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Noob fcr-mx bogging question

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Hi have an 08 klx450, 160mj, 48 pj, 2.5 turns, stock needle (4500-7000 elevation) Keihin FCR-MX 40mm. The bike seems to run alright, but when I quickly twist the throttle from idle, the engine will generally die.

Also, not sure if this is the same problem but when I run a gear higher on this bike it doesn't seem to run right with low throttle I don't think I'm dropping the rpms to the point where the engine can't handle the load, but it's just not pulling smoothly. From reading other posts in the klx450 forum I am under the impression that this bike should ride very smooth in the low rpms.

I only have a handful of hours on this bike brand new and have no other bike to compare it it's behaviour to.

Thoughts?

Thank you1

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based on my limited experience, it sounds like it could be accelorator pump timing. Have you done the o ring mod yet? You might want to wait and see what some of the pros on this site have to suggest, but if it were my bike, based upon what i have learned here and in my own driveway, that's where i would start. Check out the thread having to do with DRZ 400 jetting issues. i just posted my results there, and William and Eddie were invaluable in helping me solve my problem. thanks again guys!

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Does it bog when actually riding? Nailing the throttle right at idle and getting a bog is not an accurate representation of riding.

A bog and a slow speed running issue are not directly related. If the RPMs are too low or the gear you are in is too high, the bike may not be able to pull it, try down shifting, make use of rpms.

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They may be two separate issues.... not really sure though.

After the bike is warmed up and in neutral by my garage, I give the throttle a quick sharp twist and the engine will often die (this feels like a jetting problem for sure) - I do not to really do this when riding as l like to keep the wheels on the road in the off chance the engine keeps running when I try it 🙂

The other problem when riding a gear high _could_ just be an rpm range, but I some how get a feeling there is more to it. Maybe over reading has caused my expectations for the bike to be too high...

Again, I'm less than a competent carb mechanic... but that's why I'm here :D

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Do you ride in your garage? Does it bog when actually riding? Not to bust your chops but you are asking a real lot from a thumper to be able to nail the throttle at idle and not have a issue. We could resolve this but the side effect would be a 'rich bog' almost any time when riding and hitting the gas. So... if you do not ever have a bog when riding, the fact that it bogs in neutral in the garage is a non-issue.

Not knowing you or seeing you ride, my take is that you are lugging the engine. Does this happen in first gear at all? Does it get worse the higher a gear you are in? Then drop down a gear, get the rev's up.

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No garage riding... and I generally don't whack the throttle open from idle while riding so I couldn't tell you - I try to keep the throttle control very smooth. I've got 10 hours on this bike moving from a drz250 which has neither of these problems. I could ride that bike in 6th at 40km/h and it never complained like the klx does in 5th at 80km/h. Apples to oranges I know...

Probably just unfamiliarity with the bike but something just doesn't feel right.

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80kmh in 5th is definietely too low a gear. 100kmh should be the starting point.

The DR is a soft play bike, the KLX is more of a race bike and should be ridden accordingly. I run a WR250F and would not think of shifting into 5th below 100kmh. I also have a DRZ470, I can cruise at 100khm on it but if I am going to accelerate, I have to be in 4th at 100

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