Topic: 718cc project---transmission bearings

[paulages]

to replace or not to replace? i'm doing the rollers for sure, but the big ball bearings are #$%*ing expensive. i don't mind dropping money where necessary, but they double the cost of my parts order. i tend to hate cutting corners, especially when i have the chance to replace something that would be really hard to replace later, or could undermine the whole project, but i can't help but wonder if replacing the $51 countershaft bearing is necessary, for example...

[bwaller]

In this case of tranny bearings, you can definitely find better quality bearings for cheaper from a local bearing source than ordering from Honda. Maybe you've already checked??

[paulages]

that's what i thought---but when i priced the same bearings at Mc Guire Bearing locally, they were actually more expensive than from service honda. mind you, this is considerably cheaper than straight from the dealer. currently the bearing total from the trans is about $140. total order for seals, bearings, etc. (not including the head or case bolts) is around $400.

[paulages]

bump to top...i need some answers!

[tsflstb]

Don't have  a definate answer...how many miles are on the current set?  I struggle with stuff like this too - it's the old "since it's already apart" theory.

I can tell you first hand that bad things happen when bearings seize up in the tranny.  Make damn sure everything's getting plenty of oil.  If those bearings dry up they'll turn a nice shade of blue and your back wheel may suddenly stop spinning.

[bryanj]

You are way overboring the 550 right? in which case I would replace with the Honda ones as they have grooves/pegs for location and to stop rotation, also you are adding approx 30%cc and hopefully power so you need to be supercritical when inspecting gear selectors and dogs

[paulages]

when i examined them upon disassembly, i found no discoloration or apparent wear. i guess you just never know when one's gonna give. the ones particularly in question are the big ones that hold the end of the shaft. i'll replace all of the needle rollers for sure.

[isred]

Just a thought, could you maybe enlarge the openings that the bearings go? That way you could try the 750 bearings. Or something like that, with the type of power that the motor should produce, you want it to get to the pavement. Iwould replace them with new ones at lest and really look for a heavy duty version. good luck have been following your other tread on the motor build with much intrest.

[paulages]

maybe i'm thinking about the physics of this wrong, but i fail to see how increased power to the rotational force at the shafts will increase the strain on the bearings. the shaft bearings should be taking little lateral pressure that i can think of? they spin and spin, and surely wear at some point from heat or foreign particles, but they spin on a fixed axis, right? am i understanding wrong, someone?

BTW, my local jap/euro mechanic was telling me that i need not worry about the sturdiness of the transmission, saying that the cb160's they build into racers have about the same sized (or sturdy) gearbox as a 650 ninja.


also, decided just to order them all. #$%* it, why cut corners...

[cafe75-550]

With straight cut gears the lateral force on the bearings should be minimal, and they should (at least in a perfect world) rotate strictly on a single axis. Now if the shaft isn't perfectly on center, or if you get a deflection of the shaft with a large power input this would be transmitted to the bearing, but a larger bearing in itself wouldn't be a huge improvement unless it was a better made bearing...and I don't think you'll be getting much deflection out of those tranny shafts.

But thats just my .02 

[paulages]

you can actually witness a bit of lateral force (in direction of it's radius) at the bearing, simply by hand cranking the clutch basket (with the case split) and then locking it up in between gears. the resistance at the counter shaft causes the primary shaft to climb up out of the case as it still has torque but is hitting resistance. i imagine a large amount of power at the crank and any road resistance would create a similar force, but with the case closed the force seems it would be transferred a bit more evenly to the top side of the bearing. Most importantly, it seems that the force would be passed evenly across the balls, as they all pass the same point. in other words, it seems like they would wear evenly if at all.

in any case, they certainly aren't very small to begin with. i can't see how larger bearings would help...but i'm certainly no expert...

[CB750F2]

The following is what happend when I changed all of the bearings in the tranmission of my CB750 F2. There are two or three bearings that have a groove in the outside race. These grooves hold locating split rings and mate with grooves in the transmission housing. I found that the new bearings had a narrower groove than the original Honda bearings. I went back to my bearing supplier to see if the bearings could be changed with one that had the wider groove only to be told that bearings supplied had the standard width groove and that was the standard for all bearings regardless of brand. I solved my problem by machining locating rings with a "step". I suggest that you check this out before handing out your hard earned cash. Hope this helps, Pat from Australia.

[bryanj]

As always Honda have their own "spec" whether it is to stop compatability or whether the original supplier had shed loads to sell cheap (like the Amstrad computers with the 3" drives!) who knows. loading tends to happen at the same place/time every revolution which is why bearings do suffer damage--usually brinnelling---where the hard casing gives up, I would suspect that the originals are way over speced and should be OK, BUT that is an (un)educated guess from past experience!

[paulages]

it's hard to see how a transmission bearing would experience brinelling, when it is almost constantly spinning. i guess the countershaft bearings would do some start/stopping. now a steering bearing---that's a brinelled mother#$%*er...

[paulages]

okay....so the question was maybe pointless. i can't find the bearings anywhere.

