DRZ new carb shpluttering like a good thing..

[Matt 300]

Hi lads and lassies,

I did a carb swap on my DRZ. I opted for replacing the stock 36mm carb with a 40mm CVK carb off a KLX650. It is a popular swap and many DRZ owners have done it. The bike started straight up with the choke and idle'd a bit high so i adjusted the idle screw and brought her down to normal.

Ive been riding the bike for about a week and ive been playing with the fuel/air mixture screw to get it running sweet, but im still finding it is popping and backfiring loads coming down the gears and into corners. Even spat a few flames and got me pulled over!
To view pics on this biker's forum - your post count must be 2 or greater.
Running lean? Also if i snap the throttle open from idle it just shuts off, you need to slowly roll on off the lights etc but once moving it seems to pull great. Currently running a 148 MJ. Diaphragm and all is fine. Do i need to rejet or should the fuel/air mixture screw sort out my backfiring and bogging?

Any help appreciated!
To view pics on this biker's forum - your post count must be 2 or greater.

Matt

[generalisimo muldoon]

I'd say she sounds a bit rich. Start coming down the sizes on the jets. It's been a few years since I did any rejetting but from what I remember the main jet is for mainly full throttle so I'd be looking at the needle and pilot jet??...I think.

[doctorchopper]

My wr popped on decel as well, i dropped the needle 1 clip and this helped it out

[GreenRex]

Dunno if your SM has Exhaust gas recirc ( usually some hoses coming from the top of the head into the carb. Emission shite, if it does , pull all that shite off and get a set of block off plates for the top of the head. My Rex and KTM really popped on the overrun with that crap. Much better now , though if Im really getting on it , it will shoot flame, keeps the cager assholes of me butt
To view pics on this biker's forum - your post count must be 2 or greater.

[chopper]

overfueling/ bogging

[hotboxzerox]

that cvk 40 has a "coasting enricher" meant to stop it popping on decel, id bet its a lean pilot circuit that being the pilot screw or the pilot jet itself too small.
similar to what im finding with the new klx as they are lean as fuck as standard.
my idle was hanging when revved and that first 1/8 throttle caused a bog that was stalling it.
turned the pilot screw out to 3 turns which has sorted it mostly apart from a lean main now but they more than 2.5 turns out and they recommend ya go up a pilot jet size instead.

[Matt 300]

Problem is sorted! The fuel mixture screw was way off. Screwed it back in to zero and tested the bike every half turn i moved out. Best setting was 2.5 turns out. Runs great now!