1982 Johnson 90 hp carburator question.

[RBoyd1971]

The model number is J90TLCNB. Has power tilt and trim. I've noticed that if I trim the motor up a little while idling, it starts to cough and idle a little rough. If I trim it all the way down it idles perfect. I assume it has something to do with the float adjustment or needle. Anyone have experience with this. Can't decide if it's going lean or rich when tilting. I would assume lean since fuel is pooling away from the pivot point on the float and closing it off sooner? Is this normal. I've had some smaller motors sensitive to this and others not. How would you proceed with a fix of at all? I've cleaned the carbs a couple of times and they seemed nice and clean with all jets wide open. Floats were level when holding the carb upside down. Slight ring on the needle tip, but seem to be sealing of well. Thanks.

 

[racerone]

Perhaps you have already done a compression test.----If so post your numbers.

 

[RBoyd1971]

I just replace head gaskets on both sides. The two on the port side both were exactly the same: 132 top and bottom. On the starboard side they both were around 130. When I first started fooling with it, it had been sitting for years. Going off of memory, I believe starboard compression was 139 and 135 top and bottom respectively. Everything evened out after running it a while. Was getting a little water in the #1 cylinder is why I changed the head gaskets. Man I ran into a huge problem on one of the bolts closest to the center of the head, when a previously installed helicoil pulled out. Has to put an aluminum plug in the hole and rethread it. Wasn't enough threads for a helicoil to be reinserted. Was running about the same before all that.

 

[sludgeguy68]

I had this problem on my ‘89 110. Rebuilt carbs with no change. Wound up doing a whole re-bore due to scuffed cyls - wish I could tell you what the fix was in particular, but I can tell you it now idles fine trimmed all the way up now, so it’s not normal. My cyl heads were resurfaced, new fuel pump. Also saw my plastic carb bowls bowing a bit and sealed those up, but I believe yours are aluminum.

 

[RBoyd1971]

This motor has had quite the life. I noticed it has 0.030 oversized pistons, black head on one side, blue head on the other, white block and a gold crankcase cover. One of the heads had marks on it where a ring had broke loose at some point. You could tell it been repaired cause the cylinder or piston had no marks. I pulled the intake cover on the side of the block off and looked into where the crank was and you could see old scars where a part of a piston or something had come loose and was rotated through there. Piston and rings looked good through the ports. Rings were free. I don't think this motor has 1982 carbs on it though. I noticed the float bowl more closely resembles an 83 or newer. Has plugs for the high and low speed jets on both sides instead of one.