Low End bog on KM 30.5CC engine

[MikeRC]

Hi guys,

im having troubles with a km 30.5cc. After replacing a bad leaking manifold, the engine bogs really bad on the low end. Acelerates very slow, and if a pull all the ways on the gas, it wants to shut down. Only if i gas very slow, i can be able to pass to the high end. The high end seems ok. I changed the carburetor with an original walbro 668, and improved just a little, but the bog is still there. I also tried to adjust the low end needle, tried rich, a little lean, but didnt fix the problem. What could it be?

 

[X2Boss]

I had same problerms with my KM X2 which has there Fuelie 30.5cc engine.

I had to rebuild the whole engine from scratch and the exhaust manifold kept coming lose also the carb kept coming lose. Cleaned the carb also added full force v2 full lines Also the gaskets are crap on them every single gasket had perished so again replaced all then and uses copper gasket spray to make them last longer, used blue thread lock on all bolts had to play around with the L and H settings again back to factory settings.

She's running well no however I'm on my 3 coil after on 5 tanks of fule put through it.

Also what's your fuel to oil ratio mix and are you using an high octane fuel 91+ such as supreme unleaded (as its know in the UK)?

Once I done all this like I said its running well now !

 

[X2Boss]

Oh also check your carb full needles .... Especially your low end as it could have dirt or grease stopping the end need from performing as its should.... Make sure it's not damaged from over tightening again letting in to much full...

All it can be if your sure you have no other air leaks as you mentioned before as every nut and bolt likes to come undone on King Motor cars.


Cheers

 

[MikeRC]

Thanks X2, great help!

Im using 91 octane fuel and 25:1 mix ratio. I haven't check head bolts or cluth. One thing i noticed is that on the clutch area there is a lot of dark fine dust, seems liek dust from wear. But the clutch pads doesn't look to weared. Also the last time it worked well, the exhaust also came loose.

What carb stock settings are you working with?

Why ad to replace the whole coil? where was the failure on the coil?

 

[X2Boss]

No probs,

Your fuel mix is good 25:1 is standered for these types of engines.
As for the clutch he's they make a right mess mines the same not sure if heat build up makes the clutch dust worst but I went ahead and installed the vertigo open clutch housing and seems to improve but not totally eliminate the cluth dust.

L factory setting is 1 1/4 turns
H factory settings is 1 1/2 turns
That's going with the Walbro WT 668 Carb

For your exhaust I would recomend adding hex bolts inserted of Allen key heads as you can frape then up easier then using the ball end of the Allen key as with the XS you get supplied an FatBoy pipe but is a poor manifold design which means you can't frape up one side of manifold.

As for the coil the first problem was the engine would not turn off due you faulty primary winding on the coil.

Second coil got wet and shorted inside the coil creating no spark, I did try new spark plug fly lead but no luck.

Also would recomend rebuilding your center diff all grease/oil had leaked out on mine after the 2nd tank of gas.

Basically once all the little problerms are fix and replaced the X2 is a weapon but I've speak a lot of time rebuilding and replacing with expensive hop-up parts to get where it is now!