Guys I bought this motor on a Triton 1650 last fall. It had 2 hours on the motor, so it was still brand new, but something hasn't been right with it since I got it. I only took it out twice last winter because when I'd get to about 3/4 throttle or punched it, it would start dying or sputtering and back firing. I've put on new fuel filter, pulled the revlimiter pill, changed gas a dozen times, keep Stabil in it when not using it, adjusted the idle screw....nothing's helped. The thing is, it doesn't start doing it as much till the engine is good and hot. Anyway, I'm losing power, especially top end, and the more load it's under, the worse it gets. Oh yeah, I've checked and both spark plugs are firing. This particular motor has the Mikuni carb and the BPS duel exhaust. After running it today, I noticed that there is a yellowish liquid that smells like gas on the motor, and it appears to have come out of the air intake on the Mikuni. I thought I was smelling fuel when I was locking the motor down for the ride home.

I usually just read through the posts here trying to get ideas for how to fix mine, but I'm no mechanic by any means, and I am desperate. I need this beast fixed or I'm gonna go insane. Any help would be MUCH appreciated.

Thanks,
Sandy Bottom

The gas is probably coming out of the bowl overflow tube. If so, ya need to pull the bowl & bend the tabs on the float a lil so the fuel flow to the carb isn't so much. Doubt if that fixes the other problem, but it's a start.

A partially clogged main jet may allow enough fuel flow for part throttle operation and yet starve the engine at full throttle. Also, do you know what main jet you are running?

If you don't know what main jet you are running or know how to check, you can go to the Mikuni web-site here http://www.mikuni.com/fs-carburetor.html and look at the manual and figure it out.

Couple of things. If the needle and seat were not changed then you could have the gravity feed needle and seat. If that were the case the overflow tube and fuel pic ups inside the venturi would be pissen fuel big time. Other thing is that the main is too big along with the pilot. The motor just does not have the power or rpms to flow the correct AFR on the top end. The more load you put on it the worse it gets. If you hold it wide open and the motor starts losing power with anything over a 165 main then you are too rich. You should not need anything larger than a 165 main with a 22.5 pilot or a 160 main with a 25 pilot with the clip set in the middle notch on the needle. Another thing you need to do is either get rid of those duals or open them up to flow better cuz those make the motor run richer as well. Hope this helps you out.

Thanks guys, I'm going to have all these ideas checked out. I looked at the Mikuni Tuning site and it appears that mine is the HSR42, which has a 160 Main. However, the carb and exhaust were installed by Mudbuddy, so I assume they replaced it with a 165 per the suggestions from Mikuni for engines that have dual exhaust.

I was reading back in some the earlier posts about problems with this same motor, and one guy said he had a motor that ran like champ out of water, but once he put it in the water(and under load) he had no power and the engine would try to die with throttle. He had it checked out and found that he had absolutely no compression on one cylinder. This is exactly whats happening to me. On land I'm getting to the rev-limit, but the minute is get the prop in the water, I get to about half throttle and start losing power with the engine trying to die.

Makes me think I'm not having a fuel issue, maybe a cylinder.

I'm deathly afraid to tear into the carb, if that is the issue. I have small engine mechanic close by, would he be a safe choice to work on a Mudbuddy. Otherwise, the closest dealer is an hour and a half away. I live in Camden, Tn. Anyone on here in West Tn?

As Drake1 said- the symptoms sound like you have the wrong float in the carb. The float valve and seat is supposed to be changed when you get a kit- maybe they forgot to do it on yours. Call Micah at MB and describe the problem.

If you are worried about compression then take it to your mechanic and have him do a compression test (make sure throttle is open). If there is a problem- have him do a leak down test to see what is leaking. Don't mix your problems though, one thing at a time. You have fuel pouring out your filter- the only way they can be related is if your valve lash is way off or a valve is not opening.

Gotcha. I am definitely ahead of myself on this, but I can't help it. Like I said, I'm mechanically declined, and I thought this was a "simple" engine. Now, I'm thinking going stock would have allowed me to avoid these problems. First thing, I'm gonna get the compression checked just to get that off my mind. If that's not it, then I can completely focus on the Mikuni. I really appreciate all the help guys!

Well, it turned out to be lacking fuel instead of too much fuel. Guess it shows my ignorance in combustion engine mechanics. I took it to my local small engine mechanic and I saw the blood leave his face when he saw it. Apparently he wants no part of a modified Briggs engine, but I told him what it was doing and after every scenario all he'd say is, "not gettin' fuel." I just couldn't accept that it was that simple, so I told him, "it has to be getting fuel cuz the fuel filter was full when I ran it!" He looked at me and laughed saying, " if it's full then it's plugged! Get you a new filter." So I did, and he was right. It ran like a scalded dog....for about an hour. Then it started doing the same thing again. So, I looked at the fuel filter and noticed air bubbling up into the filter. The more throttle, the more air. I tightened up all the bands....no more air. Planed it off and good as new.

Moral of story: I learned that no matter how big a problem I think I have....start small and work my way up. Just because I had put that new filter on three months ago, didn't necassarily mean that it wasn't already plugged again.