Hi all,

Bought my new 2009 KLX250sf only last week. Already have the edge2 kit and 601 flashers ordered.

Really would like to order a new end can for it too.

At the moment, I am just running stock everything and for now, I'd like to keep it that way. Apart from a new end can.

Later on, I will do a 351 and pumper carb and new powerbomb header. + whatever airbox modification that needs to be done..

But for now, I am looking for just a simple end can replacement.. Can that be done without rejetting? or modding the airbox? Or will i get a load of flat spots?

Which brand is best suited to a stock carb, airbox and header? I'm looking at this upgrade as purely cosmetic at this stage, to go with the new tail kit. , and of course I'd like the bike to sound better than it does now.

Keeping in mind that I will be buying the 351 and all the other typical upgrades later down the road.

What are my options at this stage.

Thanks in advance.

 

I'm thinking a FMF Powercore 4 slip-on... without the FMF Factory 4.1 Quiet Core Insert


What are your opinions? Mainly on flatspots with no carb changes..

 

My FMF said in the package insert that no jetting was required and I installed it that way and ran it for about a week. It was a pretty good performance boost all by it's self, I'm not sure how much leaner it was but it ran well with no airbox mods at that point. I then installed the jets and modded the airbox about a week later and got a little more out of it. The pipe alone was the biggest boost, more so than the jets and airbox. Like I said the instructions that came with the FMF said no jetting required, and it did add some HP alone. Was it safe to run like that? I don't know and didn't do it long myself.

 

Most the pros here tell us the stock bike is very lean (very much agreed for my '06). Putting on a new can that increases air flow, without adding more fuel (jets) may put you into a dangerously lean condition. I did airbox (removed lid, then put it back on with snorkel removed), muffler (HMF), and Dyno Jet kit all at the same time per their recommendations. Maybe by leaving the airbox alone and not trying to run WOT too much you may be okay???

 

So how do you know if you are running too lean? If I just change my end can for a FMF and make no changes, how do i find out I'm running too lean? By only the engine overheating? Checking the plug? How?

I'm just not an experienced mechanic in any way. I'm sure I'd be fine with a little guidance on the air mods and jetting. But right at this moment I'd be going in blind, hence my hesitancy.

i was going to just buy an upgraded carb at the same time as the 351 kit.. I think I'd be able to install the 351 by following a good write up. I did switch out a piston a long time ago on a old two stroke. I do like to have a go, but normally in the past I've ridden sports bikes which have never needed modding & all my cars have been new enough to never need to go in the hood, unless for general maintenance.

 

I found it intresting that FMF would make the blank statement that no jetting was required, I'm sure some research went into that as there would be some liability with that suggestion. Lean motors generate more heat and you could check the plug. Look at it now so you can compare to what happends. Don't even add a more free flowing air filter without a rejet as that adds more air than a slip-on will. As far as how to run it if it's lean it could be at idle or mid or wide open. That's where reading plugs becomes a science as you need to run it at specific rpms and shut it off and look then. Also lean damage is cumulative, even if it is lean a little won't matter too much it's time and heat that really causes issues. Most people on this forum will tell you to jet for either intake or exhaust mods and that is good advice.

 

What Linkin said on the HMF blanket statement is interesting. Kind of goes a little contrary to what most others say on the risks of opening up without more jets. Would they have some liability? That would maybe hard to prove their product caused a problem. Read some of the FAQ threads and search on jetting & carburation. This one from HMF was really helpful for me in jetting the carb, which isn't too difficult and is a good way to get to know your bike better . Maybe backing off the mixture screw on the stock could help (counter clockwise adds more fuel in the pilot circuit) but that takes removing the carb and pulling out the plug that hides the screw, and if i were that far into it then I'd just re-jet.
http://hmfracing.com/forums/showthread.php?t=1617

Do some searches and you'll find some other symptoms of lean conditions. One thing I noticed was the tendency for the rpms to drop slowly after releasing the throttle. Now that its jetted better, the rpms drop down pretty quick on throttle release.

Feel free to ask questions. There are lots of folks with much more experience than me around here willing to help.
Cheers,
Scott

 

Thanks, its all a learning process for me. Never rejetted before, but it sounds like providing i don't mess with the airbox, the end can might be ok.. But mess with the airbox and i'm asking for trouble. As i said, i do plan on getting a pumper carb when i get my 351 kit later down the road. That's probably when i'll play around with the airbox..

Thanks for the link and good advice.

 

As far as jetting changes go, there is alot of info here and in old threads. Ask for some links when you get ready as there is one thread I remember that walks you throught it with pics and is well written. I'm not computer savey enough to do it now but some of the old dogs here will. It dosen't take many tools and nothing exotic, post any questions as they come up. For someone who has done it before it is less than a 2 hour job. But since you seem new to it I'd plan on a weekend of it with many breaks to think it over and read as you go.

 

Here's a few of the ones on my classics list:

https://www.kawasakiforums.com/forum...ead.php?t=8886

https://www.kawasakiforums.com/forum...ad.php?t=34211 see esp post 29's image.

http://www.dirtbikeworld.net/forum/s...ad.php?t=26074