View Single Post
Old 11-01-2010, 01:46 PM
Nougat Nougat is offline
Motorized Bicycle Elite Member
Join Date: Nov 2009
Location: Montgomery, IL
Posts: 1,332
Default Re: First build done but have a question!

One of my concerns about the CNS carb is that the Yamaha engines it was used on had oil injection. I know the pilot jet is *extremely* small. I wonder if two-cycle premix fuel would clog the pilot jet more easily. Perhaps not, as I recall reading about people with their PW80s disconnecting the oil injection pump and just using premix without difficulty. Still, that was also on the OEM Mikuni carb with a proper Yamaha engine, not a knockoff carb with an HT motor.

One last point: the "vacuum" hoses on the carb. I've not seen the CNS carb in person, but I'm looking at the pictures at Spookytooth. I can tell you that the port on the bottom of the float bowl is an overflow. Attach a tube to that, and route that tube away from the motor. Any fuel overflow will drip to the ground. *Don't* hook it up to another port!

It looks like there are three ports on the top of the carb; two on the left side pointing up, and one on the right side, pointing at an angle. The right side angled one probably goes to the carb intake. On the Yamahas, I think that was to provide vacuum for a diaphragm-powered fuel petcock. For our machines, it needs to be capped off.

The other two ports - one of them is a bowl vent. Attach a tube to that and route that tube so it's pointing down, too. This will prevent crap from getting in the carb while still allowing venting. The other port - I have no idea what that's for. It might be the air intake for the idle circuit. On the OEM carbs, that was a separate little hole behind the air cleaner; maybe they changed it for this one.

I would *love* to see some good pics of this carb, from multiple angles, and disassembled even.
When asking for advice, you did not specify whether you wanted only good advice.

Get on the member map

Reply With Quote