Topic: Oil pump rotors and kickstarter gear

[persson-johan@hotmail.com]

Hello all!

I recently bought a 72 cb750. It has been sitting since 99 so i wanted to go trough the engine and the whole bike before i crank it up.

 
(dont worry, already have the original handlebars mounted )

Now i have 2 questions for you guys:

The oil pump rotors have some scratches, the clearences are all ok but alot of marks. Is this ok to run with? Ive read that these pumps are well over dimensioned. I dont have a oil pressure gauge but maby thats something to look into.
I borrowed a picture from ebay, this is pretty much how it looks like:



After splitting the cases i notice that the kickstarter gear can rotate both ways without a stopper. Shouldnt this be a one way gear? I didnt try the kickstarter while picking up the bike.


I know atleast i like pictures in forum threads so here´s a few from the process!




Always a fun step!


Nice suprice!


Finally bought a cheapo engine stand. Well worth the money


Best regards
Johan
Sweden

[Whaleman]

Maybe Hondaman will see this or PM him as at one time he was rebuilding oil pumps. I think they ALL have some scratches. Every one I have seen has had some. Dan

[Bodi]

The only pump I have seen that could not manage decent pressure on a good engine looked much worse. The engine had been totally rebuilt because of a failure that sent a lot of shredded transmission bits through the oil system. We tried the pump but, while passable on cold oil, it did not succeed with hot oil.
The big pump is the scavenge (and transmission) pump, everything that gets through the pickup screen goes through the rotors: every used pump I have opened shows some damage but they still manage to do their job.
The small one is the pressure pump, yours doesn't look too bad. End clearance is more critical to pressure loss than the face condition in my experience, your end faces look well worn so I would check that at the least.
My theory is that most metal chunks (what else could do the usual damage?) that get through the scavenge pump settle out in the tank, and don't get into the pressure pump.
New pumps are no longer available. Internal parts were never available.
I have heard rumors that someone is getting new pump rotors from somewhere (either parts for a different vehicle - almost all Japanese bikes and many cars use the same basic pump technology - or sourced directly from one of the trochoidal pump suppliers) but I haven't tracked them down.
Any used pump you buy is a gamble. They will all be worn, maybe less and maybe more.

[persson-johan@hotmail.com]

Thanks for the answers!

The picture is not on my pump but similar in wear to what i got. I will post pics on my rotors next time im in the garage. What kind of gauge is recommended to check the oil pressure? I can drill and thread myself so i dont need a fancy aftermarket one =)

/Johan

[Bodi]

Any appropriate range gauge will work: fluid filled is best because of the pressure pulsations that will destroy the Bourdon geartrain over time, but for temporary use any cheap pressure gauge is ok. a 100psi/7bar gauge would be fine, pressure should be limited at 50-60psi by the pump relief valve but can go higher with cold oil (the relief hole can't flow enough with cold oil).
You can either thread a gauge into where the pressure switch goes (possible thread issue, it accepts a 1/8 NPT but is apparently really a different thread) or drill and tap the gallery plug on the right side of the crankcase (round thing with a hex head - looks something like a tappet cover); a 1/8NPT threaded hole fits nicely in the middle of the hex head. Threaded plugs are easy to find that seal the hole when you take the gauge off. You can see a gauge in the gallery plug whilst sitting on the bike, not so with it replacing the pressure switch.

[persson-johan@hotmail.com]

Sweet! Thanks. Ill go for a cheapo gauge and plug the hole when im done using it.

So what about the kickstarter gear? Is it normal to be able to spinn it both ways when the case is apart?