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YZF 450 WR450F Carb Differences?

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I'm wanting to buy to carb rebuild kit for my 2004 WR450F.  However, on eBay I can find kits for the WR450F from 2005 models onwards or YFZ 450 2003-2004 models.  My question is will all of these carb rebuild kits fit my 2004 WR40F? or is there a difference between the carbs and kits?  As it stands I'm having to import the kits from the US because apparently I cannot buy them here in the UK and I'll have to buy the parts individually which of course will cost a small fortune. I'm also planning to purchase a JD jetting kit too which I also have to import.  Of course, I'm having to buy both because I need the gaskets to eliminate an air leak I have. Looking at > this < old 2004 post it seems like all my popping, backfiring and snapping throttle response was caused by the air leak and an unsuitable jet setup.  I'm planning on also going 45 pilot and 168MJ.  I have a DEP end can so I'll also do the air box mod. 

 

I've had this bike for over two years now and it's never ran right. The throttle response has been all or nothing and the popping and decal has been awful.  Where I ride there's a lot of horses, cattle and other wildlife so I need to get it sorted. Rather than mess around trying to diagnose the air leak I've ordered a new boot (the other one was cracked) and of course I though it was wise to renew the carb's gaskets too.  I've already replaced the exhaust head gasket to eliminate that from being a source of the leak. The leak itself has been substantial as when I removed the carb I noticed the idle screw was wound in a lot. I think overall that the bike's been running like a dog because of the air leak and incorrect jetting for the UK.  As I understand it being close to sea level I need to run richer than my American counterparts because of the altitude and temperature differences.    

 

Help much appreciated guys.

 

 

 

Cheers

 

 

Ian

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If you don't drop the slide as far down as it will go, and then use the FUEL SCREW to raise the idle back up, you will continue to have a lean condition.

You must start with the lowest possible idle (& fuel screw as a starting point) in order to properly tune the pilot circuit.

 

What makes you think you have an air leak?

 

It's easy to determine: get the running, warm it up, and with a can of spray brake cleaner, spray all around the carb, carb boots, header crush washer, etc; when the motor ingests the spray (from the leaking part) your idle will go way down immediately.

 

If you do this, and you do not get the idle to change, your problem is not an air leak, just a lean condition like a missing fuel screw oring, or poor jetting.

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I would strongly recommend against using " brake cleaner " as a leak finder. When combusted it produces phosgene gas which is quite toxic. Use spray carb clean on a cool engine.

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If you don't drop the slide as far down as it will go, and then use the FUEL SCREW to raise the idle back up, you will continue to have a lean condition.

You must start with the lowest possible idle (& fuel screw as a starting point) in order to properly tune the pilot circuit.

 

What makes you think you have an air leak?

 

It's easy to determine: get the running, warm it up, and with a can of spray brake cleaner, spray all around the carb, carb boots, header crush washer, etc; when the motor ingests the spray (from the leaking part) your idle will go way down immediately.

 

If you do this, and you do not get the idle to change, your problem is not an air leak, just a lean condition like a missing fuel screw oring, or poor jetting.

 

The bike's idle is erratic.  Or should I say unpredictable.  I set the idle @1000RPM and when it wants to it climbs to around 3000RPM and drops back down after a while.  I've replaced the head crusher and I've stripped the carb.  The front boot was cracked so I've ordered another one and a carb rebuild kit.  Tonight I've also ordered a JD jetting kit so I'm hoping it'll sort out the power delivery too.

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I have been doing some research on this topic triing to figure out what carb I have on my 2004 yz450f with a 2006 yz450f motor in it. Thats another story in itself. from what I understand the wr's came with a coast enricher jet and the yz's didn't.  But most of the carb kits don't come with the accellerator pump or the coast enricher jet diaphragm anyway but if they did it would make a difference. I am no authoraty on this so please somebody clear this up if you know about the difference. It would be a big help to me also. I was wandering if a bad coast jet diaphragm could be causing your symptoms. Thanks for this forum. I have hours of reading on it so far. Some of very informative and amusing!

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Not sure what you mean by a 'carb kit', as usually they are incomplete and generic at best, especially the ones on ebay.

 

To rebuild any FCR carb, follow this;

 

  http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

 

All parts can be gotten from a yamaha dealer or sudco.com

 

You should upgrade the apump and other things too:

 

This is the standard upgrade list:

 

Edited by TheKoolAidMadeMeSick

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