Is this Toast?

CALfeRacer

Fat man on a little bike
In all seriousness though, I finally got around to working on my CB350 and I don’t like what I found while cleaning the engine out. Lots of sludge, metal shavings in the oil passages by the filter, and one of the bearing surfaces doesn’t look great. I’m not sure if the bearings are ok since I’m used to a car engine with main bearing caps, not a ball bearing pressed on the crank with a mating surface in the case.
If it IS Toast, I’ll hold off on the build and debate looking for another engine or just cutting my losses. Thanks!
 

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Tim

Administrator
Staff member
I'm no professional, but it seems to me the mating surface of the engine case for the outer race of the bearing shouldn't be super critical.

I expect there is a positioning pin of some sort to keep the race from rotating (I seem to recall this on the main bearings of the XS650 crank).

Perhaps the shavings you have are the pin, which I expect would have been in the holes shown in your photo. If the bearing locked up I guess the pin might shear, but I would have thought it would spin on the crank first (it's probably pressed onto the crank and then positioned with the pin in the case).
 

CALfeRacer

Fat man on a little bike
Tim said:
I'm no professional, but it seems to me the mating surface of the engine case for the outer race of the bearing shouldn't be super critical.

I expect there is a positioning pin of some sort to keep the race from rotating (I seem to recall this on the main bearings of the XS650 crank).

Perhaps the shavings you have are the pin, which I expect would have been in the holes shown in your photo. If the bearing locked up I guess the pin might shear, but I would have thought it would spin on the crank first (it's probably pressed onto the crank and then positioned with the pin in the case).
There are pins on the other 3, but not this one as far as I can see. When you say it like that, it totally makes sense that it wouldn't be absolutely critical, so long as its not allowing the crank to wobble or anything.
Also, all 4 bearings do seem to spin fine, but definitely not great. I assume they're fed by engine oil and not packed with grease?
 

adventurco

Nick Ol' Eye
DTT BOTM WINNER
CALfeRacer said:
There are pins on the other 3, but not this one as far as I can see. When you say it like that, it totally makes sense that it wouldn't be absolutely critical, so long as its not allowing the crank to wobble or anything.
Also, all 4 bearings do seem to spin fine, but definitely not great. I assume they're fed by engine oil and not packed with grease?
Yes they are fed by engine oil. The bearing surfaces are not really critical, though I would guess that the bearing pictured may have overheated at some point. I would replace it, its pretty straightforward with the correct puller. Heat the bearing and freeze the crank to put the new one on. I use PVC pipe that just fits over the crank as a drift to seat them.

The damage on the race looks superficial but its hard to tell. Maybe try and polish it out with a dremel buffing wheel. It looks just like staining from the pics.
 

CALfeRacer

Fat man on a little bike
If I’m gonna pull one I’d pull all 4, I think the internals may have seen some weather in their time (aka open top end outside in the desert). How do you get the two seater bearings out?
Also, I think Tim’s spot on with the “broken pin” theory. Looks like the spot on the bearing above is the bottom half of a pin stuck in there, there’s a corresponding spot on the top case where a pin should go. So probably needs a new bearing anyways.
 

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adventurco

Nick Ol' Eye
DTT BOTM WINNER
The crank has to be disassembled for the inner bearings. Honestly there should be no wear on the other bearings. The balls ride between a thin film of oil between the inner and outer race, so unless it was run with very low oil, there's no reason to suspect that the other bearings would need to be replaced.

Just my .02. I'm a firm believer in "if it ain't broke, don't fix it"
 

CALfeRacer

Fat man on a little bike
I'm concerned that the center bearings might be broke :-\
Cam and rockers are MIA, when I got the bike it was for free out of a dead guy's shed in Bakersfield, cam and rockers (along with most of the top end) were nowhere to be found. This is part of why I'm concerned moisture got in to the bottom end/center bearings. Maybe I just need to pump oil in and turn a bunch to see how they feel.
Also after some internet digging, Honda might have gotten rid of the pin on the 4th bearing during the production run??
 

Tim

Administrator
Staff member
Before you waste anytime pulling bearings, make sure you can get new ones.

XS650 crank bearings for example are difficult to find, at least one of them if memory serves. Like they don’t make them kind of hard.
 

adventurco

Nick Ol' Eye
DTT BOTM WINNER
CALfeRacer said:
I'm concerned that the center bearings might be broke :-\
Cam and rockers are MIA, when I got the bike it was for free out of a dead guy's shed in Bakersfield, cam and rockers (along with most of the top end) were nowhere to be found. This is part of why I'm concerned moisture got in to the bottom end/center bearings. Maybe I just need to pump oil in and turn a bunch to see how they feel.
Also after some internet digging, Honda might have gotten rid of the pin on the 4th bearing during the production run??
Well in that case I would just look for a complete engine, and use what you have as spares or sell to offset the cost. I've pieced together engines and its not a cost effective way to get yourself a good powerplant.
 

CALfeRacer

Fat man on a little bike
So I picked up a whole ‘69 top end with the type 1 cam back in the day, I’m browsing used cranks on eBay right now. Haven’t seen any complete engines near me (brief Craigslist scan)


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CALfeRacer

Fat man on a little bike
I gave the bearings/crank some love with brake cleaner and WD40, everything spins real nice now. Not too worried about the bearings anymore, worst case something seizes when it’s running and I have to get a new engine anyways


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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
CALfeRacer said:
I gave the bearings/crank some love with brake cleaner and WD40, everything spins real nice now. Not too worried about the bearings anymore, worst case something seizes when it’s running and I have to get a new engine anyways


Sent from my iPhone using DO THE TON
That's the right attitude. ;)
 

CALfeRacer

Fat man on a little bike
Wouldn’t be the first time I killed an engine
Spun a rod bearing on my Katana 3 or 4 years ago.


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Pete12

Member
If you need any, the bearing locating pins are really cheap from.Partzilla, just a couple of.bucks each.
 

CALfeRacer

Fat man on a little bike
Bumping this thread instead of making a new one... taping everything up to go out for media blast and noticed this. It’s where the chain tensioner mounts. Should I just slather some JB weld in there or is this Toast?
I do have another set of cylinders, but the bores are gross and would need to be bored out for the bigger pistons (unlike this set of cylinders).
 

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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Is that a threaded insert in there? Might be okay, but not totally sure. Which set of jugs is this? Swapping cylinder sleeves may be an option.
 

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