Honda bf 40 loses power after 30 sec on plain

Hi
I have a 2007 honda bf 40 with carburatores
First I had an electrical fault because the cable for the power start was rotten out in the main power connector, that took a while to find
The engine starts exellent, runs fine on idle but once it gets to plain after aprox 30 sec it loses power and starts working on minimum but the engine starts shaking, after lowering the gas back to neutral it works fine

it does not go into limp mode because that lowers rpm from 6000 to lets say 3000
this is complete power loss and it allows me to get back to plain instantly and then over again

no warning lights came on, oil pressure light is green and the overheat light stays off, I dont know if any warning sounds come on because my speaker doesnt work
I checked thermostat, even tried without it, water on the tell - tale is normal warm, not hot
checked fuel pressure

I would be grateful for any advice, please help

Hi,


Whilst I don’t have any experience specifically with the bf40 I have had many motors that have carburettors.


The first thing I would do is take the carburettors off, strip and clean them. Specifically, the jets, I suspect you have a blockage. Clean out the jets using compressed air, don’t be tempted to poke anything through the small holes.

I'll try that first
Could A dirty carb show those simptoms? It seems like clock wise precision, it seems the same every time

I am worried that it could be maybe something electrical

Sounds like a fuel issue here as well, but it could be anywhere. SOMETHING is allowing air to be sucked into the system or restricting fuel flow causing the engine to starve when fuel demands are no longer met. A plugged/shut off fuel tank vent for instance, would act the same way. A tell tale there would be the primer bulb collapsed/sucked dry. When it does this, you could check that primer bulb, and if it's NOT collapsed, try pumping it to see if that improves the performance (hopefully you'll have somebody giving you a hand here!). You mentioned you "checked fuel pressure". How was that done?

I tried with another fuel tank that i know for sure is good and I tried pumping the primer bulb while driving, same effect
I didn't follow up the fuel sistem up the motor
The primer bulb had pressure but i did have to pump 2 3 Times for it to be totaly hard

If it is an air leak somewhere these are a nightmare to find

RE:sucking air, generally if they are sucking air it's at either end of the fuel line, and that area will be wet with gasoline as a rule, or maybe a fresh fuel stain if it's been sitting. The other places might be a cracked/broken fuel filter, or possibly the pick up tube inside the fuel tank, but you've already eliminated that with the tank change. It's not too unusually to get 2-3 squeezes on that primer bulb when the motor is running right.

I'll check those places for any fuel stains/leaks
Is there anything else I could check that could cause this issue?
Did you ever hear about these simptoms?

I go with easy stuff first. If what we've already talked about doesn't produce anything, it'll be time to get into the carbs.

So you definetly think this is fuel related problem

Not a doubt in my mind....