125-200cc Husky Boy 50 - Lacks Power

I'm at the end of my tether with this bike, hopefully someone can help as I'm losing my mind and just about ready to give up, pour petrol all over it and set it fire.


Bike revs out nicely with rear wheel off the ground but lacks power when put under any load.


History:
Recently purchased a mint early 2000 era Husky Boy for my step son. Very clean looked like it hadn't had much use at all. (It has the Morini Franko S5 engine, same as early KTM50, italjet, motorama, LEM etc).

Gave it a quick once over, new plug, trans oil, air filter etc and the first two outings it ran perfectly, absolutely rips for a little 50!

Third outing the fun begins, died halfway through the day, put it down to the coil as no spark being generated.

Struggled to find a replacement, ended up buying a Black Dragon ignition kit which retrofits the ignition system from the original combined coil/pickup to a stator plate/rotor & black box CDI?




While fitting the new ignition kit I also fitted new tyres, the replacement rear is wider with bigger knobblies (=much heavier than std) not sure if this makes any difference?
Also changed oil, air filter, plug & cleaned carb.

Bike fired straight up with the new ignition and with the wheel off the ground revs out nicely, but as soon as it is put under any load it lacks power bogs and doesn't pick up at all even with a 6yr old on it.

I have tinkered with the carb setting but it doesn't seem to help.

The new ignition rotor has a keyway on it to match up to crankshaft and the stator plate has no angle adjustment so the timing is fixed but I'm starting to think this could be timing related?


I know these 50's can be finicky but this is driving me nuts so any help greatly appreciated.

Hi,
You say you tinkered with the carb? Does that mean you dismantled it and inspected/cleaned all jets and passage ways. If not that's the first thing I would do. I'm no expert but in my experience and based on what you've described it sounds fueling related to me. Perhaps someone with more experience will chime in. Best of luck.

Isn't the clutch engagement adjustable on those bikes? I borrowed one once and I vaguely remember the owner telling me that you could adjust it.

Thanks for the advice guys

Yes carb fully stripped, pilots removed cleaned with thin wire, carb cleaner & air line.

I have the 2 shoe clutch which isn't adjustable (unless I purchased different springs I guess).


I think the KTM 50's of the same era used a 3 shoe clutch which instead of springs had stacks of bevel washers which could be installed differently to achive different settings, I quick search on the web shows that these needed constant tweaking.




Could the new ignition system have changed the timing or the way engine runs enough to require changing the bite of the clutch? From what I've read if the clutch engages to soon (out of the narrow power band) the bike will struggle to pull.

Also would fitting a much chunkier/heavier rear tyre make a difference to engine pick up?

Now thinking about gearing aswell

One of my friends had the orange version of that bike and his kid went through 3 clutches in one year. They are expensive and unfortunately other brands of bikes that don't have clutch problems aren't as fast as the KTM 50. I think the 65 is even worse but I'm not sure, it might be because he was woods riding and doing hare scrambles so he was slipping the clutch a lot more compared to motocross.