Race Prep A RD350YPVS

By Spencer reeves, May 2009.

Firstly there are a few models to choose from, and each have there good and bad points.

These should be considered if you are planning on starting from scratch.

The best starting point for a race YPVS would be an RD350F2 as its chassis and suspension are the best of all models. Its wheels are lighter, and its brakes are opposed piston. So that's where I started. The following is what I did to get a tuly competitive bike and as such is not necessary to get you out on the grid but will give you your best chance at success.

Firstly strip the bike down to a bare frame, remove any unwanted or unused lugs and brackets - you'll be surprised how much weight can be saved. Remember this is less to stop and less to turn! Put all the road gear and autolube pump etc in a box for later, or sell it on Ebay to fund your build. Once all the unwanted steel is removed, weigh it then bin it.

You'll need to get the frame coated at this point so its off to the powdercoaters.

Once its returned you can fit taper roller headrace bearings in place of the stock ball and cup arrangement - this makes a big difference to the handling for £20. I also removed unused brackets from the swingarm - then gave it a lick of paint.

Check and grease all suspension components, make sure your shock is servicable and has damping. It must be a standard shock to be within the rules.You'll want to raise the rear of the bike for increased ground clearance and sharper handling. I fitted some shorter tie-bars from BDK, NK Racing do them as well.

Front forks are a little soft as standard, so fit uprated springs either Hagon or WP do a fitment for all models of YPVS. The airgap should be roughly 140mm.

You can also help the forks by fitting a thicker forkbrace.

Lower the forks through the yokes about 55mm, I fitted clipons below the yokes this requires some cutting of the fairing - or you can leave them in the standard position.

Your choice.

For the brakes, run two separate braided lines from the mastercylinder using a double banjo bolt as per ACU spec. Standard disks are fine, if you want to fit new ones the EBC ones work very well. Pads, well that's personal preference.

I fitted drilled caliper bolts to mine, but you could simply drill the standard bolts.

You really don't want a caliper coming undone at race speeds, I've seen first hand the aftermath. Its costs next to nothing but could save you and your bike, plus it looks cool.

For the rear you can ditch the mastercylinder and just run a tube type like HRC do.

This is lighter and looks the part and only costs £12 for the kit. Again fit a braided hose and drill the bolts for lockwiring.

To lose a bit more unsprung weight you can ditch the speedo drive and get a spacer made from aluminium, NK racing do these but anyone with a lathe and some ally bar can do it.

Bob Farnham made mine.

The F2 wheels are lighter than the earlier 31K model wheels, they are cheap and plentiful, so fit them if you want.

Best tyres to fit are undoubtedly the Avon AM22/23 they work well wet or dry and last well. Only disadvantage is that they are circa £300 a set - shop around. Make sure you buy Club compound, they are marked not for highway use.

Install a 520 non o-ring chain for best results, with Renthal or similar sprockets.

16/39 suits most circuits with the exception of Snetterton when you might go down to a 38.

Tuning is a subjective subject, but within the YPM you have a ceiling of 59bhp. It's the YPVS's main advantage that it can make this power easily so use this against the TZR's nimble handling. To get the most from your engine pick your tuner carefully. There are lots to choose from and we all have our favourites. I chose Bob Farnham for my build.

But you have Gerry Pell, Taymar, Stan Stephen's, Graham File etc etc who all do excellent work. Ask them for a full race tune and hand over the money basically.

Get your ports flowed, head skimmed, flywheel lightened, and at this point decide whether you want to run a charging system or not. You can then have the charging coils removed, for less weight and less drag. Only down side to this is that you'll need to charge the battery for the tacho/YPVS unit and the stator can sometimes overheat and crack up. To save a bit of weight you can ditch the massive stock battery and fit a little1.2ah 12v battery from Maplins. For extra punch you can fit Vforce3 reed blocks they are twin tip and add a couple of bhp throughout the rev range but notablely in the middle. Remove the oilpump and worm drive and fit a blanking plate over the hole in the clutch cover as you'll be using premix.

For carburetors you can fit anything really, the stock F2 ones are usually junked in favour of the earlier 31K non powerjet type as they are easier to set up. KR1-S carbs are a good replacement, they are flatslide for more throttle response and a slightly larger diameter 28mm. The other option is the full on 34mm Mikuni's for maximum power, but lose out on driveability of the stock carbs. Remember to block the connector's on each carb for the two stroke oil lines as it'll suck in air, lean out your mixture and blow the motor.

Easiest way is to cut a length of pipe and join the two together.

For exhausts you'll want to ditch the standard items in favour of race type as they are lighter and allow the bike to rev out more. Paddock favourites are Gibsons - but you have Lomas, Swarbricks, Nikkons and a host of others to choose from - your tuner will advise you on what you should get for best results.

With all this extra tuning comes more heat, so you can fit bigger and better rads - the RGV250 is a common upgrade.

The ignitions or CDI's on the YPVS are all different - by far the best of the lot is the 52Y 50 CDI from the F1 model. It has the best curve and allows it to make power 500rpm above any of the others. Next is the LC2 or 29K CDI, the 1UA as standard on the F2 was retarded so they finish at 9000 rpm. The Brazillan or R model has the worst CDI of all and it stops at 8000 rpm.

I tend to build my looms from scratch and just split them and use the length from the YPVS control unit to the servo motor. I junk the fuse box and replace it with a blade type for a kit car. I put in an illuminated LED on off for ther tacho and YPVS unit. I fit a HRC kill switch and ditch all switchgear. Then I fit a quick action throttle, Venhill do an excellent dual action one. Requires some alteration to the throttle cable but is an easy job.

Grips I use are Renthal ones, they have grooves for lockwiring and have excellent feel.

Thers nothing wrong with the stock throttle set up and you can mod the lights switch to become the YPVS/tacho on off.

For clocks you can use the stock ones, just remove the speedo or you can go all out and fit Scitsu rev counters and temp guages, the other option is the Vapour Trailtech - these are multifunction LCD units with all sorts of warning lights like over temp and over rev etc. They are a bargain for £80, but take some getting used to, they are very light though in comparison. Always try and get a decent temp guage, the stock ones are vague and not really suitable for racing.

Fairing brackets as standard are heavy lumps of steel and are aching to be modded, you can chop lumps off to make them lighter. Alternatively get something knocked up out of aluminium and junk it totally. The standard fairings themselves are no lightweight affair - you can get lighter bodywork in fibreglass form from the likes of ARD. It is much lighter but comes off worse when you do crash. You will need to fill in the headlight apperture with fibreglass if you run the standard or road version top fairing for your front numbers.

For the rear you can fit a one piece tailunit and lose the saddle and sidepanels most fit a TZ one. You can leave the saddle/sidepanels and fit numberboards via the bolt holes for the grab rail.

Rearsets are a must as the footpegs are way to low. You can modify the stock hangers by welding them up and fitting pegs, bending the rear brake lever backwards on itself and then fitting a gear lever backwards. The other option is buy some proper rearsets, Raask and some others still manufacture for the YPVS.

Fuel taps and fuel caps can also be changed a TZ one or a Pingel with its dual outlets is better than the stock vacuum diaphram equipped one. Petrol caps are standard across the Yamaha range so you can by any flash one you see for an R1/R6 etc and know it will go on. This saves having to have a key or butcher a good cap with a screwdriver.

For scruitneering you will be required to have a drilled sump bolt and it be lockwired.

Find something suitable like the tube on the bottom of the crankcase or one of the other bolts holding the engine stabiliser bars on to wire to. Your transponder will need a home to, most fit it somewhere on the fork leg.