Topic: Lower Crankcase - Countershaft bearing

[Ericcb750]

Hello everyone, I hope you're all doing great out there. It's been while since i've been rolling on the CB project but i have finally gotten around to starting work on the motor... but i'm having a hiccup and I want to see if i can get some advice from those who have done this before successfully.

I tore down my entire 78 CB750K motor and had it blasted by the guru Nils over at Resto cycle. Now that i have everything back and am beginning assembly, I've run into a problem with a bearing.

In the lower crank case there is one bearing that is kind of "captive" (held in the case) for the countershaft. It is on the end of the countershaft towards the center of the motor (Bearing 6204). I have tried to heat the lower case with a heat gun and also freeze the bearing with no luck, i've watched videos where they seem to drop right in but i can't seem to get it to do so.

I"m wondering if i'm not heating the case enough or if this bearing has to be pressed in somehow? Before i damage this absolutely beautiful case, i wanted to ask for some opinions/advice. I am also wondering if the vapor blasting may have roughed up the surface just enough for the bearing not to drop in since it's a really tight fit?

If anyone has installed this bearing, it would mean the world to me if you could let me know how you did it.

Please let me know if you have any questions at all...Thank you guys so much for your help/

[bamacb]

For the most part they are not that tight. I've had them come out with the shaft , fall out with a light bump , and require a few taps with a hammer. Installation has been easy with a wooden block and a hammer. No heat or freezing. Maybe I've just been lucky. I would look at cleaning up the case area and maybe mic it for size. 

[millla03]

You could try heating the case half in the oven. Think I used 200F for 30-45 minutes. Bearing in the freezer as well and it dropped in with no persuasion. In my experience, it's hard to get much heat in a big chunk of aluminum like the case with a heat gun. An oven also heats the whole part up relatively evenly, which I can't imagine is a bad thing.

I've had good luck with this general approach for installing bearings into an aluminum housing.

[Ericcb750]

Good Afternoon Gents, Thank you both for your help.... I agree , i think the heat gun is pretty uneven when heating the cases up. I'm going to try the oven then.... I don't think the heat gun is getting it hot enough either. I'll also check with a Mic but i think the oven idea will be great.

I definitely didn't want to be too rough on it without getting some solid info from you guys. I'll stop back and let you know how it goes!!! Thanks guys, have a great day.

[Ericcb750]

Hey guys, I know it's been a bit. But I got the bearing in seated absolutely perfect without any banging or pressing... With some good tips from you guys as well as Nils from Resto cycle, and a couple others... Heated up the lower case in the oven this time up to 270 for a few moments (i stepped up the heat slowly so not to stick a cold case into a hot oven)...

Bearing in the freezer and that baby dropped right in by hand.... Seated absolutely perfectly. I held it in place with a glove on for a bit so the heat would transfer to the bearing and cold to the case and the bearing wouldn't fall out...

It is now sitting absolutely perfect and a brand new OEM bearing for the countershaft.... now i can get rolling on this little hot rod 836 / JMR ported combo.... Thanks so much guys, you're the best

[millla03]

Glad to hear you got it sorted! A bearing just dropping in like that is a good feeling, for sure.

[PeWe]

Work fine with a heat gun too

[Ericcb750]

Good Morning Guys,  I wanted to just say thanks to those who helped and gave me a hand with this. The bearing dropped in beautifully by hand and seated all the way like butter. I held it there with a leather glove until the heat transferred and held it in place.

I've gotten the transmission all back in and had a bit of  a tricky time figuring out the kickstarter but all those pictures I took before tearing it apart came in handy and its back in and working perfectly. New Crank and Rod bearing shells going in for the JMR balanced crank and the Cycle X super rods.... This little hot rod motor is finally beginning to take shape!!! I will start updating my build thread from what seems like 100 years ago.

Thanks again guys.