Crank bearings... replace every time you split the cases?

reepicheep · May 27, 2009

I'm getting ready to split the cases to replace my splineless transmission output shaft. While in there, I will be replacing all seals and gaskets.

What about the crank bearings? Thats another $50 I would rather not spend, and I don't know if it signs me up for a bunch more work beyond splitting the cases... I think those bearings are pressed in somehow (manual is at home, I'll have to check)...

This is a 95 that looks to have had a lot of hard riding. That being said, I checked the crank and rod from the top with the piston removed, and it is well within spec, with no discernible play, slop, or crunchy noises. The rod and wrist pin bearing look perfect as well, in spite of the fact that the piston skirt was cracked.

Historical indications (by excavation) are also that the previous owners ran this thing insanely rich and with a high oil mix ratio. So I don't think those bearings were ever wanting for lubrication...

I'm hoping that an old bearing in spec is just as good as a new bearing. I'm also not going to be going nuts riding this bike all the time... with 4 kids and a demanding job (both of which come first) I am lucky to get 10-20 days riding in a year... so I won't actually be putting a lot of hours on it.

So is it foolish to not unconditionally replace the crank bearings if you split the bottom end? And does replacing them require special presses and processes? Or are they wear items that just drop into the cases...

Thanks all!

cash_62 · May 27, 2009

well, those bearings are pressed in, and the act of splitting the cases puts sideways motion/stress on the inner races of the bearings, which is not good for bearings. While you're in there, it just makes sense to replace bearings that are probably original to the bike. If you're doing everything else, to me it just makes sense. If those bearings did go, it could take a lot more with them. To me, it's cheap insurance man!

julien_d · May 27, 2009

Yeah it's pretty common to replace the main bearings while you have the cases split. That $50 now could save you many dollars in the future.

sr5bidder · May 27, 2009

do it...... you are spending ALOT to have the top end done by eric gore

more importantly I would get a rod kit ...comes with new crank pin/big end bearings..

I would say if you want to go cheap you should find a used in good shape cylinder and put new piston/rings and sell your new top end from eric gore replace seals and hope for the best.

if your insistant on using the new top end then you should also be insistant on using everything else new........ rod kit....main bearings.....etc..

ranger306ci · May 27, 2009

Would you rather do it now, or later?
You are already there. And it can be done at home. Heat the case with a propane torch- they come out. Put the new ones in the freezer for a couple hours, reheat the case, and drop them in. When I dig into ANY engine, car, bike, whatever; I replace everything that is considered consumable. That way, knock on wood, I will not be going back into it anytime soon!
I am replacing a shot water pump on my bronco II this week. I am putting all new hoses on it, new belts, and a new thermostat. Might as well, coolant is drained, and belts are off anyway!

reepicheep · May 27, 2009

Ouch. This is adding up. I've never messed with a crank before, do you have to press the crank pin out to replace the rod? Are "Hot Rods" connecting rod kits decent?

sr5bidder · May 27, 2009

don't see many bronco II around

Ive always had one side stick to the crank I think the flywheel side and let the machinist screw with it when they do the pin and rod

glad2ride · May 27, 2009

Send the crankshaft to Eric Gorr and let him deal with the crank rebuild.

Rebuilding a crank is NOT something to be done at home for 99.99% of the people.

reepicheep · May 27, 2009

Or just leave the big end bearing and rod alone if they are well within spec... Hmm. I'll have to think about it. If I wanted a no risk at any cost bike I would have bought something new. I wanted a low cost with manageable risk bike and rolled the dice. If the transmission shaft hadn't been de-splined, I would have done pretty well. As it is, I'll be about $1700 into a 95 and up KDX-200 with the 225 magic big bore kit (and new piston, new rings, porting, cleaned and serviced KIPS) new seals through the bottom end, new air filter, new plastics (mostly), new seat cover, new tires, new jetting, etc.

Not a killer deal, but not a bad one either. At least if you assume the 50 hours of work I put into it is billed out at $1 per hour :nener:

Y'all talked me into replacing the crank case bearings and seals though. Hopefully I can get them both off the crank.

julien_d · May 27, 2009

You are contradicting. If you say you were after a low cost bike then the big bore kit was an unnecessary expense. You would have been better off to find a cheap cylinder, replace crank bearings and tranny shaft, and roll with it. Spending the money on that big bore kit, your feelings are going to be hurt really bad if the crank bearings go out and destroy your piston, rings, and plating.

cash_62 · May 27, 2009

buy the crank bearing remover/installer and case splitter tools from rockymountainatvmc.com
They'll be a few extra bucks, but WELL worth it!

glad2ride · May 27, 2009

... due to the parts already being worn and now having more stress from higher compression due to the new parts in the top end.

_JOE_ · May 27, 2009

julien_d said:
You are contradicting. If you say you were after a low cost bike then the big bore kit was an unnecessary expense. You would have been better off to find a cheap cylinder, replace crank bearings and tranny shaft, and roll with it. Spending the money on that big bore kit, your feelings are going to be hurt really bad if the crank bearings go out and destroy your piston, rings, and plating.

Umm, correct me if I'm wrong but I would think the cost of a replacement cylinder and piston kit would be about the same as the big bore.

mideastrider · May 27, 2009

Brand new 225 Top-end. Got the cases opened up like a book. No way I would put together without fresh crank bearings and new or rebuilt crankshaft. Unless of course you know within about 30 minutes how many hours is on the bottom end. One piece of bearing cage comes loose and its all for nothing. Just my 2 cents.

reepicheep · May 27, 2009

My original intent was to just replate... I chose the big bore kit for two reasons:

1) Eric indicated the plating results are better and more reliable with the big bore kit. It removes more material that could be infused with the stock plating (tungsten?) and gives cleaner aluminum for a better bond.
2) It sounded like the difference between big bore and stock was only going to be about $150... and the big bore kit included the custom porting.

