New rebuilt engine. Hit rod light weight crank, high compression forged piston 13.5 to 1 cam mod. Oil squirter, oil pump mod, hmf pipe, air box lid removed ,uni air filter. I had the carbs done and re jet. I cleaned air filter and run 91 octane. It has a hard time starting. Then the idle sticks and idles high. If I set idle screw low, then it dies at a stop.

 

Try adjusting the mixture screw....and what size pilot do you have installed?

 

I always have to mess with it during the ride. I'm sure that's bad and idk what size jet but the people that build the engine said it was perfect

 

I'd at least see what they installed for jetting compared to the stock #155 main and #48 pilot jet the breakdown shows. Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse

 

Yea I'll look into it. I'm not a mechanic tho :-(

 

If you still have it, put the air box lid back on and try it...ride it, see if it changes the problem, or rather improves the existing problem. And as OPT recommended, it might be a good idea to have someone check the size of the currently installed pilot and main jet. The Yz450's are very lean on the pilot when engine/exhaust is stock.....and much more so with an exhaust, engine work, and no lid installed. And you might check the carb boots to ensure carb is fully engaged into the boots, and boots are tight.

 

Thanks guys. Yes I do remember mechanic saying i need air filter lid. I thought people removed those for better air?

 

^^^^^They do but ( for more air ) , it requires the proper jetting, and its a bit of a pain, the jetting that is, and it trashes the air filter much faster. Your mech could have changed the jetting for it, not sure why he didn't. Unless you drag race or run the track in competition, leave the lid on

 

Try that with a Polaris and it'd run crappy too.. People just seem to forget or get in a hurry a lot of times when they rebuild a carb to try it out and wonder why it bogs,then after several posts finally reveal that they have the air box and filter off.. That's why I started asking. Same for the lid being off,just causes them to run lean and bog,idle erratic,etc.

 

Is there a temp fix. I'm broke.