Billme
06-26-2007, 12:53 AM
Had a call from one of Centurys dealers in Fla, Doug Burins in Winter Park, Fla
He has been selling a lot of gassers lately, anyway, he brought something to my attention...He had tried using felt clunks(Remember Raja's rant o RR about using the Stent type, so everyone went to the felt type)) on his machines getting them ready for customers..
He said all of sudden, the engines started running lean, and he could take the clunks off, and the engine would richen and run right...
He wanted me to find out why? well, after working on this, I had figured it had to be in the pump side of the carb. These clunks were design to run with these engine after all..
To make a long story short, the Teflon flappers on the pump side are very stiff, and don't seal well, hence less fuel flow.. This is one of the reasons we have to run richer settings on the carb, besides the big induction ports in the engine...
This may explain why some engine do well, and some don't according to what type clunk you use..
I have found that just a slight decrease in fuel flow, can make the engine not run as good, but be hard to detect for the novice..
With this said,you can buy the repair kit for your carb. the kit has both type flapper designs, rubber, and Teflon wafer...
Most clunks were probably tested with holder type rubber flappers which allowed more fuel to be pumped.
What to do?
First, if your running fine, then don't do anything
But, if you suspect this, and your needles are open more than you like, and not running smooth then read on...
You can use a straight type heavy metal clunk that comes with the Century, and Vario, MA kits, if you don't want to change the flappers, or,
You can change back to the older rubber type flappers, and use a clunk filter, or you can change the flapper, and still don't use a filter clunk, and just depend on the carb screen in the carb for the most fuel flow pressure...If you do this method, then you need to double filter your fuel before it gets to the model.. I use a filter clunk in my supply tank with a paper filter pass the pump..Having a filter pass the pump will catch debris from the pump if it starts to go bad..
One other problem, what to do about engine hiccuping during a roll or flip. If you elect not to use a filter clunk, you will need to make sure your steel clunk is heavy enough to move fast to keep under the fuel in the tank .
.
BTW, Walbro knows of this lean condition using the wafer type flapper, but stated its within specs, and last much longer..
Hope this helps ....
Bill
He has been selling a lot of gassers lately, anyway, he brought something to my attention...He had tried using felt clunks(Remember Raja's rant o RR about using the Stent type, so everyone went to the felt type)) on his machines getting them ready for customers..
He said all of sudden, the engines started running lean, and he could take the clunks off, and the engine would richen and run right...
He wanted me to find out why? well, after working on this, I had figured it had to be in the pump side of the carb. These clunks were design to run with these engine after all..
To make a long story short, the Teflon flappers on the pump side are very stiff, and don't seal well, hence less fuel flow.. This is one of the reasons we have to run richer settings on the carb, besides the big induction ports in the engine...
This may explain why some engine do well, and some don't according to what type clunk you use..
I have found that just a slight decrease in fuel flow, can make the engine not run as good, but be hard to detect for the novice..
With this said,you can buy the repair kit for your carb. the kit has both type flapper designs, rubber, and Teflon wafer...
Most clunks were probably tested with holder type rubber flappers which allowed more fuel to be pumped.
What to do?
First, if your running fine, then don't do anything
But, if you suspect this, and your needles are open more than you like, and not running smooth then read on...
You can use a straight type heavy metal clunk that comes with the Century, and Vario, MA kits, if you don't want to change the flappers, or,
You can change back to the older rubber type flappers, and use a clunk filter, or you can change the flapper, and still don't use a filter clunk, and just depend on the carb screen in the carb for the most fuel flow pressure...If you do this method, then you need to double filter your fuel before it gets to the model.. I use a filter clunk in my supply tank with a paper filter pass the pump..Having a filter pass the pump will catch debris from the pump if it starts to go bad..
One other problem, what to do about engine hiccuping during a roll or flip. If you elect not to use a filter clunk, you will need to make sure your steel clunk is heavy enough to move fast to keep under the fuel in the tank .
.
BTW, Walbro knows of this lean condition using the wafer type flapper, but stated its within specs, and last much longer..
Hope this helps ....
Bill