07 KTM 250sxf/500kx conversion

[hunter]

New guy here, really enjoying the site and learning a crap ton. My conversion started the second I bought the KTM with a blown motor, was hopeing for a simple topend fix but the head was toast. Off to google for alternatives and that's where I found you guys. I have not made it to far yet but have started ordering parts I know I will need.

What I have so far :

2007 KTM 250sxf
3 -1987 KX500 engines (1 Running supposedly, 2 in parts but could have a second running one with piston and rings)
Service Honda kx500af pipe on the way

Need to order/do:

Decomp valve
Hydro clutch actuator
Misc tid bits

Hold ups:

1. Reaming the rear engine mount hole to 17mm. I live in a small town so its hard to find someone who can do this and I wouldn't mind keeping the case oem. I have a few ideas.
-- Have a bushing made for the swing arm holes 17mm OD and 15 ID, would use a Different pivot bolt (maybe one from a earlier year KTM?)
-- I sent allballs a email asking if they could put together a bearing kit for the swing arm that would have a 15mm hole, effectively doing the same as above

2. Exhaust:
-- From what I can tell it seems the KX500af pipe is the best route to start with, but I also assume its not going to just line up. Anyone else use one of these and if so what mods did you have to do to make it work with the KTM frame?
-- Still researching on what muffler to use, hopeing maybe a KTM 300 2stroke one will work maybe different Cone Diameter?

Anyways, this will be a slow moving project as money is the main factor in the way but working on getting that handled the best I can.

[dave916]

hi
What your engine/ swingarm  clearance  both sides?
I Have done 17-15mm bushing {not on ktm} they worked out good  they do turn out pretty thin[only  1mm thickness}
On my build  12 mm clearance one side and 2mm other side 
One bush ended up a straight sleeve and the other sleeve had 6mm collar and need to be about 3mm longer than swingam bush to slide into the frame /   

Changing bearings in swingarm will still leave u with 17mm holes in frame

[hunter]

hi
What your engine/ swingarm  clearance  both sides?
- I have not checked this as of yet, trying to get the engine in there first with the rear pivot mount and then will cut the old mounts out and mock everything up where the sprockets are aligned.

I Have done 17-15mm bushing {not on ktm} they worked out good  they do turn out pretty thin[only  1mm thickness}
On my build  12 mm clearance one side and 2mm other side 
One bush ended up a straight sleeve and the other sleeve had 6mm collar and need to be about 3mm longer than swingam bush to slide into the frame /   

I assume the 6mm collar was to get the engine offset for the sprockets? I remember reading that somewhere.

Changing bearings in swingarm will still leave u with 17mm holes in frame

Yeah was thinking about that, though maybe some small short bushing for the frame but I am not likeing the idea.

Sorry its taken a bit to get back with you. Crazy busy at work.

My answers up in blue, I loved the idea of changing the bearing until you reminded me about the frame. So I think I am back to the bushing idea or just buying a reamer and taking the plunge on the cases then its just a done deal. Bushings are pretty easy for me to get made up, just need to tell my buddy what I need.

[dave916]

A quick drawing to let u know what i done / very important that bushing are right  length  
U dont want to end up with swingarm  or motor not tightening properly  
The reason for the collar is so u can remove swing arm without removing motor


17by15mm Bushes or in purple  

[hunter]

Dave,

Seriously appreciate the diagram and all the info. I was talking with my gunsmith today and he said he had adjustable reamers that would make short work of reaming out the hole, done by hand. Now that this could be a option I am leaning that way just to make life simple. Hopeing to get that done this Sunday if all goes well.

[hunter]

Small Update:

Things are finally moving forward, Got the hole reamed out last weekend and got the engine in the bike to get a rough idea how things are going to fit. I lucked out and got this Saturday off and was able to get a welder/fabricator to work with me on it to get the Mounts done, pipe fitted w/mounts along with modifying the left radiator. Pretty much all welding done.

Issues that need to be addressed that are obvious and appear to be a common issue:

Stator cover hits the left frame cradle
Kick starter hits the frame as well
250sxf air boot appears to might be able to work


Where is everyone mounting there coils and such?

Anyways should have some pictures to post up after this weekend of some progress.

