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Discussion Starter #21
Got it torn down today and here are a few pics to show the condition. Not very pretty especially the valves. One thing I found out the piston in there is 1 mm oversized which is what my extra one is. So it won't do me any good if I need a bore...
 

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Can you post pics of the cylinder walls and the side of the piston?


That's a fair amount of carbon in pic #1.



One thing you can do at home.... Carefully remove the top ring from the piston, keeping the top of the ring oriented the way it has been running. Put the ring, top facing up, about 1/4" down into the cylinder. Using the piston to push the ring down can help make sure it's square in the bore. Now using a feeler gauge, measure the gap between the ends of the ring.


If the top ring breaks, try the second one. You have to work the rings off in a spiral, unless you happen to have a ring spreader.



The oil rings are the bottom rings on the piston. How do they look? If you push the oil rings inward on the piston, how much do they stick out on the opposite side?
 

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Discussion Starter #25
Can you post pics of the cylinder walls and the side of the piston?


That's a fair amount of carbon in pic #1.



One thing you can do at home.... Carefully remove the top ring from the piston, keeping the top of the ring oriented the way it has been running. Put the ring, top facing up, about 1/4" down into the cylinder. Using the piston to push the ring down can help make sure it's square in the bore. Now using a feeler gauge, measure the gap between the ends of the ring.


If the top ring breaks, try the second one. You have to work the rings off in a spiral, unless you happen to have a ring spreader.



The oil rings are the bottom rings on the piston. How do they look? If you push the oil rings inward on the piston, how much do they stick out on the opposite side?
I will give it a try tomorrow with results...
 

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Discussion Starter #26
Didn't get the valves out yet but took a few pics you requested. The cylinder pic kinda sucks but tried to get the best light. The pic of the rings show with having them pushed flush on one side how far they stick out.
 

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Seems like quite a bit of scuff on the piston, all over the sides, above and below the rings. Not sure how much is just dirt and smudges.



Oil rings don't seem right to me, like maybe they're for a standard bore? Or they're oversize, for a 350cc? At best, they don't appear able to have much pressure against the cylinder wall. In the first pic, the bottom oil ring is on top of the spacer, but it has been disassembled and handled, they don't normally slip out of place like that though. The spacer should cover the ends of the rings and help hold them in place on the ring lands.



I wonder if the top rings are installed upside down. Rings normally have marks that get installed facing up, then the marks also tell which ring goes where. Or maybe the bore job wasn't done right?



Hard to judge the pic of the cylinder. I would get it measured and see what's up. it does have some scoring, and marks that look like it may have sat a long time ... Unless that's just the bottom of the stroke, but I don't think so.


Small chance that it could be honed and a new set of rings installed, but it needs measured with an inside micrometer..



The rings and ring lands do appear carbon-free, so they most likely weren't stuck, but the oil rings just don't look right.


Did the shop remove the head when they lapped the valves? The gaskets should still look new.
 

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Discussion Starter #28 (Edited)
Seems like quite a bit of scuff on the piston, all over the sides, above and below the rings. Not sure how much is just dirt and smudges.



Oil rings don't seem right to me, like maybe they're for a standard bore? Or they're oversize, for a 350cc? At best, they don't appear able to have much pressure against the cylinder wall. In the first pic, the bottom oil ring is on top of the spacer, but it has been disassembled and handled, they don't normally slip out of place like that though. The spacer should cover the ends of the rings and help hold them in place on the ring lands.

I will also take a closer look at the outside of the piston and inside the cylinder. Honestly looking at the pics are not like looking at it in front of you. I have tried to do the best but will look for evidence of scuffing by wiping clean as it has oil streaks and dirt from being handled since removing....

I wonder if the top rings are installed upside down. Rings normally have marks that get installed facing up, then the marks also tell which ring goes where. Or maybe the bore job wasn't done right?



Hard to judge the pic of the cylinder. I would get it measured and see what's up. it does have some scoring, and marks that look like it may have sat a long time ... Unless that's just the bottom of the stroke, but I don't think so.


Small chance that it could be honed and a new set of rings installed, but it needs measured with an inside micrometer..



The rings and ring lands do appear carbon-free, so they most likely weren't stuck, but the oil rings just don't look right.


Did the shop remove the head when they lapped the valves? The gaskets should still look new.
Lots of info from you. Yes they did remove the head and gaskets do look new. I will take a look at the new piston I have to compare the rings. I'm thinking as a kit the rings came from Wiseco installed and should be correct. Went out and did a quick comparison of the two pistons rings. On the installed one the 2 top rings extend about the same with the bottom one less. On the new one the 3 rings are staggered, the top extend most, second less and bottom one less.
 

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I've never received a new piston with the rings already installed, but I suppose that could be something new. ???


How do the new bottom rings compare to the ones you just took out?


Definitely something off somewhere. The piston still looks fairly new, but it has all that scuff, it's smoking, and the oil rings appear too small to do much.
 

