATF/Acetone on my 83 750E & it unlocked my seized engine. That stuff is magic.

Paul