Do I go by the manual on this one? 350X Crank Bearings

[wonderboy]

So I'm a service manual junkie. I've got it printed out and I'm constantly looking through it reading up on stuff. Trips to the bathroom are accompanied by the manual (I know, I know, TMI). I like to do everything by the book.

I'm in the middle of a complete 350x motor rebuild. I've got the motor stripped down and am reading through Chapter 10 on the crank and transmission.

Page 10-11 actual says: "Always replace the left bearing with a new one whenever the crankshaft is removed from the left crankcase".

The left bearing on mine stayed on the crankshaft and required some small taps from a deadblow on the crank to get the bearing out of the crankcase. I get it, The act of pulling the bearing out may cause notchiness in it, but really? This bearing is massive, and I didn't have to hit it that hard. The bearing feels just as smooth as the right bearing, and any other bearing from the motor.

Do you think they are being overly cautious in the manual? Am I being overly cheap to not just replace the bearing (it's 50 friggin dollars)?

Any real world advice regarding this bearing and an assessment of the manual's advice would be appreciated.

[WIkid500]

50 friggen dollars is cheap compared to an engine when she grenades. Pounding on the crank causes brinelling in the bearing races (tiny divots where the balls contact the race when you are pounding), you won't feel it now but the loads the races and balls feel at 8K rpm will. Now how hard did you really pound on the crank? If it was light taps like you said you will probably get away with it, but you have to look at the age of the bearing... 85-86? idk, those bearings are almost 30 years old, they lived a good life. Put em on a shelf and put in some new OEM bearings and not worry about it.

[Flyingw]

If it were a 2 stroke, I'd say yes. Every time the cases are split, replace the crank bearings due to the nature of the motor but 4 strokes are to me a little easier on crank bearings. You have probably inspected enough bearings to know if a bearing is bad. Clean it and if it the balls aren't pitted, put it back in and run it.

[Flyingw]

That's why you heat the case to 200deg and freeze the bearing. Pounding on the bearing is usually not required when you use this method.

[wonderboy]

Darnit, you guys are saying what I know deep down is the right answer, but it is painful. $100 in two ball bearings, here I come! I'll give them a really good cleaning and close inspection on the chance that they look perfect. The left side is still on the crankshaft though... Disassembly is harder to use the differential heating method on.

[Flyingw]

To get it off the crank you may need a split bearing tool to pull it off of there. The same heat/freeze method still applies to installing the bearings in the case and the crank in to the case. It's a little time consuming but its the best way of doing it.

[barnett468]

I'm in the middle of a complete 350x motor rebuild. I've got the motor stripped down and am reading through Chapter 10 on the crank and transmission.

Page 10-11 actual says: "Always replace the left bearing with a new one whenever the crankshaft is removed from the left crankcase".

The left bearing on mine stayed on the crankshaft and required some small taps from a deadblow on the crank to get the bearing out of the crankcase. The act of pulling the bearing out may cause notchiness in it, but really? This bearing is massive, and I didn't have to hit it that hard. The bearing feels just as smooth as the right bearing, and any other bearing from the motor.

Do you think they are being overly cautious in the manual? Am I being overly cheap to not just replace the bearing (it's 50 friggin dollars)?

Any real world advice regarding this bearing and an assessment of the manual's advice would be appreciated.

The contact area of the ball on the race is extremely small though, this is why its possible to get little dents in it if it gets hit too hard.

I have reused bearings before out of necessity, however the crank came out with a few lite taps. Only you know how hard you hit it.

If the bearings say NTN on them they are orig Honda bearings. I don't know anyone else that makes them. They are "special" therefore the "special" price. Nice huh?

If you think they have never been replaced, I would definitely change them.

You can clean them thoroughly and see if the outer race wiggles at all. If it wiggles more than a hair [however much that is] it is likely pretty worn.

Below are the cheapest prices I could find. Not sure which one you need. The sizes are metric.


91001-KE5-018, 32x76x17, $41.00

http://www.partzilla.com/parts/detai...1-KE5-018.html


91002-HA0-008, 36 x 76 x 17, $35.00

http://www.partzilla.com/parts/detai...FeHm7AodQQgAPA

[wonderboy]

Thanks again guys!

@ FlyingW: I've got an oven in the garage for just these purposes, so I'll definitely use the hot-cold method for the new bearing install (wife is ok with the regular freezer for bearing, since they don't stink up the place like oily engine parts in the kitchen oven!). I've got the puller (with the split sheeves) to pull the bearing off of the crank, so I'm good to go.

@ Barnett: The bearings are in fact NTN, so they look like original Honda OEM bearings. Other areas of the motor showed a good amount of wear, so it makes sense to replace them. I pulled the number off of one of them and it definitely doesn't look like a stock bearing number. (NTN TM-SC0775CS20PX1 <-- crazy number). All previous posts are correct, since I've got it this far down, it doesn't make sense to skimp on replacing these bearings considering how critical they are. Mentally, it is just difficult since it wasn't part of my initial budget for this rebuild. Stuff sure does add up...

Good thing I hadn't ordered all the replacement seals yet, now I can add the two crank bearings to my seal order.

Thanks again guys!

[Flyingw]

Cool beans Frank. Rock on...

[Outlaw #24]

So I have this 86 250R engine and the thing wouldn't spin and it had been peed in by mice so the crank lobes were stuck to the cases. This engine was a take out that I got in a box from a vocational school in Oklahoma back in late eighties early 90"s. So I split cases last week and the left bearing stayed on and the right bearing stayed with the case. I had a puller sheeve and I had to grind it so it would fit under the bearing without boogering anything up. So be careful with your Wonderboy ! When I installed I put my cases in the Grill and the bearing in the freezer. The right side went right in but the stator (left) side, started ok but I ended up having to tape it in with a and ONLY hit on the Outside of the bearing. When I assembled the cases , the crank shaft was tighter than heck so I smacked it on the crank shaft s right side. It Loosened right up. Just letting you know cause it sounds like what I Just went through. I am running this engine Today after I get it in my racer. If it all works out I will be running it at the Battle @ the Barn weekend after next. Thanks for letting me interject guys? Hi Jim!

[barnett468]

Hi;


Did you check the cogs and slots on the gears for wear, like excessively rounded edges?

The cogs are fairly sharp when new with a very small machined bevel on the edge/corner.

2nd and 3rd are typically rounded the most.

The shift forks occasionally bend also, however it still might have shifted ok if they weren't exceptionally bad.

[wonderboy]

@Barnett: tranny is next on my inspection list. I was initially reluctant to slide everything off of the gear shafts, but the book has very good diagrams of where everything goes. I'll also try to just take my time and lay things out in order so that they don't get all jumbled up.

My plan is to carefully inspect all the gears for any signs of trouble. I'll pay particular attention to the areas you mention.

@Outlaw: I'm going to try to make that rig they show in the manual to first carefully press the bearing onto the crank, and then to pull the crank into the case half. That way there is no beatings! (that's the plan anyway). I'm hoping that the hot-cold treatment makes this quick and painless...