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Old 05-16-2013, 01:00 PM   #17041
crypto666
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Quote:
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, 02:40 PM   #17042
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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, 05:17 PM   #17043
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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, 07:42 PM   #17044
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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, 09:34 AM   #17045
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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.
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, 10:18 AM   #17046
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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, 02:16 PM   #17047
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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?
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, 06:11 PM   #17048
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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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Old 05-17-2013, 07:31 PM   #17049
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I sure hope I don't have a bad one!
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Old 05-18-2013, 08:12 AM   #17050
crypto666
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Originally Posted by RideFreak View Post
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.
Remember the years?

Mine was failing at the small end, as have a number I have seen on here and elswhere.
Most likely a product of inexperience and lugging the motor too much, and opposite of what the sumo guys are doing to the engine.

So I guess it is prone to failure at high and low speeds, atleast on certain years?
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Old 05-18-2013, 08:50 AM   #17051
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Remember the years?

Mine was failing at the small end, as have a number I have seen on here and elswhere.
Most likely a product of inexperience and lugging the motor too much, and opposite of what the sumo guys are doing to the engine.

So I guess it is prone to failure at high and low speeds, atleast on certain years?
It seems to be the earlier ones from what I can tell, but there's been a couple cases of it occurring on some newer ones too, even early enough to have a few fixed by the dlr but no recall. I heard it's a tolerance issue when the crank is pressed together at the factory. Seems that would be easy enough to check prior to assembly. If one is lucky enough, they notice flakes of babbet in the filter which is the thrust washer material. It doesn't take long for them to deteriorate once it starts, then the oil pressure drops. Sometimes this is followed by a big vent hole in the case if being run hard. I wouldn't call it a problem though, there was allot of XRRs sold and by far it's a very reliable motor. Luggin 'em isn't good but lets face it, you can't ride it fast all the time (at least I can't) and as far as I know, the problem isn't related to a type of riding. I think the lugging is hardest on the cam chain.
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Old 05-18-2013, 09:54 AM   #17052
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It seems to be the earlier ones from what I can tell, but there's been a couple cases of it occurring on some newer ones too, even early enough to have a few fixed by the dlr but no recall. I heard it's a tolerance issue when the crank is pressed together at the factory. Seems that would be easy enough to check prior to assembly. If one is lucky enough, they notice flakes of babbet in the filter which is the thrust washer material. It doesn't take long for them to deteriorate once it starts, then the oil pressure drops. Sometimes this is followed by a big vent hole in the case if being run hard. I wouldn't call it a problem though, there was allot of XRRs sold and by far it's a very reliable motor. Luggin 'em isn't good but lets face it, you can't ride it fast all the time (at least I can't) and as far as I know, the problem isn't related to a type of riding. I think the lugging is hardest on the cam chain.

God damn, that makes me worried. I don't remember checking the side gap on my rod after getting it pressed together. I just remember the shop telling me the number and it being in between the specs, so I took their word for it, and I am pretty sure its good.

The reason I blame lugging on small end failures, and I am sure its bad for the cam chain as well, is because of oil jet that lubes the small end. I assume that at low speeds it has a hard time squirting oil all the way up to the wrist pin. I have no proof, but it was the only thing I could come up with for the failure, besides that it uses a bronze bushing instead of rollers. My motor was not even close to wore out in any other area, just the small end and a hole in the case.
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Old 05-18-2013, 10:31 AM   #17053
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Engine Lugging/Engine Damage

Lugging is a relative term, obviously. It's different for different engine configurations. Generally it's running an engine at low rpms while under a load. To go a given speed, a certain amount of energy-per-time (work) needs to put through the motor through the transmission to the ground. When 'lugging", you're causing that amount of work to be done on few cycles (rotations) of the piston/crankshaft assembly. Think of riding a bicycle. It's easier to pull shorter gears (higher rpms) than taller ones. With tall gears, you have to really push on the pedals to go slow. Now think of your piston and crank assembly doing the same thing while you're lugging your motor. All that pressure on the piston crown, piston pin and big end on the connecting rod is just like your quads trying to push the pedal down. The oil film can only handle so much pressure before collapsing and causing metal-to-metal contact. Plus, at lower rpms the oil film will have more time to collapse than at higher rpms.
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Old 05-18-2013, 12:04 PM   #17054
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And I'm the guy with a low mileage 2001 that has high Iron, copper and silver content in the oil.

I'm remembering my first oil change where I cleaned the strainer in the frame. It had a bunch of of metal bits, did'nt pay much attention to it. I'm almost certain it was the first time it had ever been cleaned so i just figured it was production shavings left behind. (the frame oil reservoir is after the oil filter correct?) No way bottom end bits would end up in the frame unless there was a filter failure.

Next change I'm going to cut apart my filter to inspect and clean the strainer in the frame......
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Old 05-18-2013, 05:52 PM   #17055
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Like I said, it's not what I'd call a common failure, I'm not trying to scare anyone, the XR motor is uber relaible compared to many others.

Ron, that's a great explanation of lubrication's characteristics and I think you're right on the money with it's effects. It sounds like a plausable cause for crypto's prob. The plain brg in the small end is a proven design but there is allot of mass in the crank/rod/piston assy on a 650. Lugging definately taxes the brg areas.
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