AIRCOOLEDRDCLUB FORUM

Tech Zone => Aircooled RD Tech Help 250cc and Above => Topic started by: [Mossi398] on February 08, 2020, 05:00:32 AM

Title: Crank shaft Bearing options
Post by: [Mossi398] on February 08, 2020, 05:00:32 AM
Hi just wondering, has anyone used crank shaft bearings other than Koyo. I know they have pips to stop spinning but can NSK or FAG for example be used with out pips & use some loctite product. Regards Phelim.
Title: Re: Crank shaft Bearing options
Post by: D Peacock on February 08, 2020, 08:21:40 AM
Yep, I use pegless bearings and glue the crank in place with Loctite bearing fit. Let’s just say they won’t spin....
Title: Re: Crank shaft Bearing options
Post by: [Mossi398] on February 08, 2020, 09:40:49 AM
Good news.Thanks.
Title: Re: Crank shaft Bearing options
Post by: doggone1 on February 08, 2020, 10:07:29 AM
I was going to fit mine with o ring cord 1.6 mm I think I haven’t got around to doing it yet but there is a thread on here somewhere with details I think
Title: Re: Crank shaft Bearing options
Post by: doggone1 on February 08, 2020, 10:08:54 AM
Get my koyo bearings from George lodge find them very reasonable
Title: Re: Crank shaft Bearing options
Post by: [Mossi398] on February 08, 2020, 01:32:10 PM
Hi doggone 1, did you mean Viton seals you make yourself? That would also work. Ive got 5 crank shafts that need rebuilding , rebuilt a crank shaft a few years ago with Koyo bearings so just looking at options to keep costs down some what.
Title: Re: Crank shaft Bearing options
Post by: vannerman on February 08, 2020, 04:00:35 PM
I bought SKF 6206 NR explorer  and SKF 6305  NR explorer bearings which come complete with a snap ring, which you remove and replace with a 58mmx2mm viton o ring ,I think that is the set up used by HV cycles in america.By the way I can not say how good they would have been as in the end I had the crank rebuilt by Grampian 
Dave
Title: Re: Crank shaft Bearing options
Post by: AndyDean42 on February 08, 2020, 07:13:12 PM
Any brand should be OK, but remember you need a C3 grade bearing. It has a different radial clearance to standard bearings.

Andy
Title: Re: Crank shaft Bearing options
Post by: doggone1 on February 08, 2020, 07:18:19 PM
Yes thats what ive been told to use the seals you make yourself as they are not available in the correct size ive got to do mine soon so will be better placed to comment once its done i think its important to do a dry assembly to make sure everything goes together correctly
Title: Re: Crank shaft Bearing options
Post by: doggone1 on February 08, 2020, 07:20:27 PM
I was told 1.6 mm but this is not first hand knowledge so I will try that and 2mm as mentioned above and see what is best I think it seems to be a common use in the states instead of pips at least they wont groove the cases if they did spin
Title: Re: Crank shaft Bearing options
Post by: [Mossi398] on February 09, 2020, 01:25:51 AM
AAH I see so basically all four bearings need to be NR bearings,6305NRC3 & 6306NRC3 with groove/ snap ring for seal .Thanks guys.
Title: Re: Crank shaft Bearing options
Post by: 350GUY on February 13, 2020, 05:43:32 PM
Any brand should be OK, but remember you need a C3 grade bearing. It has a different radial clearance to standard bearings.

