On satuarday I tested a new self mod engine, it was great but after some runs the engine stoped try many times with no result, WOT any it run like it is idle, today I strip the carb and found that one of the reed vales left open I got a new kit and the reed vales where blue. What is the difference between the blu and the black ?

That was TOUGH read

What or Who's reeds you referring too ?

On the bottom of the 257 crab there where black reed vales and replace them with the blue one, are they good?

golfvits wrote:
Those little FLAPS are CHECK VALVES within the FUEL PUMP CIRCUIT. The piece is referred to as the FUEL Pump Diaphragm.

Given a choice, stay with the BLACK nitrile diaphragm, it is more flexible giving higher fuel flow for the high rpm use. You can try the blue MYLAR diaphragm, but if engine starves for fuel at higher RPM, you will have to go back to the black one.

Scott

Thanks for the info Scott
I was talking about this

The K10 kit only gives you the blue diaphragm, The K20 kits gives both.

I traced alot of carb problems back to ethanol based fuel. stay away from this stuff,I know regular gas is hard too find but E-10/E/85 fuel will eat carbs quicker then you can say WOT! Good luck,Bruce.

HMETALH wrote:
That is a good point, The BLUE mylar diaphragm is designed to more alki tolerant, but due too it being stiffer, it pumps less fuel per cycle.

Well I give it a try and tell you what happened

I have been running the blue ones for a while now without issues. The black ones were being damaged by some gas blends with Ethanol. Now that even we northerners are 'blessed' with the ethanol blends, it was becoming a real problem up here too. The blue ones seem to withstand better. Wish they would come out with an ethanol compatible diaphragm also! I have had some carbs with a beige check valve but haven't seen any in a while, only the black and blue ones now. The beige seemed to last very long too.