[bryanj]

DSS or Westernhills honda

[paulages]

i haven't actually looked at david silver yet, but i imagine they'll be twice what honda lists if they do have them. my plan was to check as many honda dealers as possible, hoping that someone's still got them sitting on their shelf. i'll try western hills first---do you have the contact?

[Bodi]

CMSNL.com has the 91002-283-000 sprocket shaft bearing (which takes the most abuse), and show it as superceded so maybe there was an improvement?
Not cheap of course as always with CMSNL...

[paulages]

they didn't have: "ring, bearing(5205), bearing (5205hs), bearing
( 25x29x17), and bearing (20mm)"

i believe that's part #'s: 13491-283-000 (57mm set ring---not such a big deal), 91002-283-000 (countershaft ball bearing), 91002-286-008 (mainshaft ball bearing), 91007-323-000 (primary shaft needle beaing), 23931-323-004 (mainshaft needle bearing).

the two 52mm ball bearings are common enough, but the set ring groove is in an unusual place. i was told by my local bearing supplier that the original manufacturer told them that it was an OEM bearing only.

[Bodi]

Are they actually 5205 bearings? These have 2 sets of balls in one case, to allow thrust from either side. The 5205HS would be a special one, probably with larger balls - the other HS Honda bearings I've seen (for a CB77 I think) had larger (and fewer) balls than the "normal" one.
You could have new bearings EDM machined with the required groove, this would cost a few bucks though and the HS one may be unobtainable.
Anyway, unless the bike has been abused (ie no oil or very dirty oil for extended periods) the oiled bearings should be in good shape. You are putting more power into the transmission but in my opinion the bearings should be ample.
I would carefully inspect the needles shafts and races, and if questionable either find better used parts or new if you can - but if they look and measure OK they're good to go.
The normal problems with hotrodding are the clutch and primary drive, both will be taking the brunt of the power. The HyVo chain should be OK I think, and there aren't any affordable options anyway. It's supposedly stronger than the two CB750 chains put together and there are some very powerful 750 hotrod motors out there. I have replaced one HyVo chain because I though it had too much slack and must have stretched... the new chain was exactly as sloppy as the old one.
The clutch should be checked over carefully and new Honda plates fitted if you feel a need for improvement. I avoid Barnett plates after bad experiences with them on street bikes, they wear very fast and stick solid (and take serious effort to free) after sitting even overnight.

[HITMAN]

Paulages,

Have you tried any of the bearing houses in clackamas, International Bearing (I haven't been there in a while) or Applied Industrial (www.applied.com).  Unfortunantly Macguire is one of the best places around here, but more than the dealership?

[paulages]

hitman--no, i haven't tried the others, but mcguire called all of the manufacturers of these bearings (i brought the actual bearings in), and had no luck. and yes, the couple that they did have were more expensive--for example the 63/22 is $15.40 from servicehonda, and $22 from mcguire.

Bodi--i'd have to look at the 5205 to see if they are as you are describing, but i'm just repeating the honda part#, and their decsription. all of the 650 bearings are the same, except for the countershaft needle bearing, which has a different style outer race than the 550 (but same sized, so i could theoretically use the needles, cage and inner race with the 550 outer race). the 650 engine had 18,000 miles on it, and appeared to have been babied. worse case scenario, i'll just use these.

when i talked to my machinist about bearing wear, he said that the races weren't so much of a worry as the balls and needles themselves. because they are constantly spinning, the shock is distributed pretty evenly. however, he said that what happens is fatigue of the balls/needles from precisely the "climbing" motion i was talking about before, resulting in brittleness...which could obviously be pretty bad. 18,000 miles though...not too bad.

[bryanj]

www.westernhillshonda.com and as long as you have the part numbers you can look up yourself. Be aware that one of the shafts comes complete with a bearing and i found it cheaper to buy a NOS shaft than a new ordered in bearing.
I have built a gearbox for a 500 using 500, 550 and even some 650 parts, most gears will fit as long as you use the mating gear as the tooth profile changes with age--hard part is getting the end clearances right

[paulages]

i tried that address initially, but it looks as if their website is no longer up and running. yeah, i'm considering a mix and match of 550 and 650 gears to obtain close ratios, but haven't decided yet.

[bryanj]

Sorry mate, since i was last on there they have changed to www.westernhillshonda.net Thats why you couldnt find them!

[paulages]

thanks!

[Jim F]

Check out a company called bearings and drives
If they dont have it then nobody will
Good luck
Jim

[paulages]

thanks--i'll check them out. the problem is, however, not that noone make bearings in these particular sizes, but that honda had them machined in a way that is non-generic. for example, the shafts' ball bearings both have locating grovves in them that are atypical. haven't given up yet though...

western hills had one of them, at double the normal honda price! maybe if i can't find them at all...but in the meantime, $60 is too much for one little bearing.

[bryanj]

You gotta be carefull with all these NOS "vintage" parts places, some are working off years old price lists and yes, believe it or not, some Honda prices have gone DOWN, depends on overall stock and wether they want rid of them or not!