possible engine failure?

5 replies to this topic
  • steed2

Posted February 03, 2008 - 04:44 PM


I got a question for all you 650r owners...last march i was out on my 2004 xr650r and we were riding at a local track...me and my buddy we head and head comin across a set of woops that ends with a small jump
the brp started to swap just before the jump and i basically did an unintentional ronnie renner 90 degree whip {minus the part were he straightens the bike back out) lol
after the small high speed crash we continued to ride some dunes for about 4 hours.when i got home I noticed that the airbox clip that always pops off from the boot had been poped off.(probably from the crash) when i pulled the air filter out what i seen made me sick....a 1/4 inch of canadian sand on everything all the way into the engine..i changed the oil , cleaned everything up and called my local shop they said the bike is bullet proof dont worry about it....i then bought a 06 crf450r and the bike sat for the season minus the odd ride once a month to keep everthing loosened up. Well now ive got her back out for ice riding and ever since that day she doesnt seem to be at 100 percent...runs great but with less power ...any ways my question is has anyone expierienced this and what damage am i probably looking at to cause a power loss but not a reliability issue

thanks again guys --steed2

  • Thumpmeister

Posted February 03, 2008 - 04:52 PM


Did you replace anything at all when you went through the motor?

I took a spill out at the dune a few years ago, and sucked a bunch of sand through my airbox as well, unknowingly. I had a little more top end noise than usual, the bike smoked a lot on start up.

When I tore the engine apart, I found that the sand had essencially ground down my valve faced, and ate up my rings, and also made me have some serious piston slap. Enough slap to actually wear through the nikasil lining. I sent the cyl off to be re-plated, and sent the head off w/ the valves to have them machined.

After I finished the rebuild, I had a significant amount more power, no more smoke on start-up, and it ran a LOT smoother.

What I'm saying is, if you feel its down on power, then you might want to consider a rebuild. Bottem end should be okay, but the top end has been pretty much sandblasted. Its not real hard to rebuild, and that is just in a worse case scenario if your really worried about it. I did all the assembly/disassembly myself, and spent around $300-$400 for all the parts.

  • steed2

Posted February 03, 2008 - 04:56 PM


ya thats what im think ...im in the mids of rebuilding my 450 right now and ive never had a problem rebuilding motors...(im a transmission rebuilder)...but i was concerned about bottom end ....what i dont get is it doesnt smoke or anything runs great ...just a significant power loss ...probably top end ...like you said

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  • Thumpmeister

Posted February 03, 2008 - 05:56 PM


Usually smoking is related to two things on Honda's; rings and valve guide seals. Sounds like your valve guide seals are still fine, as those are major contributors to smoking. However, if you were to rebuild it, you should replace the seals anyway.

Your probably low on compression, like you sucked a bunch of sand over the valve faces, and wore them down. You might have to get some new valves, and then have the faces machined as well. However, new rings and a hone wouldn't hurt while the engine is apart, as long as the lining isn't worn away on the walls.

  • resurrection

Posted February 03, 2008 - 09:17 PM


These things mentioned should be aperant with valve clearence check and leak down test

  • Thumpmeister

Posted February 03, 2008 - 10:22 PM


These wouldn't necessarily be clearly apperant w/ a clearance check, unless its WAY out of spec. However, if the valve seats got worn down enough to just lose a little compression, it might be hard to detect w/ a valve check.

However, it would be apperant with a leakdown test.

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