TBR7 Spark Plug

[Thvxxmvru]

I had just installed a NIBBI PEZ28, new air filter, and new exhaust. The bike runs, but has misfire and cuts out when I full throttle off start. I was told to buy a new 3 prong spark plug, but I don't know which one would suit my bike

[Megadan]

Spark plug isn't going to fix that issue. It's not an.ignition cut, but the air fuel ratio is going so far lean when you crank the throttle open that it can't fire.

[Thvxxmvru]

Does it change anything if I say that the bike runs perfectly fine when I don't yank on the throttle off start. After I'm going I can do whatever I want to the throttle, works great.

[Crossbar]

If you're running a pod filter, try removing it and see if anything changes. I've seen some of the cheaper pods restrict too much air flow.

[Megadan]

Does it change anything if I say that the bike runs perfectly fine when I don't yank on the throttle off start. After I'm going I can do whatever I want to the throttle, works great.

No, doesn't change a thing. When you yank the throttle open it's natural to get a lean moment. You cause a sudden spike in air, but the fuel needs a moment to "catch up." On a well tuned carburetor you would only experience this as a small bit of what feels like soft throttle response. This is why accelerator pumps were created.

Your idle mixture and/or pilot jet are likely just a bit too lean.

Or, it could also be a weird issue like Crossbar mentioned, and it is actually causing it to go so rich the same result happens. Too rich and it can't fire either.

[FreshestTorqWrench]

I had to do quite a bit of experimentation with my Nibbi 30mm here in SC. Ended up with a 42 pilot and a 130 (I believe) main. Sounds like your bike may be running too lean. If it runs fine except under a snap of the throttle to wide open, you can try raising your jet needle one or two spaces. Personally, I’d start with going one size up on the pilot jet and if the issue continues, try the jet needle and see where that puts you.