237 replies to this topic

[Jeezo TT Bronze Member]

So here it goes, after being relentlessly told I'm wasting my time, I'm determined to build my ultimate dirtbike.

I'm not sure what section to put this in, the KTM people hate me because they think it's and insult to their steadfastly defended linkless rear end, and the kx250f and rmz250f sections are all 4t riders. I figure the engineering section will have some open minded folks with valuable input.

I've been talking about doing this for awhile, and I've had alot of people laugh, tell me it's pointless, tell me I'll never start it, or never complete it, etc. Well, here you go haters, I'm doing it.


Uber Dirty: 1996 KTM300exc engine going into a 2004 KXF250 chassis.

Got a decent start, looks promising:

Here's the messy garage:


Here's the donor bike. I rode it a week ago, took me about a half hour to get the engine out, here's how it looks:



Better look at the donor frame/engine mounts:




Front cradle:

[Jeezo TT Bronze Member]

Here's the engine, looks filthy right here, but it's actually extremely low time, prob under 20 hours since brand new, and about 10-15 hours on a brand new top end with new plating. Def needs a good cleaning. I'm also gonna replace the countershaft seal and shift shaft seal. They are notorious on these KTM for several years.





Box o parts, I need to get a dent out of the pipe, and the shock needs service. I'm not sure which shock I should use. I'm not even sure if I have a choice. I'll prob have to use the OE kawi shock.




Here's the lucky recipient, 2004 kxf250, same bike as RMZ250 2004-2006

[Jeezo TT Bronze Member]

KTM swinger pivot:




KXF swinger pivot:





Caliper shows width of KXF engine:










PO screwed up the clicker, hopefully that's not a sign of a big internal problem. I plan on rebuilding them anyway, so if possible, I'll replace that part. These forks are the late model KYB bladder forks. I've heard the bladder system is not great, but they are supposedly really good when converted to open bath. I'll prob seek some advice revalving them and do that myself. From what I understand, basic changes aren't too complicated. More on that later.




Caliper shows the corresponding distance in the kxf chassis from the swinger edge to center of chain.

[Jeezo TT Bronze Member]

Anyone know where I can get that clicker?

It isn't real clear to me on the microfiche.

[huskymad127 TT Silver Member]

Are you gonna use this for an MX or trail bike? Looking forward to see how it goes and good luck :thumbsup:

[gmoss357 Get Help Now]

nope, not hatin', just not in love with your attitude toward the advice given. why ask if you didn't want to hear it?

where's my popcorn, look forward to watching this... :smirk:

Edited by gmoss, 30 March 2011 - 05:47 AM.

[adam728 TT Addict]

11065 is what you'd need to get a new clicker.

I think it's a great project. Seems on all these forums engine swaps are usually met with a fair amount of poor attitude. Nothing wrong with liking an engine's characteristics but wanting a more modern, or nimble, or tunable chassis. KDX hybrids are quite common, and even those threads get their bashers.

[gmoss357 Get Help Now]

adam728 said:

11065 is what you'd need to get a new clicker.

I think it's a great project. Seems on all these forums engine swaps are usually met with a fair amount of poor attitude. Nothing wrong with liking an engine's characteristics but wanting a more modern, or nimble, or tunable chassis. KDX hybrids are quite common, and even those threads get their bashers.

go back and read his other threads and his posts, I think you will find that there weren't many haters, mainly just sound advice. His posts provoked many of the responses he his talking about.

interesting project and I have nothing against what he is doing. It's his money and his time. I personally would rather just invest in a sound bike and mod it to my liking, but that is me. I will be curious to see the end result.

it's funny because if he didn't want all these so-called haters to show up here, he wouldn't have revived those threads, providing a link to this thread. sounds like he just likes the attention to me.

[KcDavis TT Addict]

Something pretty catastrophic must have happened for an engine with only 20 hours on it to need a top end and replate withing the first 5-10 hours!

[Jeezo TT Bronze Member]

I'll admit I am prodding a bit, I just got annoyed with the people saying I was a trolling and would never do any of this. This is the kind of thing that was pissing me off:

Jays07WR450 said:

The excuses are confirmation of what I suspected all along...you have no intention, money, ability, or facility to do anything you stated in your post...you're probably not even old enough to "party" legally. ZX6...really:lol: and I'm sure it's yours and you ride it all the time, blah, blah, blah...:p

You're digging the hole even deeper. Lies compounding lies...how many posts do you have on this forum now...12? Maybe enough to match your age...maybe.

That being said, this is largely academic. I love working on bikes as much as riding them. I got the KTM for almost nothing, and the kxf for almost nothing, so I'll be happy if I can build a bike I love. If I just wanted to ride, I'd buy another KTM or KDX, but this will be a fun project, and hopefully spend alot less money and have a unique bike that suits my needs. For now the KDX is still my main ride.

