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High Performance Bicycle Engine Tips and Motorized Race Bicycles We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds

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  #11  
Old 01-01-2016, 02:26 PM
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sbest sbest is offline
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Join Date: Nov 2015
Location: Nova Scotia
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Default Re: 20mm Walbro on a China Girl

Cutting an old cylinder in half is an excellent learning tool.
This was a Yamaha Blaster cylinder cut apart as a learning tool:


From what I learned from it I stuffed it with several tubes of JBWeld epoxy in this manner (photoshopped):


Which in real life looked like this comparison:


The result was easier carb jet tuning because of fuel staying in suspension, wider powerband and of course, more power.
All gleaned from studying a sectioned cylinder.

Steve
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  #12  
Old 01-07-2016, 07:24 PM
chrisme chrisme is offline
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Join Date: May 2009
Location: Maine
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Default Re: 20mm Walbro on a China Girl

Where did you find that carb / what model is it? I've been having a hard time finding a non-return style carb with an external pulse line. You've found just what I'm looking for.
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  #13  
Old 01-12-2016, 09:35 AM
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cannonball2 cannonball2 is offline
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Location: Colonial Coast USA.
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Default Re: 20mm Walbro on a China Girl

You can also use the carbs with the internal pulse passage just by Dremeling a small channel/port into the manifolds carb mounting flange to allow the pulse in the intake to reach the port on the carb.
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  #14  
Old 01-12-2016, 10:14 AM
chrisme chrisme is offline
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Default Re: 20mm Walbro on a China Girl

Sure, however It would be nice not to have to deal with a fuel return. The external pulse port is just the icing on the cake with this carb!
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  #15  
Old 01-12-2016, 11:16 AM
curtisfox curtisfox is offline
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Join Date: Dec 2008
Location: minesota
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Default Re: 20mm Walbro on a China Girl

Can one just take the return line and hook it the main fuel line from the tank, instead of going all the way to the tank?.............Curt
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  #16  
Old 01-18-2016, 02:14 AM
FFV8 FFV8 is offline
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Join Date: Oct 2013
Location: Spring Valley NV
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Default Re: 20mm Walbro on a China Girl

Porting the pulse circuit in to the intake is not the best plan.

The fuel pump was designed to work with the crankcase pressure pulse as well as the intake vacuum. That drives the diaphragm both directions.

With vacuum only, you get a half stroke of the fuel pump. This can make the high speed tuning very sensitive as the fuel pressure drops at WOT.

I have carbs and manifolds on the shelf. Just finished making a new batch of throttle arms too.
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  #17  
Old 11-09-2016, 06:26 PM
mike carter 2 mike carter 2 is offline
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Join Date: Nov 2011
Location: west virgina
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Default Re: 20mm Walbro on a China Girl

cool kit . are you still makeing them?
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