1976 Johnson 25hp Lean condition

[bob1123]

Recently got a 1976 25hp Johnson from a friend. He used the motor for several years fishing local lakes. The lower unit blew up on him. Clutch dog came apart and took out most of the lower unit. Chowdered up the gears and put a hole in the side of the upper housing. He got a bigger motor and give this one to me because he knows I like to fool with old OMC outboards. Here's what I've done to the motor so far:

1. checked compression ~125psi per cylinder
2. rebuilt carb with sierra kit after soaking in carb cleaner for 24 hours.
3. replaced lower unit with one from another motor that I resealed, pressure tests fine
4. strong spark on both cylinders
5. adjusted points to .020
6. replaced fuel lines
7. removed electric start components because the electric start bracket was cracked. Replaced electric start bracket with manual start bracket

I tried to run it in a can today. It was fine for about a minute and idling perfectly. After that it started sneezing constantly. Adjusting throttle and idle mixture made no difference. It seemed to sneeze no matter how much throttle I gave it. Is my crankshaft seal bad? How can I check my crankshaft seal? When I took the flywheel off there wasn't any oil/residue underneath the flywheel or on the ignition components. There did seem to be some oily residue underneath the ignition plate and on the top of the motor. Any suggestions?

 

[oldboat1]

There is a flexible "needle valve bearing" at the point of the l.s. needle valve. If a second one was put in from the kit (i.i., two in place), the mixture needle cannot be properly adjusted.

When you soaked the carb, did you fully open it up? (domed fitting on top and screw plug (h.s. jet underneath) removed from the bowl)

 

[bob1123]

There is a flexible "needle valve bearing" at the point of the l.s. needle valve. If a second one was put in from the kit (i.i., two in place), the mixture needle cannot be properly adjusted.

When you soaked the carb, did you fully open it up? (domed fitting on top and screw plug (h.s. jet underneath) removed from the bowl)

I actually totally missed the ls needle bearing. Didn't take the old one out (if there was one) or install the new one. I'll tear into the carb and check that. I did remove all three welch plugs and replaced with fresh ones after soaking. I didn't remove the high speed needle from the bowl (I've had issues getting those out) but blew it out to verify that it was clear.

 

[oldboat1]

I usually don't remove the jets either, as they are easily damaged. It sounds like you have it covered. Might be able to very carefully fish out the bearing with a piece of wire. The fool things often come out with the needle, so maybe try fitting the needle in again to see if it backs out. But don't break the point of the needle.

 

[bob1123]

I usually don't remove the jets either, as they are easily damaged. It sounds like you have it covered. Might be able to very carefully fish out the bearing with a piece of wire. The fool things often come out with the needle, so maybe try fitting the needle in again to see if it backs out. But don't break the point of the needle.

I checked in there. The old bearing had come apart and was in pieces. I fished out everything I could with a dental pick. I think I got most of it out. The hole for that jet is so deep it was hard to be sure. I put the new one in and installed the needle valve. Screwed in to a gentle seat then back out a turn. I'll see if that makes any difference.

 

[bob1123]

So I removed everything I could of the old bushing from the carb. Now the motor will start and idle just fine. Adjusted idle appropriately, motor responded to changes in low speed needle. Took the motor out on the lake. Only issue is that the throttle is really jumpy. I'll very slowly give it throttle but after I get past "Start" on the tiller hangle the motor will suddenly jump and rev. Makes it very hard to easilly come off plane. The motor wants to idle or really rev with no inbetween. I cleaned and greased the throttle components and under the ignition plate to make sure it wasn't binding anywhere. If I very slowly twist the throttle while looking at the roller that rides along the throttle cam, the throttle roller consistently rolls along the cam and doesn't jump. Any Insight? High speed jet problem?