WR450 Need Suggestions


11 replies to this topic
  • philinms

Posted December 07, 2011 - 01:51 PM

#1

I bought a pretty clean looking 03 WR450 for cheap last month (there may be a lesson here). It was running real ragged but had been sitting up and had a bunch of goodies (recluse clutch, etc) and I figured it probably just needed the carb cleaned.

Cleaned the bottom end of the carb twice and it actually ran pretty good with the choke on but immediately went real bad with it off. Took it to a local retired indy mechanic with 20 years of dirt bike experience. He's recleaned the carb twice and says it looks good and checked static timing but without a bike specific service manual he's stumped. He thinking it may be CDI related a this point but hates to buy a non returnable CDI without being sure.

I did a search and will tell him to try disconnecting the TPS. What else would you try?

  • ur2silly

Posted December 07, 2011 - 02:26 PM

#2

Definitely check the o-ring on the fuel screw. They tend to deteriorate.

Make sure there is nothing going on with the hot start circuit including a sticking cable. The plunger should move up and down freely in the carb body.

Make sure all the electrical connections are clean, making good contact and there are no broken or shorted wiring. Check that the voltage regulator and stator are consistently putting out the correct voltages. Plug wire and plug. Valve clearance.

  • zlathim

Posted December 07, 2011 - 03:24 PM

#3

it actually ran pretty good with the choke on but immediately went real bad with it off.


This seems to indicate a lean condition. I would definately be looking at fuel before arbitrarily replacing ignition components. After soaking, blow through all fuel passages in the carb with compressed air. Be sure to check the o-ring on the fuel screw and the hot start (which leans the fuel mixture) as was previously mentioned.

  • Krannie McKranface

Posted December 07, 2011 - 07:15 PM

#4

I bought a pretty clean looking 03 WR450 for cheap last month (there may be a lesson here). It was running real ragged but had been sitting up and had a bunch of goodies (recluse clutch, etc) and I figured it probably just needed the carb cleaned.

Cleaned the bottom end of the carb twice and it actually ran pretty good with the choke on but immediately went real bad with it off. Took it to a local retired indy mechanic with 20 years of dirt bike experience. He's recleaned the carb twice and says it looks good and checked static timing but without a bike specific service manual he's stumped. He thinking it may be CDI related a this point but hates to buy a non returnable CDI without being sure.

I did a search and will tell him to try disconnecting the TPS. What else would you try?


If your 'mechanic' is not an expert with the FCR carb, don't let him touch it.
It's a fragile precision device that cannot have Auto carb cleaner put through it without possible damage..........

You need to do what was already mentioned. More than likely, you have a partially clogged pilot jet, or a partially clogged pilot jet passage. The symptoms you mention are a classic sign of these issues.

  • Snarfie

Posted December 08, 2011 - 01:58 PM

#5

If it runs fine with the choke on, then craps out when you take it off- the issue is in your carb. Dont let that moron start messing with your electronics if he cant even diagnose a fueling issue correctly.

Also, as previously stated, FCR's are complicated little monsters. You cant just spray carb cleaner in there and call it a job well done. You need to strip that thing thoroughly, and inspect your seals/o-rings.

Make sure you give great attention to your fuel screw. There should be a spring, washer, and o-ring [in that order] on the screw, and if you're missing any of those three parts, the bike is really gonna act weird.

  • philinms

Posted December 09, 2011 - 06:36 AM

#6

Snafie: I think youre right. I dont see where the mechanical choke would have any connection whatsover with an ignition problem as application of the choke shouldn't advance the timing, etc.

Before taking it to the mechanic, a friend of mine who's pretty knowledgable and I loosened the carb and rolled it to clean the bottom end and jets (twice). The leak jet was totally stopped and one other partially. At that point the bike was very rideable with the choke on (enough power to lift the front wheel) had very little hesitation, but the idle would fluctuate somewhat. The second you closed the choke spit, sputter, backfire, and you had to really work the throttle to keep it running.

I'm not sure if the mechanic totally removed the carb to clean it or not. The only other place for me to take it that are not just part changers is two dealers both about 3.5 hrs away.

I think before I do that I'm going to totally remove it and have it rebuilt top to bottom with new jets, acelerator pump,needle etc and set it back to factory specs. I've got a service manual and a good automotive carb guy to help me. If that doesnt work I'll punt and take it to the dealer.

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  • zlathim

Posted December 09, 2011 - 07:23 AM

#7

Before taking it to the mechanic, a friend of mine who's pretty knowledgable and I loosened the carb and rolled it to clean the bottom end and jets (twice). The leak jet was totally stopped and one other partially. At that point the bike was very rideable with the choke on (enough power to lift the front wheel) had very little hesitation, but the idle would fluctuate somewhat. The second you closed the choke spit, sputter, backfire, and you had to really work the throttle to keep it running.

I think before I do that I'm going to totally remove it and have it rebuilt top to bottom with new jets, acelerator pump,needle etc and set it back to factory specs. I've got a service manual and a good automotive carb guy to help me. If that doesnt work I'll punt and take it to the dealer.


Yep, you probably have clogged internal passages. Be careful which carb cleaner you use, I hear that automotive carb cleaner can be harmful to these carbs. After spraying or soaking the passages with cleaner, use an air nozzle to blow them out. I also like to use a piece of fine tag wire to poke around in the passages too. Again, blow everything out with air. When possible, I'll blow air through each passage using my mouth to make sure there are no obstructions left. You might think about getting a JD jetting kit ($75 at the TT store) as well as the other stuff you mentioned. It makes it really easy to get the main jet and needle clip position dialed in. The kit comes with an assortment of main jets, two different needles, a couple of o-rings for the AP, and instructions. You should also get an extended fuel screw with a new spring, washer and o-ring.

Good luck!

  • philinms

Posted December 25, 2011 - 05:58 PM

#8

Eureka!!! JD jet kit, new AP diaphragm, JD fuel screw and good off the bike cleaning got me going. Did have a problem setting the float but finally got it.

THANKS FOR YOUR HELP ALL!!!!!!!

  • zlathim

Posted December 25, 2011 - 07:41 PM

#9

Eureka!!! JD jet kit, new AP diaphragm, JD fuel screw and good off the bike cleaning got me going. Did have a problem setting the float but finally got it.

THANKS FOR YOUR HELP ALL!!!!!!!


Nice work man! Glad to hear that you got it up and running!:bonk:

  • Sknight

Posted December 25, 2011 - 07:55 PM

#10

Good to hear it! I got skunked by my float this past week (In 20+ years of building carbs on cars I've never seen a float with a plunger.) but with it sorted I'm set to get it muddy this week, I hope.

  • MaxPower

Posted December 26, 2011 - 09:55 AM

#11

keep any eye on or better yet replace with an alumiunm nut on the end of the hot start cable where it enters the carb.
I cracked mine and it cause a lean condition.


  • ur2silly

Posted December 26, 2011 - 08:34 PM

#12

Sweet. Glad to hear you got it sorted out. Now go ride:ride:




 
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