Crankshaft "Aluminum inserts"

[titoislaidlow]

I have a 2001 RM 125. It recently had a fresh top end. It has also had a new bottom end done within the past 2 years. This is my question. There are 2 aluminum inserts on the crank on both sides. Somehow one of the 2 bolts that hold these inserts in worked its way loose and destroyed 1 of the aluminum pieces. I was lucky that it ONLY damaged the inserts and the piece it broke was large and did not fall into the case. Now for my question. I do not want to do an entire new bottom end because this one was a new Suzuki one. I am assuming it was a crap bolt that broke it loose and caused this. Suziki does not sell just the aluminum, they only sell the entire crank set (over $200). I know Yamaha makes theirs out of plastic, What can I do? Or am I stuck with a crank thats no longer good because of this aluminum. Any help is greatly appreciated! ~tito :coocoo:

 

[SFO]

aprillia used wood to stuff the cranks on their gp250's.
It would swell and seize the cases.
I have used styrofoam and epoxy to stuff cranks with success
Any competent crank builder or machine shop can manage this issue.

 

[titoislaidlow]

Well since I am not a pro crank builder and the 2 suzuki dealers in town arent either. Is there a way around this? I have been tempted to try filling them with an epoxy of some sort. How does this throw off the balance? I assume I would have to have it professionally balanced somehow after this? Im suprised there arent aftermarket pieces for these...any help is greatly appreciated.

 

[Jaybird]

If your bike was blue...crankstuffers from promotobillet go for about $60.00
Not sure if they make them for yellow bikes.

I'd find a compitent machinist and have it done right.

Do a search for this guy at DRN and shoot him an e-mail: 147leeman
He may be able to steer you to the right place.

 

[titoislaidlow]

Thanks for the help. I emailed leeman.

I have come across a 2001 crank off a 250. Does anyone know their cranks well enough to know how much bigger it is than a 125? The crank is a few thousand miles away. I am thinking of buying one and trying to use the inserts. Maybe machining them down a little if they are too big. Not sure though? any ideas?

 

[Ol'89r]

I have come across a 2001 crank off a 250. Does anyone know their cranks well enough to know how much bigger it is than a 125? The crank is a few thousand miles away. I am thinking of buying one and trying to use the inserts. Maybe machining them down a little if they are too big. Not sure though? any ideas?

titoislaidlow.

The 250 crank is larger than your 125 crank. Seems like a lot of trouble just to get a aluminum stuffing block.

Do what SFO suggested and take the crank to a machine shop and have them machine one from some aluminum stock. Have them machine it about .001 to .0015 thousands oversized. Put the insert in your freezer and heat the crank in your oven and press the insert in the crank. Be sure to back up the crank half with a steel plate so that you are not pressing against both halves of the crank. Pressing against both halves could throw the crank out of alignment.

The machine shop should also be able to press the insert in for you. I can't imagine this would cost very much.

Also, if you heat the crank in the oven, make sure your wife or mom is not around. And when she asks why her chocolate chip cookies smell like two stroke oil,, :yikes: Well, you just might have some splainin' to do mister. :laugh: :rotfl:

Just my $ .02

 

[sunnyboy]

im confused while not a susuki pro.i do not understand about the broken bolt and the pieces not falling into the case,the crank is in the case and i have never seen crank stuffing being bolted in. just want to make sure we are talking about crank stuffing.your dealer should have a local machine shop that they use.i have in the past stuffed many a crank it is simple.get some balsa wood stock and wittle a plug that just fit the hole not to tight,coat it with the best epoxy you can find,24hr or more curing time, and insert it in and let it dry for several days then put it back together.the weight differance between that plug and the aluminum is very close so dont worry about the balance it will be fine.i stll have a bike a stuffed over 15years ago and it is still fine. had a friend who didnt coat the plug just did the ends and lost the plug the balsa is so soft it did 0 damage it just passed it through so do a good job and you will have no problems

 

[titoislaidlow]

Those are the best awnsers that I have heard. Thanks alot. We are talking about the same thing.

