Very low compression. 700x

Compression test results:
Pistons 1 and 2 move the needle but won't maintain pressure at gage. Pistons 3 and 4 barely move the needle. I had intake wide open (no carbs).
Any ideas?

 

Recheck with a different compression gauge.

Also, please keep everything in one thread so we can have continuity and context about the machine.

 

^^^^+1 what Kmoe said ...have you check valve clearance yet?

 

I should have added , is your battery fully charged , this can also appear as low compression because engine is not spinning fast enough. Also ensure all the plugs are out .

 

Just recharged the battery, read above 12v with my fluke. I checked valves but my gage is too thick for intake side, exhaust readings are ok. Timing set ok too.
I dont have access to another pressure gage, but there is no vacuum at the intake side for cylinders 3 and 4. Feels like the compression is gradually lost from 1 to 4.
At this point I'm hoping for something in common, like head gasket.

 

Sounds like a junk gauge--- where did you get it, and what brand?

 

You can rent one at autozone...or buy one for like 25$

 

Is the cam timing correct? If it's way out you may get no compression. Intake valves close when piston is 1/4 way down or exhaust opens just after top dead center.

 

I got my compression tester from ebay. The readings match the status of the spark plugs, #3 and 4 looked almost new, carburators 3 and 4 were very nasty. I believe due to a vac leak we stopped sucking fuel and the fuel plugged the carbs, I will put the bike together and give it a shot, but if no luck, I will remove the head, i hope is just a gasket.

 

Timing is ok. The shaft dots are up when I line up marks at igniter

 

As long as #1 cylinder is on tdc with both valves closed. A leak down gauge will tell you the whole story. Worth getting hold of one to tell you if any valves burnt or holes in pistons.

 

Do not remove the head yet!!!!
Either borrow a compression gauge from an auto parts store (they all have tool lending programs), or use your gauge to check compression on a known-good engine.
Make sure that you e-bay gauge is good before taking things apart (because odds are that your gauge is faulty).

 

I really hope so k-moe! I will follow your advice.

 

That says a lot......

Even a blown engine usually has some compression. For the needles to barely move or not move at all, you'd have to have holes almost the size of the spark plugs...... Or have the plugs out. Get a KNOWN TO BE GOOD gauge

 

Can you put your thumb over the spark plug hole ...crank over engine does it push your thumb off the hole..then you have compression ....but do as we avised get another gauge.