Compression test with plugged carbs?

[Anonymous]

I haven't cleaned my carbs yet.... will that screw up the compression test results?

[daveo]

you need to hold the throttle all the way open when testing but the grunge shouldn't affect that

[Anonymous]

When I switch the gas tank to PRI, I get gas spilling out... it looks like it's backing up out of the carbs...

[Anonymous]

Sounds like your floats are not closing,it shouldn't be running out like that. Looks like an overhaul is on your to do list.

[Billy Ricks]

If you have CVs you'll have to physically get the slides out of the way in addition to opening the throttle. Besides stuck float needles you may have dried out o-rings on the float needle valves.

[Anonymous]

I think I'm going to rebuild/clean the carbs first then. Otherwise It sound like the test won't work.

[Billy Ricks]

You're going to get the same compression readings regardless of whether the carbs are clean or not. You just have to have a large enough throttle opening to let the cylinders breath.

[lhanscom]

If you're going to clean the carbs anyway, just do the compression test with the Carbs off the bike. Then you don't have to worry about the throttle opening. I don't think it would cause any problems.

[Anonymous]

Can I do it with the tank off too?

[lhanscom]

Yes.

[Billy Ricks]

When you do your compression test if the numbers aren't up to spec squirt a little oil down each cylinder through the plug hole. If compression goes up then you have worn rings. If it doesn't go up then a valve job is in order. As Luke pointed out, if you are going to pull the carbs for cleaning anyway that's a good time to check compression.