Maintenance & Technical > KX500 Steel Frame Conversion (SFC)
2003 KX 250 SF Conversion
zz3gmc:
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.
umberto:
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
umberto:
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!
dave916:
--- Quote from: umberto 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.
--- End quote ---
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
umberto:
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.
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