lo speed idle screw

I bought a 2016 used bf8d from a dealer. The carb was so rich that I got a lot of black soot and some liquid fuel from the small rear exhaust, and some gas in the oil. I paid the dealer to adjust this. (thanks a lot). They said the idle screw was out 2 turns, and factory spec. was 1 1/2.
It ran much better, but I still get a little black soot, (no liquid) and some fuel in the oil. Its much better, runs good, but still too rich.

Can I just turn the idle screw clockwise 1/4 turn to stop this. The idle screw seems to be in the same place as NHfishermans new post on his carb.
I just run at slow speed to troll in a north Idaho lake. Thanks for the help, as I don't want to use this dealer again.

Check your thermostat hasn't stuck open , this can cause the motor to run too cold thereby not burning the fuel properly

Agree with checking operating temperature. If that's a cold water lake the combination of lots of slow trolling and powerhead temperature below 140 farenheit is going to cause poor combustion and carbon forming in the combustion chamber as well as oil dilution.

At what altitude is your lake? If it's above 3,000 ft. that could be a factor too.

Can you just open her up and take a boat ride every so often? Doing that will help keep the cylinder blown out some.

You can try messing with the idle screw but I don't think it's going to make much of a difference. Just remember to count your turns so that you can put it back if it gets worse.

jgmo said:

Agree with checking operating temperature. If that's a cold water lake the combination of lots of slow trolling and powerhead temperature below 140 farenheit is going to cause poor combustion and carbon forming in the combustion chamber as well as oil dilution.

At what altitude is your lake? If it's above 3,000 ft. that could be a factor too.

Can you just open her up and take a boat ride every so often? Doing that will help keep the cylinder blown out some.

You can try messing with the idle screw but I don't think it's going to make much of a difference. Just remember to count your turns so that you can put it back if it gets worse.

Click to expand...

Thanks for the reply, the lake is 1600 ft elevation, and the water is not very cold. Part of the problem is continued slow trolling. However when the dealer closed the slo idle screw 1/2 turn, it reduced the soot and fuel in the oil by 75%. so I thought a little more would stop it. I agree to be sure I can return it to its original setting. I just wondered if I got it too lean if that would be a problem, other than running poorly.

You need to turn the idle mixture screw in until it starts to misfire, then back it off just enough to where it smooths out, no more. This is only the idle mixture you are dealing with and not near as critical as high speed/high load conditions, where valves burn, etc. if it's too lean. You want it as lean as possible at idle. If you continue to notice gas in the oil, you may have a leaking fuel pump diaghram.

Thanks OldHondaGuy. I pulled the thermostat and it opened at140 Deg. When I got it the motor was way rich, liquid and soot in the exhaust. The dealer closed lo idle screw 1/2 turn and it helped a lot, but I still got 1/2 inch more liquid on the dipstick in 4 hrs. trolling. Your way to adjust it sounds perfect. I'll do it when I go back to the lake on Aug. 12 for a few days.

Whew! 1/2" in 4 hours??? THAT'S a BUNCH! I'm guessing you're going to find OldHondaGuy hit the nail on the head when he said you're fuel pump is probably leaking.

Ummm, yeah, 1/2" in 4 hours, you need a new fuel pump.

Unless the oil looks like a milkshake... then we have a different problem.

Thanks guys, The oil looks just like regular oil, I can't tell the difference except the oil level rises on the dipstick. I'm going to the lake aug. 12-14 and will close idle screw as oldhonda guy recommends. If I continue to get oil, I'll change the fuel pump. woudn't think the fuel pump would be bad on a 2 or 3 year old motor?? who knows.
I'll post my results after I return.

Be assured that it's NOT just like "regular oil" anymore. If it has gasoline in it, which it likely does, the lubrication qualities of that oil have been SEVERELY DEGRADED!

The more you run it with that contaminated oil the more you are genuinely risking MAJOR ENGINE DAMAGE! Especially in the area of the crankshaft main journals and camshaft bearings.

I would not recommend running it AT ALL until you find and repair the source of contamination.

Just sayin'.

jgmo said:

Be assured that it's NOT just like "regular oil" anymore. If it has gasoline in it, which it likely does, the lubrication qualities of that oil have been SEVERELY DEGRADED!

The more you run it with that contaminated oil the more you are genuinely risking MAJOR ENGINE DAMAGE! Especially in the area of the crankshaft main journals and camshaft bearings.

I would not recommend running it AT ALL until you find and repair the source of contamination.

Just sayin'.

Click to expand...

Thanks jgmo, your right, I just changed the oil and filter again, and will adjust the lo idle as low as possible before I run it. I'll run it for a few hours on tue. the 13th, then I'll know if its stopped the fuel leaking or not.

Idle circuit will not contaminate your fuel no matter how it'd set, only the fuel pump can do that.

I took the boat to the lake on the 12th. I ran the Honda for 3 or 4 minutes, then adjusted the slow jet. This is on top of the carb. left side. I turned the small screw 1/4 to 1/2 clockwise, and the screw fell off. It looks like it twisted off, no threads, but rough on the end. This piece is about 1/4" long with a tiny washer attached to the end and then tapers smaller, and this is where it seems to have twisted off. I trolled 2 days, 12 hours with no gain on the oil dipstick.

I didn't notice a change in the engine when I twisted this screw off. This doesn't look anything like a jet screw. What I have now in the hole is a flat round brass plate about 3/16" dia. with a tiny rough spot in the center, where the screw was. I can turn this plate slightly with a pick to know it can move. Should I try to pry this plate out to reach the jet screw. All this stuff is on the surface, outside of the carb.

The motor seems to be running fine, should I quit while I'm ahead. Thanks all of you for your advice. This seemed simple to start.

Yes! Quit while you're ahead! But keep a weather eye on that oil level.

What you screwed off is the "dummy" top of the idle screw. The idle screw is the flat, brass part you now see. It can be removed with sharp ended picks but if all is well, why bother?

The screw was made intentionally to snap off to keep it from being over tightened and ruining the taper seat. It was one of the first attempts at "tamper resistance" for these carburetors.

If it aint broke (completely anyway) don't futz with it.

Also, if you do ever decide that you have to remove the screw, use your pick to turn it counterclockwise many turns....you'll notice that it won't back out of the hole. Turn it as much as you think it needs to be turned to have it loose and then double the turns to make dang sure.

The reason is that there is an oring under the flat head that seals the idle passage from dirt. But the oring also acts as a locking device not allowing the screw to back out. Once you are very sure all the threads are disengaged you can then use something like a pocket screwdriver to pry it up and out.

jgmo said:

Also, if you do ever decide that you have to remove the screw, use your pick to turn it counterclockwise many turns....you'll notice that it won't back out of the hole. Turn it as much as you think it needs to be turned to have it loose and then double the turns to make dang sure.

The reason is that there is an oring under the flat head that seals the idle passage from dirt. But the oring also acts as a locking device not allowing the screw to back out. Once you are very sure all the threads are disengaged you can then use something like a pocket screwdriver to pry it up and out.

Click to expand...

Thanks jgmo for explaining what I have. The motor is running fine, I'll keep aware of the oil level. If I knew what I was doing I wouldn't have tightened it that last little bit to make the motor run rough. I couldn't believe that the little screwdriver could twist it off.