Mikuni probs

[tgus3]

well I've had my motor built and on my kart for awhile, (well 2 days of it working) but now the engine won't run right. So id been driving it for about 2 days and then I run out of gas. I put new gas in and now it will only start on choke.

As soon as I turn of choke it died. Now a day or 2 later I've been messing with trying to start it and it won't run even on choke anymore. it revs up and dies. I took the carb off and blew out all the lines and as far as I can see nothings wrong there.

Whats wrong? Im prob being dumb and missing something but tell me what you think.

If I have to I might find all my old parts and put on the stock carb to see if its for sure the mikunis problem.
Thanks

 

[JTSpeedDemon]

Could be running rich, but I'm confused with the fact that is was only after you changed the gas.
Was it running perfectly before?

---------- Post added at 05:17 PM ---------- Previous post was at 05:17 PM ----------

Ah! Perhaps a seal or something failed, releasing more gas into the engine.

 

[Tpdingo]

Could be running rich, but I'm confused with the fact that is was only after you changed the gas.
Was it running perfectly before?

---------- Post added at 05:17 PM ---------- Previous post was at 05:17 PM ----------

Ah! Perhaps a seal or something failed, releasing more gas into the engine.

Ummm...it can't be running rich. If anything lean. Choke increases fuel, not decrease.

 

[tgus3]

Could be running rich, but I'm confused with the fact that is was only after you changed the gas.
Was it running perfectly before?

---------- Post added at 05:17 PM ---------- Previous post was at 05:17 PM ----------

Ah! Perhaps a seal or something failed, releasing more gas into the engine.

That's what I cant figure out it was running fine, then all of a sudden, doesn't start..weird...

---------- Post added at 05:53 PM ---------- Previous post was at 05:52 PM ----------

Ummm...it can't be running rich. If anything lean. Choke increases fuel, not decrease.

right after I filled it with gas it ran fine on choke. but now a few days later it revs up on choke and dies

 

[JTSpeedDemon]

Check the fuel filter, it might've washed some garbage out of the gas tank and plugged it up.
If you want, try taking the carb apart, and simply inspecting and cleaning it.

---------- Post added at 05:55 PM ---------- Previous post was at 05:54 PM ----------

'Cause it sounds like a fuel delivery problem from the tank to the float bowl.

---------- Post added at 05:55 PM ---------- Previous post was at 05:55 PM ----------

What engine is it in particular?

 

[tgus3]

Check the fuel filter, it might've washed some garbage out of the gas tank and plugged it up.
If you want, try taking the carb apart, and simply inspecting and cleaning it.

---------- Post added at 05:55 PM ---------- Previous post was at 05:54 PM ----------

'Cause it sounds like a fuel delivery problem from the tank to the float bowl.

---------- Post added at 05:55 PM ---------- Previous post was at 05:55 PM ----------

What engine is it in particular?

its my 212 and ive tried running with the air filter off;no diff
all the lines are clear of debris and I can see it getting fuel

 

[JTSpeedDemon]

Hmm, that rules out clogged fuel line.
Tpdingo, I might've been thinkin' of my Briggs' choke, which makes an air restriction. Do some chokes increase fuel instead? I wouldn't think so.
But yeah, try dismantling the carb.

 

[Tpdingo]

Hmm, that rules out clogged fuel line.
Tpdingo, I might've been thinkin' of my Briggs' choke, which makes an air restriction. Do some chokes increase fuel instead? I wouldn't think so.
But yeah, try dismantling the carb.

Well yeah, you gotta get a good understanding of the carburetor for this to make sense. The choke cuts off air, but due to the way the carb work and the vacuum from the intake stroke, the same amount of fuel gets shot up into the engine. There is less air, but the same amount of fuel gets put in there...and as a result the air-fuel ratio decreases.

In a modern car with EFI, they just shoot stupid amounts of fuel into the cylinder instead because there is no choke.

If you want some info on how it works, check out this old Chevy video. I love these old chevy videos. https://www.youtube.com/watch?v=ICzBGDnA9OA

 

[landuse]

When you ran out of fuel you probably got some gunk from the bottom of the tank in your carb. Take it off, clean it thoroughly, and then report back before we try diagnose anymore

 

[JTSpeedDemon]

When you ran out of fuel you probably got some gunk from the bottom of the tank in your carb. Take it off, clean it thoroughly, and then report back before we try diagnose anymore

'Cause otherwise we'll be telling you to get a new carb.

 

[tgus3]

When you ran out of fuel you probably got some gunk from the bottom of the tank in your carb. Take it off, clean it thoroughly, and then report back before we try diagnose anymore

Well got the carb apart, made sure it was all clean blew all the lines and holes out, put back on same thing
what now?

 

[Kaptain Krunch]

Air leak somewhere? improper valve adjustment?

 

[landuse]

Well got the carb apart, made sure it was all clean blew all the lines and holes out, put back on same thing
what now?

Now I'm not sure.....but if it happened after running out of fuel, it still sounds like dirt somewhere in the fuel system

 

[tgus3]

Air leak somewhere? improper valve adjustment?

well it still runs on choke so the lash can't be too bad but I'll make sure and check it today and tighten everything up to make sure no leaks

 

[tgus3]

got the lash reset today, was a little off
now it runs pretty well on choke but still instantly dies when I flip the choke off

when i put my hand down by the sparkplug and gas tank I feel air coming out while its running.Is that from the flywheel or could it be a leak between the head and block?

 

[JTSpeedDemon]

Check the head bolt torque. And the head gasket just in case.
Probably not the cause, but it doesn't hurt to check anyway.

 

[tgus3]

Check the head bolt torque. And the head gasket just in case.
Probably not the cause, but it doesn't hurt to check anyway.

I have a stud kit on it so their nuts and their real tight.
I can see the gasket as it sticks out a little bit all the way around and theirs no gaps or anything.

It really felt like the air was coming from the flywheel tho

What shall I check next?

---------- Post added at 04:44 PM ---------- Previous post was at 04:42 PM ----------

Now I'm not sure.....but if it happened after running out of fuel, it still sounds like dirt somewhere in the fuel system

My fuel line is clear and I can see the gas going thru it fine when its on choke..
maybe I missed something in the carb but I think I got it all

 

[JTSpeedDemon]

Did you run a pipe cleaner through the little passageway behind the float needle?
That tends to get clogged in most engines.

 

[tgus3]

Did you run a pipe cleaner through the little passageway behind the float needle?
That tends to get clogged in most engines.

I made sure every hole and well, everything was blown out and no dirt.

But what else can it be be than the the carb?
If I have time tonight ill take it apart again...

 

[JTSpeedDemon]

At this point, I'll leave it to someone else to answer that.