This page is for the racers among us who need to know where to get those special parts needed to build a racer.

Ultimate Flow Optimizers

Thunder Products in the USA make these things called UFO's for Mikuni VM roundslide carbies and from all accounts they do what they are claimed to. Read on and if you think you can use them contact Thunder Products at http://www.thunderproducts.com 

Without the U.F.O., the air hits the forward wall of the slide cavity creating a rolling air turbulence which forces the poorly atomized fuel droplets to the lower portion of the carb bore resulting in poor fuel atomization and poor performance.

With the aerodynamic U.F.O. filling the slide cavity, the rolling air turbulence is eliminated.  The higher velocity air flow pulls the fuel further up the needle and higher in the carburetor bore resulting in superior fuel atomization.  This means more HP, quicker throttle response, improved fuel economy and a cooler running engine.

If you want to know more download their installation guide.

UFO installation guide in .pdf format

Ivan Hoey has decided to start making some of those exclusive parts needed for racing. First item to be produced is the High Ratio Primary Gear Set.

On the XS650 the primary gears are 27 teeth on the crank gear and 72 teeth on the clutch basket. The gears that Ivan is having made are 20% higher than the original ratio, these are exactly the same as those produced by Halco Tuning in England that are now unavailable.

So, why do we need to use the higher ratio primary gears?

The available options for secondary gearing on the XS650 are limited, the largest front sprocket that will fit the XS is 18 teeth and the smallest rear sprocket that will fit is about 30 teeth so if you want to go faster you would have to rev the engine higher and getting more horsepower to the top end might not be best option, you'd like to keep those rev's down a bit and make the engine live a bit longer.

By using the high ratio primary gears you speed up the gearbox allowing more scope for final drive sprocket selection with the added bonus that you also effectively reduce the load on the gearbox and transfer that load onto the engine.

Let's dream here for a minute, you're going down the main straight at Eastern Creek or Phillip Island and the tacho is pinned at maximum rpm's and all the other bikes are passing you like you're standing still and you know you have the maximum gearing that will fit your XS 18t front and 30t rear sprockets and power to spare but no more rev's. What do you do? Instantly the answer comes to you, fit a set of high ratio primary gears

Ivan has now had a second batch made so if you want some get your order in before they are all gone.

The price remains the same for now at $700 per set + postage and packaging for overseas buyers.

If you think that's expensive then consider this, Halco lists these in his 2001 catalogue for £285, on todays exchange rate that's AU$679 so you are effectively buying these at six year old prices. Name something else you can buy today for the same price it was six years ago!

Here's what they look like

Top:- This pic compares the stock on left and high ratio gears on the right

The conversion does require some modifications to the clutch basket and back plate. 

Some clearance needs to be gained with the side cover as well (see below pics) but this is only minor work.

Ivan is also making some sump extensions, if you want one give him a call.

Disclaimer

These are experimental parts and as such no warranty is given or implied and if you decide to buy it is on the understanding that you do so at your own risk.

Contact Ivan Hoey at ltr.management@bigpond.com to place your order.

There are many other suppliers for racer parts, for big bore kits (750cc and 840cc) as well as Carillo rods, electronic ignitions etc. then 650-XSories is the place to go. 

If it's a 90° rephased motor your after then a visit to Professional Motorcycle Tuning will be able to supply the necessary splined shaft for the conversion as well as a number of other parts. Talk to Daryl Hutcheon on 03-9330490 or email him at promctun@bigpond.net.au 

For a clutch conversion contact Terry Gliddon at toota@internode.on.net 

22/05/2008