NEED URGENT HELP, BANDIT HAS NO COMPRESSION!!!!!!

[Grand_Journeyman]

Hey everyone, its been a long time since i was last here, glad she's got a major update.

I own a 1995 GSF-250S, that has now done 21,000kms, in mint condition.

Alright here's the story, went for a ride on a wednesday ages back bike was fine, went for a ride with the vintage & vets/ulysses/ general morning ride with my father and friends and my bike isn't right, like i've got no guts, really lacking in the power.

We work out there is no compression, after months of searching the web i find the engine spec's, compression, value width the whole nine yards. After adjusting the carbies, in/out tappits, we decided its a compression issue for shore. So we kick her over with a compression guage in each cyclinder, a steady 60psi + or - a point or 2 for each cyclinder. Then we put a teaspoon of oil down each cyclinder in turn and redid the test, no change in compression on all cyclinders hmmm....so the rings are fine....what now....

We then hook up an air compressor to each cyclinder in turn and turn on the compression, each cyclinder holds pressure...hmmmm.....well if that happens then why no compression????

Thats my question, why do i have no compression? and what could cause the loss of pressure? Now the spec's i have say it should be close to 160psi per cyclinder, but i only read 60psi. I also would like to know where i can get a manual in english or at least a diagram on how to remove the engine head etc etc so i can get to the pistons and values, so i can re -hone the cyclinders, replace the rings and grind the values. i've got some work ahead of me but its worth it, i love that little bike and want to ride her again soon.

help anyone?

Barts

[Red01]

What about cam timing?  If the cam chain has jumped any teeth on one or both cams, that could have an effect on compression readings.

Good luck finding a 250 manual in English... if you find one, I'm sure you could make a lot of other 250 owners in the UK, NZ & Oz very happy!

You should be able to use a 400 manual for some basic instruction, though it isn't going to be able to serve you in all areas.  If you can find a 250 manual in Japanese for the important numbers, like torques, bore specs, etc, along with a 400 manual in English, you should be able to manage.

[pmackie]

I'm with Red here...possibly check cam chain and sprockets, as incorrect cam timing could be your issue.

You should try to document your "leak down" test. Once you pressure up each cylinder you need to measure how long it takes for the pressure to leak down. A pressure gauge and and watch will be necessary.

If you have less than 5 psi change dry to wet on standard compression test, you are likely looking at valves.

[Grand_Journeyman]

We actually did cam timing aswell, checked timing marks with value positioning, made them all to spec aswell. What we didn't check was the cam chain nor cam chain sprockets.....that will have to be next.

We had no leak down on the value compression test, we'd pump the pressure and it'll hold for over 10 minutes, we had it hooked up that the pressure readings were through 2 seprate pressure guages. We are really confused, i've neer seen that look on my fathers face before, utter confusion....my old man has some many year experience with bike it isn't funny, anyway will keep trying.

If i can find a full tech manual in japanese it wouldn't be such a big deal, my cousin teaches japanese at a uni in adelaide, i'll get him to translate and i'll reformat it. So if anyone has a Jap copy let me know and i'll english-a-rise it for the greater good.

[Red01]

How much pressure were you holding with a compressor? 60? 120? 160? 



With a couple of folks that read this 250/400 section living in Japan, hopefully one of them will pipe in and offer to help you locate a Japanese copy of the 250's service manual.

[pmackie]

We had no leak down on the value compression test

Sounds odd doesn't it. I assume that you did check against the intake and exhaust valves separately on each cylinder?

I also assume you did your compression test using the electric starter motor? Is is possible that 60 psi using starter engine rpm is within factory specs?

I think you need some info from the factory service manual.

[Grand_Journeyman]

pmackie, don't worry we check each intake and exhaust values speratelt on each cyclinder, WHAT A TIME CONSUMING PROCESS THAT WAS.....had to make ourselves a tool to do, these engines were built to put together easy but not maintain just as easy.

I'd love the factory service manual if anyone has a copy.....

Red01 we has the compressor up to 120psi before we blew the hose off, and it held steady for well over 5min each cyclinder.....this really boggles the mind.

we'll keep plugging on, come japanese help me out......please....

[bandit250]

Compression (Accel full open, Starter motor ON)
    Standard: 11.5-13.5kg/cm 2 (450 r/min.
    Use limit: 8kg/cm 2 Use limit
    Difference between cylinders: Less than 2kg/cm 2 Difference between cylinders

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[Grand_Journeyman]

Thanks Bandit250, well at least i know the data i had collected was correct. 11.5-13.5kg/cm 2 is equal to around about 160psi.

cheers for the help its greatly appreciated.

Any special way to remove the engine head? anyone? anything to take into account with the chain and sprockets??

Thanks people