Topic: "Extra clearance" ball bearings (paging hondaman?)

[drumstyx]

In the transmission section of hondamans book it says that only one bearing (6304HS, grooved) has extra clearance, but I noticed while going back to deal with the crank that it says both the bearings on the main shaft should be high speed, or "extra clearance" (aka C3).

Which is the case?

If the issue is speed, it makes sense to me that all the grooved bearings (both mainshaft plus the one primary drive) should be high speed/extra clearance, no?

[drumstyx]

I put some thought into it and I can take a guess as to the reasoning of only the one bearing being a C3; at the outer edge of the case more or less, the outer race might be significantly cooler than the inner race and balls.

[drumstyx]

Calling hondaman?

[HondaMan]

Yeah, when Honda "scrubbed" their parts fiche on the Internet (2006 or so) they swapped them to the post-K4 bearings. Both of them are C3 class bearings on the later bikes, which lets the gearshifter find NEUTRAL slightly easier. This works OK if you're not building a high-HP monster bike. The ones that are grooved are an issue today, so I hope you're not looking for one of those? Starting in 1997, the whole world decided to (conspired to?) change to ISO bearing dimensions so everyone made the same general layouts. Prior to that, the JIS methods had slightly different bearing retainer groove dimensions, so if you need one of those you'll have to either look for a used one or spend some $$ to get a blank one grooved at a (big) bearing shop, to match the old one. They used to do it here in Denver at United Bearing Supply, but they got bought in 2014 and are gone now.

[drumstyx]

Yeah, when Honda "scrubbed" their parts fiche on the Internet (2006 or so) they swapped them to the post-K4 bearings. Both of them are C3 class bearings on the later bikes, which lets the gearshifter find NEUTRAL slightly easier. This works OK if you're not building a high-HP monster bike. The ones that are grooved are an issue today, so I hope you're not looking for one of those? Starting in 1997, the whole world decided to (conspired to?) change to ISO bearing dimensions so everyone made the same general layouts. Prior to that, the JIS methods had slightly different bearing retainer groove dimensions, so if you need one of those you'll have to either look for a used one or spend some $$ to get a blank one grooved at a (big) bearing shop, to match the old one. They used to do it here in Denver at United Bearing Supply, but they got bought in 2014 and are gone now.

I found a machinist locally that would groove all 3 grooved bearings for $75 Canadian. Big money compared to the bearing price, but skf bearings so I'm hoping I'm making a solid investment. I found the machinist before removing the bearings, just in case.

Unfortunately, I don't followed the transmission section advice and ordered up all bearings at normal clearance except the one on the end. I don't imagine it's a huge deal.

[HondaMan]

Yeah, when Honda "scrubbed" their parts fiche on the Internet (2006 or so) they swapped them to the post-K4 bearings. Both of them are C3 class bearings on the later bikes, which lets the gearshifter find NEUTRAL slightly easier. This works OK if you're not building a high-HP monster bike. The ones that are grooved are an issue today, so I hope you're not looking for one of those? Starting in 1997, the whole world decided to (conspired to?) change to ISO bearing dimensions so everyone made the same general layouts. Prior to that, the JIS methods had slightly different bearing retainer groove dimensions, so if you need one of those you'll have to either look for a used one or spend some $$ to get a blank one grooved at a (big) bearing shop, to match the old one. They used to do it here in Denver at United Bearing Supply, but they got bought in 2014 and are gone now.

I found a machinist locally that would groove all 3 grooved bearings for $75 Canadian. Big money compared to the bearing price, but skf bearings so I'm hoping I'm making a solid investment. I found the machinist before removing the bearings, just in case.

Unfortunately, I don't followed the transmission section advice and ordered up all bearings at normal clearance except the one on the end. I don't imagine it's a huge deal.

The only one that really needs to be "extra clearance" type is the one Honda calls "HS Special" in the parts diagrams. The reason is: the engine cases twist upward on the clutch side at high engine speeds under heavy throttle and hiway speeds. This extra clearance lets the mainshaft run without bind, which greatly increases the torque, lowers the stresses, and prevents transmission misalignments.

