Carburetor Problems

[KatieRose]

I have a 2HP 1980 Evinrude that I found in the trash and rebuilt. I replaced the points, sparkplug, coil - rebuilt the carburetor, water pump Etc. The problem is that I can only start it in full throttle with the choke. After starting I can release cshoke and she will respond to hs needle valve adjustments and run great at wide open throttle. When I attempt to slow the engine down it will run at about half throttle but no slower. Also I have taken the carb off about 20 times and examined it but find no obvious defects save one. Where does the notch in the throttle plate belong? Next to the jets or opposite? I have tried both ways to no avail but would like to have it right before proceeding.

 

[Xcusme]

Re: Carburetor Problems

Welcome to iboats!

Well, from your text, it sounds like your high speed jet is open
, which is good. Sadly, it sounds, despite your best efforts, the slow speed idle circuit is still clogged or the Boss gasket isn't sealing in the carb.

Follow this link:
http://shop2.evinrude.com/ext/index.aspx?s1=4f76ddb5db91185fdbe9e919aa8784de

Enter your motor's info and look at the carb section. Part # 21 is vital. If it doesn't seal, the motor will draw in too much fuel directly from the carb bowl and you'll never get it to idle right. Did you remove, clean and replace part # 6? This small disc covers the idle jets. The jets below this disc must be open and clean.

The mixture needles should be adjusted per J. Reeves destructions:

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[KatieRose]

Re: Carburetor Problems

Dear Excusme, Thank you for responding to my problem. I did remove the plug in the low speed circuit and clean out the holes. The gasket in the bowl around the high speed nozzle appears to seal. I will examine this more closely when I next remove the carburetor. I can do this now blindfolded. I tried your recommended adjustments but still cannot operate below half throttle. I am still not sure if the throttle plate is upsidedown or not. I do not know the past history of this motor except that someone tossed it in the trash with a broken starter return spring. Frustration? The flat side of the throttle plate is currently on the opposite side (bottom) of the bore from the low speed holes in the carb barrel. This means that only two holes are exposed when the throttle plate is fully closed when looking from the engine side. If the plate is turned around 180 degrees all of the holes would be exposed in closed throttle. I do not know which orientation is correct. I have tried both with no success. I looked for a photograph or diagram but could not find one. What are your thoughts?

 

[tashasdaddy]

Re: Carburetor Problems

the flat side of the trottle plate goes to the engine side of the carb, also make sure the little hole as clear in the top of the carb. red circle in pictures, this is a larger carb. the shot is from the motor side of carb.

 

[KatieRose]

Re: Carburetor Problems

Tashasdaddy, Thanks for taking the time to send the photo. That is how the throttle plate is currently installed in my carb. Now at least that is eliminated as a contributing factor to my problem. I will remove the carb again and check the internal gasket to make certain that it seals when assembled and then report back. Thanks again.