2003 KX 250 SF Conversion

[umberto]

I will try to get a pic tonight of the 2 airboxes. I have both.
 

Can you please do a visual and see if the 04 airbox will go in the 03 subframe?  Thank you!

[mixn-gas]

I'm not looking at the problem yet, so this may be an easy "nah that won't work because" But can you modify or make a different boot from the carb to the reed block to move the carb position to make it line up with the factory kx250 intake boot? Maby out of alloy?

[umberto]

I will try to get a pic tonight of the 2 airboxes. I have both.
 

Can you please do a visual and see if the 04 airbox will go in the 03 subframe?  Thank you!

The part numbers are the same for the two frames, so it should fit. The airbox itself was used from 04-07, which helps with supply.

[umberto]

A guy listed a 2004 KX 250 airbox on eBay today.  I snatched it up and should be able to button this dude up now.  Every guy I know wants a ride on this beast, just to scratch it off his bucket list.  $5 a ride?  

[umberto]

I'm not looking at the problem yet, so this may be an easy "nah that won't work because" But can you modify or make a different boot from the carb to the reed block to move the carb position to make it line up with the factory kx250 intake boot? Maby out of alloy?

I think the 2004 airbox should fix it.  I looked at my 2004, and the airbox has an indention where the air boot attaches that should be set back enough to fix the issue.  I only needed a fraction of an inch more to get the boot to fit. 

The 250 air boot is much longer than the 500 air boot, because of the difference in engine size and airbox placement.  I think if you made a new intake boot, it would really have to be shorter to connect the carb to the 2004 air boot. I think making it shorter would mess with the angle the carb has to turn to get around the shock as well.

I'll keep you posted on the progress.  Hopefully this will fix it.

[zz3gmc]

I forgot you had a 04! You have all you need right there. Atleast for the mock up. As long as nothing changed between the position of the intake on the 88 500 cylinder versus my 02 500 cylinder it should work fine.

[umberto]

I bought one on eBay yesterday, and the guy got it boxed up and shipped in an hour.  It should be here Friday, so I'll be able to fit it (and the new clutch) this weekend and possibly ride this beast next weekend.  Getting pretty pumped!

[dave916]

Why not try and make something out of thick rubber 1/4 inch , gives alot more movement when fiting carb ,the kx has smallesh air filter so could be pushed back into the airbox a little

what wrong with clutch?

[umberto]

Why not try and make something out of thick rubber 1/4 inch , gives alot more movement when fiting carb ,the kx has smallesh air filter so could be pushed back into the airbox a little

what wrong with clutch?

zz3gmc has done an 04, and he just put a plate across the air box and used the 500 air boot.  He said it was a simple bolt up.  The 03 and 04 air boxes are different, so I think that is why his was so easy and mine wouldn't work at all.

The clutch is just fried.  It will move the bike, but any additional throttle just causes slippage.  I adjusted on the perch for a couple of hours, and couldn't make it any better.

[motopunk]

rob is the man with the right knowledge to the kx250 - R - frames 03 and 04 .. its an interesting fact with the airboxes ...   

meanwhile a pic of my modification on the 86 motor that i sqeezed in the 93 frame .. intake itself is a brandnew 87-2004 kx500 intake boot...   the airboot is oem kx250 1993 ...  i had to lean it a little bit downwards to get the carb in the perfect position ...
maybe it helps a little bit for some inspiration..




... and lets see some pics of your progress... 

[umberto]

rob is the man with the right knowledge to the kx250 - R - frames 03 and 04 .. its an interesting fact with the airboxes ...    

meanwhile a pic of my modification on the 86 motor that i sqeezed in the 93 frame .. intake itself is a brandnew 87-2004 kx500 intake boot...   the airboot is oem kx250 1993 ...  i had to lean it a little bit downwards to get the carb in the perfect position ...
maybe it helps a little bit for some inspiration..




... and lets see some pics of your progress...  

I'll definitely take some pics this weekend.  I'm using a 94 KDX 250 intake boot, 88 K5 reeds, 96 K5 air boot, 04 air box, and the 96 K5 filter and cage.  I think it should work pretty well once I get the extra setback from the 04 air box.

[zz3gmc]

I cut the plate to the shape of the flange or opening in the airbox. then bolted up the KDX250 intake, 500 carb and mounted the 500 airboot to the carb. Then I bolted the subframe and airbox assy onto the frame. I traced where the airboot pressed up against the plate, adjusting it accordingly, and cut the hole needed to fit the boot to the airbox. It was easier than I thought it would be!

[umberto]

I got my 04 air box in today, and there is quite a difference in the two years.  If you look at the photo below, you can see the area where I'm pointing with the pencil is set back 3/4" more than the 03 air box.  That is all the space I needed to get the boot to fit.  



I went ahead and made a template from the ring that clamps the boot to the box adding a little bit around the outside to seal the airbox.  I kept testing it and trimming where necessary:



I then cut it out of aluminum sheet I got at Lowe's, sealed it with gasket maker, and added sheet metal screws for security:



I ran out of time today.  I'll fit it tomorrow and hopefully get this dude buttoned up and ready for a ride report.  

[zz3gmc]

Pretty much what I did! Pretty easy isnt it!

[umberto]

Yep, it was really an easy process.  I can see now why it was so much easier on the 04 you did.  The 04-07 air box has a ton more room.

I did notice a problem with the mounting flanges at the top of the air box.  I'm going to repair them and then I can mount it up.