Jump to content

03 WR450F Leak Jet?

Recommended Posts

I recently acquired a "New to me" 03 WR450f. There was a bit of a misfire when riding so I wanted to go in and sort out the jetting. When I took apart the carbs, I was unable to find the leak jet. I believe it's supposed to be in the float bowl, correct? The space where it looks like it should be is just filled in. Am I just missing it? In looking through some of the other posts, I see others with an 03 450 talking about the replacing their leak jet. Did they not put a leak jet in some of the bikes? Maybe the CA models?

Assuming I'm not an idiot, and there isn't a leak jet, should I just ignore it when jetting? I believe it's mainly for the AIS system, but would it affect anything else? Does it make much of a difference? Would it be worth it to drill/tap a hole to put in a leak jet?

20200520_025745.jpg

Share this post


Link to post
Share on other sites

It appears you don't have one.  It goes in the lower right spot inside the bowl, in line with the two o rings on the flange.  I think the earlier bikes (wr400??) might not have had a leak jet.  It's for the accelerator pump circuit.  A bigger jet "leaks" some of the ap squirt back into the float bowl.  A zero or closed jet leaks nothing and send the full ap squirt to the nozzle.  Not sure what you have, but the leak jet was definitely important for tuning my wr.

Edited by bg10459

Share this post


Link to post
Share on other sites

Looks like you might not have the stock carb or it’s not an 03.  I see a red plunger in the background, if that’s the hot start, that wasn’t the normal setup in 03.  Is the bike e-start?   Did it get the upgrade to the 04 starter gear?  If not you will shear the flywheel key at some point.  
 

i would add a leak jet either by drilling and tapping or by buying a new float bowl with a leak jet.  It makes tuning a lot easier.  I did that on my 06 Ktm as they didn’t have leak jets either.  Just ran a shorter stud on the diaphragm to control squirt volume.  That has some issues as well as it changes the throttle range that the pump works. 

Share this post


Link to post
Share on other sites

Yeap I just went through a couple older carbs for my 99WR400 I did a light restoration on ... no leak jets - really old school. I got a newer generation carb from a WR and swapped that one in. The newer Kehin requires the newer style throttle cable and throttle housing. You can get them cheap on Ebay. Worth every penny.

Share this post


Link to post
Share on other sites

Weird. 

It does have a hot start plunger, not the cable. Its tucked up under the tank on the top of the carb in what appears to be the correct place for the 03. I think for earlier years it was on the side of the carb by the choke.

I dont think its an earlier carb. It appears to be the correct Keihin FCR MX. It looks correct when comparing it it to a 426 carb. Just the hot start plunger instead of the cable (and now a missing leak jet). I'll take a picture of it tonight when I get home and post it.

Share this post


Link to post
Share on other sites

I checked the parts fich as I don’t remember if mine had a leak jet or not.   It doesn’t appear that the 03 had a leak jet.  Would still be a good tuning option if you added one. 
 

Share this post


Link to post
Share on other sites

That is not an 03 WR450 FCR Carb.  It should have a leak jet and by the picture the hot start is a Red Plunger.  The 03 has a cable plunger that goes to the handle bar.  Most likely a 98-02 carb off a WR400 or WR426.

Share this post


Link to post
Share on other sites
4 hours ago, JVP said:

That is not an 03 WR450 FCR Carb.  It should have a leak jet and by the picture the hot start is a Red Plunger.  The 03 has a cable plunger that goes to the handle bar.  Most likely a 98-02 carb off a WR400 or WR426.

So I really dont think its off a WR400 or WR426 (at least the main carb body). Below is a picture of a WR426 carb (not my pic).

It shows the hot start on the side, right underneath the choke. My hot start is on the top, where the cable would normally connect. It looks like someone just replaced the cable with a plunger for some unknown reason.

Here are some pictures of my carb. It was all taken apart, so excuse any missing bolts on the bowl or slide cover. I roughly put it back together just to take pictures.

And possibly where the original hot start lever was:

Also, to add more mystery to an already unknown bike, I checked the VIN number and it appears to be an 04, not an 03 as I had been told (didn't get the title with the bike, bill of sale only). I least I don't have to worry about the starter.

As slotracer577 said, I think at this point I either have to get a new float bowl, or drill and tap a hole for a new jet.

Share this post


Link to post
Share on other sites

With those additional pics you may be right. Very strange.  Not sure how or why someone would do this.  Getting a new float bowl may be tough.  You will need to make sure the circuit works if you decide to tap a hole for the jet.  Getting to that hot start will be hard because of the gas tank.  I would suggest getting the parts for the original hot start and cable.  The cost is minimal. Having the Hot Start on the handle bar is a real plus.

Share this post


Link to post
Share on other sites

I have that exact same carb on my 99 426 - I inherited it from a friends 03 WR450 that went bye bye. Of course the carb was taken from his parts bike and I never got the hot start cable. So I plugged up the hole in a hurry. But I do need to get a cable assembly as well... this reminds me actually. I haven't looked that close at the bowl but I'm pretty sure the old ones we have never came with leak jets that you can swap out. Looks like I'll be doing the same thing you are going through. I know the accelerator pump isn't flowing like I expected it too. I've gotta order a new fuel tank, cams and now carb parts... great =] $$$

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×
×
  • Create New...