03 Barely Starts and Idles at 1/2+ Throttle


8 replies to this topic
  • SpeedBlitz

Posted June 28, 2006 - 06:02 AM

#1

I'd appreciate some suggestions for next steps in order to try and figure out this problem.

DESCRIPTION (03 WR450):

Bike was running fine and starting fine (start right away with e-start and 1-2 kicks to start). No problems in the past either. Then I started it and it was idling poorly and stalled as I tried to take off. Then I wasn't able to start it. When kicking it, it would barely start and stall within 1-2 seconds. I generally I try to kick from TDC, so sometimes, after a good kick, when I go to slowly move the engine back to TDC, the sligth movement of the kickstart would cause it to kick back and and almost start. Also, it backfires sometimes while kicking.

WHAT I HAVE DONE SO FAR:

The only changes from the time the bike was running well to when it starting running poorly was putting in a new filter which I think I may have over oiled. So I did the following:

- Put the "dirty" filter on with which the bike ran well previously and it didn't really change anything. Although I was able to start it on occasion (after 15-20 kicks) and would only idle if I held the throttle about 1/2 or more.
- Took the carb off and took out all the jets and cleaned with carb cleaner to make sure no carb circuits where clogged (i.e. as I sprayed cleaner in one orifice, I looked to make make sure it came out where it was supposed to). I didn't touch the slide or TPS though. Put the clean carb back on and similar situation, although it started a bit easier, it wouldn't idle unless the idle screw was fully turned in. I tried to ride it and it would stall as soon as I got off the throttle (even with high idle). I tried with TPS connected and disconnected. No noticeable change.
- Knowing that 03's have the woodruff key issue, I checked if the flywheel timing mark lined up with the cams and they all lined up, but I still thought it may have gotten knocked out of time, so I pulled the flywheel and the key is still intact. I replaced the key, put the flywheel back on. I can barely start it now, but behaves as before, starts for 1-2 seconds and dies. Runs only if held at 1/2 throttle or more.
- Put in new plug. Same problem.
- Drained gas and put in new gas. Same problem.
- Disconnected TPS. Same problem, although seemed a bit easier to start, that is instead of 15-20 kicks, it was 10-15 kicks, but still wounldn't idle unless I held the throttle 1/2 or more.

Next Steps:

- I'll check my valve clearance, but I doubt that's the problem since they were in spec last time I checked them and I only rode about 2-3 hours since I checked them and they only where out of spec once, which was after break in.
- Check throttle slide for cracks (note that when I cleaned the carb, I didn't touch the slide. I heard similar symptoms from older WRs which had issues with cracked slides).

After the above steps, I'm at a loss. I'm doing to have to start going by process of elimination, but at the moment, I suspect an electrical/ignition problem.

Anyone has some insight, ideas, things I should check?


Much appreciated.
SB

  • SpeedBlitz

Posted June 28, 2006 - 07:37 AM

#2

Acutally, two additional steps I'd like to try:

1- Borrow a friends carb from a 2004 YZ450 in order to see if it is carb related.

2- Borrow a friends CDI from a 2004 YZ4540 to see if it's an ignition/CDI issue.

Does anyone know if I can simply plug the YZ CDI on my 03 WR? The 2003 & 2004 WR list the same P/N for the CDI, but the YZ lists a different P/N from the WR and also changed from 2003 to 2004. Does anyone know what the second and third digits of the P/N mean? I want to try a 2004 YZ CDI on my 2003 WR.

2003 YZ450F 5TA-85540-00-00 C.D.I. UNIT ASSY
2004 YZ450F 5XD-85540-00-00 C.D.I. UNIT ASSY
2003 WR450F 5TJ-85540-00-00 C.D.I. UNIT ASSY
2004 WR450F 5TJ-85540-50-00 C.D.I. UNIT ASSY

Thanks.
SB

  • SpeedBlitz

Posted June 28, 2006 - 07:50 AM

#3

On the YZ side, I found some info which suggest that the the YZ & WR CDIs don't interchange, but the info seemed to be mostly for 98-02 WRs & YZs, not for the the 2003+ 450s.

  • Dodjy

Posted June 28, 2006 - 12:51 PM

#4

I'd be replacing the plug before I did anything else. Sounds like the overoiled filter may have fouled it.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • SpeedBlitz

Posted June 28, 2006 - 01:33 PM

#5

Thanks. I realize my post is long so you must have missed it, but after thinking I over oiled the filter, I swapped, to the old filter, cleaned the carb and also tried a brand new plug with no luck.

  • Dodjy

Posted June 28, 2006 - 06:54 PM

#6

OK, then it is still pointing to the pilot jetting. You really gotto look closely at the PJ. I've had problems before where you clean it and blow it out but don't get everything. The only way to make sure is to pull the jet out and poke a wire through it, clean it, compressed air etc. Pull the whole carby apart and clean all the jets including the fuel screw, pilot air jet and leak jet. While the jets are out, blow the passages out. When you get it idling does the choke or hot start do anything?

  • waynus

Posted June 28, 2006 - 10:45 PM

#7

Good point about the choke Dodjy. If it runs better with a bit of choke then it is a blocked jet or air leak. If you have a timing light it's a good idea to connect it. This way you can see if its sparking or missing just by watching the strobe. If the valves and valve timing are ok, then generally its either spark or fuel. Good luck :ride:

  • SpeedBlitz

Posted June 29, 2006 - 04:55 AM

#8

Thanks for the input guys. I was actually going to install a friends carb to see if it solved the problem, allowing me to isolate the problem, but since I had already thoroughly cleaned the carb, I was going to check a few other simple things, and surely enough, it was a faulty kill switch! The intermittent starting and idling at high RPM only really threw me, but it was the kill switch!

Thanks for the posts guys!
SB

  • Dodjy

Posted June 29, 2006 - 04:03 PM

#9

Thanks for the input guys. I was actually going to install a friends carb to see if it solved the problem, allowing me to isolate the problem, but since I had already thoroughly cleaned the carb, I was going to check a few other simple things, and surely enough, it was a faulty kill switch! The intermittent starting and idling at high RPM only really threw me, but it was the kill switch!

Thanks for the posts guys!
SB

Awsome, finding the problem. F'me, I'd never have picked that one.




 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.