I need expert advice about pistons, rings, and cylinders. - Yamaha Rhino Forums - Yamaha UTV Forum
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post #1 of 10 (permalink) Old 12-01-2009, 05:38 PM Thread Starter
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I need expert advice about pistons, rings, and cylinders.

Guys, here is my history.

I bought my rhino new. I didn't know it when it happened, but I clogged the radiator with mud. The result was the engine got hot and ruined the piston, rings, and cylinder.

I have since replaced the piston, rings, cylinder, and wrist pin. My next mistake was to break-in the motor per Yamaha manual instructions. After following those instructions to the letter, using Pennzoil conventional 20w-50. I then changed the oil using Castrol semi synthetic 20w-50.

The second time out with the new parts, I was climbing a long, steep hill and had the gas pedal flat-footed. A friend watching from the bottom of the hill said he saw "a little bit of smoke puff". About 2 hours later, while idling the motor shutdown. Cranking it over it was obvious that it had jumped time. My buddy towed me and my wife out with his rhino.

I got it home, checked the timing, and sure enough it had jumped 1 tooth, and it was about 4 ounces low, and the spark plug was sooty black.

Evidently, when it got hot that one time, it had also stretched the timing chain, but I saw no evidence of it when I reassembled it, and it timed correctly, and ran great. But only 200 miles later the defective chain manifested itself.

I replaced the timing chain, the water pump chain (it too had stretched), and the water pump chain guide. Thinking that the rings had properly seated, I reasoned that oil may be passing by the valve stem seals. I replaced the valve stem seals, checked the valve stems and guides, with my finger nail and a soft plastic scraper I gently removed any carbon on the valve seats and valves. The cylinder wall was a kind of dark brown color. The cross hatch was gone, or covered with what might have been a dark brown glaze. But, the cylinder wall was uniformly smooth with no defects, and no ridge. I drained the oil and replaced filter and topped it off with conventional Pennzoil 20w-50.

The next time out, it was low again when returning home, and the spark plug was again, sooty black.

Then I read the way that these guys break-in their engines Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power. So, that led me to believe that the rings had not properly seated. So, with the advice from that site, fresh dino oil, and a new purolator filter (as always), I took off down the road to a friend's house, 12 miles round trip with WOT.

The next day I removed the spark plug and it was a light tan color, but the oil was again 4 ounces low. I have been driving it on the trails in Low gear only, and keeping the RPM's as high as I possibly can to try to get the rings to seat. It has been low of oil after every single ride, but the spark plug now looks good. I have 450 miles, and 50 hours on the piston, rings, and cylinder.

I stuck a scope in the cylinder through the spark plug hole, and it looks the same as it did before, with the brown color.My question is this. What are my best options?

1. Just accept it. It runs great, but the oil burning issue bugs me. I think that the Yamaha break-in instructions are the reason that so many of the rhinos burn oil.

2. Should I re-ring it and re-hone it?

3. Should I only re-ring it, and not re-hone it

4. Should I replace the piston with an 11:1 Wiesco, re-ring, and re-hone it? Then just continue with a build up from there?

5. Or, can my original cylinder be bored and sleeved to original diameter and go 11:1 with it?

Or do you have better advice?

I'm pretty certain that the compression rings have seated, as indicated by the spark plug color, but the oil rings appear to have not seated.

Also, one last thing. When I installed the new rings and piston, the rings didn't require a ring compressor. I have one, but I was just able to squeeze each ring together and slip it in the cylinder from the bottom utilizing the chamfer machined into the cylinder.

Thanks for the help.

Gil

2008 700, totally stock with a few things added here and there.

Last edited by Gildo; 12-01-2009 at 05:52 PM.
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post #2 of 10 (permalink) Old 12-01-2009, 08:19 PM
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If you want good advice call Chris @ BENCHMARK

If you live in Vegas and need a General Contractor...call Manning Construction @ 497-5127
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post #3 of 10 (permalink) Old 12-01-2009, 08:35 PM
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If you want good advice call Chris @ BENCHMARK
X2... cant go wrong with this advise. here is benchmarks # 760-484-0986

btw, i would never re-ring with out a re-hone... you will just end up taking it all back apart at some point or another.

Fuck'em and feed'em cabbageI have found the richer your friends are.....the more they want you to suck their asses.......I guess these fools havent figured out yet I dont suck ass ~ the bigg anonymous
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post #4 of 10 (permalink) Old 12-02-2009, 09:41 AM
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use a CP piston also with DLC pin.

you are correct, the loss of oil is from rings most likely. cylinder can be resleeved, but not an optimum way really.



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post #5 of 10 (permalink) Old 12-02-2009, 04:56 PM Thread Starter
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If you want good advice call Chris @ BENCHMARK

I'm sure he's great. But I'd feel kind of funny calling him, asking for advice, taking him away from his work, and then probably not buying anything, and then him not getting anything for his time.

Gil

2008 700, totally stock with a few things added here and there.
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post #6 of 10 (permalink) Old 12-05-2009, 07:04 AM
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What happened here is that you never use synthetic oil when you have a new bike or when you rebuilt an engine TILL it is broken in!I would say around 1500 to 2000 miles.
I would get it rehoned and yes you need new rings remember,no synthetic till brake-in!
YAMADOGDE
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post #7 of 10 (permalink) Old 12-05-2009, 08:40 AM
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i'm sure he's great. But i'd feel kind of funny calling him, asking for advice, taking him away from his work, and then probably not buying anything, and then him not getting anything for his time.

Gil

every builder gets those
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post #8 of 10 (permalink) Old 12-08-2009, 02:36 PM Thread Starter
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every builder gets those
I'm sure they do, but I don't want to contribute to that.

2008 700, totally stock with a few things added here and there.
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post #9 of 10 (permalink) Old 12-15-2009, 12:40 PM
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trust me, it is OK to call him. early evenings are better though.


synthetic is OK for the get go.



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post #10 of 10 (permalink) Old 12-15-2009, 12:42 PM
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are these factory parts? we have had some ring issues lately from yamaha. the gaps exceed specs while brand new.



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