'03 WR450F. Low voltage to TPS. CDI?


29 replies to this topic
  • - Jake -

Posted September 01, 2010 - 07:20 AM

#1

I've got a 2003 WR450F that was running badly when I picked it up last week. The engine won't rev beyond mid-range. It feels like something is holding it back badly. At low to medium revs it feels great and pulls hard.

I've changed the spark plug and checked all the connections. The air filter is clean and I've tried running without the airbox side cover fitted.

I haven't stripped the carb down yet because, if I remember right, you have to remove the rear suspension etc, it sounds like a balls-ache.

I'm getting a good voltage at the battery when the engine is running.

I checked the voltage at the TPS plug with the engine idling and the plug disconnected but it only showed around 1v. The manual says it should be between 4v and 6v. It says to replace the CDI if the voltage is out or scope.

Does it sound like CDI is the fault? I thought the engine would run OK with the TPS disconnected if that was actually the problem?

Any suggestions what else to check before wasting more money on a CDI?
I guess you're all gonna tell me to strip and clean the carb first, right? :bonk:


Anyway, thanks for any ideas you might have.

  • - Jake -

Posted September 01, 2010 - 08:06 AM

#2

OK so it seems you don't have to remove the rear suspension etc to get the carb off.
So, I'm going to look at that now.

  • William1

Posted September 01, 2010 - 11:58 AM

#3

Unplug the TPS and test ride.

Drain the fuel from the tank, remove the bottom cap from the carb and rdrain it, refil with new fuel.

It is not the CDI. Either bad fuel, mis-adjusted/bad TPS or failing crank position sensor or a poor connection/bad ignition coil.

  • - Jake -

Posted September 02, 2010 - 08:50 AM

#4

Thanks for that William.

I've now stripped the carb down and cleaned it out, although it seemed ok anyway. It has fresh fuel. I've tried with the TPS disconnected but it still struggles to rev, even in neutral.

What makes you say that the problem is definitely not the CDI? I thought that low voltage to the TPS indicated that it might be a problem with the CDI, no?

Thanks.

  • - Jake -

Posted September 02, 2010 - 09:21 AM

#5

Where do I find the crank position sensor? I can't locate anything about it in the Service Manual.

Thanks.

  • William1

Posted September 02, 2010 - 09:32 AM

#6

If the TPS is disconnected, the CDI falls into a default mode. Since unplugging it made no difference, it is not the TPS.


CDI's either work or they do not. The mapping does not change.


Crank position sensors and stators do fail. Typically as RPMs rise, you get misfires. What usually happenes is at first, you experience a high RPM miss. Over time, the top RPM decreases to the point where the bike will not run. Your first hint it is a stator problem was the low voltage. When you buy a OEM stator, you get a new crank position sensor, it is part of the system in the left case. The sensor is the little black box.

You can do the tests the service manual list for teh stator and sensor but they are only conclusive if you have a complete failure. Sometimes they test within spec but are actually NG.

  • - Jake -

Posted September 02, 2010 - 10:40 AM

#7

I still can't find the sensor in the manual. Is it what the manual (on page 4-77) calls the pick-up coil? (#21)

  • RickyStator

Posted September 02, 2010 - 10:44 AM

#8

Yes the pick up coil. It should read about 300 ohms across the pink and white wires.

  • - Jake -

Posted September 02, 2010 - 10:57 AM

#9

Thanks.

  • - Jake -

Posted September 02, 2010 - 11:59 AM

#10

Yes the pick up coil. It should read about 300 ohms across the pink and white wires.

I tested it with two different volt meters because it's hard to read the small scale dials. One showed between 250 and 300 ohms
with the other voltmeter it showed between 300 and 350 ohms.
So I guess that's OK.

Now what?

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  • - Jake -

Posted September 02, 2010 - 01:39 PM

#11

So I've been using the search button trying to find a solution.
In this thread Williams said

The YZ box is run off of AC from the stator whereas the WR is riun on DC from the battery


Now, my bike is fitted with a dead battery. Would that make any difference to how the bike runs? I didn't think it would matter because there's good voltage going to the battery when the engine is running.

Would me having a nearly dead battery cause the bad high revs running or the low voltage to the TPS? Which? Both?


