need help with bike not running well. PBE 140

[jaybus90]

hey,

i Have a Pit boss empire 140. when i bought the bike second hand it ran well. i decided to drain and clean carby out due to slight hard to start issue. after cleaning the carry it started and ran well for a few days. now the bike is hard to start and backfires/pops and bogs down when riding. i have tried to adjust the carb in slight incriments but still have no luck. its a mikuni 26 i believe. when checking for spark there does not seem to be a strong spark which may be the problem but i may not have been turning engine over fast enough to generate a spark. i took the carb off this afternoon and put back together taking care to ensure it was well sealed to the motor incase there was any leaks. after this it ran well for a few mins but then back to backfiring and cutting out. it has a 95 main jet and a pilot jet.

I'm pretty good at working on cars and that just not very experienced with bikes and carburettors

I have been reading heaps of posts from this site but can't seem to find any thing that sounds like my problem.

thanks in advance for any help you can offer.

 

[my67xr]

Welcome to Miniriders,

When you have taken the carby apart, do you take both jets out and check all the holes through them are open/clear ?
Also where the pilot jet screws into the bottom of the carby, check at the bottom of the threads that you can see though the small hole into the carby bore.
It sounds like you pilot jet could be partly blocked, or that there's a blockage somewhere before it in the pilot circuit.
do you blow out the 3 ports on the filter side of the carby with compressed air ?
you should be able to feel it blowing out through one of the jets as you blow through each hole.

You didn't mention what Pilot jet you are running, if it's a 15 then i'd recommend fitting a #20 to it.
That will richen it a bit down the bottom, and make starting it easier, will improve the response, and get rid of the bogging.
It'll need a bit of adjusment on the mixture screw, but once that's done it should be good for a long time.
You might be able to raise the needle clip too, try it on the second notch down from the top once the bigger pilot is in.

the pilot jet in your carb is like the one on the left in the pic below



Weak spark could be a couple of things,do you have a new NGK C7HSA spark plug in it ?
And what spark plug cap is on the end of the lead?
I have found a couple of spark plug caps that have had corrosion in lately.
Inside the cap you'll see a brass terminal with a slot in it.
Unscrew it and there's a small spring inside, the ones i've had apart recently have both had some corrosion on the spring.
A clean up with a wire brush,
then spray the spring with WD40/CRC or smear it in dielectric grease (bulb grease) then reassemble it has made the spark intensity a lot better.
The other thing you could do is to fit a better quality cap, NGK have a direct replacement cap that suits our pitbikes
Or fit a better lead,
i like these Splitfire leads, it can turn a faint spark into a blue/white crackling spark if your current one is faulty.
Performance Coil Spark Plug Lead CAP 50 110cc 125cc 250cc PIT Quad Dirt Bike ATV | eBay
And a few other members here run the NGK lead on their bikes too
Racing NGK Ignition Coil Lead 110cc 125cc 150cc 200 250cc PIT ATV Dirt Quad Bike | eBay


let us know how you go , and what you find

Cheers, Craig

 

[jaybus90]

Thanks so much,

I can see light through the jets, will take apart tomorrow and blow out the ports. The big jet says 95 and the small one says 15. Does that sound right? I will look into getting the different jet. Would any motor bike shop have them? Also I do have a new C7HSA plug. I will also check out the plug cap and let you know how it all went.

Thanks so much for your help

 

[my67xr]

Yeah , no problems.

That #15 Pilot jet is too small, even the 125's i've worked on like the #20 pilot.
A few bike shops sell the Mikuni jets, one near me in SA sells them for around $12ea.
But you can find them cheaper on ebay etc


The other thing i'd be doing to your bike is to adjust the rocker arm clearances to the valves.
Set them to .003" on the inlet, and .004" on the exhaust.
check out this video it explains how to do them if you haven't adjusted valves before, but use the settings i mentioned above

[video=youtube;QJciyJRJh8Q]https://www.youtube.com/watch?v=QJciyJRJh8Q[/video]

 

[jaybus90]

Hey, I attempted to check valves but when I removed the magneto cover there was so markings to align the magneto up with the mark on the casing.

 

[my67xr]

You will have to kick your engine over slowly till it starts to get hard to move the pedal, TDC isn't much further from there.
If you pull the spark plug out when the kick lever starts getting firm, and put a long thin straw or skewer etc down through the spark plug hole into the bore, then push the kicks tart lever down and you'll feel the piston come up in the bore.
TDC is where the piston is right at the top, so if you go too far, you'll feel the piston start to drop back down the bore so turn the flywheel back till it's at the top.
Put a mark on your flywheel then for future reference, and double check that the mark on the cam gear is lined up at 9 o'clock too.

 

[jaybus90]

Hey, I did the valves thanks to your advise. They were a bit out not too bad though. I also used compressed air to clean the ports in the carby but still no luck. It runs better the more I turn the fuel screw (4+ turns out) but it still Carrys on backfiring and running badly. The spring in the spark cap was all good no corrosion at all. Im really stumped now on the engine running badly now. Will try to track down the new jet over the next few days and try that.

 

[my67xr]

Try tuning it so the mixture screw is around 1- 1.5 turns out, until you fit a #20 pilot jet.
4 turns out is waaaay too lean

 

[jaybus90]

I started at 2 turns and It will not start at all until almost 4 turns. When I got the bike when it also ran well it was at 4 turns

 

[my67xr]

So it's running at 4x 360° turns out ?
Float level must be too high then , or a bit of dirt/plastic is stuck in the needle and seat ?
It shouldn't even run at 4 turns out.

 

[jaybus90]

yep it sure is 4 full 360 degree turns outwards on the screw that's under the carb just before the intake manifold

 

[my67xr]

Ok, you might want to check your float level then, it should be around 25mm down from the top of the fuel bowl
You'll need some clear hose to fit on the fuel bowl drain post, run it up past the top of the carby.
Then open the drain screw on the bottom of the fuel bowl.
You will see fuel go up the hose and it'll stop at the level it is inside the fuel bowl.

 

[jaybus90]

Hey, I just went and tested and the fuel levels out at about 8mm from the join in the carby

Thanks again for your help

 

[jaybus90]

That was with the bike level also

 

[my67xr]

Right so the centre tab on the float needs to be bent upwards about 2-3mm,
the angle of the tab should look something like the picture below.
bend the tab up with the float removed from the carby, or you will chance bending the floats out on an angle.
It is easy to remove, just push the pin through the tower and out the other side.
then refit the fuel bowl and measure the level again.
take not of how the tab sits against the tip of the needle too, so you can put it back together correctly.

 

[jaybus90]

Ok done this, runs ok but now fuel continually comes out over flow hose?

 

[my67xr]

Sounds like the needle and seat could be stuck ?
Try tapping the carby fuel bowl with the handle of a screwdriver a few times.

If that doesn't stop it, then it could be the float
Take the carby off again,
remove the fuel bowl and take a pic of it upside down so i can see the angle of the centre tab on the float arm

 

[jaybus90]

I bent it half way back to where it originally was. Seems to run ok is with the problem still faintly there

 

[my67xr]

So if you try checking the float level again with the hose up and drain bolt open on the bottom of the carby,
what is the fuel level at now ?

 

[jaybus90]

Roughly 25mm from join. It ran yesterday ok around the back yard with only a couple of splutters.