WR450 wont start when hot

[TwIzTeD NuTz]

Ok guys, heres my delima. My bike is an 03 WR450 I can not kick start the damn thing. Long story short jetting has been gone over 1000 times, there is nothing in the jetting that has made any bit of difference in the way it starts. current settings(i know they will be asked) Pilot 48, 1.5 turns on air screw, 168 main. all the others are stock. If i let the bike sit over night, i can walk out choke the bike and start it in 2 kicks. once the bike has been running and i stop I cannot restart the bike. I can kick start it till my foot is numb, and cannot get it to refire. If i roll start it its almost instant start up. I am to the point of wanting to torch the bike. I cannot figure out why it wont start. on occasion i have trouble starting it cold, but that is rare. its 99% of the time when its hot i cant get it restarted.

[William1]

Pilot jet is to large. S/B a 45 with the fuel screw at about 2 turns.

[TwIzTeD NuTz]

Pilot jet is to large. S/B a 45 with the fuel screw at about 2 turns.

Im on a 48? still too large? if so ill have to go find a 45.

[rich1167]

When was the last time you checked the valve clearances?

[TwIzTeD NuTz]

When was the last time you checked the valve clearances?

about 1mnth ago, when i still had the engine out of the frame. everything was in spec.

[TwIzTeD NuTz]

Ok new news, went home today to get it on lunch, wouldnt start kicked and kicked(this is how i broke the kick shaft the first time). I need this stupid thing to start!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[TwIzTeD NuTz]

would the grey wire mod have anything to do with this? timing maybe? how many pins should be between the 2 cam shafts?

[Hot Rod Todd]

i also have a 03 and have had problems re-starting once hot. the first thing 'my guy' asked was about my valve clearance (like rich1167 said). we checked and sure enough one of the intake valves needed a shimming. after that, i still have no problems re-starting my old gal. it does't take but 15 min. to check. it couldn't hurt.

[rich1167]

If you worked on it then started having this issue. I would start retracing my steps. Here's are a pic that may help with your cam question. It's from my 05 450.

[William1]

Valve clearance and starting issues are apparent on cold starts, not hot.

Grey wire does not affect it though the blue wire can.

You have too large a pilot jet. Select the pilot and adjust the fuels screw thusly:

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.

[TwIzTeD NuTz]

If you worked on it then started having this issue. I would start retracing my steps. Here's are a pic that may help with your cam question. It's from my 05 450.

Timing is spot on, I have been playing with this engine since 04. I only checked/adjust valve clearance because I was already having issues getting it started. It hasnt started well since the day I got it. If i have the electric starter on it will start instantly(as long as the starter works).

Valve clearance and starting issues are apparent on cold starts, not hot.

Grey wire does not affect it though the blue wire can.

You have too large a pilot jet. Select the pilot and adjust the fuels screw thusly:

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.

Ok I am going to pick up a pilot tonight after I get off work, I will readjust all this again tonight. What is this blue wire you speak of? Maybe i need to check it to make sure something hasnt happened. Also I took and started going through all the ignition components last night, everything checked out good but something i noticed is im not getting a very strong spark, and it only seems to spark for a split second at the end of the kick stroke. and it wasnt consistent. Didnt seem right thats for sure.

[TwIzTeD NuTz]

So skimming through some post regarding spark, I think i might be onto something. https://www.thumpertalk.com/forum/showthread.php?t=751609&highlight=weak+spark

I have eliminated my battery on the bike cause the electric starter crapped out. Could having the battery removed cause the problems I am having?

[CanadianWR450]

I have a 04 with no battery in it, because my starter also died , and the bike starts with no problem with 1 or 2 kicks....hot or cold

[phynx]

Valve clearance and starting issues are apparent on cold starts, not hot.

Grey wire does not affect it though the blue wire can.

You have too large a pilot jet. Select the pilot and adjust the fuels screw thusly:

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.

Yep, pilot and fuel mixture screw:thumbsup:

[TwIzTeD NuTz]

Ok I seemed to have fixed the starting issues thanks for the help guys. it was either the ground to the harness had a bad connection or the jetting. also i have one more problem and im not sure which way to go with it. when i let off the throttle i get a lot of popping. whats causing this?

[CanadianWR450]

Ok I seemed to have fixed the starting issues thanks for the help guys. it was either the ground to the harness had a bad connection or the jetting. also i have one more problem and im not sure which way to go with it. when i let off the throttle i get a lot of popping. whats causing this?

Lean, or air leak in your exhaust.

If it's popping BAD my money is on exhaust air leak...I would look there first regardless, gasket/seal on head to exhaust, and the seal on the connection between head pipe and tail/mid pipe.....