Andy

Howdy Andy! are C4 rated bearings considered superior or an upgrade over C3 for the RD350 crank? I have a pair and I am hesitant to use them.
Title: Re: Crank shaft Bearing options
Post by: doggone1 on February 13, 2020, 06:47:27 PM
C4 are looser than C3 so I would stick with the C3 thats specified for sure.
C3, C4 and C5 bearings are bearings that have an additional internal radial clearance to cope with high speed environments where excess heat is generated. They are not suited to environments where critical alignment is required from the onset e.g. Where blades and cutters are set up to each other. Applications like motorcycle wheels or bicycle wheels do not require C3 rated bearings. Unless the bearing you are replacing specifically says C3 on it then you should not replace it with a C3 bearing, C3 Bearings are loose to the feel from new and often people complain at the quality of the bearing being poor and having more movement than the one they are replacing. C4 and C5 are even looser still than C3 clearance bearings. This is the characteristic of these higher than normal clearance bearings marked C3, C4 and C5.
Title: Re: Crank shaft Bearing options
Post by: 5port on February 13, 2020, 08:59:34 PM
Applications like motorcycle wheels or bicycle wheels do not require C3 rated bearings. Unless the bearing you are replacing specifically says C3 on it then you should not replace it with a C3 bearing, C3 Bearings are loose to the feel from new and often people complain at the quality of the bearing being poor and having more movement than the one they are replacing.

Some RD wheel bearings are specified C3, probably due to brake heating.

5port
Title: Re: Crank shaft Bearing options
Post by: Bluehaze on February 13, 2020, 10:55:50 PM
Sometimes C3 bearings are specified for rebuilds, when the original ones had tighter clearance.
I noticed this in a repair manual for a USA made stationery engine.
No explanation was given. Perhaps a C3 is more forgiving of imperfect alignment control out in the field?
Title: Re: Crank shaft Bearing options
Post by: [Mossi398] on February 14, 2020, 09:46:31 AM
If one goes down the vitron 1.6mm seal route with all four crank shaft bearings being NR type with groove, what do you do with the labyrinth seal? Umm !!!
Title: Re: Crank shaft Bearing options
Post by: G Jones on February 14, 2020, 10:33:15 AM
If one goes down the vitron 1.6mm seal route with all four crank shaft bearings being NR type with groove, what do you do with the labyrinth seal? Umm !!!
This...
(http://tz350.co.uk/images/Labseal.jpg)
Title: Re: Crank shaft Bearing options
Post by: 5port on February 14, 2020, 05:24:03 PM
Hi Gordon.  Those pics look worryingly like the pattern lab seals without the cut-outs in the outer (side) faces, that can stop the oil feeding the main bearings?  :-\

5port
Title: Re: Crank shaft Bearing options
Post by: G Jones on February 14, 2020, 08:15:15 PM
Hi Gordon.  Those pics look worryingly like the pattern lab seals without the cut-outs in the outer (side) faces, that can stop the oil feeding the main bearings?  :-\

5port
I can assure you these are not the seals that caused you (and me) so much trouble - I have these made for the TZ - and superb tolerances give us no trouble - I also have a way to use on the RD too - but that's another story...
Title: Re: Crank shaft Bearing options
Post by: [Mossi398] on February 15, 2020, 01:43:15 AM
Thanks for the picture, nice solution would be interested to know the other story for use on RD if possible.
Title: Re: Crank shaft Bearing options
Post by: 350GUY on February 15, 2020, 04:12:01 PM
C4 are looser than C3 so I would stick with the C3 thats specified for sure.
C3, C4 and C5 bearings are bearings that have an additional internal radial clearance to cope with high speed environments where excess heat is generated. They are not suited to environments where critical alignment is required from the onset e.g. Where blades and cutters are set up to each other. Applications like motorcycle wheels or bicycle wheels do not require C3 rated bearings. Unless the bearing you are replacing specifically says C3 on it then you should not replace it with a C3 bearing, C3 Bearings are loose to the feel from new and often people complain at the quality of the bearing being poor and having more movement than the one they are replacing. C4 and C5 are even looser still than C3 clearance bearings. This is the characteristic of these higher than normal clearance bearings marked C3, C4 and C5.

Thank you Sir for your very detailed explanation, now things are much clear. For some reason, them 2-stroke Polaris Ski-doo & Rotax crankshaft main bearings are C4 rated. So I guess those bearings are used on their cranks since they generate more heat and rev at higher RPM's? In fact I was planning to use the two 6206 C4 bearings for the center that I have on the crank I plan on recondition. For the outer bearings, I do have a pair of OEM HIC (6305N) . So I guess this combination wouldn't be recommended? Thank you for your time, much appreciated.