By the way,
I did spend 50 on a new battery but the acid leaked out of it the first time I rode the bike with it in. It was a Varta battery that I had to put the supplied acid into myself. I don't think it liked the angle that WR450's have the battery at.

  • William1

Posted September 02, 2010 - 02:15 PM

#12

YES!!!!!!!!!

You have to use a battery as spec'd by Yamaha.

  • - Jake -

Posted September 02, 2010 - 02:35 PM

#13

No battery can cause bad running at high revs???

Jeez, I'm gonna go slash my wrists if that was the cause of this problem :bonk:
I've spent bloody hours stripping things and reading manuals and searching the net!

I still find it hard to understand/believe. I hope you're right though.

It's too late at night for me to go starting the bike up (I've got to put if back together first anyway) but I'll update this thread after the weekend when I've tried it.

Fingers crossed.

  • tribalbc

Posted September 02, 2010 - 03:28 PM

#14

No battery can cause bad running at high revs???

Jeez, I'm gonna go slash my wrists if that was the cause of this problem :bonk:
I've spent bloody hours stripping things and reading manuals and searching the net!

I still find it hard to understand/believe. I hope you're right though.

It's too late at night for me to go starting the bike up (I've got to put if back together first anyway) but I'll update this thread after the weekend when I've tried it.

Fingers crossed.


Yes, dead battery and mine will barely run above idle. CDI needs DC.

  • - Jake -

Posted September 02, 2010 - 03:35 PM

#15

Well I hope you're right. I'm pretty sure I've read people saying that they've removed the battery, starter, etc without problems. (On the 2003 WR450, because so many of them don't have a working starter anyway)

  • William1

Posted September 02, 2010 - 03:42 PM

#16

When they remove the battery, they install a large capacitor. The YZ CDI has one built in.

See, this sort of problem, when the OP does not tell you everything that is out of whack or recently changed is why it takes many posts to fix a problem.
It is very important if you need help to list everything you recently did and everything that is not working.
This post was a low voltage issue and it has a dead battery. Sort of self-answering.

  • - Jake -

Posted September 07, 2010 - 10:38 AM

#17

This post was a low voltage issue and it has a dead battery. Sort of self-answering.

Well I've fitted a new battery but the problem still remains, the engine just won't rev past about 4000rpm

I haven't yet rechecked the voltage supply to the TPS.

I'm all out of ideas what to check now. :ride:

  • William1

Posted September 07, 2010 - 11:03 AM

#18

Did you clean the carb very carefully? Did you ensure the slide fully rises and is not cracked?

Did you check the cam timing, bith by looking at the marks and by checking the lobe positions?

If the bike still will not rev, you have made no changes to the bike at all since it did run right, it probably is the crank position sensor aka ignition pickup. When these fail, they manifest as a high RPM miss that gets worse and worse. But since you bought it used, I would not buy a stator until you have checked everything else.

You just bought the bike, I hope you got a good price.

  • - Jake -

Posted September 07, 2010 - 01:27 PM

#19

well I'm getting a good voltage at the TPS feed since fitting the new battery; 4.94v with the ignition on but the engine not running.


Did you clean the carb very carefully? Did you ensure the slide fully rises and is not cracked?

Yes.


Did you check the cam timing, bith by looking at the marks and by checking the lobe positions?

No.


If the bike still will not rev, you have made no changes to the bike at all since it did run right

It's never run right since I've owned it.


it probably is the crank position sensor aka ignition pickup. When these fail, they manifest as a high RPM miss that gets worse and worse. But since you bought it used, I would not buy a stator until you have checked everything else.

I'll see how much a CPS costs then.


You just bought the bike, I hope you got a good price.

I thought I did at the time. If I have to spend a fortune getting it to run right then it won't have been a good price.

Ah well, I've got it now - I've just got to get on with it and sort it out.


Thanks again for your help.

----
Edit to add;
Damn, seems I can't buy the CPS without a new stator.

  • William1

Posted September 07, 2010 - 01:51 PM

#20

Check the cam timing, confirm both the marks line up and the lobes look right (cams have been known to move in the sprockets unless welded).

Ususally, the sensor only comes with a stator.You replace the entire assembly.




 
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