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Hi, can anyone tell me what the spec is for the cam bearings in a 175 narrowcase?

I know that they are a 6202 size, but am unsure if they need to be a C3 or deep groove etc.?

Any advice from the Wise Ones in here would be much appreciated

The parts list says "RIV 02A", which is equivalent to a std. 6202. According to a cross reference list from FAQ, the C3 type must be named RIV 02A/053.

cheers Hans

Bearing manufacturers are really good about publishing technical specs- if you do a search you'll find lots of info. The standard bearing clearance, in the US anyway, is usually called a 'CN', with a C2 being lower clearance and C3 being a higher clearance- just the clearance between the races and the balls, not the 'fit' of races, that's another spec.
But, the clearances are small, and overlap. For a 15mm shaft the CN clearance is 3-18 micrometers and C3 is 11-25 micrometers. My brain still defaults to inches, and a micrometer is 0.00003937", so it's a very small number- less than 0.0003" difference at the max. Plus, with the overlap, a loose CN has more clearance than a tight C3.
If the fit of the shaft on the inner race or the outer race in the head are really loose than I'd use a CN- not much need to worry about clearance. Usually the fit of the shaft and the housing bore are really tight, an interference or shrink fit- than I'd use the looser C3 to avoid too much preload.
I go with too loose over too tight- maybe a little noisy, but a tight bearing overheats and compounds the problem.
Rick

ducwiz wrote:The parts list says "RIV 02A", which is equivalent to a std. 6202. According to a cross reference list from FAQ, the C3 type must be named RIV 02A/053.

cheers Hans

Hans, you're a star old son, many thanks

Rick wrote:Bearing manufacturers are really good about publishing technical specs- if you do a search you'll find lots of info. The standard bearing clearance, in the US anyway, is usually called a 'CN', with a C2 being lower clearance and C3 being a higher clearance- just the clearance between the races and the balls, not the 'fit' of races, that's another spec.
But, the clearances are small, and overlap. For a 15mm shaft the CN clearance is 3-18 micrometers and C3 is 11-25 micrometers. My brain still defaults to inches, and a micrometer is 0.00003937", so it's a very small number- less than 0.0003" difference at the max. Plus, with the overlap, a loose CN has more clearance than a tight C3.
If the fit of the shaft on the inner race or the outer race in the head are really loose than I'd use a CN- not much need to worry about clearance. Usually the fit of the shaft and the housing bore are really tight, an interference or shrink fit- than I'd use the looser C3 to avoid too much preload.
I go with too loose over too tight- maybe a little noisy, but a tight bearing overheats and compounds the problem.
Rick

Wow, loads of info! Many thanks for the education Rick

Rick wrote:If the fit of the shaft on the inner race or the outer race in the head are really loose than I'd use a CN- not much need to worry about clearance. Usually the fit of the shaft and the housing bore are really tight, an interference or shrink fit- than I'd use the looser C3 to avoid too much preload.
I go with too loose over too tight- maybe a little noisy, but a tight bearing overheats and compounds the problem.
Rick

Sometimes a C3 bearing is specified for a rebuilt assembly, even if the original bearing was not.
I took this to mean that a used machine benefits from some extra clearance, due to possible slight warpage of cast housings, and difficulty of getting things clinically clean in the average workshop.

Good point.

Seeing as most of the bearings that I've bought for the bottom end from Lacey Ducati have been C3s this makes sense.

That, together with the high speed of rotation and possibility of heat build up if there is any chance of inadvertant preloading due to wear, leads me to think I'll put some C3 spec ones in there to be in the safe side.

Thanks for all the advice, it's much appreciated all

Samurai wrote:

ducwiz wrote:The parts list says "RIV 02A", which is equivalent to a std. 6202. According to a cross reference list from FAQ, the C3 type must be named RIV 02A/053.

cheers Hans

Hans, you're a star old son, many thanks

Sorry, that was a "freudian" - FAG of course ! The list is here: http://www.fag-ina.at/explorer/download/waelzlager/Waelzlagervergleichsliste.pdf
Btw, I even used C4 grade more than once, for the w/c mainshaft bearing, RH side (parts catalog no. 75120.1747, bearing RIV 01A). In many engines I worked on, it's bore was too tight, no free play remained after the new C3 bearing was pressed in - one could still "feel" the balls when the bearing's inner race was rotated with a finger in it.

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ducwiz wrote: In many engines I worked on, it's bore was too tight, no free play remained after the new C3 bearing was pressed in - one could still "feel" the balls when the bearing's inner race was rotated with a finger in it.

Thanks ducwiz. It's not something I've noticed, but I'll be checking from now on.