Honda Idle Problem

[FarleyNB]

Hello Folks,

I have an older Honda 15 hp 4-stroke which will not idle. It will run with the choke on or with throttle, but will not idle at all. I'm also having a hard time identifying the year it was manufactured.

The housing is the old white one and says it's a 9.9, but I'm aware that these were built as 15 hp motors and had a restrictor bolt in the throttle assembly to limit the revs.

The Model Numer is BF15A
The Serial Number is 1002657

So first, I'd appreciate it if someone could help me to establish the year of manufacture.

Troubleshooting so far:
-ran engine with throttle and 3 gallons gasoline mixed with Seafoam
-new plugs (both show good fire)
-carb removed and jets cleaned, twice

Still the problem persists. I started to take the fuel pump apart today, and discovered that once the pump was unbolted from housing, the bolts holding it together are a star-shaped (torx-type) head with a small tab in the center. I have torx keys, but not the ones with a hole in the center for this type of bolt.

So does anyone have a magic bullet for this or info on date of manufacture? I don't know whether to search out special tools or take it to a shop, and was hoping someone on here has dealt with this before.

Thanx in advance,

FarleyNB
-new fuel filter

 

[ahicks]

My suggestion would be to clean the carb, again. This time, note the tiny holes in the carb bore very near the throttle plate. These supply the fuel to the motor when the engine is idling. For some reason, they are not getting fuel. Figure out why and you'll have the answer to your headache.

I've never had one of those carbs apart, as I work on just the bigger ones you generally see used on the back of pontoon boats. That said, I can almost guarantee you are missing a plugged up jet when you are cleaning. Don't try to soak the parts expecting them to be clean at the end of the cycle. To find this culprit, you are going to have to do a very close inspection and while you're at it, blow compressed air (or carb cleaner) through every passage.

BTW, when I started doing these on the bigger motors with 3 and 4 carbs, it was not unusual to have to go back through them, again, to find the spec of dirt that was making them run rough. When it comes to the frustration that causes, I get it!

Take your time, and be thorough! -Al

 

[MattFL]

Small 4 strokes have tiny low speed jets. Seafoam isn't going to help. As said above, you need to take it back apart and verify that none of the tiny little jets or holes are plugged up. Shoot carb cleaner through it followed by compressed air (wear goggles!). If you have an ultrasonic cleaner then give it a good soaking in there for a while, nice and hot.

 

[km1125]

I just went through a similar issue with a Honda 8HP. Does yours have a keihin carb? If so, it could be the same issue. I took mine off and cleaned it several times, even chasing every single passage I could with a wire or micro brush. ALL were clear but there is one little place that's capped with a welch plug (little aluminum disc) and that's were I think my blockage was. It was affecting all the low speed circuits but not the main jet. I could run at full throttle all day and it was fine, but anything less than 1/2 throttle and the engine would die. After I had chased and sprayed every passage, I escalated to soaking the carb in dip. 4 hrs didn't do it, 8 hrs didn't do it, but a full day (24+hrs) and it was back to working like brand new.

 

[FarleyNB]

Thanks for the replies guys- I guess I'll pop the carb off again for a more thorough cleaning. I will post an update with results.

 

[MattFL]

If you don't mind spending a few bucks on a new tool for the garage, I've had fantastic luck with a good ultrasonic cleaner. You can get a small one for around $100 on Amazon or eBay. I've had good luck using both simple green + water, and WD40 as solvents. So far I've used it with old fishing reels that were full of old hard grease, and with the carburetor off of an old (1986) minibike that now runs like a top. The combination of the heat and the ultrasonic impulses really gets things clean, including the places that are difficult or impossible to reach manually.

 

[FarleyNB]

Problem resolved!

Thanks everyone for your suggestions and input.
Following advice posted above, I took the carburetor apart and gave it another very thorough cleaning. Like before, I used normal carb spray- the only thing I did different was to use compressed air to blow out all passages after using the spray. Really took my time with fine wire on the holes near the throttle plate (thanks ahicks for that one), and noted better jet of carb spray after that. Mounted it back to the outboard, and it started and would idle like brand new.

 

[ahicks]

Love those happy endings!

Good job at maintaining your patience to see that issue through....