HELP: Why does engine smoke after sitting for 2 years?

[oldskool]

100cc 2 valve 4 stroke engine has not been run for 2 years and now when started up, clouds of smoke which is gradually clearing up after running for 30 minutes. Still puffs out clouds of whitish light blue smoke when deccellerating down a hill. Idle has cleared up. Brand new plug is now caked black.
Hardly any engine noises and the engine was sweet when last ridden 2 years ago.
Does the carby need an overhaul?
Is there a special oil I can use that may free up valves etc?
Is there something I should be doing to get the old girl running sweet again?

[MSTRS]

It's probably just the rings. They will be gummed up, and not floating free in their respective grooves. Just use the bike normally (perhaps gently) for a few days, then give it an oil/filter change. All should be fine, if it was before.

[oldskool]

It's probably just the rings. They will be gummed up, and not floating free in their respective grooves. Just use the bike normally (perhaps gently) for a few days, then give it an oil/filter change. All should be fine, if it was before.

Okay, fingers crossed the rings just need to free up. The colour of the oil is like honey so I didn't think it would need changing, even if it had been sitting for 2 years, before I tried to start it.

I read somewhere that on this particular model (XR100R) it is common for the needle and jets to tarnish and gum up if left sitting too long. It's easy to start but wondering if I should get a mechanic to replace the jets to make sure the mixture is correct anyway?

[jonbuoy]

Could be valve guide seals gone hard as well.

[MSTRS]

I read somewhere that on this particular model (XR100R) it is common for the needle and jets to tarnish and gum up if left sitting too long. It's easy to start but wondering if I should get a mechanic to replace the jets to make sure the mixture is correct anyway?

That wouldn't make the engine smoke tho. And you don't mention poor running, just the smoke issue.

[oldskool]

Could be valve guide seals gone hard as well.

I've read somewhere (I do a lot of reading!) this model only uses one seal but can't remember whether it was on the intake or exhaust valve.

Does the seal soften up or brittle means will crack and crumble. Does this lead on to a bent valve?

I've read (again!) the 2 valve XR's have weak springs and a history of bending valves (if you play too much with the jetting and exhaust flow that is)

[oldskool]

That wouldn't make the engine smoke tho. And you don't mention poor running, just the smoke issue.

Engine runs sweet. Good torque. Clutch has a good bite. Easy to start. Smooth idle. Just the smoke issue which is gradually clearing up except under load but mostly under deccelleration down a hill.

Like you said, sounds like gummed up rings. Hopefully they'll free up.

I just want to make sure they will have trouble free riding on the trails before we venture out. I guess my idea of a carb overhaul was to ensure eas(ier) starting for them.

[MSTRS]

Engine runs sweet. Good torque. Clutch has a good bite. Easy to start. Smooth idle. Just the smoke issue which is gradually clearing up except under load but mostly under deccelleration down a hill.

Like you said, sounds like gummed up rings. Hopefully they'll free up.

I just want to make sure they will have trouble free riding on the trails before we venture out. I guess my idea of a carb overhaul was to ensure eas(ier) starting for them.

If it aint broke, don't fix it.

[Crisis management]

A rough guide.....blue smoke under hard acceleration is piston rings, a "cloud / puff" of blue smoke when cracking the throttle after deceleration under closed throttle is valve guides / seals.

Give that it has sat for some time I would strip and clean the carburettor with a carb cleaning solution / aerosol spray, change the oil and filter and clean any other filters, lube all movement points etc....service the bloody thing. :msn-wink:

Once it is serviced run it very carefully for a couple of hours and see what happens, get a few heat cycles thru it and then review what may need doing.

Iain.

[oldskool]

If it aint broke, don't fix it.
Over protective dad :doctor:

[oldskool]

A rough guide.....blue smoke under hard acceleration is piston rings, a "cloud / puff" of blue smoke when cracking the throttle after deceleration under closed throttle is valve guides / seals.

Thanks for the timely guide Crisis, I'll keep it in mind after a few gentle runs and an oil change. :niceone:

[jonbuoy]

Early CB's only ran intake seals as well, exhaust guides had none. If they gone hard they might soften up after a few heat cycles or maybe not. Weak springs would mean valves might not close as quickly as they once would, meaning higher chance of piston and valve having a close encounter, as long as you respect the red line I wouldn't worry. Mixture won't have anything to do with it, unless it means someones riding harder and well into the blood.

Cheers

[rphenix]

I remember my old XR didnt take kindly to sitting in the shed. After changing filters, petrol, cleaning spark plug etc.. it might go but can remember one time I must have kick started it a hundred times in the end got my brother to tow me down the road with the 4 wheeler and ran start it which did the trick after a few hours of riding was purring like a kitten.

[Subike]

put a cup of diesel oil in your fuel tank.Then go for a long ride, fun the tank dry if you can
This will make it smoke more for sure, but it will also get down to the rings and lube them, they are probably stuck from sitting, the diesel will free them up and help them to reseal your cylinders. The smoking should then stop, you rings and bores will be nice and clean. Give it an oil change after this too, as a cetrtain amount of the diesel will get past the rings and into the sump.
I have done this with success to car engines that have sat around for a few years in abandoned cars and wreakers yards exposed to the elements. 90% suscessfull.