Unexplainable loss of mid range

**noobi** · 12th November 2009, 17:51

What reasonable explanations are there for a sudden loss of mid range power.
it started last Sunday when the bike wouldn't run properly, it was either throttle wide open or idle. nothing in between. just burbling, i changed the plug, same problem. i checked for blocked jets, same problem, i dropped all the fuel and rinsed tank and carb with meths to disprove water, same problem
. cleaned air filter, same problem. replaced fuel with different fuel/oil mix. same problem

the only thing i can think of is reeds, but i cant check them because the reed block is bolted is with a bolt with no head

the pipe is cracked but its been like that for a while and the loss of mid range is new

I'm going to get the pipe welded and the muffler re packed.

the jetting was fine last summer.

before you say oh its a gasgas, the carb is made by keihin, same as ktms

**klx kid** · 12th November 2009, 18:03

i had a similar problem.....i ended up taking the kill switch off and it went fine. so i put the kill switch back on and it started to fell my plugs and have no mid power. i ended up leaving it off my bike 4 a while and then i put a new coil and kill switch on and now im back at moto-cross going hard haha...

(oh and my bikes an 07 so its not like it had a hughe amount of use to burn out the coil or anything)

**noobi** · 12th November 2009, 18:28

Originally Posted by klx kid

i had a similar problem.....i ended up taking the kill switch off and it went fine. so i put the kill switch back on and it started to fell my plugs and have no mid power. i ended up leaving it off my bike 4 a while and then i put a new coil and kill switch on and now im back at moto-cross going hard haha...

(oh and my bikes an 07 so its not like it had a hughe amount of use to burn out the coil or anything)

did you unplug the switch and just connect the 2 wires together?

**K6K** · 12th November 2009, 18:33

Is it loss of midrange or loss of mid throttle position? If it is throttle position it points to the needle jet fuel circut.

**klx kid** · 12th November 2009, 18:37

Originally Posted by noobi

did you unplug the switch and just connect the 2 wires together?

u mean the switch wire and the main 1 it connects to? if so yes but it had to be repositioned so that it would work.... it might not be grounding on ur bike either?????? that was part of the problem with mine...

**cheese** · 12th November 2009, 18:41

It could be a stuck power valve, check its moving freely. Also check the reeds.

**noobi** · 12th November 2009, 19:13

Originally Posted by cheese

It could be a stuck power valve, check its moving freely. Also check the reeds.

checked the pv, it moves freely, but also found that there is watery oil splashed up onto the pv cover. so i dropped the g box oil and its just like new, which it is, less than 1 hour old.

i have no idea how to check the reeds as one of the bolts has not head to undo

K6K, im not sure which it is, as the bike wont run on either.
i checked the carb, cleaner the pilot jet, which did have some crud in it. but it still wont run properly.

**noobi** · 12th November 2009, 20:20

Originally Posted by cheese

Also check the reeds.

checked the reeds, still carbon fibre and mint. a little bit of scuffing on the top reed but otherwise seal well and un chipped

very quickly running out of things it could be

**vazza** · 12th November 2009, 20:26

GG's aye.. Cant trust 'em :P

**flyingcr250** · 12th November 2009, 20:34

Originally Posted by vazza

GG's aye.. Cant trust 'em :P

ha ha i didnt want to be the first one to say that lol

**rossrc** · 12th November 2009, 20:37

I had the same thing happen to me with a KTM 300, but that time it was the PV - screw came loose so the mechanism wasn't engaging. Can you run it with the covers off and see it's actually moving?

**noobi** · 12th November 2009, 20:37

Originally Posted by vazza

GG's aye.. Cant trust 'em :P

your electric start broken yet?

**vazza** · 12th November 2009, 20:38

Nah mate its working 100% sweet. I love e-start. Was riding up a tree and I stalled, lucky I had the e-starter!

**noobi** · 12th November 2009, 20:41

Originally Posted by rossrc

I had the same thing happen to me with a KTM 300, but that time it was the PV - screw came loose so the mechanism wasn't engaging. Can you run it with the covers off and see it's actually moving?

i took the l/h side cover off and watched the pv open and close when the engine was revved. i think its a jetting problem as the bike runs fine at idle and just above idle and it will run WOT as long as its revving like crazy.

although i already cleaned the pilot jet out. time to strip it down i guess.