Two-Stroke Hybritza: Yamaha 350 YPVS Cafe Racer

A project dream for 30+ years!

At the Cologne Motorcycle Show in late 1982, Yamaha unveiled their new RD350 YPVS, featuring the breakthrough Yamaha Power Valve System, which utilized a servo motor to change the height and size of the exhaust valve at different engine speeds, revolutionizing their two-stroke engines. Known as the RZ350 in North America, the 58-hp, 374-pound YPVS would be the most sophisticated two-stroke street bike ever known to man:

“The factory claim the ’83 RD unveiled in West Germany is the nearest thing to a road going racer ever produced.” –MCN

Enter our new friend Dusty Miller, a 54-year-old retired UK firefighter who’s been riding and wrenching on bikes since he was a teenager:

“I’ve always modified my bikes and like to pull them apart, ‘improve’ them, and put back together again!”

In recent years, his focus has been on building Yamaha two-stroke hybrids based on the YPVS, LC, and air-cooled RD platforms.

“Detail is key to me, and I leave no part untouched, even down to the smallest fastener.”

The build you see here has been a dream of his for some three decades — a TZ-style cafe racer that would incorporate modern technology around the aluminum tank and tail of the legendary TZ race bikes:

“Key for me, and the focal point is the TZ/TD style aluminium tank, and as long as I could incorporate that and the TZ seat into the build, I would build everything else around it. I wanted to build something different to the norm, so it’s not meant to be a TZ replica, and I deliberately used more modern running gear to express that.”

The frame is from a ’77 RD250D, to which Dusty added a YPVS 350 engine — an engine swap which required some 11 hours of engineering work, including new sets of engine, tank, seat, battery, and coil mounts, as well as several frame-strengthening plates. Dusty made up all of the templates in cardboard, taking hours and hours to get all of his measurements right:

“It’s easy bolting a PV engine into an LC, with no engineering required, but this was a challenge. If my templates were wrong, it would be an expensive mistake and luckily, everything fits as it should. Centering the engine for exhaust exit and chain run was critical, so that was something I took a long time to get correct. I had to pre-plan everything as trips to the engineers get expensive, and I’m on a tight budget, so I couldn’t afford to miss anything.”

He completely rebuilt the engine with several upgrades, fitted a set of RGV250 forks and powder-coated wheels, GMX radiator, Alonze pipes, digital Powerdynamo/Vape system, Motogadget “M” unit, NOS LC switchgear, and much more.

The result is not quite a hybrid, and not quite a bitza — a bike built of bits from other bikes.

“It’s a bike meant to get people guessing what parts are from where, and the added bonus for a builder is there are no constraints as to what parts must be used, as I’m not following a pattern. It’s meant to be unique, and a bit different to what you may have seen before. Not quite a hybrid, or a bitza, more a ‘Hybritza’!”

Below, we talk to Dusty from the full details on the incredible YPVS-powered cafe racer.

Yamaha RD/PV Cafe Racer: Builder Interview

• Please tell us a bit about yourself, your history with motorcycles, and your workshop.

I’m Dusty, 54, retired firefighter living near London, UK. Had bikes since I was 16: DT50M, RS100, GT250X7, RD400, plus many others. I’ve always modified my bikes and like to pull them apart, “improve” them, and put back together again! I’ve learnt a lot over the years, and my focus now is to build hybrids based around Yamaha strokers like the LC, PV, and air-cooled RD’s. Detail is key to me, and I leave no part untouched, even down to the smallest fastener. A back injury causing ongoing problems means my main focus is on building nowadays, as I find riding painful, even on the bigger bikes I’ve owned like an XJR1300 and an FZ1N. I try and do as much of the build as possible, building my own engines and designing any frame changes before pro fabrication work. I have no engineering background, but do own a lathe and a pillar drill, so turn out most of my own spacers, etc.!

• What’s the make, model, and year of the bike?

This bike is built on a 1977 RD250D air-cooled frame. Everything else is from something else!

• Why was this bike built?

Ever since I had my first 50cc bike, I’ve enjoyed modifying them, with varying results! I bought an RD400eE in 1986 — a bike I had always wanted when growing up — and I kept that 400 for 13 years. It went through many reincarnations during that time, but the final version was a modified cafe racer with a TZ seat, no side panel or oil tank for a “straight through the frame” look, running premix, custom large tacho and small speedo and other parts to make it look more like a TZ. It never really ticked all the boxes though as it was still very much an RD400, albeit modified.

I had wanted to build that Cafe Racer/TZ style bike then, and have wanted to again, ever since, so this is a project dream of mine for over 30 years now. Key for me, and the focal point is the TZ/TD style aluminium tank, and as long as I could incorporate that and the TZ seat into the build, I would build everything else around it.

I wanted to build something different to the norm, so it’s not meant to be a TZ replica, and I deliberately used more modern running gear to express that. It’s a bike meant to get people guessing what parts are from where, and the added bonus for a builder is there are no constraints as to what parts must be used, as I’m not following a pattern. It’s meant to be unique, and a bit different to what you may have seen before. Not quite a hybrid, or a bitza, more a “Hybritza”!

The rough frame came up for sale on Norbo’s Rdlc crazy forum, along with the tank and seat unit, but nothing else. The frame had radiator mounts added as a previous owner had a TZ engine fitted in it (long since removed), so I started out with nothing else.

