1991 v4 90hp carbs help

[arthurj12]

hello i just got a 1991 90hp and i replaced thermos and impeller, new fuel/water separator completely dissembled and cleaned everything in carbs took out jets and orifices checked floats, gaskets are good look new, i found something strange on one of the carbs the two idle circuit nozzles were filled in with melted metal like it was done by someone ?? anyone know wtf that is about?? if somone has a diagram of carbs can show which nozzles i mean thx

 

[wired247]

Re: 1991 v4 90hp carbs help

If you are talking about the idle jet its located on the outboard side of the carbs just in front of the throttle plates . Idle jets flow air to mix with gas and emulsify it in the idle circuit passages. Its not a good idea to do it with gas but on air jets like OMC idle jets and Holley idle air jets you can fill the jet with solder and redrill them to whatever size you want. It works and there is no shame in it.

 

[arthurj12]

Re: 1991 v4 90hp carbs help

yes thats what im talking about thx ok good i drilled then out to match the other ones on the other carb, seems strange they were plugged with solder should i get new one ?

 

[wired247]

Re: 1991 v4 90hp carbs help

If they were PLUGGED then someone didnt know what they were doing. Plugging and drilling is old school carb tech. Usually you fill and drill until you find a combo that works then you buy the same size factory jet. If the size is right I wouldnt worry about it. You have to gauge the holes properly though. Remember these are air jets. The smaller they are the more fuel goes in at idle. LARGER = less fuel ie leaner. For a 90 you should be in the 33 ( thousandths ) range unless you are running fiber reeds. Venturi or throttle plate size doesnt mattter for the idle circuit in relation to the idle mixture circuit. When I had a 90 I was running 32's and switched to 28's with the boyssens to smooth the idle out. currently I run 25's with the Carson reeds in a 140 crossflow. The 90 has a stronger vacuum pulse than the 115/140 and it doesnt need as big of an idle mixture to run.

You wouldnt want to drill fuel jets. Reamers work better but they need a transition cut on the inlet side that you cant do without a specialty reamer. Not a problem with air jets like OMC side draft carbs. A drill bit will work fine if you have tiny drill bits.

 

[arthurj12]

Re: 1991 v4 90hp carbs help

really good info thx alot so what would u suggest i do? i dont want to damage my motor ? get new ones and if so were can i get them??

 

[wired247]

Re: 1991 v4 90hp carbs help

This site sells jets as do others. What may have happened is someone didnt have the throttle plates closed fully on the bottom carbs and "fixed" their idle problem by plugging the idle air jets. Do a link and sync first then figure out what size jets you need from the model year . What it came with is probably what you need unless you are running fiber leafs..

 

[arthurj12]

Re: 1991 v4 90hp carbs help

ok thx alot ill get new ones do a link sync and give it a try

 

[wired247]

Re: 1991 v4 90hp carbs help

FWIW I looked up your and they spec a 38 jet in the idle air position for that year.

 

[arthurj12]

Re: 1991 v4 90hp carbs help

ya thx abunch i went to shop guy gave me two 40 jets for free told me to try them out

 

[wired247]

Re: 1991 v4 90hp carbs help

I'd go a little richer than that. If its bucking and sneezing at idle try kicking them down in the mid 30's range.

 

[arthurj12]

Re: 1991 v4 90hp carbs help

alright thx 40 is all he had and they were free so if they dont work ill try a 35 i can get them from this site right?