Do I need to replace the crankshaft?

[D3luxe]

The lower connecting rod bearing locked up, and when we got it unlocked something happened to it.. I havn't had a chance to tear it apart yet to look (getting into it this weekend.) I talked to one of my step-dad's friends who used to rebuild dirt bike engines and he said that if there is still enough of the bearing that the rod didnt shave any metal off of the crankshaft itself, then I can just replace the bearing and it will be fine, that I would not have to rebalance the crank.

Just wondering if that would actually work, to just replace the bearing. I know it would be better to just go ahead and replace the whole crankshaft, but I am tight on money at the moment so I figured just replacing the bearing would be a lot cheaper.

I have a '97 RM125, btw.

 

[IndyMX]

Yeah, replacing the bearing might be cheaper in the long run.. And it may be a fine fix.. However, I believe you'll still need to rebalance the crank.

 

[D3luxe]

Hmm..Alright, i'll talk with a few other people then before I order the bearing.

Would it be better to just replace the bearing and (if needed) rebalance the crank, or just buy a whole new crank + assembly?

 

[whenfoxforks-ruled]

You are talking about disassembling the entire motor,split the crankshaft,replace the needle bearing,thrust washers,wrist pin and re-using the rod. The rod kit is about 90 dollars,the oem parts that you are talking about cost double that! Go to http://www.wiseco.com/ ,unless you have a better idea?

 

[Rotorranch]

What WFFR said...why scrimp when you have to pull that all apart? You got to split the crank to replace the bearing...might as well do the rod too! Big end crank pin, bearings, etc. It's cheap insurance.

Splitting the crank will require aligning the crank halves, and most folks don't have the equipment to do that themselves.

Spend a little more, and DO IT RIGHT the first time.

Rotor

 

[D3luxe]

I'll just get a crankshaft from Wiseco then..I don't feel like having to split the case twice because I messed something up the first time.

I have a question though..At Wiseco, it says a forged crankshaft for a '97 RM125 is $200..When I added it to my cart, it says it is the Crankshaft Assembly. Is that $200 for the crankshaft AND the assembly, or just the crank, or what? I am just suprised because I thought a new crank and assy was ~$500.



EDIT: Actually, that crank was for a '99-'00..It doesnt look like they make cranks for '97s. The part box for crankshafts is empty in the '97 row..

 

[whenfoxforks-ruled]

What,200 is high,I thought they were 180,oh well. Crank assembly is the crank only,with the new rod,bearing and washers already to go. You still need a complete gasket kit(with seals) and main crank bearings(make sure the crank seals are included or you need them also) and the top end. 380 was what motosport sold complete engine kits from hotrod,I believe the wiseco is better.

 

[D3luxe]

I dont need a new top end though, the piston, ring, and cylinder is fine. But, its only 380 for a complete engine kit? I might end up replacing everything anyway..

 

[adam_co]

you're a lucky one then, when my crank locked up on my kx80 it scored the barrel in the head and knackered the piston and rings so i put a new topend on and the crank seemed to spin again so we didnt bother replacing it (very stupid i know) when we got it back together and started it, the bike ran for about five minuites ticking over sweet and then crunch and it locked up again, actualy it was good in the long run because we got a new crank in and my dads mate bored the head out to 89cc and got a piston and rings to fit it nicely then the bike was sorted so i would say its best to replace the whole thing instead of one bit because even though it learnt me quite abit it cost me a load more lol

 

[D3luxe]

Where could I go about buying a complete engine kit? As you guys said, I might as well make sure everything is fixed the first time, and if its under/around $700 i'll be happy.

 

[whenfoxforks-ruled]

Try wiseco,hot rod and moto sport. My dealer was getting deals from moto sport,through parts unlimited,but it was for newer engines. Adding up the separate parts is about the same price,oem parts is where you get bent over. If it ends up you can only get a rod kit,I would send it to Eric Gorr to press,I know of no one else who changes rods and does not align them with a hammer! Pressing the rod should cost under 100 dollars,the parts should be about 380.

 

[D3luxe]

Well, it seems that no one makes crankshafts for '96-'97 rm125's..Does anyone know if an '01-'03 model crankshaft would fit my '97? Or how could I go about checking?

 

[whenfoxforks-ruled]

Did you check for a rod kit? Cheaper?

 

[D3luxe]

Yeah, Eric Gorr is selling a new Hot Rod kit for a 97 RM125 for $30..

Should I send the crank out to him and have him put that in?

 

[whenfoxforks-ruled]

You question yourself? Yes send it to him,STAT!

 

[D3luxe]

Just emailed Eric to ask him how much it would cost for him to install the kit and repress/balance the crank. Hopefully I get a reply from him soon, as I would still like to ride this year before snowfall

After a few days of checking as well, I have found out that no one makes '96-'98 RM125 crankshaft's, unless I order it from OEM. Hopefully the hotrod kit from Eric will fix the problem though..

Thanks guys.

 

[BSWIFT]

Just emailed Eric to ask him how much it would cost for him to install the kit and repress/balance the crank. Hopefully I get a reply from him soon, as I would still like to ride this year before snowfall

After a few days of checking as well, I have found out that no one makes '96-'98 RM125 crankshaft's, unless I order it from OEM. Hopefully the hotrod kit from Eric will fix the problem though..

Thanks guys.

Forward Motion is the way to go. If a new piston and rings are around a $100 do it and you'll have a complete rebuild.

 

[D3luxe]

Just got a reply from Eric, here is his response:

Hi Cory, I don't do that kind of work anymore and I recommend Ryan Callies of Finishline Engines, call him at 1-920-382-2897

So i'm going to give him a call and see what he can do..Hopefully I can still get that hot rod kit from eric though.

 

[todd36]

Hello. If you are still looking for someone to rebuild your crankshaft. I live in southern Michigan and I use a fixture and bench centers to rebuild them.

 

[D3luxe]

I have someone to rebuild it now, thanks though.

Does anyone know of any '97 RM125 crank assy's that aren't OEM? Hot rod and Wiseco don't seem to make crank assy's for '97's =(

My mechanic said that all it needs is a new crank and (obviously) the gaskets. The rest of the engine is in great shape.

 

[whenfoxforks-ruled]

http://www.hotrodsproducts.com/index.cfm?fuseaction=cProducts.list&photos=true

 

[D3luxe]

I could get a rod, yes, but then I would have to have a machine shop rip the crank apart, replace the rod, and re-balance it back together..Wouldn't it be better to just get a new crank assy?

 

[whenfoxforks-ruled]

Some models do not have full assemblies available, except maybe oem.

 

[D3luxe]

Yeah, that's the problem that i'm having. Would it be better to get a new crank assy OEM, or just a new rod and have a shop rebalance it?

 

[whenfoxforks-ruled]

If you can find a decent mechanic, let me know! Ryan Callies is recommended by Eric Gorr 1-920-382-2897. It should be a lot cheaper getting it fixed. The aftermarket should be a lot better!