Flywheel movement = bearing play?

S

steve.emma

Member

Oct 21, 2002

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• May 15, 2011

• #1

Hi all, question regarding main bearing play on a 2stroke. Bike in question is a 99' kx250 and i was checking for play in the main bearings by wiggling the flywheel etc.. up/down there is the very smallest amount of play and i suspect this would be gone if engine was hot. front to back or side to side there is no play, but if i pull/push flywheel in and out there is a bit of play at and you can hear it make a noise when i do this.
Is this normal? how much in/out play should there be? haven not noticed any vibration or noise when riding bike.
Any help appreciated.

 

J

julien_d

Member

Oct 28, 2008

1,788

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• May 15, 2011

• #2

in/out is not what you are concerned with. It's up/down and front/back.

 

whenfoxforks-ruled

Old MX Racer

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Oct 19, 2006

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Merrillville,Indiana

• May 15, 2011

• #3

Why are you fooling around with the flywheel is a better question?

 

S

steve.emma

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Oct 21, 2002

285

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• May 16, 2011

• Thread starter
• #4

in/out is not what you are concerned with. It's up/down and front/back.

Click to expand...

Well im kinda worried about play full stop. but if you think that some in/out play is normal then cheers as thats what i thought also.

Why are you fooling around with the flywheel is a better question?

Click to expand...

I dont really think checking for play in the main bearings is 'fooling around' as you put it. but if you are wondering what i was doing there i was in the process of installing a flywheel weight at the time.

 

RM_guy

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Damn Yankees

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• May 16, 2011

• #5

I was fooling around with the back tire the other day and I thought it might have been flat but I was just folling around so I didn't do anything about it. :bang:

 

whenfoxforks-ruled

Old MX Racer

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Oct 19, 2006

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Merrillville,Indiana

• May 16, 2011

• #6

Usually if there is an issue, you check the end play? It was not mentioned? Now it makes sense Steve, thanks. About the side to side though, there should be a tolerance on how far it slides in and out, this does keep your rod centered in the bore. I have a 99 book to reference, and like I thought, there is no number for how much you can actually pull the crank in and out of the engine. Usually the collar on the drive gear, at the other end, when torqued properly, keeps it centered and tight. If yours moves enough to see, I would be concerned. The spec on adjusting it to center is not mentioned also, I take that as no play is good. Are there signs of seepage around the left crank seal? Putting on a fly wheel weight usually means you are after more bottom end? When a motor wears out of spec, the bottom end power goes first. I do not believe it is a flat tire.

 

RM_guy

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Damn Yankees

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• May 16, 2011

• #7

whenfoxforks-ruled said:

... I do not believe it is a flat tire.

Click to expand...

:laugh:

 

1

1998RM250

Member

Nov 5, 2008

426

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• Jun 28, 2011

• #8

My 2002 CR 250 I just picked up has a tiny bit of play side to side in the flywheel too and has me worried because I'm not sure whats acceptable!

 

2-Strokes 4-ever

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Feb 9, 2005

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Missouri

• Jul 4, 2011

• #9

RM250 w/ all new lower end...

Slight in-out play, no front/back - up/down movement at all.

The lower end is new because... I noticed some play in the up/down - front/back directions, thought I could still get our big yearly 200 mile ride out of it... well, a main bearing cage came apart. New mains and seals, rebuilt crank, new rod, and had to replace a new top-end and replate a "perfectly good" cylinder... ($$$)