Oil in the cylinders. Engine shagged or fixable?

**El Dopa** · 15th April 2006, 16:26

Ok, anyone who has read this post:

http://www.kiwibiker.co.nz/forums/sh...882#post578882

will have a good idea of the problem and my question, but to recap:

I fired up the VTZ this morning, and managed to get the engine running on both cylinders. A small victory.

It ran fine for 2-3 minutes. I left it running to get it warmed up and generally get things up to speed, lubricated, blow out the cobwebs, etc.

Then, after 2-3 minutes I noticed the revs were rapidly increasing from idle to full bore, without me touching the throttle or even being anywhere near the bike. There was also a sodding huge cloud of white smoke pouring out the back of the exhaust.

So I shut the engine off sharpish. After a couple of minutes I tried to turn it over on the starter motor. The engine appeared to be 'sticking'. That is, not turning over, or it would turn over once or twice, and then stick again.

I took the spark plugs out, and spun the engine. It spins fine on just the starter without the plugs in, but flung out a fair bit of viscous goop that looks like oil from the cylinders. This and the smoke makes me think that somehow there is quite a lot of oil getting into the cylinders and causing problems.

So, the question is:

Does this seem like a correct analysis?

If so, what is causing it, and how do I fix it, assuming it is fixable, and isn't terminal?

**Ixion** · 15th April 2006, 16:35

Need some history.

Have you checked the oil level in the crankcase. In case it is the old Hinda "petrol leaking past floats into cylinders, running into crankcase, diluting oil and raising (diluted) oil level so much that it is forced back up into the cylinders" trick

**Motu** · 15th April 2006, 17:01

Which side is the smoke?....or do you have a V twin or single muffler? The increasing revs as it warms up is caused by an air leak in at least one carb - you need to isolate your cyls somehow.

[edit]....I now see the resurection thread - you've had those carbs apart haven't you boyo? Simple diagnosis.

**El Dopa** · 15th April 2006, 17:02

Originally Posted by Ixion

Need some history.

Have you checked the oil level in the crankcase. In case it is the old Hinda "petrol leaking past floats into cylinders, running into crankcase, diluting oil and raising (diluted) oil level so much that it is forced back up into the cylinders" trick

Well, it could be. This bike has a fairly knackered fuel tap (which I noticed was leaking slightly when I put the tank back on), and worn carbs, and it has performed that particular trick before.

However, would it happen that quickly? I'd only just put the tank back on before I started it up. The petrol would only have had a couple of minutes to run into the case and dilute the oil before I noticed the smoke, etc.

Also, what I could see/feel of the stuff that was being flung out of the cylinders was pretty viscous, and didn't seem particularly dilute.

I'll check the sump level, anyway.

**FROSTY:Me** · 15th April 2006, 17:06

dude you had it on choke didn't ya? As the old gal warms up the revs will indeed rise.The white smoke is steam from all the water condensed inside the exhaust system.
If it aint on choke ya mighta overtightened the throttle cables or wound the idle up a bit too much
The viscus stuff frying out is just oil
Don't sweat it dude.check the oil level and take the ol gal out for a ride.

**El Dopa** · 15th April 2006, 17:08

Originally Posted by Motu

Which side is the smoke?....or do you have a V twin or single muffler? The increasing revs as it warms up is caused by an air leak in at least one carb - you need to isolate your cyls somehow.

V-twin to a single exhaust. There is actually a leak (I think) in the muffler just where the two headers meet at the junction before going to the exhaust proper, as there appeared to be a bit of exhaust smoke coming out from this junction when it was running. I was going to put some exhaust tape around it, but surely that woudn't be causing all that smoking?

**Ixion** · 15th April 2006, 17:10

You just refitted the carbs did you not? Mr Motu is correct the racing engine indicates an air leak, or carb misassembly. It may be unrelated to the smoke and oil. I don't know if it is so on the Honda 250 V Twins, but some engines, if left sitting, oil will leak down past worn valve guides and seals, and accumlate in the cylinders. It can take a while to clear this when the engine is restarted.

Check your carbs first. Then once they are right, and you have checked crankcase oil level, restart and see if the smoke clears after 10 minutes or so (I presume it did not some before you tok it to pieces ? ).

**El Dopa** · 15th April 2006, 17:11

Originally Posted by FROSTY

dude you had it on choke didn't ya? As the old gal warms up the revs will indeed rise.The white smoke is steam from all the water condensed inside the exhaust system.
The viscus stuff frying out is just oil
Don't sweat it dude.check the oil level and take the ol gal out for a ride.

It was on choke, but this was a REAL sharp and rapid rise in the revs, well beyond what I'd have thought you'd get with a choke and warmup.

I did change the oil recently. I'll check the level and try again.

**Ixion** · 15th April 2006, 17:16

It's not uncommon for engines to produce a fair bit of smoke when first started after a prolonged period of idleness (flames, however are more serious). If there are no nasty noises, and the crankcase oil seems OK, and the motor sounds "clean" just keep it going at a fast idle (maybe 3000 rpm or so) and see if the smoke clears.

But sort the carbs and raci ng first

**FROSTY:Me** · 15th April 2006, 17:21

mate they will rise fast NOW--cos you've cleaned all the shit out of the system propperly. it doesn't sound unusual to me.

**El Dopa** · 15th April 2006, 18:12

Originally Posted by Ixion

It's not uncommon for engines to produce a fair bit of smoke when first started after a prolonged period of idleness (flames, however are more serious). If there are no nasty noises, and the crankcase oil seems OK, and the motor sounds "clean" just keep it going at a fast idle (maybe 3000 rpm or so) and see if the smoke clears.

But sort the carbs and racing first

Just tried it again, still a lot of smoke, but the engine is running ok-ish.
No flames yet. I'll keep trying.

Originally Posted by FROSTY

mate they will rise fast NOW--cos you've cleaned all the shit out of the system propperly. it doesn't sound unusual to me.

Ye-e-e-s, but...

When I leave the engine running at idle, all seems fine (except for the smoke). However, if I rev the engine a bit, to 4-5000, when I back off the throttle, the engine stays at the same revs, it doesn't go back to idle. Carb leak?

**FROSTY:Me** · 15th April 2006, 18:17

nope---more like a badly routed cable to me -or something stuck alongside the twisty bit of the throttle on the carbs

**El Dopa** · 16th April 2006, 15:41

Well, fired it up again today. It starts ok.

However, it's still blowing a lot of smoke (not as much as yesterday, though), even after it's been running 5-10 minutes. Surely that would be enough time to burn off any crap in the system?

Also, it's running OK-ish, but not particularly smoothly, and the revs seem to go up and down a lot without their necessarily being a connection to what I'm doing with the throttle and choke.

I started to change the oil again, and ran out after topping it up to minimum. After running the engine for a while, this level had gone down perceptibly. Has it simply redistributed around the engine, or is it getting into the cylinders somehow?