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Starting and stalling issues - KLX450F

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I have been doing some searching on this subject and have an idea of where to go, I am just looking for confirmation that I am heading in the right direction.

Bike: 08 KLX450F - full Pro Circuit exhaust system

Issues: Nightmare to start hot, stalling into corners when off the gas

The bike belongs to my riding buddy and has been plagued with problems since he bought it. Sat we went for a ride and the thing played up no end, he was getting very angry with it so I said I would take it home and try and get it running right for him.

The bike runs great from 1/4 to WOT although not as strong as I would have thought with the exhaust on it.

The bike's crap with the electric starter and runs the battery down really quickly so kick starting is required :p Lots of it! which ruins the ride as the poor guy is knackered!

It is a bugger to kick start hot or cold, when it does fire up the stink of fuel is pretty strong out the back. Not only that but it seems to have a slight hanging idle plus it dies sometimes going into corners.

I thought the best place to start was the pilot circuit, getting to the screw is a nightmare so I am going to buy a fuel screw for it and follow the procedure for checking the pilot. I had the whole bike apart today and screwed in the fuel screw 1/4 turn (because I had concerns I wasn't going to be able to adjust the fuel screw with the carb back on the bike; I was right :ride: )which helped the starting issues a bit (can get it to fire 2nd or 3rd kick with the hot start now).

Sounds to me like it is running rich, am I heading in the right direction.

I assumed that the bike might be running rich on the needle also as it doesn't pull very hard considering the pipe, plus the exhaust is pretty black. I raised the clip one slot and it seems to pull really well however when I shut off the throttle there is a slight bobbling of the exhaust note. It doesn't backfire but its not 100% smooth.

Should I put this back to its original position or could this be solved once the pilot is sorted?

Thanks in advance.

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So I got the adjustable fuel screw in tonight and took the bike for a spin. Got in nice and warm then fiddled with the fuel screw.

It started to run nice a crisp the further I screwed it in until it bottomed out. Bottoming it out made it run even crisper so I am not sure what steps to take next.

I know I need a smaller pilot jet but I have no idea what incriments they come in or even if the symptom requires one step down or two.

Some advice would be great. The current Pilot Jet in the bike is a 48.

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So I threw in the 45 pilot jet today but I am having trouble finding where the revs change. I have a pretty good ear and I am struggling to find any change in pitch. I think that the pitch is rising towards the fuel screw bottoming out... still!! Does this sound right. This was the issue last time... should I really be thinking about downsizing the pilot jet again to a 42??

I am also confused as to whether I should be listening for the change in pitch with the idle revs up or as low as possible. Any help here would be great.

Will the bike be ok to ride on Sunday, it must run better than it did last week with the 48 in it?

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A few things.

First check/set the float height.

Second, when setting the pilot/fuel screw, set the idle speed low for the procedure. Too high an idle speed may get you 'on the needle' making adjustment more difficult. Be sure the bike is up to operating temp when tweaking. You goal is to set the idle speeed as low as possible and then adjust the fuel scew for the fastest, smoothest idle. You may have to lower the idle after you set the fuel screw then revisit the fuel screw a few times to finally get where the idle speed is as low as possible (by the idle speed knob) and as smooth/fast as possible (from the fuel screw). Once done, rest the idle speed to a normal idle. Be sure to not set the idle too low. Just because you can get it idle very slow, does not mean you should. I set idle speed to between 1,700 and 1,900 rpm on a thumper.

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William, can you explain the effects of the float height on the issues I am having?

With regards to the idle, I usually set it to a little way above stalling when out on the trails (so it doesn't stall but also so it doesn't pull into corners). Do I want it lower or higher then normal idle speed when trying to find the sweet spot?

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Regarding float height.

The carb has to suck fuel up. If the fuel is level is low, it has to exert more to suck it, if it is high, it has to suck less. Float height should be correct prior to any attempts at jetting. Once properly jetted, some bikes do need a different float height to compensate for riding conditions. For example, if the rider does a lot of wheelies, the float height may need to be raised slightly to compensate for the bikes angle. But 99% of the time, the OEM float height works perfectly.

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Cheers Eddie & William.

One final question:

With regards to the pilot circuit is the rule for setting it hard and fast? For example if its bottoming and the bike is still running is the fix always going smaller on the pilot.

The reason I ask is that I have seen a few threads of people that have a full system (Pro Circuit) on their bike who are recommending a 45/48 as the pilot. I assume that every bike is different so this shouldn't be too much of an issue, but my understanding of adding an aftermarket pipe was that it would require more fuel to compensate for the increased air flow.

Do I have this right?

One upside is that I can pull the carb off a KLX and have it back on in about 15 minutes now!

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