So valid points all about the crank. I suppose I'll have to fix that also.

For what it's worth, Pep Boys had a harmonic puller that was better then the harbor freight steering wheel puller, and was cheaper as well. I think it was $12 or something. I'm not sure the metric bolts it has with it are the right size and pitch, but if not that's an easy enough hack. The harbor freight puller had only SAE bolts...

Off to get quotes to get the crank rebuilt... :(

reepicheep · May 28, 2009

For the sake of the archives...

Crank rebuild labor: $125
Crank rebuild parts: (Rod, big end bearings) $90
Crank case bearings and seals: $50
Bottom end seals: $50
Misc other parts and shipping: $50?

And for me, with stripped splines, thats another $100 for the transmission output shaft.

Ugh.

_JOE_ · May 28, 2009

For the sake of the archives...

Crank rebuild labor: $125
Crank rebuild parts: (Rod, big end bearings) $90
Crank case bearings and seals: $50
Bottom end seals: $50
Misc other parts and shipping: $50?

And for me, with stripped splines, thats another $100 for the transmission output shaft.

Having a nicely tuned and reliable bike to ride for years to come.........PRICELESS!!!!

whenfoxforks-ruled · May 28, 2009

Are you replacing the main shaft bearings also? The left bearing is the most abused. Water pump seals and bearings also.

liven07 · May 28, 2009

I like to do a lot of shopping around, I see on here a lot of people talking about prices on stuff and sometimes my bottom jaw hits the floor. Awhile back I rebuilt the engine in my kdx and found one place wanted $27/pc. for main bearing and the next was $7 and is what I ended up paying. My local dealer wanted $65 for a head gasket and found one for $3.99 on a web site but ended up getting a complete engine gasket and seal kit sent to me for $60 from a shop in my old state of WI. If it is one thing I hate is some of these shops trying to make way to much money. My shop told me that it was the expensive shipping cost, but it costed me $15 to have main bearings, gasket and seal kit, rod kit, and piston kit sent with a $150 of insurance. Basicly a little research on the net and a few phone calls will save you a lot of money.

sr5bidder · May 28, 2009

I would shop around for the crank labor man thats nuts!!!! I have a guy that does mostly airplane engines and he does the cranks for me for an hours labor =$55

whenfoxforks-ruled · May 28, 2009

liven07 said:
I like to do a lot of shopping around, I see on here a lot of people talking about prices on stuff and sometimes my bottom jaw hits the floor. Awhile back I rebuilt the engine in my kdx and found one place wanted $27/pc. for main bearing and the next was $7 and is what I ended up paying. My local dealer wanted $65 for a head gasket and found one for $3.99 on a web site but ended up getting a complete engine gasket and seal kit sent to me for $60 from a shop in my old state of WI. If it is one thing I hate is some of these shops trying to make way to much money. My shop told me that it was the expensive shipping cost, but it costed me $15 to have main bearings, gasket and seal kit, rod kit, and piston kit sent with a $150 of insurance. Basicly a little research on the net and a few phone calls will save you a lot of money.

Are you buying them substandard Chinese bearings off fleabay? Be very careful whom you are getting smoking deals, and what you are actually getting. Not too many places suggested around here are out to gouge your beer money, you get what you pay for. sr5bidder I would shop around for the crank labor man thats nuts!!!! I have a guy that does mostly airplane engines and he does the cranks for me for an hours labor =$55. Once again, you are getting what you pay for. Eric does dirtbike engines, not airplane or boat engines. If he ever hangs it up, I will have a hard time finding someone with enough sense to use a jig, and not beat it up with a hammer.

liven07 · May 28, 2009

Parts I get are from parts unlimited good place to get parts from but you got to get there parts threw a dealer. As far as the crank goes it's really not as bad as one would think I did my first on this kdx. I bought a big metal adjustable hose clamp from home depot, it works as solid tube to aline the crank and then I payed a local shop $20 to use there 50 ton press. I like to do new things, the crank works good no problems. I think $55 would be fair considering it only takes about 1/2 to 45 min.

whenfoxforks-ruled · May 28, 2009

It very well may work on a kdx, and the way its used. From a performance standpoint, and someone who scribed a line, pressed it apart, and put them back together, then strike it with a hammer to get it within spec? Eric is priceless. Guys with tools are a dime a dozen. An oem crank is sometimes a solid choice, especially if your paying 20 percent over dealer net, half price?

liven07 · May 28, 2009

I think striking it with a hammer would not budge it one bit, that pin is on there. The purpose of the metal pipe clamp is that you put it on before you take it apart. you tighten it up, take it apart with the clamp still on then put it back together and it's dead nuts on. But I know what your saying, having a good guy that knows what he is doing is a lot better then someone that is going to half ass it to save a few bucks, but that also does not mean that someone that does it for cheaper is going to do bad job.

whenfoxforks-ruled · May 28, 2009

Thats how you true the crank flywheels, +-.002. You would not believe how easy it moves! And in my opinion, moves back. Shorter bottom end life and vibration.

Crank bearings... replace every time you split the cases?

reepicheep

cash_62

julien_d

sr5bidder

ranger306ci

reepicheep

sr5bidder

glad2ride

reepicheep

julien_d

cash_62

glad2ride

_JOE_

mideastrider

reepicheep

reepicheep

_JOE_

whenfoxforks-ruled

Old MX Racer

liven07

sr5bidder

whenfoxforks-ruled

Old MX Racer

liven07

whenfoxforks-ruled

Old MX Racer

liven07

whenfoxforks-ruled

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Crank bearings... replace every time you split the cases?

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