Author Topic: 2003 KX 250 SF Conversion  (Read 169933 times)

0 Members and 2 Guests are viewing this topic.

Offline motopunk

  • Hero Member
  • *****
  • Posts: 1,150
    • www.der-motopunk.de.tl
Re: 2003 KX 250 SF Conversion
« Reply #105 on: July 24, 2015, 09:50:23 PM »
nice progress... more pics please and waiting for ride report...  8-)
big 2 stroke bikes are weapons for real men, who don´t fear death or devil. ;O)
´83 kx250, ´87 kx250 (with 360 big bore), 87 kx500, ´93 kx500 sfc

---  www.der-motopunk.de.tl  ---

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #106 on: July 25, 2015, 05:16:14 AM »
I got my airbox bolted up today.  It was a breeze with the 04 model.  Thank you zz3gmc for figuring that out, it saved me a ton of work.  Here is a picture of the finished product (the filter is the old one that came with the airbox, I have a new UNI one on there now):



It clears nicely around the shock as well:



I got the bike all buttoned up for a picture or two (forgive the dirty garage, I have too many dirt bikes and too much stuff in it  :-D):





After lunch I'm on to the clutch, and then I'll try to plan a ride.  It's so stinking hot in Oklahoma right now, it may be a bit before I get her out.
« Last Edit: January 05, 2018, 02:36:57 PM by umberto »
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline DoldGuy

  • Hero Member
  • *****
  • Posts: 1,198
Re: 2003 KX 250 SF Conversion
« Reply #107 on: July 25, 2015, 09:04:00 AM »
Looking forward to your ride report!  :-D
Its Never too Late to Have a Happy Childhood!

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #108 on: July 25, 2015, 10:01:39 AM »
So I got the clutch swapped out.  The old one came out smelling like smoked flavor beef jerky, with one of the fiber plates in pieces.  Thankfully it was the back fiber plate, it was in several larger pieces, and it didn't get out into the motor. At least that solves the mystery of the slipping clutch.  I'm all ready for my ride, but I do need to find some brown riding pants just in case.  :-D  My riding report, or obituary, is on its way!
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline zz3gmc

  • Full Member
  • ***
  • Posts: 178
Re: 2003 KX 250 SF Conversion
« Reply #109 on: July 25, 2015, 01:36:34 PM »
Looks great! Nice to see the newer style KX represented! I was feeling lonely!

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #110 on: July 25, 2015, 01:46:52 PM »
Looks great! Nice to see the newer style KX represented! I was feeling lonely!

Thank you again for all your help and advice, I couldn't have done it without you. I rode it around the block a few minutes ago, and it feels stout but not scary.  I'm anxious to get it dirty.
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline MRDART

  • Jr. Member
  • **
  • Posts: 39
Re: 2003 KX 250 SF Conversion
« Reply #111 on: July 25, 2015, 11:18:15 PM »
Looking forward to a full ride report and video :-)

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #112 on: August 02, 2015, 09:31:38 AM »
I have been planning to go riding with my friend who owns land in Chandler for a while now, and today was the day we could both go.  I took the 500 SF and my 04 KX 250 and we were blessed with some great weather for August in Oklahoma (around 87 degrees), which is awesome because the trails were a mess with blackberry vines.  The 500 started easily, and all the mechanical parts and suspension worked really well.  The motor was a bit of another story.  It just felt lazy and didn't want to rev or come up on the pipe.  When I changed out the clutch, I discovered that the previous owner had removed all the KIPS components, including the gear and mechanism inside the clutch case.  All the stuff in the cylinder is just gone as well.  I would think that would affect the bottom end, but not prevent it for hitting on the top end.  Do you guys have any thoughts on the engine?  KIPS?  Reeds?  Timing?  Gremlins?

Also, the shifter is not wanting to return back up from a downshift.  I also think the shifter is slipping on the splines of the shifter shaft.  I am going to contact Senor Sandblaster to see if I can procure another shaft and shifter, as well as all the springs.  The transmission holds gears well, so I have my fingers crossed on that one.

All in all, I am pleased with the progress.  I have a few things to sort out, but most of the tough stuff is done.  Plus it just looks cool with that giant engine in the frame.   :-D

Once I get the engine sorted out, I will post a ride video.
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #113 on: August 02, 2015, 09:40:46 AM »
Also, does anyone know of any other KIPS valves that will work in this engine?  I know that 87-88 will work (thank you Sandblaster and your awesome reference list), but is there any other models that will cross over?
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline zz3gmc

  • Full Member
  • ***
  • Posts: 178
Re: 2003 KX 250 SF Conversion
« Reply #114 on: August 02, 2015, 01:57:19 PM »
They do look good with that giant engine!
« Last Edit: January 05, 2018, 02:38:09 PM by umberto »

Offline zz3gmc

  • Full Member
  • ***
  • Posts: 178
Re: 2003 KX 250 SF Conversion
« Reply #115 on: August 02, 2015, 02:00:37 PM »
If I remember right a friend of mine used to race a 88 500 and he was able to mod newer 89-04 valves to work. He's a member here and goes by the name ZAR. He hasnt been on in a long time though.

