66 sport twin 9.5 fuel issues

[SGR 1966]

Im working on the old sport twin for the kids. The fuel system is being a problem, i ordered up a carb kit that came with most of a fuel pump kit so im trying to tackle both.

The problem was the engine idles well but would over flow the carb vent if you throttled up. I changed out the needle and seat as well as the float. Same problem, adjusted the float and it started spitting fuel out the fuel hose at the carb inlet. Put on a better clamp and the fuel pump started leaking. i cant seem to find the happy medium here. fuel pump seems eratic, over fuel or no fuel in the bowl when i go in to adjust the carb. Pulled the pump apart and cleaned it, all looks good there.

maybe im just fighting finding the right setting for the float, without any instructions its a guessing game. Ive been searching the 9.5 posts for a couple days and have not stumbled on the right post to help out.

can anyone point me in the right direction?

Sean

 

[SGR 1966]

Re: 66 sport twin 9.5 fuel issues

Been playing with this thing most of the morning. The fuel supply seems very inconsistent. I get it tuned out and running right then it starts blowing fuel out the overflow again. Shut it off and restart and it does not want to pump. Prime it up and it will run a while again and start dumping fuel again. I'm not a 2 stroke mechanic by any means but fuel pumps don't normally go bad both ways over and under pressure do they?

 

[SGR 1966]

Re: 66 sport twin 9.5 fuel issues

read some more, checked compression, 70 psi should be plenty to drive the pump but im still not having good luck. Guess I will try a new fuel pump.

 

[Rick.]

Re: 66 sport twin 9.5 fuel issues

At the top of this forum is a Top Secret File. In there is the proper settings for you slow speed needle to get the motor started. Then you fine tune it from there. My slow speed needle was out from seated almost three full turns before it started to behave properly. Best of luck. Let us know how it is going. Rick.

 

[SGR 1966]

Re: 66 sport twin 9.5 fuel issues

I read all that as well, the issue really appeared to be the fuel running out the overflow vent on the carb, made needling impossible since it would run with the needle shut off.

I put in a new needle seat and float thinking that must be it but same problem, I located a new fuel pump just in case it was an over pressure problem there but it made no difference, I took the carb back apart and cleaned every passage with starter fluid as well as the reeds, and went to the marina and got marine fuel and tried again and it is working now. I noticed as I was playing with the idle it sped up with choke and surmised it must be lean even witht he needle out way to many turns. I think cleaning out the passage must have been the key but im not sure. At any rate its dialed in at 1.5 turns an the 12 year old can start it with one or 2 pulls now so ill call that cured for now and let them start burning fuel at their pleasure. They spent the last 2 days on the lake moving from spot to spot to fish so all is well.

 

[Rick.]

Re: 66 sport twin 9.5 fuel issues

Well you persevered and you found success. Congratulations. I trust there are no wide open throttle issues? Rick.

 

[SGR 1966]

Re: 66 sport twin 9.5 fuel issues

No wide open issues at all, starts 2 pulls by the 12 yr old now and runs great atall throttle settings. Makes no sense to me why it was over fueling but I guess I don't care as long as I got it working for the boys. Guess I will move on to tune up my old omc225 inboard today