Suppose to be going on a ride sunday and my motor messing up. Rebuilt it last week. New piston rings, all new seals, head gaskets etc. New pvt adapter and 26mm mikuni carb. Reason I did it is because my old mikuni was a little too big and was jetted wrong for a while washing the cylinders out and my oil leptons filling with fuel and blowing the mixture out of the breather tube. Also carb was filling cylinder with fuel causing me to have to pull plugs and blow it out to start it, and would then fill the water around the boat with fuel after running.
Now I rebuilt it. Started it up fine and ran in the yard great so I took it out today and it started ok but wouldn't hit the rpms I used to and was slowing down after 3/4 throttle. Tried pumping it fuel and it came to life at full throttle and then died. Now it will idle for a while and then finally cut off and if you get it idling it will not rev up with out backfiring, shooting a flame out of the carb and cutting off. Also I thought it was weird but when I pump it up with the bulb it will pour out of the breathers on the carb and the front of the carb. Any ideas what to try? I've checked the float/changed the jets between 155-165. Checked the valves. Running out of ideas

IMO for what it worth sounds like your a/f mixture is out of adjustment. These screw adjustments take very minute adjustments to get them right. Do you have a tuning manual? If so go back and recheck your adjustments. If you've got raw fuel coming out the carbs your getting plenty of fuel! Like to much. Re-check float level again as well. Wish I could be there to see and hear it run. I've done lots of carb adjustments on two strokes mostly mikuni's some tiltisons and bings.
Good luck hope you get it running for your run Sunday.

26mm carb??? What motor is this?

Yeah I tried Bending the little tab both ways on the float to get it to shut or open more when I thought it wasn't getting enough or getting too much. Im about tired of messing with it. I'll do some reading on tuning tonight and try some more tomorroe

It's an 18hp. I talked to PVT and he said its a good size for my motor.

Read it wrong shotgun... Fuel comes out the overflow when ya prime it? That's normal on certain carbs

What's the model number on that carb?

Coming out the overflow and the front of the carb. I'll get the part number in a little bit. It was running fine tho at home and then I took it out and it ran like crap.

Coming out the overflow and the front of the carb. I'll get the part number in a little bit. It was running fine tho at home and then I took it out and it ran like crap.

Check the valves, rockers and pushrods too. Kinda sounds like one maybe came loose or bent etc

Alright I pulled the valve covers yesterday to make sure they were adjusted correctly but I'll check to see if anythings bent. The carb says mikuni corp 26 606C. It's a vm round slide

Alright I pulled the valve covers yesterday to make sure they were adjusted correctly but I'll check to see if anythings bent. The carb says mikuni corp 26 606C. It's a vm round slide

Would it run alright at idle if something's bent?

Not likely... Gimme a shout

It revved up a little better today but still not right

Something else, double check that one of the coil wires isn't grounding out somewhere

Grounds are fine and its firing fine. Kinda running out of things to check as far as I know.

Unplug diodes from the coils and then run it if that's not it then u have cam problems are either carb tuning

Is it possible for one of these motors to jump timing on the cam? I checked it like 5 times when I was putting it back. Or could it maybe the flywheel have shifted on the keyway changing the ignition timing? It idled fine and rode fine when I first tried it but it cut off and hasn't done right since. I unplugged what I believe is the diode and it did the same it has. Idled fine and then started cutting off and backfiring when I tried to rev it up past idle. I'm hoping its carb related but who knows.

Is it possible for one of these motors to jump timing on the cam? I checked it like 5 times when I was putting it back. Or could it maybe the flywheel have shifted on the keyway changing the ignition timing? It idled fine and rode fine when I first tried it but it cut off and hasn't done right since. I unplugged what I believe is the diode and it did the same it has. Idled fine and then started cutting off and backfiring when I tried to rev it up past idle. I'm hoping its carb related but who knows.

figured out the running issue now I have to work on the running out of fuel in the carb problem

Running carb heads exhaust and cam. Do I need an electric pump or is it more like a float problem or drawing air through a small crack in the line? It runs and idles but won't hold enough fuel for full throttle unless I pump is. And it will die off after like 50 yards unless I hit the bulb

Running carb heads exhaust and cam. Do I need an electric pump or is it more like a float problem or drawing air through a small crack in the line? It runs and idles but won't hold enough fuel for full throttle when it is under a load unless I pump the bulb. And it will die off after like 50 yards unless I hit the bulb Can hold 3800 rpms for a little while but past that it cuts off and at that itll cut off shortly. Also my tank came with a cap that didnt breath and it worked but I went ahead and threw one on that doesnt breath. Could that have an affect on it?

So what was the issue with it backfiring above idle?

It was backfiring above idle because when I put the flywheel back on i must have accidentally knocked the key off the crank. When I first ran it the flywheel probably spun slightly making it fire out of time.

Figured id check that the stock pump is working Does that look like an acceptable volume?

That looks like enough fuel. You need a cap with a vent. Check all connections on your fuel line, especially if you have a quick connect fitting. They are bad about letting air in. Best way is try a different tank with a short line direct to motor and see if that fixes your problem. If it does then you know it's in your fuel line or connection somewhere.

I'm gonna go ahead and replace lines and connections tomorrow and try it. What ID should I go? Right now I'm 5/16 to the inline filter and everything down stream from there is 1/4.

Stick with all 1/4"

Alright.

Found broke o ring on my quick connect. Got it bypassed so gonna test it tonight. Hopefully it's all good now.

No good. It Still won't rev up without pumping it. But then it'll die. After it revs for a second. I've tried new fuel line pump bulb and fuel filter. Bypassed the pickup in the tank. So now my guess is the carb? I've messed with float opening and closing it more. Doesn't help. Could my main jet just be so lean that when I pump it it shoots more gas in the intake and causes it to rev? It just acts like its running out of fuel when it's not idling

If anyone was curious I took it out last night. Same issue. Switched from a 165 to a 190 main and it improved. Switched to a 230 main and I have a full throttle. Now I just have to fine tune it and I should be good to go.

Well thats good to hear. Glad you have it working better now.

Should I put an oil cooler on this thing?