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #116 on: August 03, 2015, 01:27:26 PM »
I found a cylinder head with the KIPS valves intact, and the centrifugal mechanism that opens the valve on eBay.  I hope to have them this weekend.  I am also going to order some reeds, just in case they are worn out as well.  They looked okay when I put them in, but they are 88 factory items and could be way overdue for a replacement.

I'll keep you posted on my progress.  Hopefully this fixes the laziness and wakes the motor up.  It's not as much fun to have a K5 if you don't see God when you ride it.   :-D
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #117 on: August 07, 2015, 04:14:06 AM »
I finally got my cylinder in today.  Stupid USPS took it to their City of Industry center and then let it sit for a couple of days without it moving.  Anyway, the exhaust valves are in place in the cylinder, almost completely free of spooge, and working very smoothly.  I should be able to transfer them over tomorrow.  I'll also be replacing the reeds this weekend as well (if the FedEx Ground guy ever gets here).  Pics and maybe a video to come!
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline dave916

  • Hero Member
  • *****
  • Posts: 547
Re: 2003 KX 250 SF Conversion
« Reply #118 on: August 07, 2015, 09:48:58 AM »
I have been planning to go riding with my friend who owns land in Chandler for a while now, and today was the day we could both go.  I took the 500 SF and my 04 KX 250 and we were blessed with some great weather for August in Oklahoma (around 87 degrees), which is awesome because the trails were a mess with blackberry vines.  The 500 started easily, and all the mechanical parts and suspension worked really well.  The motor was a bit of another story.  It just felt lazy and didn't want to rev or come up on the pipe.  When I changed out the clutch, I discovered that the previous owner had removed all the KIPS components, including the gear and mechanism inside the clutch case.  All the stuff in the cylinder is just gone as well.  I would think that would affect the bottom end, but not prevent it for hitting on the top end.  Do you guys have any thoughts on the engine?  KIPS?  Reeds?  Timing?  Gremlins?

Also, the shifter is not wanting to return back up from a downshift.  I also think the shifter is slipping on the splines of the shifter shaft.  I am going to contact Senor Sandblaster to see if I can procure another shaft and shifter, as well as all the springs.  The transmission holds gears well, so I have my fingers crossed on that one

All in all, I am pleased with the progress.  I have a few things to sort out, but most of the tough stuff is done.  Plus it just looks cool with that giant engine in the frame.   :-D

Once I get the engine sorted out, I will post a ride video.
The shifting could be down to a bent shifter shaft{may need to remove clutch to check }
Kipps missing should  not affect top end power unless some one had did locked valves in closed postion{unlikly}
Second hand  centrifugal mechanism will usually have one of the internally roller bearing worn {will loose roller if u move the unit manually}
if  you are doing full top end rebuild? you will need .2mm head gasket  for the 88,
ideally u would change waterpump seals and kipps bearings  4x608c3
KIPPS  Bolt mod etc is all easy with cylinder off
possible to do this mod on kipps rod as well {shorten the travel on rod }
IT  is also possible to mod one of the kipps valve to make the work a little better 

Offline umberto

  • Administrator
  • Hero Member
  • *****
  • Posts: 2,486
  • First Ride 02-02-19
Re: 2003 KX 250 SF Conversion
« Reply #119 on: August 08, 2015, 01:23:43 PM »
I pulled my engine apart today and was going to install the KIPS valves and put it back together, but as I held these extremely rare sets of valves I had a thought.  These were the only set of 88 KIPS valves on eBay, and I had to buy a head to get them.  What if I could have a backup set, or even a sturdier set?  I have a friend that works in a fabrication shop in my home town, and they can make about anything.  They have computer controlled CNC machines and the like, so I'm going to have him take a look at the valves and see if he can make me a set out of billet steel or something a little more hardy.  These looks very flimsy and easy to break. 

While I didn't get much assembly done today, I did get some good news.  My bottom end is in excellent shape with no bearing play and the side to side movement was right in spec.  I was starting to have my concerns about the engine, so this was welcome news.  If I can get the shifter issue fixed and wake the motor up, it should be a really fun to ride.
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144