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Occasional bog after turning

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Jul 7, 2005
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#1
Hi,

My 03 CR 250 is stock except for FMF fatty pipe. It is a little rich but starts and runs great, never fouls plugs, no spooge - The bike has approx. 80 hours of use.

I am one of the slower guys on a sand track which is fairly bumpy and turny - technical.

Occasionally (3-4 times during 20 minutes) when I roll on the gass after turns (fast as well as hairpin turns ) it bogs/hesitates.

I tried rasing the needle a single clip, which resulted in some rough running in the middle range but didn't affect the bogging.

I checked the floatlevel, which appears to be at stock specs. - needle and seat is new.

I cannot provoke the problem on a flat straight.

Have any of you tried something similar ?
 
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#2
when u hit the throtte and it bogs and hesitats then goes is a sign of your bike running lean. Check for air leaks. or it could be your float level, not nough gas getting to your cylinder in time
 
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#3
Thanks 84cr125, yes I am thinking a lean condition too, I just can't figure out why it isn't consistent - but as you said it could possibly be the float level being affected somehow when making turns on a bumpy track - I'll try and raise the float level the next time I go to the track to see if it has an affect.

If I have an air leak somewhere wouldn't it always show consistent behaviour ?
 
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#4
ya, seeing as how ur bike is an 03 the ods of having an airleak is pretty low, unless you havnt changed your oil seals.
 
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#6
my 03 was bad for that it would bog down for a few seconds but if u change up a gear it kicked into life pretty hard...it was running to lean and my float levels where perfect..lol so the shop said..
 
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#7
Thanks for all your help, I have ordered new crank seals and spacer, just to be on the safe side - they are 4 years old anyway. I need new reeds too as the oem's are just starting to peel right at the very end in one corner - but reeds affect carburation signalling thus I would preferably resolve this first.

keithcr250r did you ever resolve your bogging issue ?
 
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#8
you should be replacing your oil seals every season, riding for 4 seasons would probably be the cause of your bike running lean. the reeds will also help but not as much. Do a plug chop and it will tell you if its running lean.
 
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#9
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#10
they look extremely oil fouled.
maybe your problem going around turns is that youve got too much oil in your cases and cylinder that it just need to burn it. Have you adjusted your jetting/ float level?

ive got a good plug reading guide in microsoft word format, send me a PM with your email address and ill send it to you.
 
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#11
Yes I have adjusted the float level - 12mm instead of stock 15mm, but unfortunately I only have track time on tuesdays - noise regulations are killing me in this country - I doubt it will make much sense testriding in a field somewhere as I only experience the bogging on the track.
 
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#12
try setting your float back to stock, cuz if u want to make your bike leaner since of your FMF pipe ull need to change the needle position or somehting like that. go to the FMF website they'll might tell you what needles u have to run.
 
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#13
when u pulled the plug was it after u used a new plug and did a plug chop. cuz if it was just idling thats not really a good indication of what your jetting is like?
 
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#14
I just pulled the plug after a 20 minute practice session - there is some slow running included (getting off the track) but not really any idling.

I have a couple of other two-stroke motocycles which all produce tan coloured plugs just fine - this is the first time I have a bike that behaves like this - lean behaviour while being real rich, maybe you are right about the plug sort of oil fouling in the turns.

What would be the smart way to approach this initially - run a hotter plug, lean the bottom pilot/needle ?
 
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#15
FMF suggests that I use the richest needle available in the first clip position (3 needles richer and one clip position leaner) and then lean the main jet from 420 to 400 - They have no advice regarding the pilot. - I am not sure wether I should try this, I'd rather try little steps at a time.