2001 Honda BF90 slow to accelerate

[JoeGunz]

I've got a 2001 Honda BF90 that's slow to accelerate. If you increase the throttle slowly from idle to 2000 rpm it's OK. Sometime coughs a bit. If you increase throttle a little faster it bogs down and can stall. After 2000 it runs great. It's done this for a long time and always runs fine otherwise. I've synchronized the carburetors, changed the plugs , adjusted the valves and it's still about the same. Any suggestions?

 

[Solmar]

Re: 2001 Honda BF90 slow to accelerate

its most likely a carb issue. Im thinking accelerator pump or idle(low speed) jet are gummed up. above 2000 or so your suckin through your main jet. accelerator pump gives you an extra shot of fuel when you spike the control. Has the motor sat for awhile. Fuel starts breaking down in as little as 9 days. Do you have a water/ seperator installed? drain it in a clear container to see if there is water at bottom, and smell it too. CARBS CARBS CARBS

When you synched the carbs did you check intake vaccum on each manifold or just the throttle plates the carbs? If your not some carbs are enjoying more air than others and will run poorly but at all speeds...

 

[JoeGunz]

Re: 2001 Honda BF90 slow to accelerate

Thanks for the reply. The motor has fresh gas with marine stabil added. I've always drained the carbs and the tank when I store it for the winter. It's got a new Racor water separator and fuel filter inside the motor. The carbs were sync'ed using a "Carbtune" gauge connected to the manifold ports. I've checked the throttle cable adjustment and the adjustment of the acceleration dash pot. I've been suspicious of the acceleration dash pot and check valve too. So how do you check to see if that system is working??

 

[hondon]

Re: 2001 Honda BF90 slow to accelerate

The check valve is a one way valve with an arrow on it.Use some rubbing alcohol and a syringe and with little effort that alchohol should flow freely one way and deadhead the other.The dashpot takes a little observation and perhaps adjustment.When you stand on the throttle then back off suddenly that dashpot should hold the throttle somewhat open momentarily to prevent stalling,then relax and return to normal idle position.Keep in mind that this is not an engine that likes to be stood on.

 

[JoeGunz]

Re: 2001 Honda BF90 slow to accelerate

This morning I looked at the carb synchronization again with the vacuum gauge set. They looked OK, but I noticed that #2 and #4 carbs would cause the vacuum gauge to fluctuate allot when the motor coughed. #1 and #3 were steady. First #2 then #4 would drop to 0. Seems like this maybe an important symptom! The dash pot for the acceleration system moved a bit when the throttle was increased, so it seems that maybe working. I'll check out the check valve too. That sounds like a good diagnostic. What do you thnik about the cough/vacuum sistuation?

 

[JoeGunz]

Re: 2001 Honda BF90 slow to accelerate

The check valve is a one way valve with an arrow on it.Use some rubbing alcohol and a syringe and with little effort that alchohol should flow freely one way and deadhead the other.The dashpot takes a little observation and perhaps adjustment.When you stand on the throttle then back off suddenly that dashpot should hold the throttle somewhat open momentarily to prevent stalling,then relax and return to normal idle position.Keep in mind that this is not an engine that likes to be stood on.

This morning I looked at the carb synchronization again with the vacuum gauge set. They looked OK, but I noticed that #2 and #4 carbs would cause the vacuum gauge to fluctuate allot when the motor coughed. #1 and #3 were steady. First #2 then #4 would drop to 0. Seems like this maybe an important symptom! The dash pot for the acceleration system moved a bit when the throttle was increased, so it seems that maybe working. I'll check out the check valve too. That sounds like a good diagnostic. What do you thnik about the cough/vacuum sistuation?

 

[Solmar]

Re: 2001 Honda BF90 slow to accelerate

Dont run to far with the vaccum gauge reading. you may have something solid if two is dropping first but its more than likely a fuel delivery problem. try squeezing the bulb as an assistant revs it up and keep pump consistently to keep bulb hard. does this help? may be as simple as fuel pump diaphram. If for sure 10 out of 10 times cyl.#2 dies first then I would focus on carb and what makes fuel/air circuits function.

 

[Low_Siouxnarrows]

Re: 2001 Honda BF90 slow to accelerate

I had the same problem. It would hesitate but run fine once I got going. Had the shop look at it a few times no luck. I added a bottle of "Sea Foam" into the gas. Unbelieveable difference. Give it a try, worked great for mine.