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2005 TE250 smoking

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Hi,

Last week I took the bike for service. Most things were ok, including valve clearance and engine compression. However, the mechanic said the oil level was a bit low (again) and the bike is making too much white smoke, even when properly warmed. He advised me to replace the piston and valve seals.

I am in doubt if the piston change alone will be enough to keep the engine running for a couple of years, or if I should replace other things, like the rod or the crankshaft bearings.

The rest of the bike is in very good shape and I think it is worth to spend a bit extra cash to guarantee it will last a few more years.

Any thoughts on this?

Thanks.

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Piston alone is in my opinion only possible if the cilinder is still "round" which is not probable. This should be checked with calibers. Why not replace with an Athena 310 set? I did the same wirth my YTE 250 and am happy so far.

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Piston alone is in my opinion only possible if the cilinder is still "round" which is not probable. This should be checked with calibers. Why not replace with an Athena 310 set? I did the same wirth my YTE 250 and am happy so far.

The Athena kit is tempting but very expensive! The cheapest I found online is this one.

Did you get yours in Spain?

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My 04 Te250 was smoking and burning 80ml of oil every 100miles.

I changed the piston and while it was in bits I replaced the valve stem oil seals and cam chain, inspected the conn rod little and big ends.

:lol:

The cylinder had no marks/scores and measured with an 'Ovality Guage' I could not detect any wear.

The piston ring gaps were large but still within the service limits.

The piston skirt had quite heavy and uneven running marks on the skirt and above the top ring.

The piston surface area being so much less than the cylinder and made of Ally compared to the hard NicSil cylinder I would say it will be your piston that is ready for replacement,

(Here's the engineering theory, I've seen films of this on training courses)

The piston skirt on these engines are so shallow, It only takes the slightest amount of wear to allow the the effect of the piston tipping (refered to as Piston Slap) With the leading edge of the compresion ring not seating squarely against the cylinder it can ride over the oil film leaving excess oil on the cylinder walls to burn off,

Most commonly this is happening when the engine is decelerating, Then smokes on acceleration.

Badly worn or broken rings will give the same symptom.

When you you strip it down you can sometimes see this. Apply some finger presure at the front of the piston crown while turning the crank, try the same with presure to rear of the crown and see the curtain of oil left on the cylinder.:thumbsup:

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My 04 Te250 was smoking and burning 80ml of oil every 100miles.

I changed the piston and while it was in bits I replaced the valve stem oil seals and cam chain, inspected the conn rod little and big ends.

:lol:

The cylinder had no marks/scores and measured with an 'Ovality Guage' I could not detect any wear.

The piston ring gaps were large but still within the service limits.

The piston skirt had quite heavy and uneven running marks on the skirt and above the top ring.

The piston surface area being so much less than the cylinder and made of Ally compared to the hard NicSil cylinder I would say it will be your piston that is ready for replacement,

(Here's the engineering theory, I've seen films of this on training courses)

The piston skirt on these engines are so shallow, It only takes the slightest amount of wear to allow the the effect of the piston tipping (refered to as Piston Slap) With the leading edge of the compresion ring not seating squarely against the cylinder it can ride over the oil film leaving excess oil on the cylinder walls to burn off,

Most commonly this is happening when the engine is decelerating, Then smokes on acceleration.

Badly worn or broken rings will give the same symptom.

When you you strip it down you can sometimes see this. Apply some finger presure at the front of the piston crown while turning the crank, try the same with presure to rear of the crown and see the curtain of oil left on the cylinder.:thumbsup:

That's great info! Thanks.

The symptoms are similar in my bike.

I took it to the mechanic today and he is going to open the engine and see what it needs. Hopefully it will need just a new piston but if the cylinder is in bad shape, maybe the Athena kit is a better option.

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It's your valve guide seals. Typical issue. A good mechanic can replace them without pulling the head (there are tricks for this). Might do that before getting to carried away with a full rebuild. Do a leak down test and see what kind of condition your motor is in.

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