KDAVIS:
Good observation on the low time top end. I bought the KTM300 for $270, and when I tore it down, it was apparent that it was nearly new. almost zero wear on original tires, grips, seat, plastics, etc. One of the radiator passages was blocked off near the thermostat with a piece or rad hose, and from the what I could tell, because of that the thermostat had never opened. It appears that the bike had only been run long enough to destroy the top end. I think since the thermo never opened, it was able to overheat and melt down without ever blowing the cap off. Ive ridden the bike about 15 hours now on the new top end and it's a dream. Best engine I've ever ridden. Almost as luggable as the KDX, but with hyperdrive.


True, this is a 15year old engine in a 7 year old chassis, but keep in mind I only have around $500 in this project so far. I'm not in the market for new bikes. I love 2 strokes and the engines havn't changed much, (i'll be the first guy to sell his kidney for a DI 2t engine) I wasn't a fan of the old 300 chassis, and I think this kxf will be an improvement.



This will be a woods bike, not mx. That will be another aspect of this project. I've rebuilt forks myself several times, but this time I'd like to see if I can soften the valving up myself. I've been doing alot of reading on here trying to get a feel for it. These are the bladder forks, common recommendation seems to be convert to open bath, then valve accordingly and run traditional oil heights.

[Jeezo TT Bronze Member]

adam728 said:

11065 is what you'd need to get a new clicker.

I think it's a great project. Seems on all these forums engine swaps are usually met with a fair amount of poor attitude. Nothing wrong with liking an engine's characteristics but wanting a more modern, or nimble, or tunable chassis. KDX hybrids are quite common, and even those threads get their bashers.

Are you sure? that doesn't seem right to me. That is the cap, with the bleed off screw and 2 o-rings. The clicker looks to me like the part above 92210, but here's no number. Is it part of 92210 or 46102?

Any help here dudes?

[jar944 TT Silver Member]

how do you plan on widening the swingarm, and narrowing the bearings?

[Jeezo TT Bronze Member]

jar944 said:

how do you plan on widening the swingarm, and narrowing the bearings?

That is what I'm looking into now. I need to do this while maintaining proper chain alignment. In normal configuration, I would need to take it all off the right side of the bike. There is some offset built into the countershaft sprocket, so if I flip the sprocket, it allows me to take it evenly off both sides. The chain still has good clearance. It's a long shot, but I need to take a look at how the engine looks in the frame to make sure there's no reason later I might need the engine .0070" shifted to the right.

I would like to take it all out of the swingarm, but the inside of the swingarm has that small washer style needle bearing right there. The swinger ID is smaller where the main needle bearing is, so in order to shift it all over to the outside I would need to bore out the smaller ID of the needle bearing and put a bushing in the larger ID area to support the main needle bearing.

That seems like a big hassle, so I may just take it all out of the engine case. If possible, lol. I need something like a 1"+ countersink with a pilot the size of my swinger pivot. That is the best thing I can think of right now. That should produce a clean perpendicular cut.


Also wondering about the best way to drill out the swinger pivot. Any advice here? Is a typical metal drillbit going to make a clean enough hole? Or will I need a straight fluted drillbit designed for that? The only straight fluted drill bits I can find for my depth are carbide tipped and expensive as balls.



Any advice machinist friends?

[brentn TT Addict]

Jays07WR450 said:

It's more modern than what?

A 13-year-old engine in a 7-year-old frame? I suppose it's more modern than an early 1990's bike.:smirk:

This thread is truly heckle-worthy!:moon::p

Quit trolling this thread, your embarrassing yourself.

Academic, yes maybe that's what he's going for. He said it was his personal ultimate bike, what's your problem with that? It's what HE wants to do, we don't give a shit if it's not what you want to do because this is not your thread.

OP, I'm all ears and eyes on this, nice work, I look forward to seeing what the end result is :thumbsup:

[jar944 TT Silver Member]

Jeezo said:

That is what I'm looking into now. I need to do this while maintaining proper chain alignment. In normal configuration, I would need to take it all off the right side of the bike. There is some offset built into the countershaft sprocket, so if I flip the sprocket, it allows me to take it evenly off both sides. The chain still has good clearance. It's a long shot, but I need to take a look at how the engine looks in the frame to make sure there's no reason later I might need the engine .0070" shifted to the right.

I would like to take it all out of the swingarm, but the inside of the swingarm has that small washer style needle bearing right there. The swinger ID is smaller where the main needle bearing is, so in order to shift it all over to the outside I would need to bore out the smaller ID of the needle bearing and put a bushing in the larger ID area to support the main needle bearing.

That seems like a big hassle, so I may just take it all out of the engine case. If possible, lol. I need something like a 1"+ countersink with a pilot the size of my swinger pivot. That is the best thing I can think of right now. That should produce a clean perpendicular cut.


