Machanics are stumped

[pulpwood]

Have a 1985 70 evinrude will idle all day once choking a couple of times while increasing thottle past low speed will run great full throttle. I have clean carbs six times every passage clean have good spark on all three cylinders and compression good. was told might have cracked low speed jet but can't see inside of high speed jet tube what could my problem be.Also have tried electric fuel pump still same problem and also did link and sinc timing looks good.

 

[robert graham]

Re: Machanics are stumped

The "choking" sounds like a lean mixture at that point in RPM range. Did you clean carbs in ultrasonic bath or overnight in carb cleaning solvent, wires and air through passages? If you dead sure they're clean, then must be some other fuel delivery issue. How's your fuel tank pick-up, primer bulb check valves, fuel hose quick-disconnect, fuel pump, fuel filters, fittings, floats set correctly? When you're choking you're just overcoming that lean condition. Good Luck!

 

[pulpwood]

Re: Machanics are stumped

I have bought new fuel tank new hose and primer bulb replaced all hoses going to each carb I tried an electric fuel pump yesterday but same outcome I bought a carb kit in the gallon can soaked each carb for six hours run a small wire thru every passage and blowed air thru them also did decarb on engine

 

[psteurer]

Re: Machanics are stumped

Assuming your carburetors are properly linked and synced, it sounds like you may have a clog in the idle circuit. Did you remove the core plugs when you did the carburetor rebuilds? These are the silver discs about 1/2 inch in diameter. The plug that sits on top of carburetor covers the passage where the fuel flows at idle. There may be some crude blocking 2-3 small holes that lead into the barrel of the carburetor. To remove to plugs, get a nail or ice pick and puncture the plug and then pry it out (don't go too deep). Look for crude in there and make sure the small holes are clear. To replace the plug, use the parts you got in your carburetor kit. Put the plug in convex side up, then get a wood dowel or socket from your socket set that is smaller than the plug. Put it on the plug and tap it with a hammer. Finish the job by sealing the plug with some clear nail polish.

 

[pulpwood]

Re: Machanics are stumped

no I didn't pull out these plugs but there were screws on each end of carb with jets in each that I removed and was able to see the end of the low speed jet when I pushed the wire thru I could see it I don"t know of any passages that was not getting air thru but if you think that will help I will try that.

 

[Joe Reeves]

Re: Machanics are stumped

If what you are e experiencing is a rough idle, sounds like a mild backfire, a spitting back thru the carburetor scenario...... that spells "lean mixture" normally due to a fouled carburetor (jet) as Robert explains above.

With the engine running and with the carburetor face plate removed, stick two fingers into a carburetor throat, acting as a manual choke. When the engine smooths out, you've found the offending carburetor.

 

[pulpwood]

Re: Machanics are stumped

My idle sounds right have let it idle for thirty minutes with no problem

 

[tashasdaddy]

Re: Machanics are stumped

have you removed all the jets with the special tool. have you blown out both pick up tubes in the center of the carb? did you use a carb kit, replace float needle and seat, all gaskets, including between intake and carb????

 

[pulpwood]

Re: Machanics are stumped

Yes I have blown every inch of carbs six different times I have removed every jet exept for pickup tubes as they are pressed in I have us carb kit by soaking I have used presserized carb cleaner by spraying thru every passage and blown out by air I have made sure floats were adjusted per procedures in manual.The idle jets are not adjustable look to be in good condition

 

[ezeke]

Re: Machanics are stumped

Air silencer on and tight?

You might want to check the high speed jets; there was a production change during the year with different carburetors using different high speed jets.

 

[MudLake]

Re: Machanics are stumped

Have a 1985 70 evinrude will idle all day once choking a couple of times while increasing thottle past low speed will run great full throttle. I have clean carbs six times every passage clean have good spark on all three cylinders and compression good. was told might have cracked low speed jet but can't see inside of high speed jet tube what could my problem be.Also have tried electric fuel pump still same problem and also did link and sinc timing looks good.

I don't know the engine but I know the 2 cycle concept.

I can only presume this is a 2 or 4 cylinder engine. That being said you have two seperate chambers on the carb side of the engine.
Can the seal be weak between these to chambers thus causing the pressure to equalize and not forcing to mixture around to the piston.

I sure some older engine mechanics should have thought of that.

cheers

 

[pulpwood]

Re: Machanics are stumped

Thanks for the responses I'm going back and try again and look for any leaks around gaskets and carbs a machanic around home said could possibly be crack in low speed pickup tube that I can't see, so it's back to the drawing board.

 

[Lone Duck]

Re: Machanics are stumped

Two ways to check intake gaskets. get a spray bottle and fill it with water. Spray around carb and intake gaskets. If it dies, you've found it. Or you can spray with fuel. If it revs , you've found it. If nothing happens , thats not the problem.

 

[coolguy147]

Re: Machanics are stumped

i would use fuel.... for spraying. water id keep away from electronics...


would crankshaft seals or bad reeds make a lean condition?

are you mixing 50:1 tcw-3 gas oil mix is it pre-mixed?

 

[reeldutch]

Re: Machanics are stumped

somethimes the trothle shaft will wear out the seals and cause an airleak.

can you indentify the cylinder that is running lean?

 

[Gary H NC]

Re: Machanics are stumped

Well,He did not remove the core plugs on the carbs and replace with the ones in the rebuild kit.That would be the first thing i would do....Just saying..
There could be crud in there.Thats why the kits have new ones....

 

[Fl_Richard]

Re: Machanics are stumped

Spray fuel - that sounds risky! Really?

I regularly hose my entire engine. How else do you get the salt off?

 

[Fl_Richard]

Re: Machanics are stumped

He said he didnt have plugs - screwed on covers

 

[Tim Frank]

Re: Machanics are stumped

Well,He did not remove the core plugs on the carbs and replace with the ones in the rebuild kit.That would be the first thing i would do....Just saying..
There could be crud in there.Thats why the kits have new ones....

Bingo.
He did not remove them because he thought he could get at all passages without doing so.
Maybe his carbs are like that, but I've never done a carb that had welch plugs that didn't need them removed and replaced to do a proper job.

...on the other hand, would mechanics miss anything that obvious??

 

[Lone Duck]

Re: Machanics are stumped

Bingo.
He did not remove them because he thought he could get at all passages without doing so.
Maybe his carbs are like that, but I've never done a carb that had welch plugs that didn't need them removed and replaced to do a proper job.

...on the other hand, would mechanics miss anything that obvious??

A lot of guys work in shops . And keep changing parts till it runs. Thats not a mechanic