I had tried to source an air-cooled 400 to fit straight in, but struggled to find one, so I bought a late YPVS 350 engine instead, and then had to work out how to fit it in the frame as the engine mounts are different. Lots of cardboard templates, lots of angle grinding and measuring meant I had templates for a local engineering firm to produce steel brackets for welding in for the engine fitment. I also got proper tank mounts welded in as well as substantial seat fixings, battery box, frame strengthening plates, new coil mounts, etc.

There is over 11 hours of engineering in the frame mods alone. A lot of time was taken to make sure every component had a proper fixing and looked neat and “factory” made. The early days of making something fit with a steel plate from a hardware store have long gone, and everything needs to be properly thought out and executed now!

I had some really rough RGV250 VJ21 forks, which I stripped and rebuilt with new springs, oil, and seals.

 

RGV front wheel had the lettering ground off for a cleaner look before powdercoat, and I did the rear wheel as well, before new bearings, tyres, etc.

I had Metmachex make me a box section swingarm to take the wider RGV wheel, and a new YSS shock deals with the rear suspension.

 

I totally rebuilt the engine, changing all the gearbox bearings, new gaskets, seals, circlips, new billet clutch, Siberdyne clear clutch window, cases and barrels and head have been vapour blasted, billet inlets with Vforce4 carbon reeds, Pwk28 carbs with UNI angled filters to clear the frame tubes.

The ignition has been dragged into the 21st century with a digital Powerdynamo/Vape system, a Motogadget “M” unit sits under the seat and the wiring system is keyless — operated by touching a fob onto the pick up on the left clip-on.

The instrument is a Koso Tacho with digital speedo, and there’s a dedicated temp gauge on the right clip-on. I wanted to use traditional switchgear, so have NOS LC switchgear fitted.

The radiator is a lovely GMX item with a deeper core, working with a high volume billet water pump impeller.

I modified the shift star and actuator to help with gear changes and “finding neutral” which can be an issue on these engines.

The engine is in a standard state of tune but should gain a couple of bhp over stock with the mods. The pipes are stainless Alonze YPVS fitment, which I polished after getting the rear brackets welded on — as standard, the PV brackets would be in the wrong place so I had them supply the metal strips which I then bent to shape, positioned, and then got welded on, and they fit perfectly and tuck in nicely.

I bought the smallest rear light I could find and cut out a slot in the fin on the tail unit and bonded it in. It’s incredibly bright, and has the stop light built in too — that was the most nerve-racking job as I didn’t want to mess up the tail unit!

Yokes and clip-ons are standard VJ21 Suzuki, powder-coated and polished. Nissin brakes are from Honda CBR as they are seen as an upgrade over Tokicos, and discs are RGV.

There are two alloy expansion tanks fitted to the bike. The one on the right is actually an oil reservoir or the autolube system, and is filled via the clear pipe through the top yoke. There is a sight tube spliced in so you can keep an eye on the level. The tank on the left side is the radiator expansion tank, again with a sight tube for checking fluid levels. Both tanks are fitted to brackets welded to the radiator mounts for a proper fixing.

Rearsets were designed by me and cut on a plasma cutter from 12mm alloy plate. Foot controls were new from Ebay. Paint is by Mark Cordwell in Derby, and follows a TZ scheme.

• What was the design concept and what influenced the build?

I wanted to build the bike around the tank and seat combo. Everything else was an option. I wanted more modern running gear, both for looks and operation, modern electrical system and wiring for reliability and minimization — I hate seeing wires everywhere, so it’s really important for me to achieve a clean look, especially in the “under seat” area. Better brakes, better suspension, and everything road legal. It’s tax and MOT exempt as it’s listed as Historic now, but it was still built to pass an MOT test. Horn is hidden under the tank, lights will operate as they should, and there is a magnetic speedo pick up on the front wheel.

• What custom work was done to the bike?

Everything is custom really — the engineering work on the frame is probably the biggest customisation that has gone on. It affects virtually everything on the bike, and I’m very lucky in that I have a great firm less than a mile from me who can do the necessary jobs to achieve my vision.

• Does the bike have a nickname?

No nickname as such, but I do refer to it as a “Hybritza,” as it’s neither a true hybrid nor a Bitza!

• Can you tell us what it’s like to ride this bike?

I’ve yet to find out. I need to get a bespoke loom made for the Motogadget system. It’s the last job to do, but funds have run low, and the guy that I have planned to do it is 250 miles away so it’s on hold at the moment. I made the reasets so they weren’t too extreme, and the riding position is ok, but it’s not for touring!

• Was there anything done during this build that you are particularly proud of?

All of it really. I’ve built a lot of hybrids and specials over the years, but have never done so many frame mods and parts from scratch. It’s easy bolting a PV engine into an LC, with no engineering required, but this was a challenge. If my templates were wrong, it would be an expensive mistake and luckily, everything fits as it should. Centering the engine for exhaust exit and chain run was critical, so that was something I took a long time to get correct. I had to pre-plan everything as trips to the engineers get expensive, and I’m on a tight budget, so I couldn’t afford to miss anything. The engineering went really well, and I’m so pleased it how it looks. After 30-odd years, I’ve ticked the box!

There is a comprehensive build thread on Norbo’s RD LC Crazy website.