KX Guru Racing

I bought a used 2008 SXV 550 and ran it for a summer and then in the spring when I fired it up for my first ride I checked the oil and it had the milkshake (leaking head gasket those engines are known for) on it. Then I pulled the engine apart and found the sleeves, the pistons, the camshaft were out of spec. Fairly pricey to replace all that so I thought why not put a KX500 engine in there. I tried using the frame rails from the KX500 frame but they just wouldn't work out. Used a tubing bender and made frame rails from 1" chromoly tubing.
The pipe is a Service Honda gnarly, used a dayco part # 71415 hose to flip the coolant fitting on the cylinder
Hardest part of this project was taking a recip saw to the beautiful Aprilia frame

The rest of the coolant lines I built mostly from pieces I got from Pegasus racing, they sell different bends in lots of different sizes of hose I used the stock silencer. It's a cool design on these bikes, it sits under the seat and functions as mud guard for the rear tire, then it has dual slash cut tips that come out behind the rear of the seat. Since the original engine is a v-twin I capped off the left side and ran the pipe into the right side. Works pretty well, exhaust seems to come out of the tips evenly and it's fairly quiet

Head mount Radiator mounts

Bottom of the right radiator was moved forward a little so made a bracket to adapt the rad shroud Swingarm pivot engine mount Used an MZB Penton ignition, I love the kit they make. Also used a small (1.7 farad) capacitor bank instead of a battery. Lights don't flicker and I won't have to worry about battery maintenance

Did my own decompression head, welding cast aluminium sucks but it works Got a hydraulic clutch for it too. Works great, one finger pull Nothing much done for engine mods
Cylinder is stock, just got a fresh replating
Used a cast pro-x piston
Wossner rod
Boyesen reeds
Used a keihin 36mm quad vent - 3000' around 60F 170 main, 38 pilot #7 slide, n82m needle 2nd clip

I'm busy working right now but I will go over this post carefully...

In the mean time... Ride report??

Rides really good, I have a CR500 supermoto and the KX engine is smoother, works much better as a street engine IMO. I'll try to get a video of it in action just have to get my buddy who has a go pro
I forgot to mention it has boyesen reeds, I updated my other post
Also it weighs in at 290lbs with a half tank or so of gas

I'm still going over this build.
I posted a link to it at a few FaceBook groups and have received many positive comments.
So far... I like what I see.
A buddy of mine had the same bike (Not converted) and we raced only once on the street.
It was no contest... The KX500 ran off and hid from the 550.
But, he did have a faster top speed than me...
But not by much and a small gearing change would have fixed that right up.

Ok. I really like the conversion.
My hats off to you for a fine job.
The one thing I would do different is swap to a larger carb.
38mm air striker. Biggest bang for the buck.
Smart carb 40mm SC2. Expensive but the e40mm SC2 is the easiest to tune and once set up it works at any altitude.
44mm Lectron HV. Hardest to tune but the highest performing.
They all offer superior performance over that 36mm..

Couple any of those carbs with VF2 reed and you will dd some RW HP.

What spec did you time the ignition to?
I'm currently doing some experimentation with the Power D to maximize performance.