need advice

I have a 300ex and after the below the bike has less power than before need trouble shooting advice. also not shore jetting think it might be the problem:bored .40
wiesco 11.5-1 piston
four stroke tech cam and rockers
k @ n power kit
fmf power core iv kit
head shaved port and polished and after this the bike loses to a stock 300ex

[patrick delao]

What is your altitude and what is your jetting right now. I am at 5600 feet and my main jet was 140 with the same mods you have . Nice bike though but had to up grade to a 440EX HUGE differance :)

i am at sea level or just below belive it or not and can't remember the jet size.

what's the motor tellin ya??? IS it bogging anywere,,top to bottom,,,does it pop on top end. You most definitly got a jetting problem it sounds like,,did you do the work or have it done..If ya had it done call the engine builder,,but if it's not jetted right it should be boggin, backfiring, stalling,,something,,the motors tellin ya,,,just listen..good luck.

[Dave400ex]

I have a 02 400EX and it won`t start. The jetting is stock. I just got done putting in a K&N Air Filter. It`s getting really cold around here. I tried starting it yesterday with the choke all the way on and gave it some gas. It would run for a second or so and then it would die and the engine would make a loud pop. Does mine need to be re-jetted?

[MichaelS693]

umm yea i would

[400exJOE]

if this quad is just back from the shop, it NEEDS to be broken in. It should be ridden gentely for about 10 hours. Then do an oil change and you should be all set. Your jetting could be off too though. Read the spark plug. A black and carbonized plug means too rich. White electrode equals too lean. You are looking for a golden brown color.

[kc 300EX]

11.5:compression, dumb question, are you running the right gas? thats gotta be race gas, or atleast 92/race mix, i hope yur not tryin to run it on regular!

[Dave400ex]

Were you talking to me?

[MichaelS693]

yea dowg

[Dave400ex]

I ordered a TC pipe today so I`m just going to wait and re-jet for the Filter and the Pipe at the same time.

The mods have been done some time and the oils been changed several times. I had a crack in the block by the forward motor mount. I've welded it the best i could and spot checked for cracks. If its stil a tiny gap would that effect power.Also I run cam2 110 octane or VP red.

[redrider ex]

try jetting

[400exdad]

Someone tell me if I'm wrong, but if you shave the head, haven't you just affected the valve timing? Sure the tensioner took up the slack, but it would still change the timing. Would it be enough to make it run poorly? I'm asking. With a car, say a small block chevy or ford the cam is in the block and the timing isn't changed when the heads/block are shaved to increase compression. With a two stoke, of course, there is no cam and shaving just increases the compression. But with an overhead cam motor.... you know what I mean.:rolleyes: