Honda Twins banner

Crank bearings are bad.....are they replaceable?

7.7K views 12 replies 7 participants last post by  66Sprint  
#1 ·
My mechanic just told me the bearings on my crank and one of the rods arent any good due to some water getting in the engine. They spin but barely. He said I should buy an entire engine to use for parts or a crank from a running bike.

My question is can the bearings be replaced on the crankshaft and the rod? If so where can I get them? I just bought this bike a month ago and was hoping I wouldnt find this much damage in the engine.

Any insight, info, or links to help me out would be greatly appreciated.

My bike is a 72 cb450
 
#2 · (Edited)
The mechanic gave you decent advice......It CAN be done, but is neither cheap or easy to find the parts IF at all anymore....(or an appropriately tooled/skill qualified shop)......

I don't believe even Team Hanson offers the 450 cranks......
 
#4 ·
if the 450 is the same as the 350...they use pressed together built up cranks...not many places capable of doing that competently any more and they are expensive when you do find them. used motor/crank would be my advice as well.
 
#5 ·
John.....Yes, the 450's are almost identical in design and make-up to the 350 cranks.....(other than part numbers/exact measurements...LOL....)....
He can probably find TWO engines for what it would cost for parts, (IF they are still available), and the expertise to press and true the crank......
 
#7 · (Edited)
Hi,

I got involved in rebuilding cranks in the two-stroke world (in most cases mandatory after 10k-20k miles).
These 450 cranks, and all early cranks are build the same way, not only Honda.

20 years ago I learned it from a pro and invested in the things you need to do it, being a press and some special attachments (for each crank type a different set).
Since then I'm focussing on the CB72/77, C72/77 and CB450 K0-K7 and CB500T. It's fun to make a CB77 crank from a C77 crank, or rebuild a CB450 K0 crank with new parts.

Experience, patience and a analytical insight is all you need on top of a press (and a few measurement tools).

I do this only for myself because people won't pay for it, since there are enough engines around with moderate to good cranks.

Sometimes I'm trying to sell a crank which I don't use like this one :? Honda CB500T CB500 Twin krukas - Onderdelen | Oldtimers - Marktplaats.nl

Dutch translation : revised crank CB500T, main bearings, big end bearings and small ends within spec. Direct transplant. Of course buyer is aloud to measure everything before the buy.

But it's stupid to invest 4 to 8 hours in one crank, plus parts and not get more then 150 Euro for it, btw, this crank is already offered for two months....., no one responded, there's no market for it here.

I guess that's why it's hard to find someone who can do the job.

Jensen
 
#8 · (Edited)
Agree, while fairly cheap usable cranks (or engines) are available people will not be willing to pay for the time it takes to rebuild a crank, but it is very good to know that someone on this forum knows how to do it.

On another note: Can you swap a cb450 crank into a cb500T?

Jensen, I read your add in Dutch before I realised that you translated it, but I could follow what you meant (Afrikaans being my first language)

So I found the answer to my question (On another note: Can you swap a cb450 crank into a cb500T?) - No you cannot swap the cranks as the bearings are different.
 
#11 ·
I need to throw my two cents in. I'm working on a '72 CB450 too. The engine that came with the bike was a stuck K7. Last spring I thought if I just got my hands on a good engine I could drop it in and be riding in a few weeks. After posting in Craigslist for a WTB 450 engine a K6 turned up. The engine turned over OK so I popped on it. Since the engine was out of the bike I decided to pull the top end for an inspection. I discovered the pistons were shot and the rod small ends were oversize. The valves had been lapped into oblivion and the exhaust cam & followers were shot. A set of NOS .5 mm O/S pistons, a valve job, an ebay crank, cam and followers, a gasket se and seals set it right. The lesson was a 42 YO engine is a 42 YO engine. You may get lucky and find a low mileage engine that has not rusted up. I dropped $450US on the second engine and it was really not any better than the one I had. Assuming the rest of the engine is OK, try to find a good crank that passes the Honda specs for being usable. I did find a shop online that would rebuild my crank. It was around $450. Send me a PM if you want me to dig up their address. The crank I took out has good bearings, but the rod small ends are O/S. I started down the route of oversizing the rod small end. The stock 450 wrist pins are 17mm. I bought some 18mm pins and was going to have the rods and pistons bored to match. I also have a good K0 crank along with the stuck K7 engine. Let me know if you want any of this stuff. My bike has been a huge learning experience and I'm very happy with how it is coming out. One important lesson is if you want a reliable bike you cannot cut corners on anything.