95 Contact............lots Of White Smoke, Help

[goreboy]

ok help please guys and gals, my 95 contact 250 has a very wet exhaust and lots of white smoke, runns ok at low rpm but wont rev, how do i eliminate whats wrong, help appreciated, Gareth

[yamahaty250xox]

has it been through any deep water?

or is it being run at the correct fuel mixture?

max

[peterb]

Hi Gareth,

White smoke is usually from water getting into the combustion process.

I recall covering this before somewhere, anyway it's likely to be coming from either the head O ring seals - quite common on older bikes, or getting in around the cylinder area. There is an optional sst or tinned steel base gasket to seal off any water getting through the standard gasket material, there were water cooling ports cast in the crankcase that aligned with water ports in the cylinder designed to cool the main crankcase area, it didn't work so the blanking gaskets were released. Being magnesium alloy, the cases tend to rot out with water in there anyway so best to have a look and assess any possible corrosion damage. It could be just a leak path on the base gasket area.

Bye, PeterB.

[millsy]

You say a wet exhaust, but do you mean watery or oily? I have seen on high usage and older bikes, the main crank seal going between the crank case and the gearbox. This results in excessive white oily smelling smoke from the exhaust because you are burning the gearbox oil.

As said in an earleir message, it could be water, but this would often be seen as steam from the exhaust rather than smoke. You should be able to tell if it's water or gearbox oil by checking the level of both and checking the plug to see if it's oily or rusty (It may be neither but it could help).

Check that the bike has good compression and is running on good quality two stroke oil at the correct ratio as well. Sounds like an engine rebuild may be on the cards anyway? Good luck.

[gjbiker]

I'd go with the coolant water theory, like PeterB says. Very common for head seals to go at that age and because water doesn't burn it will affect the running. Crank seals will cause lots of smoke but the bike may still run OK. Easy checked - loss of coolant = head gasket/'o' rings , loss of gearbox oil = crank seals

Pray it's the head seals as this is a simple fix compared to crank seals or casing erosion.

GJ

[goreboy]

Cheers guys thanks for the help........either way doh!!!!!!

[goreboy]

ok guys news......after leaving the bike stationary for a week or so, i dropped the crank plug out and red atf gearbox oil came out.....doh,

so what do i do next?

i presume i must change the crank seal on the clutch side of the engine............ what else should i try before i have to split the whole engine?

Cheers

Edited February 10, 2008 by Goreboy

[millsy]

Sorry mate. Looks like you are up for a complete strip down and new crank seals at the very minimum! Look at doing conrod, main, big and small end bearinga nd piston/rings while you are at it. As mentions by someon earlier, check the water passages for corrosion and replace all gaskets and o-rings. Depening on budget, I'd look at doing the clutch and going through the gearbox while you are in there. Easier to strip it once and do the lot than find you have to pull it all apart again in 6 months time.

[peterb]

Hi Goreboy,

Was there a lot of oil coming out of the crank drain plug? - are you sure it was the crank plug, the one closest to the front wheel, don't mean to sound condescending or whatever the word is, but better to check this out first than to get deeper involved with a stripdown.

I've never seen lots of g'box oil exit from the crank, if it is so, then at the minimum you'd need to replace the clutch side crank seal.

You can get there by removing the clutch, if you have an air drive unit or impact driver, you can remove/replace the clutch centre nut easily. Do not wedge the clutch centre with a screwdriver or pair of pliers! those clutch spring posts break off quite easily. You can also get the centre nut off (it has a tab washer) by removing the pressure plate, then using a small G Clamp, clamp the plates together. Very very carefully, trap the clutch basket to remove the nut, or try leaving the bike in first gear. The crank gear is fairly tight, needs a 30mm socket. All threads are RH.

Do not lose the ball bearing from between the clutch pushrod and the mushroomed rod follower.

Be very careful when re-fitting the outer housing to ensure the white plastic gear is properly engaged before firmly pressing down the cover. Unless the bottom end is grumbly, I'd leave the mains alone at this stage, sorry Craig! Big ends are very sturdy and not known for premature failure on these bikes, only need replacing if the motor has been drowned and not had the water drained. Only problem with the clutch on these bikes is if the fibre plate material has started to lift of the metal backing - have a good look.

Good luck, PeterB.

[goreboy]

so i can do the crank seals (esp clutch side) (i guess if the other side has gone the bike could suck air?) anyhow can i do these from the outside with just the side cases off? (well and the clutch etc)

[peterb]

Hi Goreboy,

You can do both seals from the outside, look at the previous posting for the clutch side. Best to have someone help you if you haven't done this before. To replace the mag side, you need a flywheel puller that fits your particular bike - not the same puller as a PRO motor.

If the mag side seal had gone, there would be an oil mist around the seal and symptoms of running lean. Very carefully prise out the old seals without damaging the housing and the crankshaft. Get the proper seals, hi temp viton.

Bye, PeterB.