Topic: CB750 Gearbox Bearings

[77honda]

Anyone know where I can get new bearings for the gearbox, namely
6008 NR
6304 NR
6205 NR
Local bearing suppliers here can get these BUT the snap ring groove is way
too thin only 1mm where as stock bearings have groove approx 2mm wide.

Thanks, Mike

[mrosso]

I can find standard skf bearings that match all but the snap ring width too. If you order bearings with "NR" instead of just "N" suffix, they come with a snap ring already installed in the narrow groove. I'm not sure if that would work, though. Here's a pic:

Anyone know if you have to have the 2mm snap rings or can you just use the small ones that come with aftermarket bearings?

I'm doing an engine rebuild too. Motor and transmission.

[HondaMan]

Generally, a bearing supplier (one who does more than just selling bearings) can cut a groove to match any existing bearing.

Barring that, you can chuck a bearing into a drill and use a Dremel tool and cutoff wheel to make your own groove.

Two of the gearbox bearings are listed as "high speed" bearings (the ones on the mainshaft). These should be the "extra clearance" bearings, available in bearing catalogs, but on special order, usually. These have an extra .0002" to .0004" clearance on the balls and races, to accomodate extra heat and, in the case of the 750 engine, case mount misalignments when under heavy acceleation loads. Using a standard bearing in those places will reduce engine output and make shifting stiffer.

[CB750F2]

The grooves need to be widened to the 2mm. I suggest that you get a quote from a machinist to have them widened. Give him an original bearing as well as the new bearing so that he can see which side of the groove needs to be machined/ground.
Pat

[NitroHunter]

I had a shop grind the snap ring groove into a bearing, the price was shocking! 
Get a quote first...

[HondaMan]

I had a shop grind the snap ring groove into a bearing, the price was shocking! 
Get a quote first...

Wow, what did they charge you? It used to be a $5 adder on a $5 bearing...

[bryanj]

Cant you just get the Honda parts?

[mrosso]

Some, but others are discontinued.

[HondaMan]

Specifically, the last time I tried, the "High Speed" and grooved bearings were NLA from Honda.
I found my research notes: the "C3" bearing clearance is the one that matches Honda's "High Speed" designation. This style has internal clearance of 33um (about .0008") nominal. A normal bearing has about .0004" internal clearance, according to the SKF/NTN catalogs.

[mystic_1]

Yamiya has what you need:

http://www.yamiya750e.com/index.php?main_page=advanced_search_result&search_in_description=1&keyword=bearing

mystic_1

[HondaMan]

Yamiya has what you need:

http://www.yamiya750e.com/index.php?main_page=advanced_search_result&search_in_description=1&keyword=bearing

mystic_1

That's terrific, Mystic!
I'm afraid to see the prices, but may have to get a set myself. I have some young ones (12k miles) from Soos, but haven't had my bike apart to install them, yet. Maybe I'll get a new set, if I can afford them.

It's cool they also have the rear wheel "bearing plug", too. These get so beat up by corrosion and removals over the years.