Max lateral play of rod & how to lighten flywheel

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Sep 21, 2000
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#1
Max lateral play of rod & broken skirt!!

For my 1990 RMX I was wondering the max. allowable lateral play of the connecting rod at the crank. My manual doesn't actually say and I do think it's a bit high, but I just need one more month or so of play riding till the winter lower end rebuild. Why do I have the cylinder off to be able to check this.... well now I only have an exhaust side skirt. Seems my intake skirt came of in 2 large pieces and many more minute ones. Now I now what the rattling noise was during acceleration on my last 3 or 4 rides. A little late now but amazingly enough my cylinder escaped any damage.The bike was bought used and I have no idea how many hours were on it. I'm wondering if the play in the rod at the crank end would contribute to this?
What is a cause of skirt slap?

If someone like myself can do a top end, how much harder a job is the lower end - at least enough to take the crank to a dealer for seperation and such. Ive been wanting to do it over the winter but am a little apprehensive.

Also Iwas wanting to lighten the flywheel for a bit more snap, has anyone done this and if so how?

Thanks in advance for your help.
 
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Mar 15, 2001
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#2
The bottom end isnt really that hard... especially if you have a manual... Is it the stock manual? I have one for my RMX (89) and it guides you through in detail. I would recommend taking the crank to a shop. My manual doesnt say the max play either.

Are you talking about the rotor? Or the halves of the crank? If your talking about the rotor you may find this interesting... Prolly wont want to try it, but i think its interesting..

Ive got something goin on with my flywheel and stator. The 4 magnets inside the flywheel broke and beat my stator to the point of no return... So, instead of buying nearly $400 of oem stuff, I found a RM stator and rotor off of an 88 RM250 for $50. So i got the rm stator and rotor thinking rm, rmx, basically same thing, should work. WRONG. The crank is bigger on the rmx, so I had my shop teacher at school bore it to the size of the rmx. Made a new keyhole too. RM key is wider by the way... So I got a RM key and made a step-key to fit the RMX hole in the crank. Rotor is fairly thin and I hope it doesnt crack, but it works. Now the stator isnt as tall as the other either. So we spaced out the plate, and the magnetic pickup. Now Im waiting on gaskets to put it all together. It does have spark, so i think it will work. I should have it together sometime next week. I'll let you know.
Sorry for the loooooong reply, and that i couldnt help more,
but it may help a little.
 
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#3
I rode my friends 2001 CR 250 whilst my bike is apart (the piston slap that turned into a broken skirt) and I like the instant response, so I wouldn't mind taking a bit of weight off the flywheel of my bike. I just have to look at it closer and see if it is possible, I don't want to take off to much since I also ride in the Rocky Mtns. up here in Alberta and some slow steady uphill battles are always in the mix.

Let me know how it works.(Your RM flywheel)

I can't believe the actual Suzuki manual doesn't say specs on the crank and bearings. I have the Clymer so it wasnt a big surprise. Calling the dealer can be hopefull at best to get a solid answer.

I would really like to get away with just replacing the top end after my skirt broke. Getting into the lower end would mean way more money and dealer time since home tools are no match for the lower end. I just need to evaluate the fit of the rod at the crank and go from there.

Any suggestions?
 

SFO

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#4
The worst feeling in the world...

Is replacing your top end, doing a really puss job, and breaking it in easy and then!!!!
Braaaap, the rod poops the bed.
If you got a question in your head about the integrity of your bottom end, DO IT!
Cheap insurance.
Or, play Russian roulette, and takes your chances.
If the skirt fell off of the piston I would say this bike has seen minimal maintenance.
If you want to experience the satisfying potential of this machine, Take the bull by the horns!
Rebuilding your bottom end is childs play, seeing as your dealer or some other professional is going to do the rod replacement.