Making big BHP numbers with some porting and tuning is the easy part on an air cooled RD or most two strokes. Getting that to the ground is a little harder. If you’re a heavy guy like me it gets harder. As soon as we where past the 45 BHP mark you could distinctly make out the clutch was slipping when the bike came into the power band. We did everything we where told to some of the stuff we tried.

Things improved for a few weeks. But later with some more porting and new chambers we where back to having the clutch start slipping. This was clearly noticeable in the first gear when the bike would hit the power band. It wasn’t so bad with lighter riders but with my weight (200Pounds) it was very noticeable.
At this time we got some TZ springs from the UK (Thanks Ric Naylor). These where much longer than the RD springs and a lot stiffer. We put these in and we where back to getting good launches and very little slippage. year past without any problems. In the mean time I started doing some engine work for friends motors. We started running into the same clutch slippage problems again. New spring for the RD are as it rare as hens teeth much less finding TZ springs for all the bikes I was porting. So what do we do. 

The Spring: 
So we thought it was best that we do our own batch of springs. We researched both the stock springs and the TZ springs. The metal from both springs where analyzed. We  researched the latest metals in spring technology. We found the latest and most advanced springs being used in the medical field where Chrome Silicone Alloys. We also studied the measurements and pressure strengths for the RD and TZ springs. The TZ springs where 35mm in height. And 17mm in diameter. The Stock RD Springs where 31mm in height and 18.5mm in Diameter. For maximum effect we thought it would be best if we combined the length of the TZ spring with width of the RD spring and made it out off the best Spring Alloy available on the market. The Picture bellow shows the 3 springs. The new springs have been coated a dark blue to prevent rust. If you sand them lightly the High Chrome alloy shines thru see pic above.  

The Steel Plate: 
A common misconception here is that roughing up the steel plates is a good thing to do. Well they are not. It may feel like performance has improved but in the long run all your doing is accelerating the wear of your friction plates. The rough edges eat into the cork liner and destroy them. And very soon your back to square 1. The same goes for sand blasting your steel plates.  

For a long term fix the steel plates have to be pitted deeper. The trick is in allowing enough space for the oil to be squeezed into. And so deep that they will not wear smooth with rough use. After testing all the possible combinations this design proved to be the most effective. You will see it’s a lot different from what you’d get with a sand blast.

The Fiber Plate:
We have the fiber plates with cork. We have the steel plates with cork and we have the Yamaha plates with cork. When it comes to the Plates nothing can beat the OE Yamaha plates.

  The Basket: There is nothing wrong with the stock basket. If you would like to improve oil circulation then you can cut shapes into the ears. These can be V shaped or simply a series of holes along the side. Or a single large hole at the center. See picture below for an early example. The better one is on the bike. Where we used the V cut and a single large hole bellow that. But you can still get an idea. Of the various things that can be done. All you need is a dremal and a drill press.    

With heavy use and the fact that some of these baskets are over 30 years old. The only problem with them is that the ears develop groves. Some people will tell you that you just need to file the ears down flat. Or get a billet basket. Id disagree with both tips. Firstly filing out the groves results in the grove width increasing. So the plate isn't sitting firmly what happens now is the groves will come back with a vengeance. Cause each time you let out the clutch the plate ears are hitting the clutch basket pillars. As for a billet replacement. If you have the money sure. But a new OE basket will last you another 20 years at least for much less.

My solution is to Have the ears of the basket Tig welded up with a hard rod. Then measure the width of the clutch plate ear which is around 14mm. Now file down the welds till you get a flat surface. You will notice that the metal added by the Tig welding is at least twice as strong as the stock aluminum. Once a basket has been treated so it will never wear out. And will even outlast the fancy Billet baskets. Ill try and get the Rod specs used by my TIG welder.

We are sharing this technical information in the hope that somebody else having the same problems can gain from what we have learnt the hard way. Contact us if you would like any further info. Or would like to know if the springs can be used for your application. In addition to the new springs we also carry new steel plates and new friction plates.

Tech Specs for the Springs: