85hp carb question

[covert]

Great site!<br />I searched the forums but couldn't find an answer so her goes:<br />Against my better judgement I took my 85hp force to a mechanic to get it running right. It's the first time in 15 years I've let anyone else tinker with any of my stuff, but this engine has me bumfuggled, so I thought what the heck.<br />After setting the timing the mechanic pronounced it fixed...yet it still wont idle and it backfires. He still charged me $93.00 though.<br /><br />The bottom carb "draws" triple the air that the top two do. It's taking in a LOT more air, but I don't know why or how and the boat mechanic said he hasn't a clue either. It quickly fills the bowl and overflows while the other 2 don't.<br /><br />The mechanic did a link and synch on everything and I had already replaced all the lines an bulb. Everything checks out. I checked the carbs and theres no funny business with the float needle or clogged jets anywhere. I did a very thorough cleaning.<br /><br />What gives??? Why is this bottom carb sucking so much air?<br /><br />Compession was 120,120,115.<br /> <br />Reed valve maybe???

 

[roscoe]

Re: 85hp carb question

Welcome covert.<br />Pretty wierd.<br />Why did you need to have the timing set? Usually doesn't get out of adjustment.<br /><br />I would sure open it up and inspect the reeds.

 

[covert]

Re: 85hp carb question

I had already advanced the timing to help it idle since it was really struggling to keep a low idle. I also imagine with all the backfiring it may have been off anyway. I've seen smaller engines actually jump a tooth from backfiring the way my 85hp is.<br /><br />After sleeping on it I've decided to look into 3 things:<br /><br />Reed valves (It runs fine WOT but falls all over itself at low RPM...could be a stuck or cracked reed)<br /><br />Carb manifolds (Maybe the bottom is actually drawing the normal amount of air and the top two are the culprit. The rubber manifolds between the carb and engine may be dry rotted and cracked causing a vacuum leak.<br /><br />Crank seals (I'm not familiar with outboards per se' but I know most older two strokes can have leaky crank seals)<br /><br />Anyone know any inspection tips for reed valves/cage?<br /><br />Thanks

 

[covert]

Re: 85hp carb question

Well the reeds were all fine.<br />The carbs were all fine.<br />I replaced all the gaskets and gave em a good cleaning...AGAIN...and replaced every fuel line and the primer bulb.<br /><br />The botom carb still draws 3 times as much air as the top two and the motor spits and backfires like crazy.<br /><br />Heres the known GOOD items:<br />Good spark<br />good carbs<br />good reed valves<br />good gas<br />Good compression<br />good timing<br /><br />What else is there??? This thing is driving me nuts!<br /> H E L P ! ! !

 

[eurolarva]

Re: 85hp carb question

I doubt this is related however you might want to disassemble the reciruilation system and make sure the screen is clear and all the parts are working properly. Probably not related however I believe when this system plugs it creates more havic with the lower cylinder.

 

[roscoe]

Re: 85hp carb question

Check to make sure the plug wires did not get mixed up.

 

[covert]

Re: 85hp carb question

Plug wires are fine. Thats the problem...everything checks out. I'm lost.<br />I figured maybe it was "Lean sneezing" but I adjusted the carbs every which way but loose and still...NADA! Zip! Zilch! No marked difference in the symptoms.<br /><br />Whats next?...FOR SALE: 1988 Force 85hp

 

[roscoe]

Re: 85hp carb question

Those other 2 cylinders are drawing air from somewhere.<br />Got new gaskets on the intake and carbs?

 

[covert]

Re: 85hp carb question

New gaskets on the carbs and reed cages. Reset the float levels and stops. Checked each float for boyancy, cleaned and decarbed each jet and inspected the float valves. <br /><br />The reeds are all fine and within spec.<br /><br />Fuel supply is constant and remains primed.<br /><br />Good spark to each cylinder.<br /><br />compression is average.<br /><br />?????????????????????????????

 

[covert]

Re: 85hp carb question

Anyone have any ideas? Do force motors come standard with gremlins?

 

[RRitt]

Re: 85hp carb question

you sure about the reeds being good?<br /><br />I thought the 85's had a dedicated reed and carb for every cylinder with no sharing. If so, then there aren't very many things that match symptoms as described.<br /><br />First, if you had a vacumm leak big enough to cut your draw by 2/3rds per cylinder then I think you'd have found it by now. Back in a past life I used to do a lot of work on big sidedraft webers & solex with one barrel per. The easiest way to find a vac leak was to spray the carb body with aerosol carb cleaner. When you hit the leak the motor almost instantly changes speed. However, Roscoe could probably advise you of something better to use than Gumout. People here say that gumout destroys 2 strokes.<br /><br />So let's assume that 85's have one reed, one intake, one carb dedicated to each cylinder. And let's further assume no vacum leaks. You say the bottom carb draws 3x air? I'd bet dollars to donuts that it's the reeds. I can't think of anything else that could match all your symptoms. If you want a black/white test, then swap reed3 with reed2 and see if #2 becomes good. (assumming that your 85 has dedicated intake paths)

 

[Tim Wagner]

Re: 85hp carb question

Had similar problem with my 89 85.<br />I think your timing is off by quite a few degrees.<br />Double check it.