hi guys

I have a 2009 KX450 that has very weak bottom end and mid range power. It has an FMF 4.1 with a PowerBomb Header and stock piston. It has approximately 40hrs of running time. The piston and ring was just changed and the valves were checked. It made very little difference in the way the bike ran.

The bike is very easy to start - 2nd to 3rd kick every time, and has excellent throttle response.

It feels very sluggish down low and labours pulling 3rd out of corners.

Do any of you guys have the same problem or do you have any advice on what the problem could be?

Thanks guys,
Rob
:banghead:

Is this a new issue for you or has it run like this for all 40 of it's hours? In other words Did the bike suddenly perform differently than when you first owned it?

either ur used 2 sum gnarly bikes or ur jetting is off... lol o woops its fuel injected. umm mayb ur ignition mapping has a problem

The bike ran awesome when new and most of the summer. I thought I was just really used to the bike, but I tried another 09 KX450 and I could not believe the difference.

We just figured it was time for a top end change; after all, it did have roughly 40 hrs on it. Everything looked good, the valves were all within spec, and the cylinder looked great.

I am stumped and pretty disappointed.

No, I never have ran the insert with the pipe.

No, it worked awesome when new. The power started to degrade over the last 10-12 hrs on the bike.

Like I said, it has approx. 40hrs on it, and it was overdue for a top end change.

I still have my 08 from last year, and the difference between the two is night and day. And, then when I rode a friends 09 KX450, it became quite apparent that we have problems.

When the bike was new, the bottom end was great. It did'nt labour at all pulling tall gears out of tight corners.

I do have the Kawi programmer and the ignition is programmed with the advanced timing curve - which is suppose to improve bottom end.

Thanks for your help.

Rob

Ed

It has been working like this for the last 10-15 hrs of use. The top end was just changed, valves checked, etc.

This made very little difference in the way the bike ran. All of this info has been stated above.

It has weak bottom end power.

Based on everything that I have stated in the previous posts, do you have any advice???

Thanks Ed

Also, does the insert for the FMF pipes make a big difference? I have never tried the insert, but plan to tomorrow - maybe that will help.

mxer701 said:

The insert is restrictive and won't help your problem.