RH4 to RH10 JS Intake Port Sleeves

seattle##gs said:
I will mention this again for you Mikuni people...there is a company called Thunder Products which has done a lot of work on the simple round slide VM carbs and his inventions really works. The best item is very simple to install and requires NO fiddling around with jets. The main improvement is in low speed to mid range. It is called The Torque Wing (this NOT the swarup and is NOT a gimmick). It really works, I've used it for several years. Look it up on their website for more info.
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What do you have yours fitted to?
And what benefits did you notice exactly?
 
I have a 34mm Mikuni on a 750 motor. Everything is stock. It boosts the power from just off idle to midrange or more. By full throttle it is no longer in play. The increase in power is really noticeable when the throttle is opened quickly. The guy who designed it works mainly with racing snowmobiles. I sent him an amal carb body hoping he could make a torque wing for them but no luck. Any waay, where can you spend $100 and actually get results you can feel? You can install one in about an hour.
 
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The first race bike I had was a 500cc Triton. The motor was made from 650 Triumph parts with a 63mm billet crank. The bike had been built with all the theories by one of my mates. It had almost killed him at Bathurst in about 1958. When I first got it, it haseparate pipes with 4 inch megaphones. It was really exciting to ride - gave a great adrenalin rush - however it was impossible to get a decent lap time around Calder Raceway with it. From the beginning, I had a never-ending search for torque. Manx Nortons had really big inlet ports, so that was obviously the way go - NOT !
The Commando 850 engine is really lovely with 30mm inlet ports. I am just amazed that it is quick enough. These days in Australia, we race in 'historic' classes - not Allpowers C grade against ZI and H2 Kawasakis. The fastest bikes are 1100cc methanol fuelled CB750 Hondas. When I came out of corners faster than them , they could just catch me at the ends of the longer straights.
 
Fast Eddie said:
I think that’s a fairly safe bet !
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Three things work in conjunction - the torque characteristic ,the gearing and the shape of the needles in the carburettor. If you have high overall gearing, you tend to use more throttle, so you are more onto the taper of the needles. A slightly over-rich mixture gives less power. I use 6D Mikuni needles which are the leanest for my 34mm Amals. With close ratio gears and very high overall gearing - that gives the fastest acceleration. Commando motors are different because of the heavy crank. When you open the throttle, you compete with the crank inertia. If you open the throttle quickly, you often use more of the needle taper than you need, so even with more throttle, the bike does not accelerate as fast as it can. It is very deceptive. The only way to findout what works is to try all options, but the only way to find out you have improved torque is to raise the overall gearing. If you don't do that, the bike gives the impression that it is accelerating as fast as it can. If you lower the gearing with the heavy crank, the bike does not usually accelerate faster.
 
The port leading up to the valve guide should be the venturi (smaller diameter) and then open up a bit to get around the valve guide. Norton did just the opposite. They opened up the port before the guide and left the choked down area at the guide - hurting the midrange and doing nothing for the top end. See illustration of RH4 port. If you run your finger down the port you can feel the smaller diameter ridge near the guide. The answer is to reduce the port diameter leading up to the guide and restore the high velocity venturi effect.

RH4 to RH10 JS Intake Port Sleeves
 
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