1987 BF8AH honda 8 hp will only run at low speeds with choke

Just purchased unit. I was tol

Just purchased unit. I was told unit did not like to idle. Cleaned carb and ran cleaner through. Unit will run allday with 3/4 choke all a slow idle. Will run a high throttle in gear with no choke. Has anyone had problems like this? It seems as if the idle circuit is not working and the carburetor has an internal bypass problem.

"Hi Jim,
When you say that yo

"Hi Jim,
When you say that you cleaned the carb, do you mean that you took it apart and cleaned it? If not, that's probably what you need to do. It should be disassembled and the jets scrutinized very carefully for any debris.

Then you need to sit down and study all the little nooks and crannies and passageways to familiarize yourself with them.

With the jets removed, take WD-40 or a carb spray with it's little straw and fire it up into the passageway that the jet feeds. At the same time, with the throttle plate fully open, watch to see that the main, intermediate and the idle holes in the carb throat are dumping the fluid. The pressure from that can should have them all puking liquid at a fair clip. You can backflush them by putting the straw over each tiny hole and spraying. Sometimes I use up a couple of cans of carb spray and a can of WD to get one good and clean. Remove the idle set screw and blast that passage out as well. Also any hole you find that you don't readily know where it goes, figure it out (so you'll know) and then blast it with the cleaner.

Check the float hieght (0.388-0.400 inch).

Check the play in the throttle plate shaft to see if it might be too loose and letting air enter the carb there. That could be a problem with any old carburetor that has had that shaft rotated thousands of times. It will cause a lean condition. It needs a bit of play so that it can rotate freely but that's it.

Other things to look for that would make the engine a "choke baby" would include:

Out of time, timing advanced. I see a lot of older engines that someone has worked on and didn't get it timed correctly.

Check the valve lash to make sure the adjustment is in spec to fully open the intake valves. Not common but possible. On most older engines it is usually the case that the valves are too tight. Either way, they should be checked and adjusted. Closely inspect the cam lobes for wear.

Something as simple as a warped mounting flange or torn intake gasket could cause you to suck air and run lean. That 's all I got for now."

I have a 1985 honda B100L 10 h

I have a 1985 honda B100L 10 horse that had the same problem with. consistently having to run at half choke. I would clean the carb. and then it would run beautifully at trolling speeds for most of the day. Then suddenly I would have start using the choke again. When I got home I again would take the carb apart and clean it. I then replaced the inline fuel filter (witch was only a few months old) with a new filter. Ran great for about two fill up's of the fuel tank then the choke problem showed up again.
I again thoroughly cleaned the carb and it ran great until the next fill up. I then clean the fuel tank and hose and replaced the fuel filter with a new one again and I have had no more problems for the past two years fishing. Great Trolling motor!

"Agree with Paul - eliminate t

"Agree with Paul - eliminate the obvious stuff first. You can clean those carbs all day, but it's a waste of time if you have bad fuel, a clogged breather or pick up tube. or an air leak in the fuel line.

First eliminate the possibility of a dirty tank and make sure you have fresh, clean gas.

Make sure the breather cap on the gas tank is working and make sure the end of the fuel pick up line inside the tank is not clogged.

Then make sure the line from the tank to the pump-up bulb has no cracks or leaks, then check the line from the pump up bulb to the onboard filter. Run a clear plastic line from the pump-up bulb to the onboard filter to look for air bubbles while running the engine.

Once all that has been cleared, then go after the carbs as J. Dixon described."

"Paul and W D,
You both make

"Paul and W D,
You both make a very good point. Sometimes I overlook beginning at the beginning."

"I agree with the others, but

"I agree with the others, but would add that the idle jets on these engines are extremely tiny. I usually drill them out at least .003in. This is frequently necessary for an older engine."

I usually clean out the idle j

I usually clean out the idle jet with a single copper strand from some "lamp cord". It requires something to hold the wire with (tweezers or a needle point pliers).

One other thing to check... Some older after market hose/primer bulbs had a lining in the hose that was solvent in ethanol.( Don't ask how I know this !!!)

"All that has been said is tru

"All that has been said is true.

Although short cuts do not always work...if you just have a little debris in the idle circuit, you may want to try removing the screw on the top side of the carburator. See part #10 in this diagram. It gives you access directly to the idle/slow speed circuit.



Just shoot some brake clean, solvent or whatever was discussed above into the passage. Then take a little compressed air (the compressed air in a can that you use to clean your computer will work) into the hole. Put the screw back in and give it a try.

You have abviously picked up some debris, so all of the other posts will also apply. This just may keep you from having to take your carb apart.

Also, the idle mixture screw (#9) should be turned out about 1 3/4 turns for initial adjustment. Improper adjustment of this screw could also be your trouble."

Where is the carb. drain plug for removing the gas in same to put up for storage in the above diagram. I suspect it is item 7.

It's item 8, see 'zoomable' diagram on this parts catalog from Boats.net.

Thank you pilotart for your reply and link.
Much Appreciated!