Engine dies at WOT

[mikepctvman]

I had my kart out and decided to floor it to see how fast it would go, I was hauling a** down the street pretty fast then as I hit top speed I felt the motor kind of surge and herd little pop and I let it slow down but I tried giving it more gas to keep going and it kept bogging down and shut off. I was able to get it started again after a few pulls. I just rebuilt and cleaned the carb, new diaphragm, new spark plug, changed oil, fresh gas and even changed the little fuel pickup tube that is attached to the carb. something out of adjustment? its a 5hp briggs and Stratton, no I didn't run out of gas either checked that (duh) lol

---------- Post added at 06:56 PM ---------- Previous post was at 06:50 PM ----------

if it helps too sometimes it sounds like it wants to cut off if I brake too hard as well, i played around with the idle and got it just perfect that its not too low where it stalls but not too high where its surging forward either, idles just fine

 

[Zombient]

Sounds like it's starving for gas.

 

[mikepctvman]

lean/rich mixture screw adjustment?

 

[Zombient]

That's what I'm thinking, but don't hold that against me. I know someone will chime in with an EXACT answer for ya.

 

[mikepctvman]

ill keep that in mind, good place to start. while I was disassembling the carb that screw was all the way in, when I reassembled and put the lean/rich screw back in I turned it out at 1 and a half turns (herd that's where it typically should be) ill go with trial and error and take any other suggestions too. BTW what direction is lean what direction is rich??

---------- Post added at 07:25 PM ---------- Previous post was at 07:19 PM ----------

I also notice when the engine is cold I have to hold the throttle SLIGHTLY when I am trying to start it and rev it after it starts for a bit then it will idle just fine after its warmed up, maybe I can get all these small issues taken care of here in one shot lol

 

[Poboy kartman]

Rich = counterclockwise.

 

[Zombient]

I'd have to play with it, I can't remember off the top of my head, but I think it's either 2 and a quarter turns or 3 and a quarter turns out.

Screw the needle all the way in, but don't damage it. Then screw it out 2-3 and a quarter turns out. Somewhere there is the sweet spot.

 

[mikepctvman]

Ok I'll give that a try

 

[mikepctvman]

reguarding the starting issue, why would I have to hold the gas pedal down slightly when trying to start the motor cold? it usually doesn't matter if the choke is open or closed I have to do that and rev it a few times. after that it starts and idles fine and I don't have to do that when its warmed up.

---------- Post added at 08:49 PM ---------- Previous post was at 08:12 PM ----------

I've had a few go karts I had to do this with is it just a typical small engine thing?

 

[OzFab]

If the governor is intact & functioning correctly, the governor will hold the throttle open when starting; if the governor is gone then it helps to hold the throttle open...

I have a few engines, different makes & models; the 8hp B&S on my riding mower simply will not start with the choke on; hot or cold, it makes no difference; on the other hand, the 5.5hp chinese clone on my pressure washer won't start without the choke on; again, hot or cold makes no difference...

What I'm saying is, although they all have the same basic characteristics & engineering, every engine is different & have different "trick" or procedures to starting them; you need to figure out what the "trick" is with your engine...

 

[mikepctvman]

Yeah there is no governor, previous owner connected the throttle cable directly to the carb. I tried adjusting the lean/rich screw and it's very lose in the carb body, the vibration of the motor causes it to move around is there supposed to be a spring around the screw?

 

[OzFab]

Yes, there is; that would help a great deal...

 

[skimf]

just a random guess but could it be that the valve springs hold open at high revs?
maybe you need heavier ones?
Just a random gues though lol

 

[OzFab]

That would be what's called valve bounce, which is normal for industrial engines at around 5000rpm; fitting heavier springs will necessitate fitting a billet conrod, otherwise engine go boom...

 

[FreeRunner15]

i enjoy these posts.