Bearing Drivers for 2 stroke rebuilds?

[Bobby Martin]

I'm trying to locate a good source for a set of bearing drivers. I plan on using the drivers during a rebuild of several honda 2 stroke motors (125 and 80).

The honda service manual lists several different part numbers for the tools, however it also indicates that the drivers aren't available in the U.S.

Anyone know where to look?

[Bill Givens]

Use the following method instead of bearing drivers...

Put the split case in an oven preheated to 250 and leave it there for about 15-20 min.

Cafefully remove with pot holders and lightly slam it on a flat surface...the steel bearing will proably just fall out on the bench.

To install the new bearing, first put them in the freezer for a couple of hours. While the are getting cold get the case ready by cleaning throughly and then put back in the oven for the same time as when you removed the bearings.

Get the bearings out of the freezer...lay them on the bench with the bearing number typically looking at you. Go get the case and lay it on the bench.... make sure the bearing is lined up and just drop them in with the bearing numbers looking at you.

If you happen to get it crossed up. Start the whole process over. After a little practice this process will become easy.

It's really easy on the bearings and the case. Much better than beating on them.

To install the crank...put it in the freezer for a couple of hours then heat the left case.... same process as the bearing...just slide the crank through the main bearing.... Be careful and not let the trans bearing fall out.

[Pete Muller]

If you go to: http://www.muller.net/mullermachine ... and then click on Docs in the menu... the top article is about removing/installing main bearings.

BTW: I would recommend against putting anything in the freezer.

PM

[John Denman]

Golly-gee-wilikers Pete, I had no idea.

After reading your website about Muller Machine, answered those questions like those of "who was that masked man".

So why wouldn't you put anything in the freezer?

[Matt Kull]

quote:

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Originally posted by Pete Muller:

BTW: I would recommend against putting anything in the freezer.

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Why is that. I don't think that a house freezer would be cold enough to make any kind of molecular change to the metal? I think that you need sub 100deg temps to make a significant change to aluminum.

matt

[Pete Muller]

quote:

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Originally posted by Matt Kull:


Why is that. I don't think that a house freezer would be cold enough to make any kind of molecular change to the metal?

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Couple reasons:

First:
The amount you "gain" is fairly insignificant. Drop your cases in a 350F oven (even assuming they only get to say... 300), you have a gain of ~230F over ambient.

Set your parts in a freezer... you might get ~50F under ambient.

Why bother?

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Second:
The chance of microscopic corrosion. Putting parts in the freezer causes moisture to form on the surface (granted, that surface probably has some oil on it, minimizing the risk)... and the sudden heating of the part (in this example, probably a main bearing) could create some microscopic rust/oxidation spots.

Why chance it?

---------

10 to 12 minutes in a preheated 350F oven is plenty to drop a room temperature bearing into most any engine case.

PM

[John Denman]

I have to admit, the corrosion on bearings from condensation has been a trifle of concern, but not much. Between the oil on the bearings (I actually spray a little grease on them before freezing) and the limited exposure, it does make it slightly easier to install. I agree, that mathematically its not that much contraction, but it seems to work.

On the lighter side, how much power range would you feel is available from a CR80 or CR125 with having the cases align-bored/blueprinted?

[Rob Martin]

I didn't see any kenmore appliances listed in the Honda service manual but if my wife doesn't mind I think I'll do a little baking.

Thanks for the valuable information.

[Pete Muller]

quote:

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Originally posted by John Denman:
I agree, that mathematically its not that much contraction, but it seems to work.

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Well... "mathematically" the gain is even less: Since steel expands/contracts at roughly half the rate of aluminum, it only takes an additional 25F worth of heat on the case to equal what a 50F drop in temperature of the bearings accomplishes.

PM

[Tim Doll]

quote:

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Originally posted by Rob Martin:
I didn't see any kenmore appliances listed in the Honda service manual but if my wife doesn't mind I think I'll do a little baking.

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Do it when the wife is off shopping or something - the technic works fine (I've used it many times) but it does tend to create an unpleasant smell .

I used to put the bearings in the freezer, but after I first heard Pete's concerns a couple years ago I started leaving the bearings at room temp. Couldn't really tell any difference.

Tim

[Chuck Bunnell]

Using the kitchen oven is definitely "AT YOUR OWN RISK" if you're married to someone who likes to cook. My wife was not pleased even though I spend a lot of time cleaning and degreasing the cases. The fuel and oil will literally dissolve into the metal and not come out until heated. If your cases fit in a toaster oven, by all means buy it. If not, beg forgiveness.

[Pete Muller]

I would shy away from toaster ovens. The problem stems from the fact that there is not much volume in a toaster oven... and consequently it's easy to overheat part of the case (or other item you're heating) that is close to the heating element.
Generally speaking, if you see any discoloration on the sealant (like the gray Yamabond), the case has probably gotten too hot.

I personally use a "wall oven" (yep, probably just like the one in your kitchen) that is converted to propane. The one I'm currently using was a "take-out" from a new house that cost me $200... but I have a "spare" that cost me $10 at the local Goodwill store.

A 5-gallon propane bottle lasts me a few months (my oven is on probably 6 hours a day and 4 days a week).

Make sure you place something like a thin piece of aluminum on the "bottom rack", as this will not only prevent bearings you are removing from falling into the bottom of the oven... but it will also prevent anything on the lower rack from getting too much heat due to being in fairly close proximity to the heat source (i.e. the flame).

PM

[ September 26, 2001: Message edited by: Pete Muller ]

[Pete Muller]

quote:

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Originally posted by John Denman:
On the lighter side, how much power range would you feel is available from a CR80 or CR125 with having the cases align-bored/blueprinted?

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John,

There's only one answer I can give on this, and it really applies to any mass produced engine:

Anywhere from nothing... to very significant.

The "nothing" would apply to a set of cases that happens to have been machined very accurately at the factory (much more likely to happen in an Italian engine, as they generally use better aluminum, and do better machine work).

The "significant" would apply to a set of cases that have any one (or more) of three problems: bearing alignment, bearing interference, and bearing bore "roundness".

Pete
Muller Machine

[John Denman]

Pete,

Any suggestions on where to send my CR125 cases, and any idea on the cost I would expect to pay?

(I am asking so its not like advertising right?)

Is it better to do this wit a seasoned set of cases or are they stable as new?

[David Tallant]

You can also just install them at room temp. We do it all the time. Drivers can be made from tubing stock, or in a pinch, using sockets. The term "carefull" comes into play.