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CRF450R side to side play in crankshaft!!

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Hey guys,

Really need some help on this one.

I got a second hand CRF450R (2009) 80hrs, prior to handing the cash over, I took it for a ride and thought it was all good. (got it cheap, and suspect its been poorly maintained)

That weekend I took it for a ride, first lap.. noticed a knocking noise. shut it off and took it home.

Once I got it home I gave it a new top end.. piston rings, pin, had the barrel checked, shimmed valves to spec, new guides and new water pump. Went for a ride.. no good. still had the noise. Have now pulled the motor out and split the case... Only bearing i could find that may be on its way out was the roller bearing that the clutch basket sits on - a small amount of movement. BUT.. then I noticed the crank.. it slides side to side with a rather good "knock" (not the con-rod, but the crank),, there's so much movement that it almost looks like there is a thrust washer missing or something - but the service manual does not show a thrust washer there.. I'm 99% sure this amount cannot be ok. However, the main bearings that the crank sits in, have only the slightest amount of wear, almost nothing.

This is my first bottom end of a dirt bike engine, so I'm not sure how much movement is too much.

Has anyone come across this? or have any ideas/remedies???

Click on this link to a youtube video of movement of the crank. 

 

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some side to side rod play is normal. Up and down on the rod is what you don't want. The side to side crank play your demonstrating is going to me normal if the gear stack on the transmission side is not installed and torqued to spec. When you tighten the bolt down on the transmission side is places the crank where it needs to be. Are you 100% positive you were hearing a knock. These motors are noisey as crap especially at an idle.....either way though if your that far into it. I would at least go ahead and put main bearings in it at the very least

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Thanks for your reply.

Yep, 100% sure there was a knock. I've been racing for 15 years, had ktm four strokes, countless two strokes, my mates have had hondas,, never heard a knock like this. very noticeable even with helmet or earmuffs on.

I think I'll just replace main bearings, the bearings i mentioned that the clutch basket sits on, have the crank inspected and put it back together. It's about all that can be done I think.

 

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Make sure the primary gear is on the crank and tight and see hiw much movement you have again. Some movement is normal but yous looks to be a bit much but hard to tell from a video. If its already split i would at least change the mains and seals. Also make sure the tensioner for the cam chain in working right and not collapsing causing the timing chain to slap around and make noise. Honestly if its got 80hrs on that crank and you already have it split and tore down i would just throw a new oem crank in it for $300 bucks and mains and seals. Then you know the bottom end will be good for awhile. Especially if you suspect the maintenance was poor on it. 

One other thing to check would be to see if the rubber cushions in the clutch basket are not all cracked and destroyed allowing the basket to make some noise since the cushions are shot. 

Edited by trvshonda

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You definitely can not judge the crank slap without having the flywheel and clutch basket torqued down.

The amount of play in the rod seems excessive since it doesn't look like you are moving it with much effort.

The knocking could be from the piston or clutch basket or cam chain as stated.  

Did you check the flywheel for up and down play before you tore it apart?

 

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snug up a couple of case screws. install the drive gear and tighten the locking nut and that play will go away. Depending on how good or bad you main bearings are

Then check for up / down movement of the crank ends.

And as has already been mentioned 80 hrs is a good time to replace the crank and mains, since you already have the motor down to the cases. Its cheap insurance.

The clutch and flywheel have nothing to do with that side to side play.

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