Topic: Inspecting gear dogs on CB750 transmission

[AshimotoK0]

Does anyone know what kind of wear to look for on the dogs of the gears on the CB750K0 transmission? The Honda manual tells you to inspect them to see if they are worn but I don't really know what's good or bad. are there any dimensions to measure?

Any other info on transmission inspection would be greatly appreciated!!

Anyone know if the Hondaman book gives any detailed description of checking the transmission components for wear.

cheers - Ash D

[MattFreeman]

Look for rounded edges/shoulder on the dogs. They should be fairly square.

[the-chauffeur]

Have a look at the thread "The thoughts of Hondaman" under the FAQ section of the forum.

Not all the answers you're looking for, but there's some useful stuff there . . .

[AshimotoK0]

Whoops !! I think mine are a nice rounded shape - anyone got a picture of one which is in good condition to compare with mine please?

Cheers!!   AshD

[Laminar]

http://aperaceparts.com/transmissions.html

[MCRider]

http://aperaceparts.com/transmissions.html

The picture above is the APE undercut transmission I think? It appears to be. THat is the dogs have been cut with reverse angles so they pull themselves together. Stock, the dogs would be parallel/square to each other. It is noticable to the eye. If worn the dogs would be worn to where they appear pointed, that angle essentially pushes the gears apart from each other.

TO the original question, was the transmission hopping out of gear? Especially hopping out of 2nd into a false neautral? If not you are probably OK and I would think twice before spending the money. Or spend it on having the gears undercut.

[AshimotoK0]

I don't know what the transmissiion was like when the bike was operational, as it was stood for 15 years. Could ask the PO though.

[AshimotoK0]

Have a look at the thread "The thoughts of Hondaman" under the FAQ section of the forum.

Not all the answers you're looking for, but there's some useful stuff there . . .

Could not find anything in 'thoughts of Hondaman' other than polishing the gears to get more efficiency. Am I looking in the right place on the FAQ's

[AshimotoK0]

Spoke to PO and he said he never had any problems with gear changing or clutch (he owned from 1975-2008) so maybe I just stop worrying and use it as is.

[UK Pete]

Hi Ash, if it aint broke dont try and fix it, i can tell your a perfectionist arnt you
pete

[MCRider]

Spoke to PO and he said he never had any problems with gear changing or clutch (he owned from 1975-2008) so maybe I just stop worrying and use it as is.

You mentioned your dogs were round? The tops of the dogs are radiused (rounded) so a little of that is to be expected.  but the sides of the dogs that actually hit and engage each other should be parallel.

From the evidence, low mileage, no signs of abuse, testimony of PO, I'd move on.

But its not my bike. 

[AshimotoK0]

Just had a look at the mainshaft second and third gear and its mating mainshaft top gear. The parts where they mate (lock together) are much more worn on the edges than the the other spare two pairs I have (same no.of teeth but from a K7 and F1 respectively).  Could I use the better parts even though the mating gears on the countershaft cannot be used because the ratios are different from the K0 or is it a definite no-no to mix mating gears.

Also what is the difference between the steel gear bushes and the earlier bronze looking ones. Which are the best and why did they change materials?

Another alternative would be to fit the complete later transmission. How would this manifest itself in rideability?

Will post some pics tomorrow of the relevant gears.

Not a perfectionist Pete, I just don't want to strip the motor ever again!!

Cheers!!

Ash D

[UK Pete]

yes i understand it would not be a nice thought to have to strip entire engine because of overlooking some things.
I always have this dilema when building engines, trouble is that on something real old usually everything in there gives you some sort of reason to replace, for example with my F2 engine its a case of do i do my primary chains, then the tensioner, gearbox bearings, crank , crank bearings,cam chain,camchain tensioner,pistons and rings, rebore, new valves, and guides ,valve springs and seats, cam, cam towers, ect, they all show some sign of wear, but also could be good for many more miles, i suppose if the budget allows then get everthing done, but you could blow the entire value of the bike just by rebuilding the engine, once you add machining work, gaskets oil seals, blasting , painting .
I do hope some body can answer your question as to wether the later transmission works and the different bushings, as these are good questions
Pete

[MattFreeman]

Perfectionist Pete

I think you just coined a new phrase.