No power under load, running bad above 1/4 throttle

[loh61546]

My son and I have been getting the bugs worked out of this Blaster we have been working on. Was running horrible. Did a leakdown test on it. Found the crank seals were shot. Have since replaced them. The machine ran reasonable before we had the seals issue. Now I cant seem to get this running right. It will fire up on the first kick. Idles good. Throttle response seems ok through 1/4 throttle. starts getting boggy after that. Tends to pop and sputter. If you keep on the throttle it will eventually rev up then. if you try to put it in gear and take of it will start to move but then fall flat on its face. Thought it might be a fuel issue fuel flow seems to have a steady stream to carb. Here is a list of things we have checked so far:

Carb cleaned and rebuilt
240 main jet
needle set on second clip from bottom
Float level checked and set to about 21.5 mm
Air filter cleaned
Normally air cover on. Tried with cover off and did not help any
Good spark plug
Leak down test good
Compression test came in @ 120 psi
very good spark
Reeds are older but seem to lay flat with no damage to them
Tors has been disconnected
We use BelRay MC1 mixed @ 40:1 ( I know most like 32:1)
Wiring is all been redone with good grounds
Coil tests out good
Flywheel & woodruff key has been replaced

I cant get this thing moving enough to do a plug chop. All I have to go off of is the inside of the plug seems to be a caramel color. End of plug seems to be more of a really dark chocolate color. Have tried a couple of plugs and they color up the same.

Only remaining issues we know we still have to address is rear bearings are in bad shape. Also I'm in the process of getting a FMF Fatty header pipe and powercore2. I know jetting will have to go up but I need this thing running right first. The current stock head pipe does have a small crack in it right after the first full curve. But I would not think it would cause these sort of problems.

Can piston and rings be an issue here? 120psi should still be reasonable. Plus it fires up good and idles well.

If I have left out any needed info, let me know.

Any help here would be greatly appreciated.

 

[YFS101]

drop down to a 230 main jet.

if it has aftermarket reeds you may have to go even leaner. If it ran better while it had an air leak its likely too rich now.
A stock blaster with Boyese power reeds I usually ran a 220 main clip in the 2nd spot.

 

[loh61546]

We were running a stock 230 main. alot of folks said cold winter weather needed
to go up one size. So we did. I have had the clip in the middle slot also, no luck.

 

[Blaner]

ok, thats quite a lot to take in, so its idling well? but dies at 1/4 throttle...that sound like the needle may be set wrong.i see your needle is 2clips from the bottom, maybe put it flat in the middle (stock). in other words, try leaning the needle out a touch. (i think ive got this right? i always get the lowering clip/raising needle mixed up.)

 

[Kgibson]

right when it starts to cutout pull the choke that will tell u if its rich or lean. u could also take the filter off and ride it in the yard and see if that helps

 

[loh61546]

We did try to pull the choke out once and it just made it worse. Also have pulled the air filter lid off and briefly had the filter off also and it did not seem to change anything. this thing has me stumped.

 

[Kgibson]

when u pull the plug is it wet, sound like your way rich for some reason, if you cant find any reason i would look at the topend

 

[loh61546]

It is a little bit. It is getting fuel. Last plug was like a dark chocolate colr on the end. Up inside where you would normally check the plug chop at is was kinda a medium brown. sorta like the color of caramel. The dark color seemed a bit strong cause the plug really does not have a great deal of run time on it. I can get a pic posted up in the morning if that would help out some.

 

[Kgibson]

If it were me i would lean the needle a couple of notches and see if that helps.Also drop the main. dont ride it alot just see if that takes it out. If it does work your way back rich. Also 120 is not real bad but u could also have a stuck ring and carry that

 

[loh61546]

I appreciate the help. i try leaning it out tomorrow and see if it does anything.