Just took brute 750 out for the first real ride since I got vdi snorkel and jet kit Everything rode alright for the first 20 min. or so and than it started acting up At first it was wanting to sputter out when going around 50- 55 or so but i would just give it a little more gas and it would get on up to about 60 or so. It didn't do it all the time just sometimes. which I know the jetting on this thing has to be off a little with it is only doing that I THINK. I only have 26in mudlites on. than after a little more riding it would almost lose all power when going slow in low gear and sputter out and would backfire out the exhaust which in my experience tells me it is running lean I think I am curently running dj 144 in the front and dj 150 in the rear WHat should i DO Change the Jets or do yuo think I may have a bad map It did this on Both map 1 and 2 Did not have stock cdi availiable at the time to switch back to it but i just dont think it is that but i may be wrong HELP

 

I would jet up a size and see if it helps.

 

Take it out for a spin again and when it starts to sputter slowly apply your choke. If it gets better then your running lean and need to jet up. I'll bet your cdi is fine your jetting is more than likely the problem. If it's acting up at 1/4 throttle and full throttle then your fuel curve may be way off. If you have access to a dyno that is the only way to go when tuning. I don't care how good of a tuner you are only so much can be done by plug reading and seat of the pants. Just look at nascar and the nhra, the greatest engine tuners & builders in the world, but you can bet the farm every motor in every vehicle has been dyno tuned and tested.

 

you may wanna contact vdi through email, they reply within a few hours. the first time i used my cdi i got up to around 50 and it stuttered and backfired, then the exhaust bolt came out. so here i am quad is backfiring and all i hear when i hit the throttle is a tingy noise (didn't realize bolt fell out). thought the motor was shot. well next day i get a email from vdi telling me the cdi was missing half a map( caused the backfire). they sent me a a free cable and pod to fix the problem. so now i can program my quad and it was free just had to wait to use the cdi.

 

yes you want to check the problem rpm areas useing the choke test but you also want to check the main/slow jet the pilot jet and the needle clip. this is a easy guide on how to.



If you want to check the pilot/slow jet do this:
Find a nice long straight where you can go fast safely, note the position of the throttle, you want to be about 1/4 throttle, let the rpm's settle and pull the choke.
If it: runs better you are LEAN and need to jet RICHER.
If it:runs the same you are in the ballpark.
If it: runs worse you are too RICH and need to LEAN out the mixture.

The same can be done to check the needle clip position. You will need to hold the throttle somewhere in the 1/4 to 3/4 throttle position then do the choke test and observe the way the machine runs.

The same for the main jet but in the 3/4 to wide open throttle position, then do the choke test and observe the way the machine runs.