Pistons?Rings?

duggyb

duggyb

where are the skis?
Due to recommendations on here from other members I decided to do my base gasket as well while I was doing my head gasket.

My motor was running fine when I took it apart and I thought it was stored well(about a year) but it appears maybe not as it seems one pistons settled pretty good. when I took the cylinders off they came off fine but I had a little bit of rust on one Piston/Rings and nothing on the other, I also had some marking on one cylinder

Looking at the pictures below what would you member's recommend? I am thinking a hone, clean up the pistons and new rings? What about pins?

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Hone the cylinders a little, then post new pictures. You can better evaluate the condition after a little clean up with a hone. Use plenty of light lubricant to flush away the debris while you hone. WD-40 would be good.

Pistons look OK to me. Some minor scratches or scuffs on a piston are no big deal so long as there is not excessive clearance. Condition of the cylinder walls, and condition of the rings is more critical, so I suggest you at least get new rings, if we decide your cylinders are useable without a re-bore.
 
Alpha after the hone are you wanting me to MIC the cylinders? I don't have a cylinder MIC but I guess now is as good as time as any to get one.

Or do you just recommend taking it somewhere to get MICd?

Thanks
Dustin
 
A machine shop could measure your pistons and cylinders for you. I wouldn't buy tools for that.

If there is no ridge at the top of the cylinders, they are likely not worn much. Pistons are not likely worn much either. The issue that you have to resolve is to determine how deep the rust damage is in the cylinders. It might just be superficial. After a light hone, it will be easier to evaluate. If you don't have a hone, you can buy one for about $30, or a local machine shop or bike shop would probably do it for you for next to nothing.

Don't use a brush or ball type of hone. Use one with stones. That way, it will not hone into the low spots, so that you can better evaluate any rust erosion.
 
AlphaDogChoppers said:
A machine shop could measure your pistons and cylinders for you. I wouldn't buy tools for that.

If there is no ridge at the top of the cylinders, they are likely not worn much. Pistons are not likely worn much either. The issue that you have to resolve is to determine how deep the rust damage is in the cylinders. It might just be superficial. After a light hone, it will be easier to evaluate. If you don't have a hone, you can buy one for about $30, or a local machine shop or bike shop would probably do it for you for next to nothing.

Don't use a brush or ball type of hone. Use one with stones. That way, it will not hone into the low spots, so that you can better evaluate any rust erosion.
Click to expand...

sounds good, I don't think the rust damage is bad, I cant feel it with my hands but just see it.

I am the third owner of the bike and know all previous owners, the bike has an original 9000 miles on it with motor never apart so i imagine everything is in decent shape but I guess I don't really know how hard it was ridden either.

I am going to swing the parts by a well known machine shop just down the road from my work and see what they say, i also printed PG 41 of the service manual with the specs on it so they can cross reference.

Will keep you posted.

Thanks
Dustin
 
If you can't feel it, it's fine.

You can feel one thousandths with your fingertip.
You can feel a half thousandths with your fingernail.
 
looks like corrosion to me in the one bore from the photo's since you will not have marks like that from anything else but then again i am looking at a photo too.....if it is corrosion you need to over bore(both) for sure to make it RIGHT. that being said i have seen a lot of these engines run ok with some corrosion in the bore due to sitting long and the rings/cylinder corroding. as alpha dog stated you can hone and re evaluate. you may be able to precision hone (if clearances are in spec) them to clean up and use as is just make sure you r&r rings , de carbon all and surface plate head/cylinder. the one pin looks a little scored also so ck rod small end and polish properly.
joe@vcycle
www.joesvcycle.wordpress.com
 
joea said:
looks like corrosion to me in the one bore from the photo's since you will not have marks like that from anything else but then again i am looking at a photo too.....if it is corrosion you need to over bore(both) for sure to make it RIGHT. that being said i have seen a lot of these engines run ok with some corrosion in the bore due to sitting long and the rings/cylinder corroding. as alpha dog stated you can hone and re evaluate. you may be able to precision hone (if clearances are in spec) them to clean up and use as is just make sure you r&r rings , de carbon all and surface plate head/cylinder. the one pin looks a little scored also so ck rod small end and polish properly.
joe@vcycle
www.joesvcycle.wordpress.com
Click to expand...

The cylinders and pistons are at a VERY reputable shop just outside of town here, he travels and works with the Rockstar Moto team, they actually just won Nationals this past weekend out in Ontario.

He is going to give them a hone and measure and let me know what my options are.

I will keep ya all posted.

Thanks again for the help!
 
Personally I would say the rusty cylinder is done for, I've seen too many that wouldn't clean up and had to be bored
If you can feel the damage with fingernail it's too deep, the rings will catch
 
Well I got the stuff back from the shop and its all good to go! he said it cleaned up nice!

He honed the cylinders and they came in within spec, he also glass bead blasted my pistons and stone ground my gasket surfaces for me and I took him the new rings and he test fit and measured ring endgap while I was standing there. All is well:)

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The one questions I have is in the manual it states to offset all ring endgaps by 120 degrees, what it doesn't state is for the bottom oiler ring do i need to offset the top middle and bottom also 120 degrees from the top two rings and each other?

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Thanks
Dustin
 
Yep, offset the oil control 3 piece rings.
Fit expander spring first, then the top and bottom rails at 120
Don't worry about the two top rings, they rotate and will sort themselves out
 
sorry this may be a stupid question. but if i have the expander spring set at say the arrow on the piston. do i move BOTH top and bottom rings to the SAME 120 degrees, or top to 120 degrees and then bottom another 120 degrees past that.

Thanks
Dustin
 
The idea is to set the rings so that the end gaps don't line up. If/when they do there's a some leakage past the rings. As PJ mentioned, rings rotate in use. I want to say it's around 7rpm but I don't recall where I read that.
 
teazer said:
I want to say it's around 7rpm but I don't recall where I read that.
Click to expand...

I think that is probably malarkey.
It's my understanding that they can walk to a different position over time, but as far as rotating around the piston, I am pretty sure they don't do that.
 
I'm looking for some information on ring rotation. I can find where it is mentioned a couple times in various tech pages, but no mention of a rotation rate that I can find. Apparently, rotation rate is related to the cross hatch angle.
 
OK, I found something that referred to a ring rotation rate of around 1 rpm per 1,000 engine rpm.

I had no idea rings moved around that much.
 
AlphaDogChoppers said:
OK, I found something that referred to a ring rotation rate of around 1 rpm per 1,000 engine rpm.

I had no idea rings moved around that much.
Click to expand...
Makes sense though, theres so much movement and vibration in the engine they are bound to move around.
 
What I had to wrap my head around was what could possibly motivate the rings to rotate. It's the cross-hatching, and the difference in ring pressure on the upstroke versus the downstroke.
 
Yeah, at the transition from up to down the crosshatch probably helps it move, but theres also the slight angle of the piston as the rod goes from the upstroke to the down, theres no way thats a frictionless transition. Which would cause some torsion on the ring i would imagine causing it to move, and any imperfection (crosshatching) would help it move.

At least thats whats happening in my head ::)
 
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