Hi Guys,
Just wondering what’s the best way to check the cylinder compression on the 84R motor. Have heard various ways like: cold with thick oil squirted down the cylinders, or at operating temp and test while everything is hot & expanded and combinations of each?
Also what compression pressure should I be looking for to get a reasonable test and that the motors OK?
Am a little bit apprehensive as the rear L/H cylinder takes a lot longer to heat up when cold started, can’t touch the other three cylinders after 20 seconds and you can hold your hand on to the other for 120 seconds. It runs smooth when stated and the cold cylinder is firing as the spark is ok and when spark lead is removed it runs rough.
Has anybody had a simular problem?
Paul F
N.S.W
Australia
Hi Paul
120 second ,you have a burnt exhaust valve , you need a long neck compresion gauge too reach the plug hole , hot/cold not important ,
do a test with out oil then add oil do test again , (oil covers ring by pass and tests valves ) first test with out oil is correct test for over all engine wear , PS where in NSW
regards Howard
Hi Howard,
Was hoping we’d catch up for a chat. I’m in Griffith, Riverina area of NSW. If you’ve read my other posts I’ve gotten into all sorts of trouble with the wife and VFs, with wrong information before the guys on this forum have straightend a few things out. My town doesn’t seem have a decent mechanic who gives a dam about older bikes (and riders) unless your cashed up or trading it in.
Thanks for the comperssion tips as I had my suspicions when it didn’t heat up after a blast down the road out to 180kmph, and could still almost hold my hand on the cylinder as well as oil stains wern’t burning off the exhaust manifold. It ran more like a lame 750 as well. The other FE motor had more pull in it than this RE motor.
Anyway would like to catch up for a chat, you can drop me an email to pandtfindlay@bigpond.com and we can swap contact details, look forward to it.
Paul F
N.S.W
Australia
OK Howardk, Update of compression test.
Well Bought a compression tester kit with the long extension as suggested and it also came with 6 different adaptors as well which none fitted the spark plug thread anyway…LOL…
Removed plug and checked #1 cylinder stone cold @ 110psi, then #4 @ 105psi, #3 @ 100psi, #2 @ 105psi. So the cylinder I was concerned about had the better compression??? So in with the plugs which were all checked as they went in for spark and warmed up motor. I decided to remove #1 plug and check compression again whilst warm, but when the plug came out it was wet and oily. Another check showed no spark. Grabbed spare plug from other motor checked it and there was spark. What I found was a faulty plug when hot broke down completely and when it cooled off sparked again!!
It can now be found across in the neighbours back yard somewhere…(#%&ng thing).
Once the motor was fired up again I burnt my finger on the exhaust of #1 cylinder. Also this time it proceeded to smoke out the shed with all the unburnt fuel and oil in #1 exhaust pipe. Defiantly a big improvement.
So how are the compression figures for this motor???
Paul F
N.S.W
Australia
quote:
Originally posted by Paul F
OK Howardk, Update of compression test.
Well Bought a compression tester kit with the long extension as suggested and it also came with 6 different adaptors as well which none fitted the spark plug thread anyway…LOL…
Removed plug and checked #1 cylinder stone cold @ 110psi, then #4 @ 105psi, #3 @ 100psi, #2 @ 105psi. So the cylinder I was concerned about had the better compression??? So in with the plugs which were all checked as they went in for spark and warmed up motor. I decided to remove #1 plug and check compression again whilst warm, but when the plug came out it was wet and oily. Another check showed no spark. Grabbed spare plug from other motor checked it and there was spark. What I found was a faulty plug when hot broke down completely and when it cooled off sparked again!!
It can now be found across in the neighbours back yard somewhere…(#%&ng thing).
Once the motor was fired up again I burnt my finger on the exhaust of #1 cylinder. Also this time it proceeded to smoke out the shed with all the unburnt fuel and oil in #1 exhaust pipe. Defiantly a big improvement.
So how are the compression figures for this motor???
Paul F
N.S.W
Australia
Nice one Paul…sounds like you’re sorted. Err…you don’t know anyone selling a compression tester kit cheap do you!?[:D][;)]
[8D]
This time tomorrow it’ll be yesterday
Dear Paul, thanks for the information, my neighbour just bought an vfr750 which has the exact same problem; guess I’ll be replacing no 1 plug!
Hi Paul
Im in Goulburn ,Got that nice little race track called Wakefield park a few k,s away .
Compresion figures just show used engine nothing to worry about ,if they were in the 90,s you need to do some work ,they are with in a few psi off each other shows no problems.
Was the plug one off the new resitor style plugs ,(Iridium)these cause lots of problems on older bikes ( especialy points coil) as they need massive voltages to fire when hot, when cold they have low resistance and fire ,when hot the resistance goes off the scale and need the latest electronic ignition to fire them ,causes hot starting problems.
Bullet proofing the VF ,I have probably pushed this motor harder than any one (turbo) in standard form its Bullet proof ,
The reason for my figh flow oil pump is that on the race track the engine spends lots off time up near the 11,000 12,000 rpm ( slow by modern sports bike standards ) the oil galereys in the crank act like a centrifical pump and pump the out side main brg,s dry ,( Honda fitted high flow pumps to its race RC30 for same reason ) not having acsess to genuine honda race oil pump I took the pretty standard turbo option of over driving the standard oil pump ,and drilling out the oil galleries to the mains and increasing the No of oil holes in the main brg to accomadate the extra flow .So as to not break the chain drive to oil pump and water pump ,I reduced the oil pressure to 50 psi (its volume not presure that is needed )and used DID cam chain instead of the standard drive chain .The extra volume makes sure that I,m not starving the engine of oil when diverting some to the turbo plus turbos are very dependent on oil cooling .