Wont start and now wont prime :-(

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

Steve2021

Active Member
Messages
28
My KM Baja was running OK but rich and bogging down so I decided to adjust the needles not now the thing wont start!!!

Adjusted them back to factory settings and still wont start just kept flooding with each pull.

Gets good spark

Tried fresh fuel

Tried new spark plug

Tried without the filter

Tried tipping it on side and pulling starter to clean flooded engine and fuel poured from the exhaust

Bought a carb rebuild kit, stripped carb, soaked carb in fuel over night and blasted it with air.

Rebuilt carb and fitted it along with new carb to engine gasket and set needles to factory setting and now it wont prime!!

Took apart, checked rebuild diagrams and all seems good...

Any ideas? It's got WALBRO on the bottom and WT-668 On the side guessing it's a genuine walbro?

Thanks
 
Check your piston ring isn't too worn.
Also try adjusting the idle screw, if it's been running rich you've likely had the idle screw in wrong potion.
Also double check you've got no air leaks between the carb and the engine and that the isolator block isn't warped.
Also make sure head is tight, and make sure coil bolts are tight too, plus battery is good and kill switch working correctly.
 
Check your piston ring isn't too worn.
Also try adjusting the idle screw, if it's been running rich you've likely had the idle screw in wrong potion.
Also double check you've got no air leaks between the carb and the engine and that the isolator block isn't warped.
Also make sure head is tight, and make sure coil bolts are tight too, plus battery is good and kill switch working correctly.

Thanks, kill switch seems to be working or it did (spark to plug is killed when pressing kill switch channel 3 on Transmitter and plug wont spark unless the the receiver and Transmitter are both on)

Battery freshly charged

Will check the engine side of things but surely that wouldn't stop it from priming?

should have left it as it was lol, it would fire first or 2nd time every time until I tried to improve it's running lol

And check fuel lines for plugs and tank vent

Thanks, checked fuel lines and they seem clear, sucked lightly on the fuel in pipe and saw fuel move freely through the pipe.

Blew down the return pipe and again no blockage.


Should I be able to blow into the fuel inlet nipple on the carb when it's assembled? Blowing in there with my mouth shows it is blocked until I press the fuel needle lever which I'm guessing is correct BUT it is also blocked while I blow and pump the primer (I thought I would have felt a change when doing this..)
And check fuel lines for plugs and tank vent
Tank vent clear :)
 
Last edited:
Blowing the carb out with air isn't the most intelligent thing to do, your risk breaking the main check by doing so, and that will cause erratic running issues. It's non serviceable as far as I know. Checking out every thing else air leaks ect will be a good first place to start.
 
Blowing the carb out with air isn't the most intelligent thing to do, your risk breaking the main check by doing so, and that will cause erratic running issues. It's non serviceable as far as I know. Checking out every thing else air leaks ect will be a good first place to start.

Thanks, when I blew it out it was stripped down to just the main carb block, that's how they did it on the carb service video I watched anyway :)

Will check again tonight.

Are the copy chinese carbs any good?
 
one thing no ones mentioned yet mate,
check you put the fuel lines back on the right way round after ya had it all in bits,(y),
clunk/fuel in to bottom of carb and return to top of carb ,
easy mistake to make, most of us have done it at some point :)
Yea, correct way around thanks :)
Carbs are pretty cheap. I usually grab one when there deal of the day. 990 for g290. 1107 for g320. 1242 for reed motors.

My buggy is running a 26cc engine would it be best sticking to the 668 carb?
NO!!!!!!
Tbh that km carb is prob ur problem get a genuine 1107
Would the carb fitted to it not already be a genuine Walbro carb? It looks like a genuine with Walbro casted on it and the model number on the side


Also would a 1107 carb work OK on a 26cc?
 
Leave the 668 on that little engine.

Will do. If it's cast with Walbro on the bottom and etched with WT668B 121 on the side does that seem genuine?

Did you replace the fuel purge plate? And how old is your primer bulb? Sounds like your losing prime due to worn parts

Is that the white plastic plate under the primer bulb.

Primer bulb probably 8 years old but looks in new condition and if I put the bulb on a flat surface and press it it stays sucked down.

the primer bulb / system worked perfect until I took the carb apart lol

Check the diaphragm under the prime bulb

Replaced that as well :-(





Is it possible to start the engine with the carb off? Eg drop some fuel in engine and start it up? To make sure the engine is ok?
 
Will do. If it's cast with Walbro on the bottom and etched with WT668B 121 on the side does that seem genuine?



Is that the white plastic plate under the primer bulb.

Primer bulb probably 8 years old but looks in new condition and if I put the bulb on a flat surface and press it it stays sucked down.

the primer bulb / system worked perfect until I took the carb apart lol



Replaced that as well :-(





Is it possible to start the engine with the carb off? Eg drop some fuel in engine and start it up? To make sure the engine is ok?
Yes it's possible but do it with either the wheels off the ground or front against a wall
 
Thanks, got a slight update

The primer bulb primes the fuel line all the way to the carb but nothing enters the bulb or comes out the fuel return
 
Seems as if you have a restriction. Fuel comes in the bottom line on the carb and then the fuel gets pushed back to the tank through the top line to purge the air
 
Seems as if you have a restriction. Fuel comes in the bottom line on the carb and then the fuel gets pushed back to the tank through the top line to purge the air
Yea, that's what it used to do in streams of fuel.. think I will order another rebuild kit incase I got a duff one

Maybe when I soaked the carb it's dislodged dirt and moved it somewhere else lol...
 
My KM Baja was running OK but rich and bogging down so I decided to adjust the needles not now the thing wont start!!!

Adjusted them back to factory settings and still wont start just kept flooding with each pull.

Gets good spark

Tried fresh fuel

Tried new spark plug

Tried without the filter

Tried tipping it on side and pulling starter to clean flooded engine and fuel poured from the exhaust

Bought a carb rebuild kit, stripped carb, soaked carb in fuel over night and blasted it with air.

Rebuilt carb and fitted it along with new carb to engine gasket and set needles to factory setting and now it wont prime!!

Took apart, checked rebuild diagrams and all seems good...

Any ideas? It's got WALBRO on the bottom and WT-668 On the side guessing it's a genuine walbro?

Thanks
 
Quick update.

Tried new primer bulb

Tried new fuel lines and fuel filter

Tried removing the carbs internal fuel filter

Blew carb cleaner through all the holes and nothing blocked.


And it still won't prime / fill the primer bulb...

My next test is going to be submerging the carb into fuel keeping the fuel lines out and not going past that breather hole bit on the top of the carb and try pumping it and see if I can see any leaks from anywhere (like little bubbles)

It's like there's a air lock in it..
 
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks