Bonneville America Forums Forums Technical Forums General Tech No bearings in our motors????

Hey guys I heard that our bikes have no crank or rod bearings and just run right in the block.. Is this true?? If so that means when these bikes are throw away bikes correct?? thats very disapointing if its true... Lets hear some input... thanks again

It would seem like this could be put to bed by someone with the cd repair manual. Personally, I've been working on/modifying my engines for 15 years and have never heard of a rotating assembly without bearings. There HAS to be bearings, anything else is just Witchcraft. Maybe Buffy knows....

Thats plain nuts. Whoever told you that is the absolute king of drug ingestion.

You should see the rotating cam setup then, no bearings at all. Never seen anything like it.

To quote from page 6.28 of the factory service manual, "MAIN BEARING SHELL SELECTION AND JOURNAL CLEARANCE CHECK".

The crankshaft has automotive type shell bearings at the rod and main bearings. The other lowerend rotating stuff such as the balance shafts are all on ball, roller bearings or removable bushings.
The camshafts don't have bearings, which seems less that desirable to me. But, if it came down to desparation, there are ways to save the head if the cam bearings became too loose.

Whew...lol...

I talked to one of the engineers at my work about there being no bearings for the cams, and he told me that is common in aluminum head motors. I had never seen anything like this till I pulled the cams to shim my valves. Anybody else seen this in any of their other bikes? Is it only Triumph that does this now?

well it must be ok because i have seen many people on here saying these motors can be good for 100,000 miles with no serious motor work.

Frank

Have to agree with you there Greybeard, since the lower end is bathed in much more oil than the top end which must be supplied by pressure feed, that I'd want replaceable journals at the top end! But, I guess it doesn't matter much, if the bottom end has journals and the top doesn't, it'll still cost an arm and a leg for a new head!!

All OHC bikes and probably cars made in the far east have no cam bearings. The load on the cams isn't near as much as on the crankshaft, so they seem to think they can get by with it. If you find your cams fitting way too lose in the heads someday in the far off future when it is hard to find a replacement head, there are a couple of ways to deal with it, but you will need to find a machinesop you trust that can do line boring and bearing fabrication. By reboring the cam journals in the head, you can either use special made shell bearings or revert to the poured babbit bearings used in the 20's and early 30's. On the end bearings, it would be possible to use bushings, but the inner bearing would take some special care.

honda single cylinder dirts bikes don't have cam bearings either. But then the head is much less complex than our's and not as expensive generally to replace. I dont much like it on the honda's and it sure doesnt seem to be the best method on our rather expensive head's. I guess time will tell.