RZ350 engine wanted - Reliving the 80's and 90's | GTAMotorcycle.com

RZ350 engine wanted - Reliving the 80's and 90's

rmwilson

Member
I am looking for a RZ 350 motor and related parts (mainly bottom end electronics, and such - looking to build a 421 stroker for the street. Any one have any RZ engines or bottom ends? (cranks transmissions, cases, clutch, magneto, etc....

Let me know what you have...

Thanks,

R.
 
You might look for a Banshee ATV motor - easier to modify. no YPVS ?
 
You might look for a Banshee ATV motor - easier to modify. no YPVS ?
Ya that's an option too ... just that the gearing in the Transmission is different as i want the street gearing from an RZ not sure if RD transmision fits banshee or if they use same cases... but open to options at this stage - thanks for the thoughts!
 
Ya that's an option too ... just that the gearing in the Transmission is different as i want the street gearing from an RZ not sure if RD transmision fits banshee or if they use same cases... but open to options at this stage - thanks for the thoughts!
Banshee motors are identical to RDLC motors.

If you can contact Geoff Robb he has a **** pile of RZ stuff still
 
Banshee motors are identical to RDLC motors.
Close... but not identical
The banshee is closer to a RZ-YPVS, but with no power valves, different gearing (both primary and transmission), much different porting and head. Everything else is the same.
You can swap almost all YPVS parts into a banshee
Some guys would swap banshee 3rd/4th/5th gears into a RZ, then gear it up with a primary or sprockets, which gives you a closer ratio transmission in the upper gears, which works on a race bike but sucks on a street bike
The Banshee/YPVS share virtually no parts with the RD-LC. You can swap ignitions, transmissions and clutches, but they're all different, and the RZ/Banshee parts are better/stronger.
... and none of these bikes share any parts with the TZs. They may look the same but are different dimensionally and a lot time functionally
 
Looked him up on FB sent him a not but have not heard back (yet)
I have his cell phone, I'll give him a call.
He may be willing to sell some rz stuff as he bought a tzr250 I believe last year and he is very into that at the moment.

Sent from my SM-A530W using Tapatalk
 
I LOVE the RZ350... my first street bike that I lusted after as a kid, first street bike. Would love to a bike with an RGV250 chassis and a bored out RZ engine.
 
Rekindling this post - now its my turn to build a RZ street motor with a bit of kick - any one still around intetrsted in building me a motor for a project RZ street bike? (want to mount the engine in a light 125 chassis) :)

What 125 chassis are you going to use? Cagiva Mito by chance? That would be epic.
 
Wow! Where did you manage to score that? Do you already have the engine cradle kit?
421 kit would be a great package in the mito chassis. Are you using Serval or Cheetah cub?
 
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Based on what I am
Wow! Where did you manage to score that? Do you already have the engine cradle kit?
421 kit would be a great package in the mito chassis. Are you using Serval or Cheetah cub?
Based on what people are saying the Athena is the way to go ...

As for the bike and pipes and and such in Europe they are quite popular - I am having a chassis shipped over, the RZ I bought here... they make pipe kits and engine mount kits so that simplifies the build a little bit ... stil lots of other work to do but ya could be a pretty cool bike - many people in europe have done the conversion!
 
Based on what I am

Based on what people are saying the Athena is the way to go ...

As for the bike and pipes and and such in Europe they are quite popular - I am having a chassis shipped over, the RZ I bought here... they make pipe kits and engine mount kits so that simplifies the build a little bit ... stil lots of other work to do but ya could be a pretty cool bike - many people in europe have done the conversion!

Right. I couldn't remember if Athena made big enough kits for the 421.

That'll be a very cool bike. Good luck with the project. I'm sure it'll be a ton of fun to ride.

Can't find it right now... but I've also seen rz500 engines in the cagiva mito 125!
 
Athena makes a 68 x 58 jug for a 421. Actually I think Athena make ONE jug and differs the deck height off the bottom, and the ports are a compromise across the board
Probably the easiest to acquire and the worst bigbore setup.
It has a 3 part exhaust port, with a 47mm exit, which is cool ( no one makes a pipe for it), but is separate cylinders which limits the size of the transfer ports, which is THE weakness of Yamaha twins, notice how all the TZ production racers had siamised cylinders, which allows for bigger tranfers.
The metallurgy sucks so they don't cool very well and are known to have hot spots on the cylinder walls and then they made the cooling passages smaller try to get bigger transfers... which makes everything worse.
There's a TON of flash in the ports and the edges are sharp.
Don't use the Athena supplied piston, cheapest POS available, use the Wiseco with the offset pin.
But the Athena's are available and cheap.
Oh yeah... and they all leak coolant at the bottom of the cylinders unless you glue the plug in.... it's a stupid setup and HAVE to run a base gasket.
And the Athena head blows chunks. Small cooling passages, and there's no thermostat but it does have removable domes. You're probably better off modifying a stock head.
If you haven't figured it out, I have Athena jugs on my 421.

The CPI Cheetah or Wampus, where the jugs are siamised, allows for much bigger transfer ports.
Good luck finding anything from CPI. There's a bunch of well connected racers that are trying to build TZ750's with 4 Banshee jugs and they ALL want CPI Cheetahs with power valves... but they haven't been made for years now, so if you want them: get your wallet out and get in line.

