1989 GPX 250 Question

**SwanTiger** · 10th May 2006, 09:20

I went around to check out Markaucklands new ride last night a came away with a few questions regarding a problem (or two) which we couldn't figure out.

Stuffed Engine

Its stuffed
But try telling Mark that

Supposedly Good Engine

It runs but blows white smoke out exhuast
the fact mark caught his bike and garage on fire and used buckets of water to put it out would explain the water in the engine
One piston seems to "Knock" and "Drag" the performance of the bike
Is this a valve clearance issue which seems to be common with these GPX motors?
Or could it be timing related
The engine vibrates/shakes and the knocking sound occurs
Or is this engine fucked as well?

I know how to check the valve clearances but would need to refresh my memory on the timing side of things. But are those symptoms likely to be caused by either problem or is it likely to be something more serious, like a fucked piston or worse?

The coils seem to be alright. Enough spark being produced. New sparkplugs. Mark cleaned the Carb's (or wrecked?).

From what I've read valve clearances are likely to be the issue.

Suggestions please.

**Ixion** · 10th May 2006, 09:44

That engine was in a box, and turned on all sorts of angles. If it's not had the head off, there may be oil in the cylinders which will take a lot of running to completely clear.

Valve timing won't produce smoke or knocking, though it may cause a rattle. Smoke may just be accumulated oil, as above. By "knocking" to you mean you can hear a metallic knocking?

**XTC** · 10th May 2006, 10:20

Most GPX's have a pronounced knock at idle but this should diminish as the revs rise.

**SwanTiger** · 10th May 2006, 12:10

Hmm if they're known for knocking I suppose it just needs a good run in and some fresh oil. Probably needs a new oil filter too.

**MSTRS:Me** · 10th May 2006, 12:33

Originally Posted by XTC

Most GPX's have a pronounced knock at idle but this should diminish as the revs rise.

Yep. Same engine used in Eliminator, and that has a knock at idle esp when cold.

**skidMark** · 10th May 2006, 12:49

thanks for the help guys.

swanny neglected to mention the smoke that wafts slowly out of the crankcase breather hose as the " good engine " is running

yes the knocking is only at idle revs seems to be ok once it revs up

and also it is an 86 bike but don't know year on replacement motor exact same motor though by the looks...

the main thing that concerns me is the smoke out the crankcase breather from the moment it fires up and you give it some revs it just slowly comes out of the breather like a smokebomb or something...this smoke is white.

and the motor is not warm at this point so i could only put it down to exhaust smoke? but could be water i'm told.

but after i shut the motor off 2-3 minutes after smoke is still wafting out of the left side exhaust.....exactly ther same color as the crankcase breather smoke by the lookis of it. but wafts out more slowly.

Cheers: ma

ps. thanks swanny for all your help in trying to get me out on the road again.

**gamgee** · 10th May 2006, 12:58

haven't had this problem myself, as mine had been reconditioned with new pistons, rings, etc. done 3000km before i purchased it, but check out;
http://www.ninja250.info/index.htm
same engine as the zzr250 if that helps

**Ixion** · 10th May 2006, 14:12

Originally Posted by swanny

Hmm if they're known for knocking I suppose it just needs a good run in and some fresh oil. Probably needs a new oil filter too.

Uh, Mark, you DID change the oil in that old (repalcement) motor before running it ?

Is it blowing oil out the breather. Oil out the breather is (maybe ) bad, Can mean piston blowby. "Smoke" may be steam, which would come form water int he oil or the zorst. Hold a bit of white paper in the "smoke" See if the smoke leaves black/oily residue on the paper. But you did change the oil ? Right?

The rings could be stuck after sitting. I'd try a bit of upper cyclinder lubricant down the plug holes. And some gentle (thats "gentle", not redlining it) running.

Sounds like the knock may just be a Kockasucky thing.

**SwanTiger** · 10th May 2006, 14:14

I'll pass that on to him if he hasn't already read it Ixion.

Will probably go over there again in the next day or so and see what progress can be made. At the moment he has the idea that one of the pistons in the "good" engine is naffed, so is attempting to transplant one piston from the "stuffed" engine into the supposedly "stuffed, but good" engine.

**skidMark** · 10th May 2006, 14:20

yeah but out the breather it's smoking from the moment it fires up well 4-5 seconds and start giving it a little rev and smoke wafts out of the crankcase breather.....wouldn't think it would be oil or water....

bacause it would take longer to heat up before it turned to smoke or steam i would have imagined.

no ddn't give an oil chnage topped up the oil to correct level though

just seems weird that it does it straight after start up

**skidMark** · 10th May 2006, 14:22

i did lean out the mixture from 2.5 to 1.5 turns on the carbys.....

still doesn't explain the crankcase mystery vapor/smoke

**SwanTiger** · 10th May 2006, 14:23

Originally Posted by markauckland

just seems weird that it does it straight after start up

Well you've only run it for 15 seconds at a time.

It might be worthwhile running it on low RPM for 30 - 60 seconds or longer and wait to see what happens with the smoke.

Have you put the "Good Engine" back in the frame, Mark?

**Ixion** · 10th May 2006, 14:29

AAACCKKK. Get that old "oil" outta there right off, for a start. Y'dunno WHAT that stuff is. Or how old. Drain the oil, pull the filter and change it , or at least look real close at it.

If it is smoke (and it's not electrical) then it can only come from the combustion chambers. For smoke from the firing cycle to reach the crankcase, there would need to be ring or valve blowby bad enough that you'd see oil blown out. It *could* be a sticky valve, or a tight valve. Or stuck oil control rings (though usually the compression rings stick first) . Or a water leak intot he cylinders of course, I was forgetting that it is water cooled. Try running with the suspect spark plug cap off. Does the "smoke" cease ?

Some parts of the motor will reach several hundred degrees within a minute or so of running. But I doubt it's smoke. Watch a car start up that's been standing outside overnight on a rainy morning in winter. What a big cloud of "smoke" almost immediately.

It could be smoke out the zorst , there might be a big puddle of oil in one cylinder, remember the engine may have been lying on it's side for ages at some point.

Try taking both plugs out, put a bit of white paper across over the plugs holes, and spin the engine on the starter (it will spin fast). See if there's anything blown onto the paper.

Do you have access to a compression tester?

**Ixion** · 10th May 2006, 14:32

Originally Posted by swanny

Well you've only run it for 15 seconds at a time.

It might be worthwhile running it on low RPM for 30 - 60 seconds or longer and wait to see what happens with the smoke.

Have you put the "Good Engine" back in the frame, Mark?

Oh pffft -. that engines sat around for maybe YEARS . A few seconds doesn't mean ANYTHING. It's going to take maybe an HOUR of running before it settles down.

Change the oil and filter. Start it up, and run it at about 3000 rpm for 10 minutes . If anything changes for the worse (eg a new noise, or the knocking sounds worse) turn it off immediately. Otherwise just keep it revving , blip the throttle a bit so it cycles between 2 and 3000 rpm. See if the smoke clears . Doesn't mean too much if it doesn't though, like I say it often takes 20 or 30 MILES to clear an engine out. And the zorsts will be full of shit, too.