Kart Conversion Recoil Spring

I recently purchased a 6” Kart .22 conversion. It misfires frequently. Firing pin is fine, it’s clean, and nothing broke. 
The recoil spring seems weak and it looks short. 
Anyone know what the spring weight/rate should be? I called Kart, no one remembers but they did say springs (with different rates) are from Wolff.

I have same issues. I bought kit from Wolf and still does not function with SV. CCI mini mags run maybe 90% of the time. If I can't get it figured out I will be selling it!

I run a 4 to 4 1/2 lb recoil spring in my Kart with standard velocity ammo. Also, I have found the unit to be ammo sensitive. One other thing I found is that the unit does not play well with standard 1911 firing pin springs. I found a lighter weight firing pin spring in my stash and that did wonders for ignition reliability. I purchased the Kart used so I don't know what the factory original firing pin spring was. This is all in conjunction with an 18 lb hammer spring.
Your mileage may vary.