Here we go,bought a 1970 650 Triumph last year and it ran great no problems at all but decided to clean the trap which I never done before.Not sure what t/s ball bearing I have as it is stll in the case but my rollor bearing says v3 which I was told is a c3?Now did the guy before me put in the wrong bearing?I have read page after page and am getting very confussed.Do I reinstall the c3 or buy a cn or c2??I can just drop in the c3 onto my crank and turn the crank over and the c3 will just fall off the crank shaft and I am thinking that is not good? but again the bike ran and sounded great?By going to the tighter cn or even tighter c2 am I doing more harm than good?BTW do the t/s ball bearings come in different sizes or are they all c3?Thanks
This bearing clearance stuff can really get out of hand sometimes... I think we talked via email. Roller should be CN and ball bearing should be C3. I have been told that "V3" stands for vibration which would not be the same as C3. Usually Hoffmann bearings have a V3 stamped on it. If that is so, I have never seen late model Triumph 650's with a Hoffmann roller bearing. Typically BSA twins had the Hoffmann bearing. Yours should be a brass cage RHP in a CN condition.
I have been told that "V3" stands for vibration which would not be the same as C3.
So V3 is not necessarily related to C3.
Deep groove ball bearings Series: 60 series Product Name: 60 series deep groove ball bearings Brand: NCKBRT Shield / closure: Open ball bearing, Z, ZZ, RS, 2RS, 2RZ Tolerance: ABEC-1, ABEC-3, ABEC-5, ABEC-7 Vibration level: V4, V3, V2, V1 Radial play: C0, C2, C3, C4, C5 Material: Gcr15 Retainer: PTFE, nylon, PEEK or (stainless)steel Hardness: 59 - 63HRC
So the question is what internal clearance is the original bearing.
With today's bearings even though the tolerance bands overlap the machining ability means a C3 is a C3 as they can keep away from the overlap, back in the 60's there was the possibility of a 30mm ID bearing with say 17 microns of internal clearance being CN or C3, have a look at the chart. 30mm ID CN is 6 to 20, C3 is 15 to 33, so there is an overlap from 15 to 20 where a bearing could be stamped CN or C3.
All this time I thought the I/s of the bearing where it slides onto the end of the crankshaft was all the different c#'s not where it rides on the race that is in the outer case .Will have someone look at my crankend to see what can be done to make the bearing fit better,not sure why the bearing I have can just slide off .Somewhere I read something about using green Loctite,any thoughts on that?Also (afraid to ask) do I reorder another c3 roller RMS11 V3 as that was what was in there?Again this bike did run great but I can tell it has been apart before and before I bolt the cases back up again I want to ask what bearing and #'s if possible should I use on the crank of a 1970 triumph 650?Thanks again
Re: Yep Another Triumph C3,CN,C2 bearing ?????HELP
#684814 02/13/1711:23 am02/13/1711:23 am
Why did Triumph change to a C2 clearance drive side bearing in 1978 (or whatever year it was)? What actually changed - the housing diameter in the cases? Or the shaft diameter? Or was this a change of bearing spec for no real reason?
If anything other than a blank space is visible here, something's wrong.
• The choice to use pre-fit internal clearance was done for a reason. It was not an arbitrary decision. It goes back to engineering practice where cost of production and weight were big factors when cost and fuel economy were big issues. Holding the bearing in the crankcase with an interference fit addressed both of these concerns.
• When you hold a bearing in place with an interference fit the bearing's i.d. will close up from half to three quarters of the interference fit. So if you have an interference fit of .0015" to .002" the pre-fit internal clearance can be be reduced by as much as 0.0015". The amount will vary from the wall thickness of the race, the actual amount of the interference and the rigidity of the casting it is sitting in.
• If the bearing doesn't have enough pre-fit internal clearance it will be hard, if not impossible, to put the bearing together and the rollers will skate. If it has too much the bearing will knock, especially on the over-run (deceleration). As little as .0005" too much clearance can make a bearing knock.
• With the introduction of the co-operative models in 1976-77 they change the specifications of the 70-2879 main bearing without changing the part number (something they did a lot). It went from CN to C2.
• Originally the inner race of the drive side roller bearing was a light press fit. This would close up the pre-fit internal clearance a few tenths. The bearing can be used if the clearance is now around .0005". If more it will have to be addressed depending on the amount of wear. This wear typically happens because the rotor nut that retains the sprocket came loose at some time in its life. To preven this the rotor nut must be tightened when the crankshaft is locked in place. It cannot be tightened by putting the bike in high gear and putting on the rear brake. This kind of work almost insures the nut will come loose (even if it is retained with loctite).
There is more to this but I do not have the time to go through the whole thing. We are getting ready to ship and UPS will be here in an hour. John
Re: Yep Another Triumph C3,CN,C2 bearing ?????HELP
[Re: John Healy]
#684929 02/14/174:33 pm02/14/174:33 pm