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08 WR450 Hard Starting

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My bike is only a couple of months old; all I have done to it is remove the restrictive baffle from the stock exhaust; Anyhow when cold my bike will start just fine with the choke pulled; the problem is that once it is good and warmed up it still will not start unless the choke is pulled;

This is a huge problem at the start of a hare scramble; yesterday i was the last person to leave the line; i had to kick start the bike

Once the bike is real hot like when i stall it during the race; it will start with out pulling the choke; but it takes several (2-3) seconds of pushing the button to start.

Is this a jetting problem; the bike has done this since new (3-months old)

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Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

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I also have an 08 WR450 that I bought new (last year's model bought in February). I had a 99 WR40 before this one. With my 99 if you touched the throttle even a little bit when kick starting it, it was tough to start. With my new 08 I have to give it a little fuel with starting it or it is tough to start. Just opposit of my 99. I did all of the mods on my 08 once it was broke in, but it didn't matter, it needs a little fuel from the throttle to get it started. It is a lot harder to start if it is really cold. Anyone else had something like this?

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I put a quickshot pump cover on mine. It give the carb 100% of the fuel instead of 60-70% that the stock gives. I had the hard starting when it got hot and even using the hotstart lever sometimes didn't help. Since I put on the new cover, it starts up right away, even when cold without the choke on. You can get a Wirtz brand off of ebay for about $40 or a boyeson for about $90. It gives a drastic improvement on the throttle response too. I had been a bit optomistic about it, but decided to try one, and it's well worth the money.

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I also had to do all of what William1 had said. I had a dirty pilot and I had the fuel air mix all messed up. But try the pump cover, I thought I was back on a 2 stroke bike with the response it had.

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