[hunter]

Heres a few pictures of the progress. Also some things to note that I somehow never even noticed that should have smacked me right in the face. Front and bottom mount holes were previously reamed out to 12mm and were filled with gasket maker to make what I assume is a make shift rubber mount. I bought M12 bolts for the mounts but I do plan to find some with a Allen head. Mounts were fabricated up and bolted on to the engine and then everything was tacked including the nuts. Then engine came out and the mounts were finished off. My sprockets were aligned with the engine pushed all the way to the left against the swingarm. A 6mm wide spacer will be needed and I already have that made up and on hand. I did not modify the frame where the stator cover hits, we just shimmed it in that spot for clearance. I know things will be tight around the spark plug area so I ordered some shorty spark plugs and the NGK short plug as well. Kicker will have to be massaged a little bit as well for it to kick freely.

Also picked up another KX500 engine today, was told it was a 86 and the cases are in pretty bad shape. Rear pivot hole was attack by what appears to be a Die Grinder and a inch or so has been removed of the right case mount hole. The hole was also reamed out to god knows how big and most likely not square.

BYE BYE KTM mounts





All done

[hunter]

Some more progress, slowly coming together.

Mounted radiators - Left radiator needed the bottom spout spun 180deg upwards
Also on the KTM they have this T inside the frame that is integrated into the cooling system. I did not need the bottom part of this T, so we took it apart. I used a m20x1.5 oil drain plug from the hardware store to plug the hole in the bottom of the T. We had to cut off head and make a slot for a flathead screwdriver to fit to screw in our makeshift recessed plug.  Reinstalled the Top part of the T in the frame and it will now act as the cross over From Left to Right.

All the Exhaust mounts are done, just need to get a small piece bent up to mate the silencer to the headpipe.
Mounted up the CDI and Coil, just reused the factory KTM locations.

For a Intake boot I used a 2008 KTM 250 SX 2 stroke boot, DO NOT put the boot in first. You have to mount the carb to engine then put the boot in and mount to the carb before trying to install the boot. Doing this, allows the boot to take on a new shape after installed and fits like a glove....you will cuss a bit trying to get it installed lol.

[reklessj]

Looking good man, she is coming along nicely!!!

[umberto]

Great looking bike, you've made some great progress so far.  How close are you to riding it?

[Foxx4Beaver]

For a Intake boot I used a 2008 KTM 250 SX 2 stroke boot, DO NOT put the boot in first. You have to mount the carb to engine then put the boot in and mount to the carb before trying to install the boot. Doing this, allows the boot to take on a new shape after installed and fits like a glove....you will cuss a bit trying to get it installed lol.

hmmm, that sounds fun.

[hunter]

Thanks guys! The bike is starting to come together, my main hold up were the welding and the rear pivot hole. My work schedule has been 6days a week so time has been a issue. In perspective this is going really fast, I bought the KTM Roller in the last weekend of July and basically in a month went all out buying up engines etc trying to make this happen.

So far the things I have left to do before I can actually Ride it, and assuming no other issues pop up:

Rebuild Water pump, and replace bearings and such in the clutch cover ( I have a upgraded water pump coming)
Go through the Carb, make sure its up to par and do initial jetting.
I ordered new controls and cables - G2 2Stroke perch, Moose ez3 Clutch perch and cables for those

I got rained out today, so if I can find someone that can do the exhaust today I am ahead! The parts I have ordered should be here at the beginning of next week. Will probably get the engine work stuff done this coming up weekend.

So if things go the way I hope, Ill be trying to kick it over in 2 weeks.

[hunter]

For a Intake boot I used a 2008 KTM 250 SX 2 stroke boot, DO NOT put the boot in first. You have to mount the carb to engine then put the boot in and mount to the carb before trying to install the boot. Doing this, allows the boot to take on a new shape after installed and fits like a glove....you will cuss a bit trying to get it installed lol.

hmmm, that sounds fun.

Its really not to bad, and when you look at it all your thinking man that's close but no cigar. My buddy suggested doing it the way above, and after its all in it look awesome. I did use a new boot though, so the rubber was really soft I can imagine with a used one it would be a &*%$&*$$*$(($@@!!!! lol.

I will try and get some pictures of it today if I can and when I strip the bike down to get the frame powdercoated I will take some pictures of all the little stuff we did to make it all work like the T in the frame.

[Foxx4Beaver]

yeah...I was being sarcastic....I enjoy a challenge just as much a the next guy.

[hunter]

Fox - I hear ya, the airboot was pretty easy, it just doesn't look like it would work. Just trying to help out the next guy that might try one of these, as it seems its the small things that are the things that seem to be the issues that need figuring out.

This is my first conversion, so I am learning a lot....

Oh and I also picked this up this last Friday, 2008 250xcf with blown bottom end, Already had a street legal title so I promptly went and got plates for it. Thinking this one will be the Supermoto one!