Honda BF90 cold start

chrisidle · 11 March 2017, 17:59

I have a Honda BF90 carburettor version, which will not start on the electric choke.

The electric choke is working. You can clearly see the choke solenoid operating the choke when the fast idle lever is held high, but whatever I do, it won't start like this.

If I use the manual choke and then I don't open the fast idle fully, the engine starts first time, every time.

It would appear that there too much throttle when the fast idle lever is held in the choke position.

Has anyone else had a similar issue or can anyone suggest a fix. I can use the manual choke, but it's a bit of a pain when I am by myself, which is most of the time?

Thanks

matata · 12 March 2017, 09:05

Ive got one of those. ( great engine ). Obviously the electric choke is doing something the manual choke doesn't.Does it idle ok when warmed up? The electric choke I have is progressive. Not simply on/off. Ive never started mine on the manual choke. The engine does seem very sensitive to the idle lever position, making it rev up very suddenly with small lever movements. Also you can't move the throttle while the electric choke is on.Is that the same on yours? I'm working on my boat this week. i'll have a look at the mechanism. Is there any particular aspect you want me to look at? Nik

chrisidle · 12 March 2017, 11:32

Thanks for the replay.

Once the engine has started, all is well. Idles ok, no issues.

My choke is not progressive. When you move the fast idle lever, nothing happens until the choke switch is triggered, which happens right at the top of the idle lever travel. As soon as you hit the switch, the choke solenoid engages and the choke is fully on.

As far as i can see when using the manual choke, the only difference is that it starts on a much lower throttle. Its as though the throttle / choke relationship is out, but u cant see any way to adjust it.

Thanks

mick · 12 March 2017, 12:44

Have a word with Mandy at Methley chandlers there Honda dealers and are very good to deal with

matata · 13 March 2017, 07:51

I'll check when my choke actuates but from memory I think the choke lever is only raised 3 cm. You can feel a resistance at about then and you can't move the throttle then. I'll know more at the end of the week. If there is something in particular you won't me to check give me a shout. Nik

matata · 16 March 2017, 13:57

Just been to the barn. I have a honda throttle assembly which has a fast idle lever which actuates the choke. I presume yours is the same.
The manual choke lever on the engine cowling progressively closes the choke flaps on the carbs. The carbs are all joined by a rod. If one choke flap closes they all will. As I said above this is a progressive nearly linear action.
Say the fast idle lever rests at the 3 o'click position.If I move the choke lever up progressively the throttle butterflys move slightly up to the 2 o'clock position. As I continue to raise the lever to say one o'clock suddenly the solenoid actuates which is an all or nothing action and this closes the choke flaps completely. My guess or the first thing I'd look at is as the fast idle lever is moved and yes the solenoid is actuated does this actually make the choke flaps move. Is there a chance a linkage has broken or become disconnected from the solenoid plunger and the choke flaps? Regards Nik