You can see the inserts on the inside faces of the crank. They are held in with 2 hx head bolts. My only idea on how it came loose it just the sheer velocity and movement of the crank. I will put locktite on the next set of bolts. The peices didnt fall in the case because for some freak incident the bike was not running when the bolt came loose, but when it did come out it rested against the crank and insert. Then when I tried to kick it over it pushed itself into the aluminum cracking it. And only 1 good size chunk came off when I touched it. It had been cracked and I broke it off.
Great awnsers for the balsa wood and machine shop. I like the wood idea. It sounds fairly easy my only concern would be swelling but it is definetly worth a shot. Do you have any recommendations on a certain type of epoxy? And just coat the 4 sides that are touching the crank or should I first coat the entire wood, then apply with more epoxy to the crank?
If this doesnt work I will definetly have the pieces machined. But I am hoping that it does. Thanks alot for all the help!

 

[titoislaidlow]

I also got to thinking. Should I do all 4 or just the 1 that is damaged?

 

[titoislaidlow]

ttt. Just want to make sure this doesnt get lost. I just had 1 last question. Should I glaze the entire wood piece and should I replace all of the pieces or just the 1 that is damaged?

 

[titoislaidlow]

OK. So I carved a perfect replica of the insert. But there is a HUGE weight difference in the two? I used balsa wood. Should I try a heavier wood or what?

 

[titoislaidlow]

Well its been a few days and no further help. I need to get riding and cant put this off much more.
I could NOT find an epoxy that would be resistant to gas/oil/temp/high stress all in the same combo.
So what I have decided to do is mix some JBWeld and try to reform the original aluminum, then I am going to JBWeld it to the crank. I hope if anyone see's a problem with this they will help me out. Any questions or comments are greatly appreciated. Thanks ~tito

 

[Ol'89r]

Well its been a few days and no further help. I need to get riding and cant put this off much more.
~tito

Well, I guess you could always have a machine shop machine one out of ALUMINUM. :coocoo:

Tito.

Sounds like you are going to a lot of trouble just to avoid the obvious. Take it to a machine shop. You could be doing this >>>>>> :ride: instead of doing this>>>>>>> :bang:

Just a suggestion.

 

[titoislaidlow]

Just a follow up. I got a insert machined. The bolt had sheared off on the crank so I tried JBweld on the undersurfaces and screwed it in. Well approx. after 5hrs of riding the piece came loose again and dropped into the bottom end. Gernaded everything in it and cracked both edges of the case. :bang: This all happened in July...Ive been bikeless b/c I just gave up. This winter I have torn it down. Im TIG welding the case so I dont have to buy 2 new halves...and Im also dropping $500 on all new parts b/c the crank was bent to **** and everything needs replaced...

...boy I love dirtbikes. :ahhh: :yikes:

 

[jar944]

JBweld

:bang: :bang: :bang: :bang: not to be a smart ass but if you would of taken the machine shop advise you could of avoided all of your current problems.........and JBweld.......are you serious. i wonder how many problems were made worse by people using it instead if actually correctly fixing the problem the first time.......yes it has it's uses but it's not steel in a tube

 

[titoislaidlow]

Maybe you didnt read my post above. I took it and got it machined at a shop. The damn bolts sheared off...wonder genuine suzuki bolts...

...basically the proper thing to do would have been to replace the entire crank assembly. I would recommend this the next time. The only reason I didnt take it to a shop was b/c I like to fix things myself...and thats the price you pay to learn I guess. Thanks alot for everyones help and knowledge. You guys helped out alot. This is a great forum.

I have the bike stripped and maybe Ill do a buildup post in the spring?

 

[ukkdxrider]

crank stuffings purpose ???????

just wondering what the purpose of crank stuffing is i have 2 kdx200, engines one has stuffing the other has none the one without is a 91 uk full enduro (fast ) version the one with is a 96 engine i picked up from the us also has flat blade type upper powervalve