HSN needle making no difference???

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rdarsa

Member
Messages
15
I have an RCMK CR300F - with a 990 carb that has been modified with 2 bearings on the throttle shaft at either end.

The carb is relatively new - was performing fine, I have checked all the gaskets and replaced a couple, checked the hose pipes, but despite all that it seems that the HSN needle setting make no difference in the tune at high speed, no matter how far I unscrew the needle, I can't get the engine to behave 'rich'?

The stock settings almost feel lean at 1+3/4 +- 1/4. It warbles a bit on WOT, I can never get it to 'gargle'?

Before another tear down, has anyone had this problem? And know exactly where to point me to - and assuming its the carb, which bit? Or are bearing modified carbs a liability??

Cheers,

Richard.
 
That sounds odd. Have you tried pulling the HSN out completely to check the tip? One of the jets could be clogged inside the carb. When I rebuilt my 668 I couldn't believe how much sand was in there. Maybe some dirt is clogging something. A rebuild kit is only $8 and easy to do.
 
I have an RCMK CR300F - with a 990 carb that has been modified with 2 bearings on the throttle shaft at either end.

The carb is relatively new - was performing fine, I have checked all the gaskets and replaced a couple, checked the hose pipes, but despite all that it seems that the HSN needle setting make no difference in the tune at high speed, no matter how far I unscrew the needle, I can't get the engine to behave 'rich'?

The stock settings almost feel lean at 1+3/4 +- 1/4. It warbles a bit on WOT, I can never get it to 'gargle'?

Before another tear down, has anyone had this problem? And know exactly where to point me to - and assuming its the carb, which bit? Or are bearing modified carbs a liability??

Cheers,

Richard.

look up metering spring mod. i have had this issue after porting and adding reeds. the metering spring controls the flow of fuel to your carb. i have also had vacuum leaks spray carb cleaner around your carb and make sure the motor does not rev or die while lightly spraying carb cleaner around the gasket areas.
 
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