Need help with new intake/exhaust install

[SethDog3200]

Hello Everyone,
Im new here and new to Karting but not new with small engines. I have a Predator 212 that was completely stock and ran great. I have just installed new intake (cone filter) and new exhaust and now when I start it, it runs rough and seems to backfire some. The kit I bought also came with 2 different main jets and an advance timing key that I have not installed. I would like to hear some thoughts of what the problem may be?

Thanks in advance

 

[ezcome-ezgo]

Less restriction in the intake and exhaust means more air, so you need more fuel to compensate, thus the larger jet.

 

[fasterSr]

If there is an air/fuel mixture screw accesible on the carb, while running, try turning it counter clockwise and see what happens. Also, you can also restrict the air flow going into the carb with your hand. Slowly block the air flow and if the engine speeds up, you have a vaccum leak.

Welcome and good luck!

 

[bob58o]

The kit I bought also came with 2 different main jets ... that I have not installed. I would like to hear some thoughts of what the problem may be?

The problem is that you didn't install the jet included with the kit. Why you think it was sold a kit?

 

[Nosandwich]

Because he has a hand???

The key usually gives you just a bit more performance, because the stock timing is really more for smooth idle and industrial rpms. Governor removal would probably give you more benefit with a key change.

Regardless, you need to re-jet.

 

[SethDog3200]

Thanks Guys! So put in new jet and it is much better. It does hesitate on first throttle and somewhat pulses at WOT. Do you think I should try the other jet? And with what Bob said should I put in the 8 degree timing key that also came with the kit?

Sorry for the noob questions I have worked on a lot of motors but never modified them like this.

 

[Nosandwich]

Yes, try the other jet (If it's larger).

8°??? ...ummm yeah, probably a bit much for a stock cam. Your biggest "bang for the buck" is governor removal.

Ought to be a piece of cake for a guy with small engine experience.

 

[sefishy]

pulses at WOT as in hitting the rev limiter?

 

[bob58o]

Thanks Guys! So put in new jet and it is much better. It does hesitate on first throttle and somewhat pulses at WOT. Do you think I should try the other jet? And with what Bob said should I put in the 8 degree timing key that also came with the kit?

Sorry for the noob questions I have worked on a lot of motors but never modified them like this.

The 8 degree key is not necessary. It should give you some more top end power, probably at the expense of some low end power.

You can try to open the fuel screw a bit. More fuel from the idle circuit might help when cracking the throttle wide open from a stop (If it is a lean bog).
Turn it counter clockwise to allow more fuel. Richer Idle Circuit. I think I used a gx140 Emulsion Tube when using a stock carb, but I didn't use a stock carb for long. Some people didn't like the gx140 E Tube, so not sure if it will help.

If you tried the smaller jet first, you can try to bigger one. IIRC, they aren't that easy to differentiate. What are they? 0.036" and 0.037"??? Try the bigger one. Some people use 0.039" or 0.040" IIRC.

 

[SethDog3200]

Yes I believe .036 and. .037 not sure which one I put in. I have opened the fuel screw so tomorrow I will try the other jet and let ya know how it goes.