Flat, bucking, good , flat

Bought 86 250r with complete top and bottom rebuild but had hole in top of new piston. Put new CDI and stator in. Have a 38mm PWK carb. Came with 152 main jet and 48 pilot. I thought the main was to small so I put a 168 main in. I have never rode this quad before. It starts first kick and will idle but not long. It then runs super flat off idle as I gradually increase throttle after about 1/4 it starts to buck a little. Then around 1/2 to 3/4 it picks up and sounds good for about 2 seconds and then from 3/4 to full it falls flat again. Top speed must be around 15 - 20 mph. I'm confused because it seems to be lean and rich all at once.

Also I have the idle screw all the way up and it doesnt seem to affect much, but when I was trying to adjust my pilot I forgot the gas was off and right when the gas was about out the idle shot to wide open and the engine kill switch wouldn't work then in about 5 seconds it ran out of fuel. But for that last five seconds it seemed to have worked how it should?

lets back up a moment............ have you made sure that the float is shutting fuel off and the the float is adjusted correctly? and are the reeds laying down as they should? this must be done before you can make any attempt at jetting.

back to jetting... the 48 pilot is a good starting point with the pilot set at about 1.5 turns out. what needle you running(should be set in the middle)? the main is about right for starters.

once you've varified the float level and that its shutting fuel off and have a fresh plug gapped at .018 - .022. warm the engine up to operating temp and get out in some terrain and run the gears. it may load up on you as gas en oil will tend to puddle in the crank case and it's throat needs to be cleared"so to speak". after running through some gears a couple of times note whether or not it tries to clear out. if it does then try to perform a wot plug chop for the main. once you've got it jetted for main. do a chop at mid throttle paying attention to how it sounds. once you've got the needle adjusted focuss on the pilot jet and pilot adjustment. once you got all three fairly close you can do a fine tune from there.

reeds look brand new. I had a 34mm keihin PWK lying around so I put that in with a 48 pilot and a 152 main. Needle is a R1470 at the 3rd clip. Does exact same thing. So from a 178 main to a 152 it performs the same. except now it only starts on choke and with no load sounds goos til 3/4 then bogs. But when I take choke off it takes a few seconds buut then revs at WOT like the throttle is stuck. Also I have ran the quad a max of 5 minutes and have lost almost 1 gallon of fuel ( I have taken the carb off about 5 times but still seems way to much) I am getting very very frustrated here.

make sure the carb vent lines are clear and not pinched. this could also be a crank seal problem on the flywheel side.

it sounds like you're not the most mechanically inclined person out there, no offense intended but you need to be careful you don't blow the thing up. your second paragraph in the original post is caused by a lean condition from there being no gas flowing into the bowl. it'll rev to the moon till it runs out of gas or blows up, usually it'll run out of gas first.

there's no set rule for jetting, 2 basically identical machines could have very different jets, but jumping from the sizes you're doing is trouble waiting to happen.

you need to start from the beginning and get back to the basics first...

properly adjusted throttle cable
good grounds
all carb passages clean
comp and leakdown test if possible
good fuel flow
carb and tank vent lines clean
new plug gapped correctly and plug boot tight on the coil wire, coil grounded, stuff like that

there's been more than one thread on here that people have all kinds of trouble with their machines and have double checked everything only to realize that they were out of gas, which they said they had plenty:ermm:

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Originally posted by cdrookie
it sounds like you're not the most mechanically inclined person out there, no offense intended but you need to be careful you don't blow the thing up. :

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No offense to you but I actually been a mechanic as a profesion for over a decade as a living and I am very familiar with two stroke motors but have always delt with CR125'S AND 250's when it comes to Honda. I know I may come off as a rookie with the 250r and it is because I am. I have never owned or even worked on a 250r and know they are not the exact same copy as thier two wheeled brothers. I was just hopeing there was something I was missing 250r specific. I am now leaning towards CDI failure as no matter what I do with jetting it alway s acts the same.

ok, my bad.

CDI's are pretty reliable, doesn't sound like that cause when they go bad they're usually toast, plus you tried a few different ones.

I did try two other but the other two I tried did not get spark out of. I just think I will try to find a whole new electrical system for the quad. It just seems odd that no matter what I try jetting wise it is the exact same result, like the timing is off.