Now... I've never ridden a RZ on the street, but I have built and run many a RZ based track bike. I currently have a WickedATV 421, and about a dozen TZ and RD racers... and I can't see a RZ based 421 bike being a good street bike. WAY TOO PEAKY. They make power from 9000 to 10,200RPM... that's it. No power valve is a problem on the street.
If you could find a Cheetah with a power valve... it might work as street bike, but probably not.
For the street, IMHO, you would be better off with a long rod 68 x 54 in Yamaha jugs with power valves.
90% of the 421's top-end power, but the thing will pull from 4-4500 RPM (Uh yeah, please realize to get the top end power on your 421, you have to run 36mm carbs at minimum, I run TMX40s, which is gonna KILL what little mid range you have)
ALL the 421 Banshee kits were designed for sand drags, where WOT is the only consideration.

Another consideration is: The widest tire you can run on a RZ based motor is a 150, and you have to carve 5mm off to clear the chain, unless you want to run offset sprockets. You don't want to run offset sprockets.

Let's not forget the RZ was originally designed as an air cooled 250, released in 1970. At 250cc it had some semblance of balance, then they made it into a 350 THEN they threw all caution to the wind, and anything resembling crankshaft balance was a distant memory at this point, made a 400... then backed off to a 350 again.
Most people think a warmed over RZ is an engine seizure waiting to happen, (and you'll probably die) and you guys want to throw ANOTHER 4mm stroke at it??

Roger at WickedATV made a 700cc Banshee that was supposed to make 320hp.
The afore mentioned TZ 750 motors with the banshee jugs are supposed to make 250hp, all day long.
 
Thanks bitzz! Great info.
Appreciate the honesty in your review of the Athena kit. That's pretty much what I've read.
 
I'm not on the forum a lot any more but have built a few of these in the past.

Bitzz is correct that you can't get CPI's that have a 68mm bore and 58mm stroke with the power valves any more. Calvin stopped making those back in 2014 as the didn't sell as there is less benefits with the valves on bigger standard cub motors

You can however still get 65x54, 68x54 and 66x58 Cheetah configurations with valves . That will give you engine sizes of 358, 392 and 396.

In theory you could take the 68x54 and use it with a long stroke crank and let the piston run 1mm into the head the way the long stroke RZ motors work. I think the problem is that the top of the exhaust port on that cylinder is 27mm from the deck, while the cylinder designed for the long stroke motor is 28.5mm. I had though about this but the 27mm will give you port timing of way over 200 degrees which is not good.

Pipes do make a big difference on these bikes. Off the shelf pipes like Lomas or Jolly's are not great with the Cheetah's or Athena's triple exhaust port so I would avoid those, but you can get pipes made for them.

Mutts (Dave Whattam) and TSA (Kenny) both do really good pipes for them and being from the UK have probably already built them for a Mito chassis. They also do different versions so you can get a mid-range pipe, all round power pipe or something that is more for top end

The other guys would be Roger (Wicked), Matt Shearer or Brian Turfrey.

It might be harder to get them to build a set of pipes to fit the Mito chassis so you may have to do some fabrication yourself to get it to fit. Matt makes these pipes all day long for 421 Banshees. I had a set on a bike years ago and did like them. Brian has been in the business since the 70's and he built the pipes for Kenny Roberts when he was riding and when he ran his own team so he knows his stuff.

I personally think the 421 can be quite streetable with the right setup.

My "Daily Driver" is a 421 Cheetah cub (no valves) with a cleanup port, a set of Mutts all round power pipes and some PWK35's. I'll dig out the dyno chart but the power is very linear and doesn't have that big hole at around 5k that you tend to get with the standard RZ. The maximum HP is 82 around 9900 which is good for crank life.

I'm also racing one in AHRMA at the moment. Its a ported Cheetah Cub 421 with a set of PWK39's and using a set of Turfrey pipes so there is very little until 7k and then it just revs to the limiter at 11k, so there are a number of ways to build these things depending on how you want to use it.

The Athena cylinders are fine, but I would use a different head. The oring groove tends to be very thin and they chip and crumble. The CPI Cheetahs are definitely better.

I think the problem might be getting any cylinders at the moment as most suppliers are out of stock and I know CPI are having problems getting the castings done because of COVID.

I'm building a 396 cub at the moment 66 bore x 58 stroke to go into a 350LC chassis that I picked up, and it was the only block I could find. I just put the motor together over Christmas and picked the pipes up last week from Brian

Oh, just one more thing. If I do a Cheetah I like to use Banshee Crank Cases. They are pretty much identical to the RZ and are completely interchangeable, however they leave a little more meat on the crankcase where the front of the cylinder sits so its less likely to leak from the water plug on the bottom of the cylinder.

And one, one more thing. You can actually get a head that takes the standard RZ350 thermostat and housing, or you can use and in line one from a KTM enduro bike. It makes a difference on a street bike. I have the KTM model number somewhere

The one I'm currently building is below (sorry. I just noticed those pictures were huge. I uploaded smaller ones)

Feel free to ask questions about any of this

Motor.jpg

pipe.jpg
 
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