Archive for the ‘needle’ Tag

XS650: High Ratio Primary Gears   Leave a comment

Years ago Tony Hall used to produce these. They became harder to find than chicken lip-socks (rarer than hen’s teeth). Ivan Hoey (Australia) began producing these once more some years ago. Fits direct to the original clutch basket.

I scored a set and have been running them ever since. Love them. 3 fewer teeth on the primary gear, 5 more on the drive gear. Increases the transmission output while decreasing crank rotation.

Original        … 27:72 … 2.66

Ivan +20%  … 32:69 … 2.16

Together with Terry’s vescanite clutch dampers. The vescanite dampers don’t break like the springs.

Two of the better modifications I’ve done.

 

original primary gear … with vescanite dampers

 

high ratio primary gears … with vescanite dampers

 

Ivan has just produced a new batch. Improved. The inner bush has been replaced with a needle bearing.

 

Ivan’s new set … + needle bearing

 

This is a small run. If interested he is now taking orders. Requires a deposit. Email contact here … ltr.management@bigpond.com

He can also do a needle bearing conversion on your stock primary gears. Dramatically improves gear and neutral selection. Also when stationary.

Includes needle, inner and thrust races, thrust washer, 3x screws/nuts and fitting instructions.

 

convert original primary gears to needle bearing

 

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XS650: VM34SC Mikuni   Leave a comment

Yamaha’s Racing Tips Manual, 1974, suggested using VM34SC Mikunis. Round slide. Magnesium bodied. No Power Jet/Accelerator Pump/Beschleunigungspumpe.

Today, TM’s are supposed to provide significant performance improvements. Flat slides and the jet blocks help create a smooth bore effect. Air flows faster and smoother through the TM Series venturi. Higher air flow velocity gives a stronger vacuum at the needle jet needle. Provides more precise metering and better throttle response.

For known geographic and climatic conditions.

However, I do a fair bit of touring. Low to High altitude. For this I actually prefer the original BS series carbs. They automatically adjust themselves for air pressure. Easier to keep tuned.

… VM34SC carb … XS750(650) Racing … adjustments … jet needle 6F9 (#2 clip position)

 

… carb adjustments

 

… carb .. VM34SC … adjustment

 

… VM34SC carb … 3/4-full throttle adj … main jet

 

 

… VM34SC carb … 1/4-3/4 throttle adj … needle jet

 

… VM34SC carb … 1/8 – 1/2 throttle adj … slide adj and cutaway

 

 

… VM34SC carb … 0-1/8 throttle adj … air mixture screw – pilot jet

 

 

… VM34SC carb … idle speed screw

Posted December 21, 2011 by xscafe in Carb - VM

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