Piston sleeve 'back on the road!!'

Should I be worried? :cry:






If I feel with my finger I can't feel the scratches so their not deep. Any idea as to what caused this.

Bike is a 2002 650 SM with 1500 km since rebuild, new nicasil on the sleeve, nearly new piston.

RE: Piston sleeve

hello BB

whatever was doing that has perhaps come and gone?

it is difficult to call that? try a little photo edit on it to auto enhance ut and get rid of the shadow?

regards

taffy

Re: RE: Piston sleeve

Taffy said:

hello BB

whatever was doing that has perhaps come and gone?

it is difficult to call that? try a little photo edit on it to auto enhance ut and get rid of the shadow?

regards

taffy

Click to expand...

I suck bigtime at photoshop so I won't even try it , the scratches like the ones you see are visible all around the sleeve. They are not deep at all, if I scratch the nicasil with my fingernail, I can't feel them.

Do I need to fix this or will I be allright?

I did get a bit excited during the breaking in period (meaning I wen't full blast practically from the first moment ), could that be the cause of this?

RE: Re: RE: Piston sleeve

well did you hone it because it looks in some ways like the rings haven't bedded? maybe someone else would like to comment?

i would be tempted to strip it and have a look and give that linar a pro hone at the local engine reconditioners. they have cone hones that don't care about the cutaway at the bottom of the sleeve. it's worth the money.

regards

Taffy

RE: Re: RE: Piston sleeve

Those little 'dots' in the piston squish band, are those really dots ín the piston are is it something laying on top off the piston?

If dots in the piston--> Detonation

Re: RE: Re: RE: Piston sleeve

Hi BB,

Considering the state of play you are at the moment, I agree with Taffy, just split the cases to see what can be found for what it will cost.
I would say the rings as well, to say you have only done 1500km there is a hell of a lot of black carbon and oily crud on the piston crown.
I'm coming close to 6000 miles on mine since the rebuild, if I shine a torch down the plug hole the piston crown is as clean as a whistle.
Am I right in saying you had some oil consumption problems in the beginning after the rebuild?.

Regards

Sparks.

Hello,

split the cases tonight, I found that on the piston there is the same kind of marking, not very deep but all the way round.




I measured the piston ring gap and the top one was 0.2mm, the workshop manual only states that it shouldn't be bigger then 0.8 but doesn't mention a minimum, could it be that the ring expands due to heat and caused the scratches?

The oil ring had a gap of 0.6 but was hard to measure because when I put them in the sleeve the ends had the tendency to turn towards the center of the sleeve, is this normal or is something wrong?



I have also checked the rest of the engine en took apart the reed valve, but everything looked ok there so don't think the problem lies there.

Still wondering as to what the cause of my problem is, but on the bright side, now I know where my oil went

On a side note, welded together this little stand to put my engine in when working on it, this makes working on the engine so much easier, took me 2 hours to take the engine apart and split the case, this inculding taking the engine out of the frame! First time when I did this it took me half a day!

Re: RE: Re: RE: Piston sleeve

sparks said:

Hi BB,

Considering the state of play you are at the moment, I agree with Taffy, just split the cases to see what can be found for what it will cost.
I would say the rings as well, to say you have only done 1500km there is a hell of a lot of black carbon and oily crud on the piston crown.
I'm coming close to 6000 miles on mine since the rebuild, if I shine a torch down the plug hole the piston crown is as clean as a whistle.
Am I right in saying you had some oil consumption problems in the beginning after the rebuild?.

Regards

Sparks.

Click to expand...

Yep big oil consumption problem around 200cc on a 50km ride! According to DaleO the carbon crap is caused by all that oil making it's way into the combustion chamber. Wich makes sense!

Re: RE: Re: RE: Piston sleeve

ElSnorro said:

Those little 'dots' in the piston squish band, are those really dots ín the piston are is it something laying on top off the piston?

If dots in the piston--> Detonation

Click to expand...

It's little pieces of carbon

RE: Re: RE: Re: RE: Piston sleeve

it would seem =that you have a heavy carbon build up that breaks off and breaks up into small particles. these hit the piston or go down the side of the piston.

another thing i suggest you do is to put the rings in the bore squarely and see if they actually touch the bore wall in a 360?

the oil ring gap being smaller isn't a big deal. the compression rings want to be .8mm minimum.

i don't think thats an oil deposit? you run a 180MJ BB don't you!

yeh well, say no more!

regards

Taffy

Re: RE: Re: RE: Re: RE: Piston sleeve

Taffy said:

it would seem =that you have a heavy carbon build up that breaks off and breaks up into small particles. these hit the piston or go down the side of the piston.

another thing i suggest you do is to put the rings in the bore squarely and see if they actually touch the bore wall in a 360?

the oil ring gap being smaller isn't a big deal. the compression rings want to be .8mm minimum.

i don't think thats an oil deposit? you run a 180MJ BB don't you!

yeh well, say no more!

regards

Taffy

Click to expand...

The compression ring is 0.2 mm, should i file it down till I have a 0.8 mm gap? Do you tink it is possible that this small gap was the reason for the scratches?

I run a 195 mj

RE: Re: RE: Re: RE: Re: RE: Piston sleeve

i used to file mine down no problem. omego used to supply gapless rings.

regards

taffy

RE: Re: RE: Re: RE: Re: RE: Piston sleeve

Do the ends of the rings look like they have been touching?
Gap too small can leed to disaster, ie top of piston comming off,
when the ends of the ring touch through heat expansion and lock
the ring in the bore.
The gap has to be just right to ensure that they do not touch when hot.
and not too big as to let compression to escape.
Check manual for correct gap.
If you file the gap you must have a good hand to keep it nice
and square.
There are hand cranked devices that do a better job

Cheers spanner

RE: Re: RE: Re: RE: Re: RE: Piston sleeve

Here is a link to some imfo on ring gaps
http://www.aa1car.com/library/ring_end_gap.htm
Quote
For a modified street performance engine that generates more horsepower and heat, the end gap should be opened up a bit to compensate for increased thermal expansion. The recommendation would be a minimum top compression piston ring end gap of.0045 to .005 inches times the bore diameter. For a 4 inch bore, the ring end gap on the top ring should be increased to .018 to .020 inches.

So about .45mm-.5mm should do it on 100mm bore
.8mm would be the service limit of a worn ring

Cheers spanner

RE: Re: RE: Re: RE: Re: RE: Piston sleeve

Damn it really sucks when you piston/sleeve comes out like this after just 1500km's

Re: RE: Re: RE: Re: RE: Re: RE: Piston sleeve

ElSnorro said:

darn it really sucks when you piston/sleeve comes out like this after just 1500km's

Click to expand...

S.hit happens

New question, the manual says that the bore is 100mm, minimum piston diameter is 99.88, I've tried to measure this, by putting the piston in the sleeve an measuring the gap inbetween with feeler gauges, problem is instead of the 0.12mm gap, there is a 0.45 mm gap. Is something wrong or is my measuring technique incorrect? The measurement I took is from the very top of the piston.

Try the feeler down on the skirt of the piston. Pistons are smaller at the top
to allow for heat expansion.

Cheers spanner

Fùckerdefùck!!

Anyone know what the maximum/minimum axial play is for the big end? In the workshop manual I can only find the max radial play.