Gp1200r lost tpms with dynafly impeller and nujet.

[Krisgpr]

Ok so Im pretty sure I need the carbs rebuilt to oside specs but I'd like to get some opinions.

I was at 7180 rpms at 67mph with the Concord 13/19 and 87mm nozzle.
Since then I've noticed quite a lot if bogging in the mid range and dulled power but still maintaining over 7100 rpms.

I installed a box stock nujet 6.0. 64mph and 6660 rpms with 87mm nozzle.

I installed a box stock dynafly 14/20 and got 65mph and 6680 rpms with 85mm 60t nozzle.

Dynafly definitely feels better and like it is capable of more speed.

Compression is at 135-138 psi on new top end with shitty parts store gauge with r&d 41cc heads.

My assumption is the stock carbs are the culprit and need to be rebuilt and updated.

Thoughts?

[TCR]

Did you try the dynafly with the 87mm nozzle? Why did you go to the 85mm?

[Krisgpr]

Speed lol. 1 MPH is 1 MPH. That nozzle won't drop that many rpms. Maybe 50-60. Not 500+

[TCR]

Depitch it to a 19 on the trailing edge and use the 87mm nozzle. Give a full list of your mods so I can help send you in the right direction. Plus a rough idea of where you are located and the water conditions that you ride in.

[Krisgpr]

R&d heads. 66e cylinders, d plate, chip, wave eater clips and couplers, r&d 800 grate, r&d plate. Oil injection delete. Stock carbs untouched. Stock air box.

Local fresh water lake, smooth water, 80* out, 108' elevation.

Im pretty sure it's lean. It's got a pretty bad mid-range bog in the 4k range.

[TCR]

You definitely need to rejet and make your high and low speed adjustment screws accessible. The machine is lean in the first place, then you added cylinders with more agressive port timing. Now you are loading the pump/engine harder with a more agressive impeller/ nozzle combo. Your fairly lucky to have not blown it up yet. I would start by pulling out the fuel baffle and check condition of the pick up. Remove the plastic flapper from the pick up and check the length of the return line to the bottom of the pick up. The line tends to swell and grow. Then rejet to bills specs and drill out the returns also. Sell the nujet and upgrade the pump fully. Invest in some flame arrestors and a jetworks valve for stinger water control. Tune and live happily ever after.

[Krisgpr]

I rebuilt the carbs to bills specs and tested on the water with the old plugs and new dynafly impeller. I picked up 150 rpms from last time with the same impeller but still about 250-300 from my target rpms. I noticed the PTO plug was darker than the rest so I assume it was just a fouled plug from running lean before. Hopefully that gets me closer to 7k.
My question is about the reduction nozzle I'm using which is 85mm from a 1300r. Does the 85mm nozzle kill your rpms that much?

[Krisgpr]

I put the 87mm nozzle on. Will test tonight along with the new plugs.

[Crazypirate]

Are you still running stock flame arrestor with the recipe? If so, it will be too rich, remove the screen and it will help. But with 66e cylinders, it may be still lean...some people use 135m for them.

[Krisgpr]

I removed screen, front silencer, and drilled (6) 1" holes in outer cover and installed uni air box vents. If it's still too rich I'll put the pro k arrestors. Just testing a theory...