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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15612
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Is this normal??? BR

Resolved Question:

Is this normal???

BRAND NEW motor. Took it out for the FIRST time today and it wouldn't start. I replaced the plug and it now starts.

I have never had a honda product run this rough.
Submitted: 5 years ago.
Category: Boat
Expert:  Jason replied 5 years ago.

My name is XXXXX XXXXX I will be helping you today. Most questions will involve troubleshooting, and usually take many posts back and forth. Post back with questions as needed.


By normal are you talking about the vibration/shaking at idle?

Customer: replied 5 years ago.
Yes. The idle seems very rough. Also, I don't understand why I would have a fouled plug on a brand new motor.

Every honda product I ever owned has been super reliable and has run smooth as silk.
Expert:  Jason replied 5 years ago.

That shakey idle is pretty typical, as it is a single cylinder engine. There is nothing wrong with the engine as long as it smooths out when you rev it up. If you were to compare it against another BF5 (and you should do so if you do not believe me) you would see they are the same.

As far as it not running on the original spark plug goes. If it was ever transported the wrong way and oil got to the plug that would cause it to fould out. Also, you can have bad spark plugs, even new out of the box, that is not all that uncommon either. But from your youtube video, it does look normal. If you youtube search videos for another 5 hp you would see they are the same as yours. If you youtube search for BF8's you would see how much smoother they are because they are twin cylinder engines, and twins idle much smoother than single cylinder engines.


Feel free to post back with questions



Customer: replied 5 years ago.

I still think my motor is awfully rough comapred to these. I have owned honda products in the past and this is the first one i've ever had trouble with.

I ran the motor on a stand before I took it out and it no fouled plug. 2 weeks later ...first time out and no start.

I've done some research and there seems to be problems with the BF5's because of the very small carb this true?

I just checked the 2nd plug and it is dark and dirty after just a few minutes of runtime. Could it be that the ring hasn't seated yet?
Expert:  Jason replied 5 years ago.

The first video the motor is above idle, so it is smoothing out like it normally would.

The 2nd one looks like it has vibration to me.

Look at this one;

Before he throttles it up you can see the vibration.

Same here,


Now you can try adjusting the idle mixture screw, that might clean it up a little bit, and get rid of some of the vibration. But you will always have some vibration. That is going to be the nature of the beast with a single cylinder 4 stroke engine. At the same time, the idle mixture screws are capped over by the factory because the EPA mandates that they are. You would have to drill and pull the cap. Being a brand new engine you would probably loose your warranty. So it might be in your best interest to bring it back to the dealer and have them do it, that way it does not affect your warranty.

Also, as far as the carb jets go. That is an issue with all 4 stroke engines. The carb jets are tiny. And the smaller the engine the smaller the carb jets are.


The rings are likely fine, as you typically do not see issues with rings on the hondas.


Post back with questions

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