Backfiring out the carb

this is how i set mine up, mine is a 10 horse, smaller carb, but same family of carbs. so, it should work for you.

i removed the fuel pump that was threaded in, and put in a 1/4 inch brass nipple.


i got a new style Mikuni pump from "jim micco and sons on ebay" for about 15 bucks



ran a line from the crankcase breather, about 6 inches long, then another from the filter to the intake on the pump, and then another, about 12 inches long to the carb.




this setup has never let me down, even hanging freely like it is. when i paint it for the buildoff, i plan on fastening it to the shroud, and making everything pretty

What model fuel pump is that? And the flywheel key is in good shape and not sheared

willis923 wrote:

good catch doc, i completely missed the flywheel key. thats why we have forums though, teamwork

Precisely.

Dipshaw87 wrote:

What model fuel pump is that?

Those pumps appear on all sorts of OEM applications, including the Vanny twins.

Quote :

And the flywheel key is in good shape and not sheared

Well, pity that the problem's not yet solved. however- eliminating it as a possibility is actually forward progress, even if it doesn't feel like it.

Oh ok so any oem fuel pump would work? And yea it honestly feels like I'm getting nowhere on this thing lol

Pretty much any diaphragm style pump, that will deliver less than 5psi, or you'll run into flooding issues.

Ok. Now I have a question am I able to use a completely different carb like a kohler #26 or something else on this engine? Or should I just look into getting a whole new walbro carb if the fuel pump idea doesn't work

Fitting a non-stock carb leaves 4 hurdles to jump.

1)Mounting. If it doesn't bolt right up in the correct orientation, you gotta get creative.
2)Venturi size. Too big is just as useless as too small.
3)Jetting. Odds are pretty good that you'll have to play with the mixtures. Easier on some carbs than others.
4)Governor linkage- if the carb didn't come off your engine type, 99% chance you're gonna have a real problem with the governor.

Never thought of that lol ok let me try the fuel pump idea. I'll see if I can get one off amazon or somewhere cause I don't have any laying around here

Is there any fuel pump I should stay away from?

None that I can think of. I like these, because they are rebuildable. ---> http://www.arcracing.com/servlet/the-23/pulse-fuel-pump-Mikuni/Detail

Have you used that pump before?

i meyself havent, however, mikuni is one of the most respected names in fuel delivery systems

Ok so let me ask this. I'm not that good with old style carbs at all. If it's running to lean then it backfires out the carb and if it runs rich will it backfire out the exhaust? Can it be backfiring because of the valves needing adjusted?

Dipshaw87 wrote:

Have you used that pump before?

Yup. Also use the one Willis showed.

If intake valve is not closing completely, or out of adjustment, it can cause backfiring in carb.

What model number was that one that Willis showed? And I thought about that but I'm not sure of the specs for the valve lash

Would a bad float have anything to do with this?

a float could be sticking or hanging up, not allowing it to drop all the way and restricting the fuel flow into the bowl. before you go buying parts, i'd take the bowl off, inspect everything one last time. THEN spend cash on parts. in regards to the fuel pump, i dont have a model number. theyre all the same anyway.

Ok I've taken the carb off 4 times and still I don't know what all to do. But I'll work on it more tomorrow and keep you guys updated. I thank you guys very much for helping me cause I don't know what I'm doing lol

Doc Sprocket wrote:

Fitting a non-stock carb leaves 4 hurdles to jump.

1)Mounting. If it doesn't bolt right up in the correct orientation, you gotta get creative.
2)Venturi size. Too big is just as useless as too small.
3)Jetting. Odds are pretty good that you'll have to play with the mixtures. Easier on some carbs than others.
4)Governor linkage- if the carb didn't come off your engine type, 99% chance you're gonna have a real problem with the governor.

All do-able, if ya have years of experience with engines like some here do... not something I'd recommend to the beginner.

Here's a video of the bolens

https://youtu.be/7-unQLWByeQ

I'd check the valve lash.... I'm thinking it is an overhead valve engine. I think the valves are gapped too small and your intake is staying open once the engine warms up


Forget the carb and governer for now, and check the basics... valve lash first, then timing

Just my two cents

What are the valve lash specs for that engine?

Google can tell ya quick. 4 to 10 thousanths on the OH16. 5-6 thousanths is a good starting point for most OHV small engines.

(ref. http://outdoorpowerinfo.com/engine_specs/tecumseh_valve_gaps.asp ) ( ... The last entry on the page)


this vid shows correct governer and carb linkage

https://www.youtube.com/watch?v=l1_QOJt_0_g

Thanks! Will these specs work for the 16 hp?

it shows 13.5 - 17 hp, so yeah