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Discussion Starter #30 (Edited)
Just went outside to compare the old and new pistons. I cleaned up the old one and there are vertical marks on it but surface. I scraped my fingernail across them and couldn't feel any scuffs. So then took a look at the new one and it has similar marks. AFAIK, it is new as it is clean. I need to look at the cylinder closer tomorrow to see what it looks like. If sand or something was in there should also be vertical scuffing? Will have my auto mechanic friend look at the piston and cylinder to see what he says. Maybe post a side by side pic of both pistons for comparison..
 

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Discussion Starter #31
Can you post pics of the cylinder walls and the side of the piston?


That's a fair amount of carbon in pic #1.



One thing you can do at home.... Carefully remove the top ring from the piston, keeping the top of the ring oriented the way it has been running. Put the ring, top facing up, about 1/4" down into the cylinder. Using the piston to push the ring down can help make sure it's square in the bore. Now using a feeler gauge, measure the gap between the ends of the ring.


If the top ring breaks, try the second one. You have to work the rings off in a spiral, unless you happen to have a ring spreader.



The oil rings are the bottom rings on the piston. How do they look? If you push the oil rings inward on the piston, how much do they stick out on the opposite side?
So I did this today with the removed piston. The 2 top rings came off very easily, figured it would more of a challenge. Neither one had any markings on to tell what position or which way should be up. I stuck the first ring into the cylinder with the top up as it came out and pushed down with the piston to sit correctly. The gap between the ends of the ring was around .030.
 

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Without marks, some manufacturers go by the "step" profile of the ring. If you look at the end of the ring, you may see a stepped profile.



The oil rings are the easiest to remove/install, they won't break. I wonder what the gap is on those? Don't need to check the spacer.



I found this info, supposed to be 450 Foreman:


Ring End Gap -Top ring ----0.015-0.30(0.006-0.012) ----service limit 0.5 (0.02)
Second ring -- 0.300-0.450(0.012-0.018) ------- service limit 0.6 (0.02)
Oil (side rail) -- 0.20 - 0.70 (0.008 - 0.028)


..Honda's serivce limit for the TRX450 cyl. is 90.00 - 90.01 (3.543 - 3.544 and the service limit is 90.10 (3.547) .. We bore if they measure 90.05 because it's just a waste of money assembling a 1/2 worn out engine (plus it will smoke before it reaches 90.10) ...

Was your air filter extremely dry and dirty when you got it? Dirt really speeds up wear.
 

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Discussion Starter #33
Without marks, some manufacturers go by the "step" profile of the ring. If you look at the end of the ring, you may see a stepped profile.



The oil rings are the easiest to remove/install, they won't break. I wonder what the gap is on those? Don't need to check the spacer.



I found this info, supposed to be 450 Foreman:





Was your air filter extremely dry and dirty when you got it? Dirt really speeds up wear.

Remember this has a 1 mm overbore. I will check the other 2 rings for gap inside the cylinder. The bottom ring is the oil correct?


I did replace the air filter when purchased but not sure how dirty it was.
 

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Discussion Starter #34
OK measured all 4 rings for end gap...


First--.032
Second--.1, yes pretty big
Top oil--.075
Bottom oil--.1 again yes big gap
Not sure about the accordian ring between the oil rings..


That doesn't sound good for a few of those...
 

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The 'accordian' is just a spacer between the two oil rings, no end gap on that one.


Ring end gap would be the same with an overbore.


Definitely a lot of extra clearance, just need the bore measured to see where it's at. It's probably ready for the next size overbore.


Sounds like you could do the assembly yourself, just need a machine shop to bore/hone the cylinder for you, with the new piston in hand. Then have your small engine guy do the valve seals, and check that valve lapping. Ebay is a good place to check for top-end kits. I see piston and rings starting around $60, Wiseco sets with gaskets at $80 and up, and complete kits with cylinder and all at $450.


I have no experience with the Namura (cheapest) brand pistons, sounds Chinese.
 

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Discussion Starter #36
Thanks for the replies..


I do have a jug off the spare engine I got with this quad. It appears to be standard size or first bore larger as my piston doesn't fit in. I have the two 1 mm oversize pistons, one off this engine the other came with my extra parts, and would be my cheapest cost to bore that one to match. From what I've read the 1 mm oversize is as large as most recommend.
 

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Ahh, well, that's the route I'd take. Use that second cylinder, take the best piston, and head to the machine shop. And get a new set of rings and gaskets, at least a head gasket. Some shops will verify the ring end gap if the rings are present when they bore/hone.


Excess heat can cause rings to lose tension, not sure if that's happened, but there it is.
 

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Discussion Starter #38
Ahh, well, that's the route I'd take. Use that second cylinder, take the best piston, and head to the machine shop. And get a new set of rings and gaskets, at least a head gasket. Some shops will verify the ring end gap if the rings are present when they bore/hone.


Excess heat can cause rings to lose tension, not sure if that's happened, but there it is.

Tomorrow taking both jugs and pistons to the shop. I will let them tell me if the removed jug can be saved or bore the spare one. I will take a couple pages of specs from the service manual for reference.
 
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