dual carb questions

[joshzimm]

1989 force 125

I did an engine rebuild last winter because piston 2 rings melted, I have fixed that now that I?m running the engine 25/1 to get the new piston and rings worn in. after 7 hours I like at the spark plugs and the bottom 2 have some carbon build up on it and they were starting to miss-fire, so I?m going to get new ones, however I looked at the top 2 and they seem like they are running hot?? This is concerning because I would not like to do another rebuild on a spent ring.

After rebuild and putting back together I check the card float and idle mix screw. When timing the engine back I checked the carbs idle mix screw and because there are 2 carbs on this engine the shop guide calls for 1 turn out and I did 1-1/4 give it a little more gas. Now one thing I noticed is that is that if I turned the idle mix screw on the bottom it would affect the overall running of the engine (racing and bogging), However when I turn the idle mix screw on the top it does nothing to overall running of the engine.

Question:
Why would the bottom 2 cylinders have carbon build up and not the top 2?

Why would the top idle mix screw not have the same affect on the engine as the bottom idle mix screw?

is there a different way i should be adjusting the carbs (to get them in sync)?

 

[thompy]

Re: dual carb questions

have you cleaned the carbs, maybe a jet passage is plugged up

 

[joshzimm]

Re: dual carb questions

i just did took apart the carb but there is limited places where is could get plugged up. did put a bunch of carb cleaner down the back side of the idle mix screw and i some black slury to come out .. crossing fingers to on that being the issue. testing tomarrow becuase it is to late to run it where i live .. i will update again tomarrow

 

[joshzimm]

Re: dual carb questions

Ok... now I have taken apart the upper card and cleaned it... and put it back together with new plugs and ran it for an hour. Pulled the plugs and cylinder 1 was wet with gas and no carbon build up, cylinder 2 has a little carbon build up. Cylinder 3 has a little build up on it. Cylinder 4 has the most carbon build up on it. I checked timing and check the fire rotation and that all checks. The boat seems to be running hard in idle and smoothes out a little at 1k RPM however I am running this in a tank with the prop off.

Does any one have any idea how I could get this motor to run smoother.

I did notice this morning when running the boat in a bucket that there seems to be gas leaking from the location of the main jet to the back of the card (to the point that you will see a ( small )_ puddle of gas in the engine area.

Could this been a issue ?

I am running a gas mix that is 25 /1 and I think that I?m going to thin that out a bit to 35/1


Anyone got suggestions (boat still running rough)

 

[thompy]

Re: dual carb questions

first off glad your making progress, you should clean both carbs and probally carb kits, make sure to check float levels, its probally going to run a little rough with more than a 50 to 1 oil mixture, plus they seem not to idle real smooth in the first place