Yoshimura R&D Superbike

Good luck. You know we here at kzrider.com are all on board with seeing this project through with you!

Fujio Yoshimura I believe still runs Yosh in Japan and he knows Z1s.

I ordered lots of Z1 parts when I lived on Maui. Then I moved to Los Angeles in the mid-1970's and when I needed more hot-rod Z1 parts, I would simply drive over to North Hollywood to Yoshimura R & D to get some. After I introduced myself on my first visit, Pops and his son Fujio immediately remembered me as the guy from Maui who purchased loads of their parts.

One Saturday afternoon I stopped by Yosh R & D to shoot the bull and Fujio invited me into his dyno room to checkout the results of some dyno runs he had made for a few customers' Z1 motors. One run caught my eye: 124 hp on a Z1 with Yosh 987 cc piston kit, Bonneville cams, ported head, etc.

Mark, what do u plan to do with this bike when finished? race , road , both??

BohicaBob wrote: I contacted Yosh R&D in California via email this morning with the question:
"Can you get such parts from Yosh Japan to the US? Like the Yosh Z1/Z2 ST-L2 Camshaft for example?"

Here's the answer I just got via email this afternoon:
"Hi Bob,

Thank you for your interest in Yoshimura. Yes we can order you anything from Yoshimura Japan just let me know exactly what do you need (Yoshimura Japan website has part numbers) and I’ll be glad to contact Yoshimura Japan for pricing and availability.

Note: Yoshimura Japan orders require a 50% nonrefundable deposit and price is subject to change upon receiving, normally Yoshimura Japan orders take 3-4 weeks to get here.

Thank you.

Danny D.
Sales Representative
Yoshimura R & D of America, Inc
5420 Daniels St.
Chino, CA 91710"

Also Bob, the Yosh parts can be purchased from Web!ike in Japan . I'm going to email Yosh R&D to see how their prices compare. Then yen/dollar rate makes it prohibitive to purchase nearly anything from Japan, maybe the prices are somewhat adjusted if purchased through Yosh R&D?

...wishful thinking :woohoo:

mark1122 wrote: Mark, what do u plan to do with this bike when finished? race , road , both??

That's the million dollar question Mark!

This will not be a bike I ride regularly, whether it's to a bike night or on the track. If I took it to the track, I wouldn't "race" it, maybe make an appearance at Vintage Days, or do a track day or two.

I'm thinking of a similarities to a rare, high-performance muscle car: '68 GT500 KR, '70 Hemi 'Cuda, COPO ZL1 Camaro. They can be driven and can be raced, but you don't... right?

As far as gasoline goes, high-test with additives. I'm only running 10.8:1 compression, so that's streetable.

mark1122 wrote: Mark, what do u plan to do with this bike when finished? race , road , both??

And the winner with the most important question is :side: Mark!

The single drawback to everything is pretty simple...it's called pump gas

nice stash of parts you have now

but for once i'll agree with wireman,

unless you are building this to be raced legaly in something like AHRMA heavyweigh SBK, leave those two ring / high crown / no squish pistons alone, nice period pieces. get a current big bore kit ( that you can also find parts for later) cams and carbs are actually usable

didnt quite get how you plan fitting those rods on a one piece crank though...

11-12K? my full race tune 90hp 750/810 with way shorter stroke peaks at 9500 and runs out of puff by 10k... but what do i know?

turboguzzi wrote: nice stash of parts you have now

but for once i'll agree with wireman,

unless you are building this to be raced legaly in something like AHRMA heavyweigh SBK, leave those two ring / high crown / no squish pistons alone, nice period pieces. get a current big bore kit ( that you can also find parts for later) cams and carbs are actually usable

didnt quite get how you plan fitting those rods on a one piece crank though...

11-12K? my full race tune 90hp 750/810 with way shorter stroke peaks at 9500 and runs out of puff by 10k... but what do i know?

900/1000 cranks are pressed together,not one piece like 650/750 cranks .
Thats how they make roller bearings work on them instead of inserts

I was wondering when you were going to thank turbo's post! You had a 5 minute delay though, gotta step it up!

turboguzzi wrote: nice stash of parts you have now

but for once i'll agree with wireman,

unless you are building this to be raced legaly in something like AHRMA heavyweigh SBK, leave those two ring / high crown / no squish pistons alone, nice period pieces. get a current big bore kit ( that you can also find parts for later) cams and carbs are actually usable

didnt quite get how you plan fitting those rods on a one piece crank though...

11-12K? my full race tune 90hp 750/810 with way shorter stroke peaks at 9500 and runs out of puff by 10k... but what do i know?

Thanks Turboguzzi! I've been following your stuff for awhile now, you've been a good waste of time for me.

Thanks for the suggestions on the pistons. I'd really, really, really love to use them, but I'll be honest, piston design, as far as the material and creation process has evolved so much in the last 30 years since they were made. I figured those would be the weak spot no matter what. Last thing I'd want would be for a piece of Yosh bling to catastrophically blow up wrecking my 2k crank and rods and Larry C. porting job. I'm definitely weighing other options.

Yosh still makes a 69mm piston (810cc)

turboguzzi what cams are you running? My little 716 makes 85 HP and peeks out at 10,500 rpm. Mark I wouldn't worry about the pistons coming apart, I've run Yosh pistons on the street for over 20 years.
Mark

Mark Wing wrote: turboguzzi what cams are you running? My little 716 makes 85 HP and peeks out at 10,500 rpm. Mark I wouldn't worry about the pistons coming apart, I've run Yosh pistons on the street for over 20 years.
Mark

Are you running 2-ring slipper pistons, Mark?

I figure with the right bore coating it's definitely possible. All the 600s/1000s these days have slipper pistons from the factory. Heck Yoshimura makes a gixxer kit that raises compression to 14:1!!!

In regards to high rpm. I rode a Z1R years ago that was lightly bored and mostly stock minus valve spring, retainers ad valves. It had huge cams in it. Even the valve cover was grinded for clearance, shim under buscket.
The power came on at 9K and would light up the tire from 9k-13k. It was insane. :woohoo:
3rd gear when power came on simply lit the rear tire up and pulled like a freight train.
How long that motor would last, might be a different story though. :laugh:
I can more specifics on that motor is anyone wants them.
I'm stiil in touch with Jay in Houston. He owns JB Cycles and does a lot of turbo work and insane modding.
His goof around bike is an 86 GSXR1100 fuel injected.