Also wondering about the best way to drill out the swinger pivot. Any advice here? Is a typical metal drillbit going to make a clean enough hole? Or will I need a straight fluted drillbit designed for that? The only straight fluted drill bits I can find for my depth are carbide tipped and expensive as balls.



Any advice machinist friends?

You need a lathe and mill.

You will need to machine up one of these:


So you can machine the swingarm


You need to keep the counter sprocket in the same plane as the original bike, and in all honesty it may not be possible. I would advise against doing any cutting/machining to the engine cases, you will need to source new swingarm bearings sized to fit the [now narrower] swingarm. You will also need to machine the bearing spacer to the new width.

Dont bore the engine pivot, use the KTM dia pivot bolt with a bushing for the frame & swingarm. If you insist on boring it, it should be done on a mill with a boring head (easier with the cases split.)

Cut the engine cradle out of the KTM and graft it onto the Kawi.

check rad plumming
check kickstart clearance (it's going to be rough if you have to push start it)
check to see if the rear brake is going to clear

[Jeekinz Get Help Now]

Jeezo said:

Are you sure? that doesn't seem right to me. That is the cap, with the bleed off screw and 2 o-rings. The clicker looks to me like the part above 92210, but here's no number. Is it part of 92210 or 46102?

Any help here dudes?

92210 is the lock nut, the small part above that with no number is the comp adj rod. It's essentially a long skinny tube. The clicker comes installed in the cap 11065.

check out the Stickys in the Kawi 2 Stroke forum for KX/KDX hybrid builds. Those builds involve the same issues you're having including boring the cases, swingarm clearance, etc.

Subscribed.

[Karlgp TT Silver Member]

Looks like a good project to me.

I've got a motor with a 16 year old design ('03 KDX220) in a 12 year old frame ('99 CR250) It's a fine woods bike. I've been riding the heck out of it for three years now, no problems. Would a $7000 KTM or GasGas be better? Sure, but I like my bike just fine.

To the OP-
When building mine I put the motor and the swingarm on the bench and started figuring. The CS sprocket HAS to go where it has to go.
I drilled the case with (in my case) a plain old 17 mm drill. I tried to rig the motor in to my drill press but it was not working out. I ended up drilling it by hand.

I had to narrow the cases on the RH side only. I scribed a line and cut it with a die grinder and finished it with a big file.

I had to shorten the inner bearing race on the RH side also and took that to a friends machine shop.

After figuring out the swingarm business you'll want go straight to exhaust and carburator/air box. I would not worry a bit about motor mounts until the carb/airbox/exhaust/tank are all mocked up. The motor mounts have to follow the motor, not the other way around.

Watch out for little things like brake lever hitting clutch cover, kick start can't swing past frame, rear brake master cylinder reservoir, clutch cable routing, all kinds of things.

I was fortunate to have other bikes I was riding at the time. I've since sold most of them.

Have fun with it. I think it will be a fine bike.

[Karlgp TT Silver Member]

A buddy of mine has two '02 YZ250 chassis' in his garage. I want them to put a 175 to 250 CC aircooled two stroke motor in.
I'm thinking an old Rotax or even a Blaster motor.

For some reason he is not too keen on the idea.........go figure.

[MetalMan1011]

Very cool I think. I did a project similar to this a few years ago, a KX500 engine in a 2005 KX250F chassis. I got a lot of negative feedback during the build, especially since I was 17 at the time and did all my own work . I posted pictures of it assembled as a prototype, which was a big mistake. It looked all ratty when I got it together for the first time, before tearing it down and rebuilding it nice. I even broke even on the project after selling the 250f motor, exhaust, carb, and electronics, plus all the other leftover KX500 parts.

Prototype assembly:


Final assembly:


Just a couple things you might haven't thought of yet. You might have to cut and weld up your pipe. And hopefully the downtube isn't in front of the exhaust port. It was for me, and that was a huge pain in the ass.
http://i47.photobuck...pg?t=1301606226

I had to modify the airbox as the carbs were different sizes so the boot wouldn't match up. I ended up putting the 500 boot on the 250F box.http://i47.photobuck...pg?t=1301607094

Other than that, there was a bunch of other little things to work around. Radiator clearance problems, rad hoses, gas tank clearance, similar swing arm issues as you have, ect...

People told me I my frame was going to break in half, but it ran and held up great for 3 years of hard riding until it was stolen from me. Good luck with your project:thumbsup:

[Vintage Not Pimpage TT Silver Member]

Sounds like a great project! Good luck with it, there is not a lot you cant do in your own garage with a hacksaw, grinder and a welder and a bit of ingenuity.
I went the other way, a 4 stroke motor in a 2 stroke chassis, its been a big job but is now 95% complete and I have just been out test riding it working out the jetting.
The one and only thing I have not done myself in my garage with basic tools it the aluminum welding of the intake manifold.

http://www.thumperta...146#post9768146