CRF450X bottom end failure

[Steve FarrellMember]

Hi Jimmy, it is hard to get a perspective with those pics. Looking at the crank shaft there has been contact there and the big end fragments have done the chewing of the case.
If the case is not cracked and seal and gasket surfaces unaffected then you might be right but I would have an engineer look at it. Steve

[James RookyardMember]

I think the brass coloured ring fragments were the big end bearing retainer. It and some of the bearing have ground around the crank and the cases. The piston has hit the crankshaft when the rollers droped out of the big end bearing.
Why would a big end fail like this anyway? Is silkolene oil no good?

[Adam RodgersMember]

Jimmy

Has anyone done any work on the motor previously ?

One area to be aware of is flywheel removal.

The end of the crank has an oil gallery and if damaged can affect oil flow to the bearings.

No other ideas sorry, looks like a few dollars are going to be thrown at it though

Adam.

[James RookyardMember]

No I bought it new and have only had the head and barrel off it before.

I pulled the flywheel off with an ordinary puller but the crank is going in the bin anyway so I could see it doing damage but wasnt worried. I had a fair amount of trouble shifting it actually. I left it with all the weight on it and when I walked past it about 5 minutes later it popped off with a bang and luckily I caught it before it hit the cement. Scared the crap out of me lol!

Yeah it sux spending money on a bike I was hoping to sell earlier this year. Not worth much as is though.

[HeathMember]

Could you please pull the piston wrist pin out and see it the is any wear on the bottom of the little end of the conrod?

Here a link to my thread on Dirtbikeworld with pictures of my conrod!

http://www.dirtbikeworld.net/forum/showthread.php?p=1265950#post1265950.

Thanks

[James RookyardMember]

Mine was caused by the jetting being too lean and pinking due to the prolonged high revs apparently. Makes sense, as it pinked on regular fuel but usually when it was lugging in pony express’. I normally use pulp but can not always get it.
I would check the big end in that bike hondahead. The price for parts for mine is $950 with no labour(I will do all the labour).

[HeathMember]

Thanks for that Jimmy.

The big end felt ok. But i’m not expert. The bike had a bit of rattle (had it for a long time! I thought it was the alloy bashplate). The piston was a bit sloppy in the bore. But hadn’t damaged the cylinder.
I ran the the factory jetting for the first 2500k’s (only a 142 main!). The put a JD kit and 160main. The bike has 5200k and 126 hours. Done a bit of high speed pre running at Finke and motarding. Plus a couple of motorcross days. But mostly just baby it trailriding!

But I do already have a new crank in stock as I was planning on running the bike Finke 2012. But was planning on getting at least 200 hours on the orginal crank. The last thing I want to do is smash the cases if I don’t have too.

I’ll post up if anything interesting happens (I’ve already got it going -hopefully it doesn’t blow!)

[James RookyardMember]

Finaly got it all back together and started 3rd kick, once I hooked the battery back up….

Had to replace the linkage bearings while I was at it and fitted a new chain and sprokets.

Off to race a pony express tomorrow. Fingers crossed.

[StuartMember]

jimmy wrote:

Finaly got it all back together and started 3rd kick, once I hooked the battery back up….

Had to replace the linkage bearings while I was at it and fitted a new chain and sprokets.

Off to race a pony express tomorrow. Fingers crossed.

Wallaroi would be a good track to run your bike in on, would have liked to have been out there myself.

[James RookyardMember]

Id just like to thank my partner, my mechanic…… bike ran like a dream and my partner and me pulled off 1st place in clubman class!

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