Topic: cb400four - anyone done an oil pump upgrade?

[thirdman]

Has anyone upgraded their CB400Four's oil pump?  I have heard some anecdotal rumblings that you could swap in parts from a GL1000, but I have no clear evidence.  Has anyone actually seen or done an upgrade?

[Glenn Stauffer]

This was posted to the greenspun forums back in 2003.  The website referenced in this message is still online.  Best bet would be to write to these guys and see if they can tell you more.  If you do find out the details, please post them here so we can add the info to the FAQ.

I'm also looking for this info! I found a page that mentions it, and I've emailed the owner for any clues he might have... http://www.oldrice.com/Cafecorner.htm If anyone has the answer, ie what model bike the donor rotor comes from (machining the case is no problem for me) I'd appreciate it. Or, does another bike (CB500/550/750?) oil pump bolt right on?

[thirdman]

I did email them (I got the reference from the old site)... one email bounced and I have not heard back from the other.   

[bryanj]

I was told some years back, but never tried it, that you can machine the 400 pump housing to accept one of the 750 pump rotors (not sure whether its feed or return) and i believe the 500 rotors are the same diameter but thicker than the 400. I can measure the 500 and the 750 as i have those but not a 400 as i dont got.

[thirdman]

Just got a response from a guy involved with that infamous website:

Hi Robert:

Sorry, that is an old site.   Actually, the mention of the mod was a plan, not yet done.  I read about a couple options, but never looked into them since the oil pressure never became an issue.  It's probably better for racing motors.  Anyway, one route was to use a rotor from a GL1000, but I don't know which one.  The other option was to buy a new one from the dealer.  The rumor was that new old stock parts were better, but I'm not sure again what to look for.  You're best bet is to buy a new one from either ServiceHonda.com or David Silver Spares and then use an oil cooler.

Eric
94 900rr streetfighter
75 cb400f cafe
www.eyhonda.com

[Bodi]

Bryan: please do measure the rotors you have.
The 400F outer rotor is 12mm thick and this one is 40.55mm outer diameter. The inner rotor has an 11mm hole for the drive shaft witha 4mm wide keyway about 2mm deep for the drive pin.
Ideally I would want the same outer diameter and drive hole sizes but a bit thicker. Because of the pump design, installing such a rotor 14 or 15mm thick would be a simple machining job. Over 15mm would be a bit more challenging as room for the O-ring seal would be lost, and more than 16.9mm would be a real trick.

[Einyodeler]

Back in the `70s  the legendary Kaz Yoshima was spinning these engines to 12,500 rpm and had them compete against the 1000cc class bikes using 492cc pistons,Carrillo rods and GL1000 oil pump rotor,they called them the 135 mph giant killers and were quicker than the KZ900`s of that time.