[AshimotoK0]

Yamiya are cheap for Genuine Honda grooved bearings :

[HondaMan]

Yamiya are cheap for Genuine Honda grooved bearings :

Wow! Those ARE cheap! I hope they are not the Chinese-made NTN brand? The old Japanese-made NTN well fine bearings, the modern Chinese versions are not. I might have to get some of these: I have 4 750s of my own apart right now, and at least one has a rusty grooved bearing.

Thanks, Ash!

[AshimotoK0]

I checked Mark  (see photo) and the 750 clutch release bearing is Nachi and the K0 output shaft bearing (grooved) is NTN BUT both are stamped  JAPAN on both bearings so assume, as genuine Honda parts, they are the best I am gonna get?
Also check out their 400/4 gearbox bearing kit ! That's good value too in my book.


Cheers !  Ash

[PeWe]

I got some bearings from Yamiya750 this week.  Ordered just for sure.
 grooved bearing on primary drive hub 6008
 outgoing double row bearing 5206
 bearing for the lower case, 6204

needle bearings in prim drive hub replaced by Fourever Classic Parts in Germany when they replaced the rubbers inside.

I replaced all bearings for about 40.000kms ago. Debris from broken clutch fiber and tensioner rubber might have caused addditional wear.
Yamiya should have a complete kit for CB750 as they have for CB400.

- How cam I determine that the bearing is worn and need to be replaced?

[drumstyx]

Those are really cheap, but I don't feel horrible about going through the bearing house because I got SKF all around except the double-row output bearing (Nachi aka NSK was half the price of the SKF, which would have been $60!). The driven primary sprocket bearing (6008) was also pretty expensive at $30. That said, each grooved bearing will cost me another $25 for the groove at the machinist. It's painful, but come on, a completely rebuilt transmission for $250 in bearing costs? Can you really sneeze at that? That's all 8 ball bearings in the engine AND both needle bearings, though I'm not sure I'm going to replace those.

All that said, anyone know the difference between a 3206 and a 5206 double row bearing? I know there's something to do with angles internally, but apparently 5206 is hard to come by these days, so I ended up with a 3206.

[HondaMan]

- How cam I determine that the bearing is worn and need to be replaced?

For the most part, it is either mileage, or rust, that wears them out. That said, mine at 140k miles were not worn out. I had a never set and installed them (10k miles on them), but the old ones are still not rough, nor loose.

In our "63nn" sizes, the C3 class bearing is "worn" when it has more than 0.0060" up-and-down loose play of the center race. It is usually easier to put the center on a shaft, then measure the outer race slop, instead...same number. 

[PeWe]

OK, so if the ball bearings do not feel like sand inside nor seems to have much play with a loose inner or outer race, bearing is OK, right?
I had some doubts due to the debris from tensioners and earlier small parts from a clutch broken outer fiber plate. I got wring plates many years ago. Got the old plates were all are same. My clutch have the outer plate with wider tabs.

[HondaMan]

OK, so if the ball bearings do not feel like sand inside nor seems to have much play with a loose inner or outer race, bearing is OK, right?
I had some doubts due to the debris from tensioners and earlier small parts from a clutch broken outer fiber plate. I got wring plates many years ago. Got the old plates were all are same. My clutch have the outer plate with wider tabs.

Those should be OK. They are usually easily detectable when "bad".

[PeWe]

Thanks for the support Mark
Its's very tempting to order all bearings from Yamiya when still available

[flybox1]

Thanks for the support Mark
Its's very tempting to order all bearings from Yamiya when still available

+1
got all mine from there.  shipping was under 2 weeks IIRC.

[HondaMan]

I checked Mark  (see photo) and the 750 clutch release bearing is Nachi and the K0 output shaft bearing (grooved) is NTN BUT both are stamped  JAPAN on both bearings so assume, as genuine Honda parts, they are the best I am gonna get?
Also check out their 400/4 gearbox bearing kit ! That's good value too in my book.


Cheers !  Ash

Nachi bearings are nice parts: I just used some in a K3 engine. They have a good reputation for being of strong metals, which is where some of them have fallen down in recent years, from China.