What would cause a Johnson 9.9 to run rich?

[ba_50]

I'm convinced the reason the motor won't get full power is because it is running to rich. The motor is a '92 J10rena. The carb had a kit put in and the plastic cover has been replaced with the upgrade. The float is adjusted as per manual. The only thing I can think of would be the needle/seat is letting too much gas through. What do you think?

 

[scanman]

Re: What would cause a Johnson 9.9 to run rich?

A vacuum leak might cause the rich condition. Try this link. I saw your carb there while I was rebuildin mine, I think. If memory serves, the plastic tops can be a bit of an issue.

http://www.sschapterpsa.com/ramblings/Johnson_9.9_carb-fuel_pump.htm

 

[raczekp1]

Re: What would cause a Johnson 9.9 to run rich?

"scanman" you promised to post video how your Super charger run

 

[dwagoner]

Re: What would cause a Johnson 9.9 to run rich?

actually an air leak will cause a motor to run lean, it lets the air through the leak and doesnt cause the suction to get the same amount of fuel in through the carb, thats standard for any motor, air takes the easiest route and thats through the leak and not thru the carb. you can spray around an area where you think a possible leak is while running with a can of carb cleaner and if it has an air leak it will such the carb cleaner in thru the leak and change the rpms. if it does have a leak you will hear idle very easily change

 

[Rick.]

Re: What would cause a Johnson 9.9 to run rich?

How much loss of power are we talking about? Best of luck. Rick.

 

[raczekp1]

Re: What would cause a Johnson 9.9 to run rich?

trotle cam and cam folower if its opening trotle plate in carb,couse fuel flow threw more then 1 hole from slow spped chamber.

 

[ba_50]

Re: What would cause a Johnson 9.9 to run rich?

A vacuum leak might cause the rich condition. Try this link. I saw your carb there while I was rebuildin mine, I think. If memory serves, the plastic tops can be a bit of an issue.

http://www.sschapterpsa.com/ramblings/Johnson_9.9_carb-fuel_pump.htm

scanman,

I've read the SSchapter and my manual dozens of times and can't seem to find a solution.

 

[ba_50]

Re: What would cause a Johnson 9.9 to run rich?

trotle cam and cam folower if its opening trotle plate in carb,couse fuel flow threw more then 1 hole from slow spped chamber.

The cam roller should start moving at the index mark at the same time the throttle plate starts to open. Guess I don't understand what you are saying.

 

[Daviet]

Re: What would cause a Johnson 9.9 to run rich?

Do you have a flooding problem on both cylinders or just one cylinder?

 

[scanman]

Re: What would cause a Johnson 9.9 to run rich?

trotle cam and cam folower if its opening trotle plate in carb,couse fuel flow threw more then 1 hole from slow spped chamber.

He's tryin to say that the throttle plate is opening & pulling fuel from the low speed circuit before the vacuum increases with RPM. Sounds plausible to me. Check the link & sync, maybe? What convinced ya it's rich?

 

[the machinist]

Re: What would cause a Johnson 9.9 to run rich?

Just had a thought, you said it had a carb kit put in. After looking at the parts list, they only list one kit for both 9.9 & the 15hp. IF the main jets were supplied in the kit for both engines, did you per chance install the 15 hp size # 54, instead of the 9.9 hp #34?

This would put more fuel into the engine, but not enough air from the 9.9 carb throat to make an efficient mix & you will be running rich, (almost like choking it) making the engine only get to about 1/2 power.

The reason I know is in my early years trying to convert a 9.9 to 15hp I did exactly that. That was one of the reasons I started writing my repair articles as no one I could find knew anything about those motors & the internet forums was not going yet, so I bought parts lists & old motors, learning from each.

 

[ba_50]

Re: What would cause a Johnson 9.9 to run rich?

It has been a few years since the kit was put in and I don't remember what came with it. The thought crossed my mind that something might be wrong with the high speed jet.

The motor would make a Waaaah... type sound when opening up. Same as my 8hp did until leaned out. Leaning the 9.9 helped but not enough. I don't know if it was flooding both cylinders. The mechanic thought it was too rich too. He didn't like small motors and never came back. He did confirm linkage was adjusted right.

I don't have the motor here so can't do much except get new ideas.

 

[jjrreb23]

Re: What would cause a Johnson 9.9 to run rich?

fuel pump can also cause it to run rich .fuel will pull in behide it , and in to the block. just takes a pin hole ,

 

[ba_50]

Re: What would cause a Johnson 9.9 to run rich?

jjrreb23,

It has a new fuel pump , but I could take a proven one off the 8hp and try it.

Machinist
The carb kit I looked at doesn't have a high speed jet included #23 323703.

 

[ba_50]

Re: What would cause a Johnson 9.9 to run rich?

raczekp1

What kind of adjustment are you talking about? Delaying the opening of the throttle valve with the cam roller? Some recommend adjusting it so it has already started to open the throttle.

So far it looks like I could do the above, try a proven fuel pump, and put a different top cap on the carb.

trotle cam and cam folower if its opening trotle plate in carb,couse fuel flow threw more then 1 hole from slow spped chamber.

 

[raczekp1]

Re: What would cause a Johnson 9.9 to run rich?

hi,
here is a carb photo taken from http://www.sschapterpsa.com/ramblings/Ramblings.html.its model 89, but earlier carb models are symiliar

when botl no 1 is screwed to far, couse trotle leaf in carb troath(there are 3 smal holes at upper inner carb wal) open more then 1 hole.
play with screw no 1 and no 2

 

[ba_50]

Re: What would cause a Johnson 9.9 to run rich?

I just remembered that the pump didn't leak out the back but I can still try a different one when I get back. The cam screw adjustment can be checked.