Johnson 9.5 only runs on choke

[sledhead26]

I have a 1970 9.5 that I've been messing with for a while but i can't get it to run off the choke. It has all new fuel lines from the tank to the carb, new fuel pump, new upper crank seal, new water pump, new plugs. I've cleaned the carb multiple, multiple times. I've reset the points. I'm running it in a barrel and have a fan on it to push the exhaust away. It starts great and idles great on choke but as soon as the choke is pushed off it has a bad stutter about every two seconds and will eventually die. It will run at higher rpm with the choke off but it still stutters and doesn't run very good. Not really sure what to try next. Any suggestions would be appreciated. Thanks

 

[kbait]

Re: Johnson 9.5 only runs on choke

Sounds like a partially obstructed main jet (just behind the bowl drain plug.. pull the plug and clean out jet behind it w/thin wire). If you clean it out and it still won't idle (assuming you've already tried to richen the low speed needle), then your idle circuit in carb is likely blocked/partially blocked. Check to see if the reed valves are closed when you have the carb off next time. Your low speed needle aims at a chamber covered by a welch plug. That chamber has small ports to the carb throat that must be free of debris to idle correctly.

Good luck!

 

[F_R]

Re: Johnson 9.5 only runs on choke

Carburetor throttle shaft not properly synchronized with the spark advance???

 

[sledhead26]

Re: Johnson 9.5 only runs on choke

Took the carb off again. Everything seems to check out ok other than the main jet. I shined a light down the hole and it looks like the hole is oblong almost oval.
Obviously That can't be good. Whoever had it before must have tried drilling it out or something. Can the jet be replaced or is it fixed in the carb?

 

[Daviet]

Re: Johnson 9.5 only runs on choke

What's your model number?
The jet is removable, but you should use your model number to get the correct parts.

 

[sledhead26]

Re: Johnson 9.5 only runs on choke

Model is 9r-70c

 

[Daviet]

Re: Johnson 9.5 only runs on choke

Here is a breakdown of your carb, #75 is the high speed jet, is that the one you are talking about?
:: iShopMarine.com ::