KR-1S.co.uk Forum

Looking very nice Rick
Keep the photos coming
Cheers Bernie

Well, it`s been six months so I guess it`s time I got back to this...

I set this project aside firstly because I was waiting for my friendly fabricator to build me an alloy fuel tank and secondly because I had a V4 engine on the bench which I needed to get rebuilt and out of the way to give me some space for building the Yamaha motor.

The prototype fuel tank did get made but it looked more like a coffin so that has gone back for a second attempt at something more curvy.

I`ve finished that engine rebuild and also constructed most of a bike around it -



- can you tell what it is yet...?

Back to the matter in hand, I have stripped the RZ350 motor and sold off the bits I don`t need - definitely got lucky there, the barrels were in good condition and only first oversize, I put them on ebay and the pair made £650...!

I`ve removed the paint from the crankcases, cleaned them up thoroughly and enlarged the transfer ports, so now my first job is to turn this -



- plus this -



- plus a 58mm stroke Hot Rods crank into a complete bottom end ready to receive the 68mm bore Athena barrels and head.

The motor for this bike came out of a 1983 Canadian import RZ350 which I bought in a scruffy state for £2200 -



I subsequently sold on the rolling chassis, carbs, exhaust and the engine parts that I didn`t need for a total of around £1800 - given that it would have cost me £1500+ to buy a half decent 350 YPVS engine from a breaker I`m pleased with the way that has worked out.

I spent Saturday afternoon going through that big box of engine parts, cleaning, measuring and refurbishing, then set to work, first installing the rev counter drive in the upper case -



Then the gear selectors in the lower one



I am using an uprated selector cam with a ball bearing detent arm and stronger spring -



It`s a shameless Chinese-made rip off of the Shift Star kit made by Factory Pro in the States - I make a similar conversion for VFRs so I know that they work well in principal, time will tell if this one has been designed correctly (or copied accurately!)

There`s another popular selector upgrade for these engines, an extra support bearing fitted where the gear linkage shaft emerges from the case on the left side - it`s generally used as a repair part for wear in the original (non replaceable) crankcase bush - the bush in my motor is fine but I have fitted the upgrade anyway as a `belt and braces` measure. I also fitted a new neutral light switch plate as the original had been cracked by over tightening at some point.





Next in were the gear clusters and crankshaft -



This donor engine seems to be a pretty low mileage example, all the gearbox components including the bearings are in good condition so I have reused everything except the old oil seal.

I bought the +4mm crank secondhand from a racer who had build himself a 72 x 58 472cc engine but made the mistake of using CPI drag race cylinders, ending up with 100+bhp and a `light switch` throttle response which tried to spit him off every time he hit the power band so he gave up and sold it off for parts.

I`ve had the crank checked for wear, trued and welded and fitted new outer main bearings and seals, so it should give no trouble.

At that point I felt I`d done enough for one day so I employed the Allen Millyard strategy and retired for a well earned cup of tea and a bun...

Great to see this project coming along, don't know how old you are but when I was younger things had to be done yesterday, now I'm getting older the jobs are stacking up but I'm not bothered how long a task takes, as long as it's done properly, good luck with the rest of the build.

The bottom end is buttoned up now -



Next job is to fit this uprated Chariot clutch basket - apart from being a billet CNC, lightweight, hard anodised thing of beauty it is also deeper than stock and allows the use of an eight plate clutch stack instead of the standard seven.



The clutch will use Yamaha FZR1000 friction plates, Barnett steels and stronger springs, I will also fit a lifter with a needle roller thrust bearing.

Thanks for the encouragement, Pookie - I`m never quite sure whether or not I am talking to myself.

Keeping it cryptic, I was born the year Geoff Duke won his last world championship and turned twenty one the year that Barry Sheene won his first, so Biblically I am on borrowed time...

Gear selector and kick start mechanisms now installed and adjusted -



Ten minutes work with an angle grinder, punch and large hammer removed the rivets joining the primary driven gear and the original clutch basket, Chariot version is secured with M8 countersunk screws which makes for easy installation - heavy doses of Loctite applied...!

why not going all the way and use straight cut gears ?

This is just a `proof of concept` build for a KR-1/Yamaha twin hybrid so I am keeping it relatively mildly tuned and inexpensive - I already have most of the parts for a second, more serious motor which will use trenched Banshee cases, a +7mm crank with TZ main bearings, 72mm CPI cylinders (the ones with the milder `dune racing` tune), Nova straight cut high ratio primary drive and close ratio gearbox, Barnett steel faced clutch basket and pressure plate, billet outer cases with an outrigger bearing on the front sprocket and a bunch of other trick stuff.

Wednesday is Clutch Complications Day...

I fitted the clutch basket and centre and the crank primary drive gear using new nuts and lock washers then assembled the 8 friction/7 plain plate stack and offered up the pressure plate.

