TOPIC:

Hello all.  I have a motorcycle shop near me that specializes in KZ's, "Performance Cycle" in Hammond Indiana.  I asked the owner, Joe Foster, for a set of Performance cams and he found a mixed set he said would work great together.  The intake is an Andrew's 3x and the exhaust is an RC424.  I can't find any specs or specifics about the Russ Collins RC424 cams.  Any help or information about the RC cams would be really appreciated. 

My setup is a 1976 KZ900 lower end.  The crank was inspected and welded by Pearson Racing.  1105cc Wiseco pistons, DIY ported head, clearanced for the cams in question.  Transmission gears are back-cut, oversized valves, intake 37.5 exhaust 31, shim on top, HD valve springs, Dyna-s ignition, 34mm Mikuni flat slides with K&N filters and a Vance and Hines sidewinder exhaust.

I've owned this bike 30+ years and this is my first attempt at a performance build.  If anyone has any technical questions I will do my best to answer, but my knowledge is limited.  I'm just not afraid to get in there and get my hands dirty.

KZB2 650 had a RC catalog. Maybe our mods cam reach out to him. He checked in last in October, not that long ago.

Will pick this up in the morning

Nice Bike 

Mikaw wrote:

KZB2 650 had a RC catalog. Maybe our mods cam reach out to him. He checked in last in October, not that long ago.

email sent 

Wookie58 wrote:

Mikaw wrote:

KZB2 650 had a RC catalog. Maybe our mods cam reach out to him. He checked in last in October, not that long ago.

email sent 

 

Thank You

This really is a great community for KZ enthusiasts.  Information on even the most obscure topics is known and shared by someone.  Thanks Mikaw and Wookie58 for the help in moving this info request to the right people.

Hey guys found the cat on the first grab. Its from 1980 and the biggest cam they have listed is the RC470 (900/1000) / RC420 (650). There are 3 smaller below it. 405,410 and the 415.

They say .......... This is a full competition grind for the motor that needs that extra lift. Provides max HP and torque for drag strip operation. No need to use this cam unless you have a cyl head that will flow up to .470 lift.

RC470/420 Timing:
Intake duration: 320 Deg
Exhaust duration: 328 Deg
Lobe centers: 115 Deg intake
Lobe center: 103 Deg exhaust
Lift: .460 intake.......  .408 exhaust
Lash: .006 intake....... .012 Exhaust.............. They recommend the racing cam followers and the head needs notching for clearance. 

This being the specs for the (RC420) and NOT the 424 of course means this info could be a mile off or it could be close enough to at least give you a idea of what you have or if it could work. I'll leave that up to the experts on here.

 

If the intake cam is a Andrews 3X, that is a .418" lift cam, usually the exhaust cam would be .418" or smaller, something around .400" sounds correct.

The only RC cam info I have gives cam numbers not specs, as its from a 1981 Cycle Guide magazine featuring high performance engine parts.



The RC405/410/415/420 are for the KZ650 and the RC370/388/400/470 are for the KZ900/1000

Measuring the RC424 cam with a digital caliper, I get a base circle of 1.1" and a .400" lift.  No idea on duration.

ez_goin112 wrote:

Measuring the RC424 cam with a digital caliper, I get a base circle of 1.1" and a .400" lift.  No idea on duration.

That falls into Injected’s guidelines, saying exhaust is typically smaller when you’re running a split/staggered cam setup. 

Looks like the RC424 was developed and marketed after 1981.

Like all other RC cams the duration is very exaggerated (advertised) "real" duration is probably around 270 degrees.

The best way to set those up is to make sure you have slotted cam sprockets installed and dial them in with a crank end degree wheel.

You will need to watch piston to valve clearance especially on the intake side.

Those will probably end up being a good combination with power coming on around 6K.