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Old 05-15-2013, 07:49 PM   #17026
rpmwfo
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Based on Flyguy's info, I am going to pass on the Ross piston. I like the lighter weight, but it appears to be just too light for longevity. I agree with the cyclic fatigue from the pics.

I do like the looks of the Wossner piston. I too would be curious about the weight of the piston relative to stock.
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Old 05-15-2013, 09:32 PM   #17027
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http://www.wossnerpistons.com/images...WOS-8718DA.swf
This is the Wossner link for their 11:1 piston. Different design than their 10:1.
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Old 05-16-2013, 03:59 AM   #17028
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Quote:
Originally Posted by FlyGuy View Post
Well Id bet its a cyclical load issue due to flex
I am also familyer of the weisco issues where the metal on the inside looked marbled indicating impurities and what you indicate happens as a cause.
but look at the picture in my post above and it becomes more clear.
And Hell ya go for the light weight and you wont go back.
but check out worrsner pistons too. I am going to try to find out there piston weights
I have looked at the pictures again , and you are right . there is not enough material in the critical areas and the flexing eventualy crack the piston . I like Woesner a lot and they are not overpriced , do you know how much is the weight ? ( i cannot find it nowhere to compare to the others ) .
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Old 05-16-2013, 07:22 AM   #17029
crypto666
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Originally Posted by rpmwfo View Post
I'm looking to get more power out of the bike(I ride from 5000' - 10000'). The elevation takes a toll on power output. I would like to turn the bike into a lightweight adv/dual sport bike. I'd like to run 15/45 gears. Maybe a rekluse to help the tall first gear. I don't plan to be riding too much single track with it, but might be nice to if I fun across a great trail somewhere.

Currently planning to build up the motor on my BRP. Thinking about doing the following:

-XRsonly 11:1 coated piston
-HRC Cam- found one, hopefully it gets here soon, if not I guess I will go with the first Web cam listed on their site
-Kibblewhite black diamond valves and springs- Going stock size
-New cam chain
-Changing from Big Gun full system to XRsonly LE race system with the reverse megaphone design.

Any advice on the above?

Buy the best connecting rod you can find, that is the weak link in that motor. Falicon are nice.
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Old 05-16-2013, 09:55 AM   #17030
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Stock Tank Thickness

Anyone ever cut a stock tank apart and happen to know roughly how thick the plastic is at the tank top? I'm thinking about sinking a couple of capture nuts into the top edge of the tank (right under the sides of the seat) for my Sumo project. It looks plenty thick enough in the center where the seat bolt goes in but I'm not certain about the edges. I don't really want to put daylight into it if I can avoid it
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Old 05-16-2013, 11:16 AM   #17031
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I just checked and too have Ross 11:1 in my bike, for probably close to +5k miles, but its a 102mm. Hopefully that failure isn't common.
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Old 05-16-2013, 11:49 AM   #17032
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FWIW I don't think 11:1 compression, even on a bore/stroke combo this large, is necessarily problematic so long as there is no detonation problem or engineering weaknesses. As an example, my old porsche 968 has a 3.0L 4cyl motor with 11:1 CR, 104mm bores and 88mm strokes. Mine has 150k miles on it now and runs just dandy. Rev range is also fairly close to that of the XR. (there are of course lots of other examples, street bikes, etc. as well).
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Old 05-16-2013, 12:00 PM   #17033
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Originally Posted by BikePilot View Post
FWIW I don't think 11:1 compression, even on a bore/stroke combo this large, is necessarily problematic so long as there is no detonation problem or engineering weaknesses. As an example, my old porsche 968 has a 3.0L 4cyl motor with 11:1 CR, 104mm bores and 88mm strokes. Mine has 150k miles on it now and runs just dandy. Rev range is also fairly close to that of the XR. (there are of course lots of other examples, street bikes, etc. as well).

I agree, if it still runs on pump gas, its probably not wound too tight.
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Old 05-16-2013, 01:40 PM   #17034
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Come on BikePilot,

and nice car so btw, but that engine has a large part of the combustion chamber in the piston crown, a large indentation, plus it is a blown engine - hence it follows that those are hardly the lightweight piston type as the above Ross is, so that apple-pear comparison aint valid. Also, that engine's way better cooled than our pigs, marginal springs to mind.


FG,

nice pistons indeed - keep us updated if you buy one please?
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Old 05-16-2013, 04:17 PM   #17035
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Originally Posted by crypto666 View Post
Buy the best connecting rod you can find, that is the weak link in that motor. Falicon are nice.
Right on both points.

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Old 05-16-2013, 06:42 PM   #17036
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Detonation causes cracked pistons. Overheating can contribute to this, but I would look at fueling (both mixture and grade) and timing first. That piston died from detonation.
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Old 05-17-2013, 08:34 AM   #17037
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Originally Posted by cragdweller View Post
Detonation causes cracked pistons. Overheating can contribute to this, but I would look at fueling (both mixture and grade) and timing first. That piston died from detonation.
Actually that was my first thought too, hence my Q's.
I believe the octane rating in the US isn't too high, so was surprised to see 11:1 mentioned. Here we've got 95, and my CRF230 with a 11:1 piston in pings low down when hot and loaded. Being aircooled this may be expected, accepted even as long as you pay attention, but on the big one I'd stay away from it. This is why I bought a 10.5:1, after all I'm not racing it.

FlyGuy may want to look, with a timing light, at the ignition. Maybe it's out a little, a worn key maybe? Check anyway, if it pings the best piston will give way..
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Old 05-17-2013, 09:18 AM   #17038
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Installing new swingarm, shock, and linkage bearings tonight. Obviously fill the bearing with grease, but should I put anti-seize on the outside of the bearing or just more grease?

I have the honda shop manual so hopefully I don't have any surprises.

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Old 05-17-2013, 01:16 PM   #17039
BikePilot
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Originally Posted by BuRPsa View Post
Come on BikePilot,

and nice car so btw, but that engine has a large part of the combustion chamber in the piston crown, a large indentation, plus it is a blown engine - hence it follows that those are hardly the lightweight piston type as the above Ross is, so that apple-pear comparison aint valid. Also, that engine's way better cooled than our pigs, marginal springs to mind.


FG,

nice pistons indeed - keep us updated if you buy one please?
I think Porsche made 14 blown 968s, which, sadly, mine is not. It's N/A. I wouldn't call the XR650Rs piston a lightweight type piston, but that's a relative thing I suppose. Anyway, just one datapoint.

US octane is roughly the same as ROW, it's just commonly measured differently.
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Old 05-17-2013, 05:11 PM   #17040
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The problem with the XRs bottom end isn't the rod, Honda had a run of poorly built cranks that caused a failure of the Big end thrust washers. Plenty of SM guys run them much harder than we do. Once the washers start going bad it's a very short time before the bottom end follows. Results are the same though, once it happens the bottom end is toast.
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