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jlow

08 wr 450 hard to start when hot

12 posts in this topic

So the past couple of times that I have been riding, my bike has been very hard to start once I got it warm/hot. When it is cold, it starts right up. Valves were in spec last time I checked, not quite due yet for another inspection. Messed with the fuel screw out of curiosity, no effect. Have not had this problem the last several years. Any ideas? Have James Dean kit with Indy450 settings for 0-2000 feet around 75 degrees.

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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. Do it with the bike fully heated up.

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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So the past couple of times that I have been riding, my bike has been very hard to start once I got it warm/hot. When it is cold, it starts right up. Valves were in spec last time I checked, not quite due yet for another inspection. Messed with the fuel screw out of curiosity, no effect. Have not had this problem the last several years. Any ideas? Have James Dean kit with Indy450 settings for 0-2000 feet around 75 degrees.

Do you use the hot start when it's hot?

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To me, if my bike becomes hard to start while hot, that's telling me to check the valve clearances. Schedule be damned!!! When exactly was the last time you did check the clearances? Maniac

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Krannie, yes I use the hot start when I need to. I also have to blip the throttle just a little bit and it fires right up(or use to). If I did that on my old 426 it would flood it and the cussing would begin. Ever since new, when using the electric start, I have always had to do this. When kickstarting it, not required.

Maniac, last inspection was about 4 month/30 hours ago. Haven't had to adjust since the break-in adjustment.

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jlow, Do you tend to scream the engine at all? Or have you ever been blasting down a road tapped out in 5th, and chopped the throttle over a rise, etc..? In these scenario's, the valves tend to get slammed into the head, which can wreck havoc on previously checked clearances. Just giving you a heads up. Good luck! Maniac

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Krannie, yes I use the hot start when I need to. I also have to blip the throttle just a little bit and it fires right up(or use to). If I did that on my old 426 it would flood it and the cussing would begin. Ever since new, when using the electric start, I have always had to do this. When kickstarting it, not required.

Maniac, last inspection was about 4 month/30 hours ago. Haven't had to adjust since the break-in adjustment.

Jetting specs?

Fuel screw used?

Plug age?

If turning the fuel screw has no effect, there is a problem in the pilot jet circuit (clog) or the hot start (stuck).

Do you have any decel popping?

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168 main, JD Blue #3, 48 Pilot, 1.5 turns, 70 starter jet, #40 leak jet

Gytr fuel screw

Plug is less than a year old. Have not had any problems with plugs in this bike. Hot start seems fine, idle goes up when I pull it in, drops back down afterwords. The pilot jet may be one size to big, but it has ran fine for 2.5 years with the current jetting. No decal popping. Will verify sunday.

Going to the Kenda TN Knockout this weekend. Going to check the valves early next week. Will let you guys know what I find. Thanks JLow

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going to a race and THEN checking the valve clearances? Yikes... you must be very brave or very rich... for the time it takes, just check them before hand... could save you tons of money and trouble...

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Not racing, just spectating. Going to build an endurocross course at my house so I can train for next years race, if they have it. would love to enter it but have a 23 month old and a 2 week old, Mama(the boss) says no!

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Want to see the different obstacles so I have an idea of what to build. Got some 10ft loader tires all ready lined up!

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very nice! Spectating is the next best thing...

I hear you on the "boss" bit... I have a 4 yr old and a bun in the oven due in Feb... mama hays a big say in when i get to ride :)

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