rough run over 3/4 throttle

this bike is starting to confuse me.:thumbsup:

bike is an 04 crf 450r, have drd pipe and one ride on a cylinder works 490 big bore kit. put the big bore kit in it two weeks ago after blowing it up this winter on the ice. changed jettin to a 180 main 47 pilot 1 3/4 turn on idle screw and raised needle one position. i live in michigan so close to sea level and mid 60's this time of year. i checked valve clearance while it was apart and its not within spec but does have some clearance (i believe 2-4 thou intake and 5-7 ex) bike ran great first weekend out on the track. no oil or cooland usage, no over-heating.

took it home and washed it, oiled the chain and put it in the trailer. went to do some trail riding this weekend and anything over 3/4 throttle it acts like its running out of fuel (hesitates, spits and coughs) roll off the throttle and its fine. hot or cold runs the same. coil ground is good, cleaned the jets and still has same problem. pulled the spark plug not cracked but looked lean, stuffed a 220 main in it and still same problem plus a hesitation off idle from being too rich got the carb completely torn apart now gonna put a 185 main in it just to richen it up a bit.

i really dont know where to go next with this thing. any advice would be much appreciated

From 180 to 220 is a huge jump! Make sure you don't have any air leaks and get your valves adjusted to spec. Why fix a symptom when you know the patient will still be sick?

Take that main jet back down to 175 and the pilot to no bigger than a 45 and it'll run fine and put the needle back in the middle.

Make sure the float is working properly in the carb too. And try loosening the gas cap. If it runs better the vent part of the cap might be plugged.

Also, make sure you've got the throttle slide plate in right side up. If that little cut away is up, its in upside down.The flat side with the cut away goes down, with the pointy side up. I know it looks wrong like that but trust me.

If all this does nothing for you, Id look at the stator pick ups. They can get debris on them that short the stator out. Iron debris. Where does iron debris come from? :thumbsup:

If all this does nothing for you, Id look at the stator pick ups. They can get debris on them that short the stator out. Iron debris. Where does iron debris come from? :confused:

Amen!:thumbsup:

mine were infested with the mystical iron you speak of. lol.

i've recently purchased a new intake boot. i think it was less than ten bux.

i cleaned the carb really well, installed the boot, and cleaned the stator. the bike was great.

Where does iron debris come from? :confused:

from the timing chain, sprockets, counter balance bearings, main bearngs pretty much in that order :thumbsup::worthy:

so... cleaned a reassembled carb with 180 main, 45 pilot, fifth needle clip position. checked fuel vent hose and all fuel lines/passaged/screens for obstruction and same problem. pulled plug wire and set it on the plug not clipped in and rode it to test coil, no difference. have to see if i have stator cover gasket tomorrow before i pull cover to inspect pickups. ist possible they could have some shrapnel left over from the last time it blew up. is thre any other good way of testing the stator, coil, and cdi short of swapping them out.

thanks for all the advice.

from the timing chain, sprockets, counter balance bearings, main bearings pretty much in that order :thumbsup::confused:

The timing chain and sprockets make very very little debris. The balancer bearings can, but that debris would be in the trans mostly.

That leaves the mains. Not good.

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