compression test

hello everybody newbie here OK I have A 1985 vf700f interceptor just recently had cylinders
honed and put in new rings my question is
how long do i Waite to do a compression test because there doesn't seem to be any improvement
with new ring in and was told if i do one now it will be a false reading your thoughts .thank you.

 

compression well below specs valves i checked while waiting for parts they are fine
did find some high spots after honing must need to be re-bored then with over sized
piston and rings problem there i cannot find any ware for that model can I use over sized
from the 86/87 vfr700f1.is there a difference in height and length?

 

test was performed cold and #s are
L/f 82
L/r 55
r/f 148
r/r 125
and threw them in and called it good because I could not find over sized piston and rings.
and could not find answers to see if the 86/87 vfr700f1 pistons would work.
valve are adjusted to .006 spec.

 

will try to do that I could see 1 bad cylinder but 2
even if those two cylinders were tapered putting new
rings in them will not help because if i re-hone it will be over sized
and no over sized parts available .

 

OK ware do i find gadget that goes in spark plug hole so i can hook up
air compressor to do test?
I did check valves while waiting for parts took carburetor cleaner and sprayed
in intake and exhaust ports waited and seen no leaks.
is there a way i could be 180 degrees off on valve timing?if so would that cause my problem?

 

I take it you honed all cylinders? Did you use a "honing" machine or a hand held type? If it was a honing machine with a good machinist the bores should be straight. Were they mic'd with a bore gauge?

"did find some high spots after honing must need to be re-bored then with over sized
piston and rings problem there i cannot find any ware for that model can I use over sized"

Uh? High spots? Dingle ball hone? (I'm assuming you oiled the rings and pistons prior to install) Your low readings may be new rings on old wall and will have to seat themselves. If they can, because of the high spots.? How did you find the high spots? Use a bore gauge? I doubt even if you aligned all the ring grooves in the same line the compression wouldn't be that low. Can't be a cam(s) because they are half of different banks.

"I did check valves while waiting for parts took carburetor cleaner and sprayed
in intake and exhaust ports waited and seen no leaks."

How did you check for valve leakage when you can't see the valve seat? Just by checking the level? Hope you sprayed oil back in the cylinder after putting carb cleaner in it.

You can make your own adapter for putting air in to the cylinder. Take an old spark plug and knock the porcelain center out (easier said than done) and braze/weld an air tip onto it. Sometimes a male air tip threads will just thread into the plug. You can use JB Weld on the threads and leave it set overnight. Works same as welding it. Or go to NAPA or the like and buy one. When you put air in to the cylinder back off your valve adjusters all the way to make sure the valves are seated.

You may want to contact Dave Dodge to see if any pistons are available. I don't know of any being made. But you can contact Wisco or others for custom made. Should be easy. Just supply them with one of your pistons (if need be) and have them make your X over the stock size. The problem then may be rings. The piston mfg can also help you there. Check first.

 

yes I oiled the piston and new rings as well as the cylinder walls as for the hone job a hand held honing device was used
as with anything you score it leaves scratch marks and you can see ware the stone did not hit cylinder
leaving a dark spot.as far as the valves go i put carburetor cleaner in the heads to check when they were off the motor
they did not leak or seep and fluid.
no the machinist did not mic the cylinders as i requested he must of been to lazy...

 

OK knowing what the problem is can anyone tell me what other piston will fit in this motor
so i can re tare down and rebuild this. have to much invested to quit now.

 

are the cams specific to front and rear cylinder banks? pull the plugs and inject a few cc's of oil into the cylinders and crank it over, if the compression changes you might suspect a ring to cylinder interface issue.

 

Oh i know it is an issue yes the cams are in the right spot i double checked that.
just need to know if there is another piston that can be used????

 

Compression test needs to be performed with good battery. Plugs out, and throttle open.
You need to take it apart and start all over.

"couldn't find oversize rings." What if a mechanic told you that? He would be fired.

No need for a compression test until 500 miles.

 

no a mechanic didn't tell me I called places like weisco J E pistons and LA sleeves I know the 86/87 vfr700f1 had same piston diameter just don't know about skirting and pin location
any of the older racers of these bikes know of a piston that is over sized that will work???

 

I am an old racer.
Oversized pistons are for oversized bores.
When an engine is bored the first time it will be .020 (twenty thousandths) over standard size, and the piston may have .020 stamped on the piston.
The over size piston has to have oversize rings to match.
The engine has to be bored at a machine shop .020 over and honed.
If you put an engine together WITHOUT honing the piston rings will NEVER break in.