WR450 Hard to start when hot

My bike starts pretty well when cold, but when it is hot, I have not found a way to get it to fire up right away-such as on a dead engine Hare Scramble start.My old WR400 would fire up right away and keep up w/ all of the 2 smokes off the line,but I have still not mastered the tecnique on the 450.

Any tips??

Jetting specs:

Temp:90 plus,sea level (houston)

Main-172,pilot-48,fuel screw-2.5 turns,needle-JD red-5 ,YZ cam

I'm assuming you know you have a hot start on the bars.............if not, you do.

Make sure you are using your Hot start on the very first kick.

Try leaning out your pilot to a 45 or a 42.

pull in the hot start, twist the throttle, let off the thorttle, hit the E start and walla.

If you're tuned right on the pilot then just pull the hot start and hit the button, no throttle. Works like a charm for me.

BTW, if you're 2.5 turns out on the fuel screw, using a 48 pilot, then you shouldn't need to go leaner on the pilot (assuming it's running good like it is). If it runs better when you turn the screw in, maybe it's time for a leaner pj.

Now maybe I didn't explain properly. My bike will start hot,but my problem is doing dead engine starts at the beginning of a race.The bike HAS TO start immediately,or else I get blown away by 2 strokes on the start.My old 400 would start 1'st kick and pull holeshots since I knew the proper way to position the kickstarter. This 450 w/ the auto de-comp is very vauge on where TDC is.While practicing starts, I have tried kicking,elect. starting ,as well as doing both at the same time, but it never seems to consistantly start immediately. I have tried 45 on the pilot but it still did not seem to help.

How have you guys been doing on dead engine start races?

just try my suggestion, see what happens...if it doesnt work my bad, but it works for me.

I race HS too, so I'm familiar with what your asking. However, I don't have an answer for you as I do not have my bike dialed in that well perfect yet.

But, I do beleive that the answer for gettting the "1-kick start" is in having your jetting dialed in perfectly.

I feel your pain. Here's what I've found works: Warm the bike up for about 2-3 minutes. Just enough so that its warm, but not hot. The trick is to keep it at the "warm" level until your line starts. This usually involves starting and stopping it a couple times. Don't start it and wrap the engine out like all the 2-smokers are doing, just let it idle. When your line starts, hit the button (no hot start), and it should crank over 2-3 times, and your off.

I've experimented with trying to kick start off the line, but just can't get consistant, so I've stuck with my e-start method. I also have a bad habit getting excited and opening the throttle too soon and flooding it :banghead: . I try to keep my right hand completely off the throttle when starting.

You really need to have the jetting perfect for this to work consistantly. At 90 degrees (2000 ft elevation with stock pipe, BMP insert, open airbox), I run a 45 pilot and a 65 starter jet. The starter jet seems to have the biggest effect on easy starting, but I could be wrong.

Good luck,


Now I have not tried a different starter jet. It makes that much difference? I thought that it only affected the carb while on choke.What is the stock size ?

The starter jet is for the choke circuit. If you're not using your choke, I don't think the starter jet will make a difference,... I could be wrong.

I am at sea level with about the same temp. I also have about 100% humidity.

I had to go to a 50 pilot jet, but I use JD red #5, 168 main.

Don't go leaning out the pilot!

If your jetting is fine (it looks like it is), just practice your starts.

Don't twist the throttle when you start also.

Before you alter too many settings, be aware that the symptoms you describe are common for valves that need adjusting. As the clearances reduce as the valve recedes into the head a little, it can actually stop the valve closing properly when its hot (and all expanded etc). Bike will start from cold OK, but be a real pig to get going when hot.

May be worth just checking your shims before you do too much messing with jets etc, especially if it was starting ok from warm a little while back.

Good Luck

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