The extra plates in the stack obviously move the pressure plate, and therefore also the bottom clutch spring seats, outward - a quick measure up revealed a clearance of 18mm between the bottom spring seat and the washer on the retaining bolt, coincidentally a dimension which exactly matches the coil bound (fully compressed) length of the uprated clutch springs, which is to say that fitting and tightening the spring retaining bolts would squeeze the clutch plates into a tight pack which no amount of lever pulling would separate.

Problems are there to be solved, so I replaced the stock retaining bolts (right) with the arrangement on the left -



- a countersunk screw and stainless steel panel washer (for the lowest possible head profile) plus a 5mm spacer to free up some usable spring travel.

The finished job looked really tidy, I adjusted it up and everything worked fine -



- but then I tried to fit the cover...

On the face of it there is plenty of space inside the stock clutch casing but there are these three lumps in the casting to accommodate the screws which hold the round YAMAHA badge panel on the outside of the cover and of course those are just big enough to now foul the pressure plate.



It`s not insurmountable, there are aftermarket billet or modified standard covers available which are designed to work with the fairly bulky centrifugal lock up clutches that they use for drag racing in the States but rather than go to that trouble and expense I have decided for the moment to keep it simple and stick with the stock 7/6 arrangement using FZR and Barnett plates and the uprated springs - if that fails to cope with whatever power output I achieve then it will be a fairly simple job to uprate it later...

Great work, was shocked to find out your age I was just 12 years old when Barry Sheene won his first world title, and I've just retired after working at the same place for 43 and a half years, did a 90 plus mile trip on the KR-1 last week, feel grateful that I can still ride it

Next job will be to finish off the right hand side by building the water pump, with new bearing and seal and more efficient billet aluminium impeller, and the oil pump drive into a new clutch casing, finishing it off with a cool laser cut stainless steel trim instead of the stock plastic disc.



Those cases are still readily available and quite reasonably priced due to the number of YFZ350 Banshee quads still at large in the world - they come boxed and labelled as `2GU` Banshee parts but a quick inspection reveals that it is actually still the same `29L` casting which has been used on all 350YPVS/RZ350 models right from their introduction in 1983...

The right hand case build was held up by a few glitches - a water pump rebuild kit which didn`t actually contain a new bearing, a full engine oil seal set which didn`t include the oil pump seal and an oil pump worm drive shaft with too much pitting to polish out -



ebay came to the rescue with a NOS Yamaha bearing and seal and a good used drive shaft from a European breaker.

Cover is now finally assembled with all new bearings and seals, aftermarket water pump cover with drain bolt and a beautifully refurbished oil pump courtesy of Gary Jones from the RD forum. The pump is also uprated for extra flow to ensure adequate lubrication for the bigger bores.





I have reworked the mounting of that stainless trim with 5mm spacers to raise it to the level of the case surface and some better looking screws.

My plan was to finish the engine build this weekend but there are always rocks in the road...

The cylinders are Athena 68mm, with Wiseco race pistons, so cool that each one is delivered in its own little monogrammed velvet bag...



This is the handy thing about Athena cylinders if you are wanting to get a big bore `sleeper` through a vehicle inspection -



I`m using the matching Athena `cool head` with some relatively large capacity/low compression domes which I hope will give me a reasonable amount of power but do it on pump petrol and with minimal risk of self destruction.



The current problem is that the domes, which were supplied by a US Banshee tuning shop, don`t actually fit the head -



You`ll see there`s a pip on the head casting which engages with a machined notch on the dome - unfortunately the notch is not quite long or deep enough so the dome doesn`t sit flush with the head mating surface as it should. It`s not really something I`d want to try and fix by filing the head and I don`t have a mill so I will have to put everything aside and get my friendly machinist to fix that next week.

Another month, another installment...

The problem with the cylinder head domes proved insoluble, no amount of machining was going to make the American domes fit the Athena head casting but a long internet search finally turned up a couple of guys in Germany who make Banshee tuning parts and whose catalogue included custom made domes for exactly the combination of components that I am using (+4mm crank, 68mm cylinders with Wiseco Blaster pistons and Athena cool head) - cost me £100 and took three weeks to get here but they do fit perfectly. New dome on the left...



Measured the bore to piston clearances, set the ring end gaps and thought at least I could get the barrels fitted but no - I opened the pack of small end bearings which came with my kit, clearly marked with the Yamaha part number and `16 x 21 x 22.5mm`, only to find the bearings inside were 16 x 20 x 22.5mm - all on hold again while I tracked down a pair of the correct size replacements but at least now we are this far -





Cylinder head going on tomorrow barring anything unforseen getting in the way...

Of course I should have seen it coming, the head studs supplied with my engine kit are 10mm too long, the nuts are wrong and there are no sealing washers - presumably that lot would all fit if I were using a ProDesign or Chariot type two piece cool head but it`s no good for the shorter one piece Athena casting so that will have to wait a few days `til the correct replacement parts arrive.

Pressed on anyway with what I could - I thought it was probably wise to fit a new alternator stator considering the state of the one that came off my donor engine...!



Also added a lightened flywheel, done for me by my friends at BDK...



The bottom end is fully built and finished now with all gaskets and seals in place and everything properly torqued up.