KTM powered Blaster

[best]

This is going to be a total overhaul, but since the engine is going to be
switched to a 2003 KTM SX, I felt this was the right forum for this.

My son bought a Blaster with hole blown in the bottom of the engine from this broken piston skirt:

We repaired his engine with JB Weld and fiberglass (I should have taken pictures) and it is working wonderfully.
I really liked his Blaster. Light, peppy, agile. I started looking for one of my own.

The ad said "Blaster with 240 kit and lots of parts, runs well but needs reeds".
I called, 20yr old told me "it runs if you push it, lots of power, yes, the brakes work."

I get there, it is rough. No compression. One front brake.
No spacer in the other wheel so it is flopping loose.
It has papers (very important here!). We negotiate a price.

One hidden danger on this gem was broken handlebars, hidden by offsetting the brake under the clamps.
Thank God it didn't run. I could have been killed on a test run! Don't ever pull this kind of garbage.
This is quickly discovered and reveals what sort of an idiot (hopefully) or a cheat you really are:

Didn't get a picture of it when I bought it. Got it home, pulled the motor.
No 240 kit, it was only 0.020" over, messed up piston, bad crank. Reeds were fine!.
A quick size up revealed a KTM 125 (35hp) would easily fit and maybe even a 250 KTM.
Here is the bike with new front and rear push bars, and the motor and rear suspension removed:

Cut the front mounts a bit and sized the 250 KTM and a 380 KTM motor to see what I could fit:

The 380 was a bit too tight. The 2003 KTM 250 SX was an easier fit.
One goal is to be able to retro-fit the Blaster motor at some later date
and I wish to keep frame modifications to a minimum.
The frame was dimpled slightly to get a lower fit in the front:

An interesting problem were these cracks in the bottom of the swingarm.
I suspect they are from torsion on the swingarm, but there are none on top.

 

[79 bronco]

Very interesting.....

 

[specialized7]

I might have to do one of these 250 swaps some day il be watching this one closely

 

[JonS]

hacked!


...but, it looks like it's in good hands now. can't wait to see it finished.

 

[best]

Tore the rear axle apart and rebuilt it:

Cleaned and painted the carrier, tapped the bearing in square:

Ground the outer diameter slightly smaller on the old bearing so it wouldn't get stuck in the bore...

... And used it to drive the new bearing home.

You don't want to put force or pounding through the rolling elements so all
your force, all your contact, has to go through only the outside ring of the bearing.

The seal was seated square and driven flush with a piece of flatbar:

Don't forget to put the spacer in before you put the other side together.

Trying out a Wilwood dual caliper for size on this baby.
What do you think?

 

[best]

Note my fancy exhaust adaptor. Grooves are for "O" rings.

I got my rad from a Mohave, as mentioned from a member here that did a YZ250 swap:

Note the header flange on the pipe. The pipe is going to have to be cut to fit in the frame.

The SX motor doesn't have a charging circuit (YET!), so I probably won't be running the fan at first.
I want to run it eventually so I'll try to make room for it.

Still gotta work out mounts for the rad...

So, tear it all apart again, rebuild the old drums (did you see the disc stuff?), and clean and paint the frame.
Just rattlecan at the moment. This frame may be welded onto, or altered
so it is Waaay too soon for good paint. That may come next season when the bugs are worked out.

 

[scotj77]

looking good man. hope this works out well for ya.

 

[stabor1122]

Looking good. My swingarm is cracked just like that too except mine is on the top crossmember.

 

[best]

Did you repair it?
Thinking of just running a bead of weld across it, wondering how you did?

 

[stabor1122]

Did you repair it?
Thinking of just running a bead of weld across it, wondering how you did?

No I have not. I was not sure how well that would work. I have a spare stock one to install on mine but I am looking for an extended one now.

 

[3 Wh33l3r Rid3r]

Did you repair it?
Thinking of just running a bead of weld across it, wondering how you did?

i had the same thing on mine but on the top, i ran a good bead on it and havent had any more problems out of it.

looking good so far, i used a yfz450 radiator in mine its a little bigger than the mojave radiator but i do like how the water outlets are on the mojave they would work out alot better on mine than the rad i have. keep up the good work and keep the pics coming

 

[88' blaster]

if u need a swinger i have one for sale

 

[best]

OK guys, IT'S A ROLLER!

Swing arm and inside bushings cut to width.
Bigger job than I thought, measurements are critical. Left side has to line the chain up,
and the right side has to be an exact width to get everything tight without binding.
The bushing are basically 2mm wider than the swingarm tubes they fit in but have to be accurate within 0.2mm if the book is to be believed. Measure, measure, measure, then cut and pray.

So this is the swingarm fitted into place. It was in and out a dozen times and this picture doesn't have the side caps on the swingarm, and it is held in place with a 1/2" socket extension. A bit of welding will have to be done on the left inner side, because of how much had to be cut. The blue carb is not my idea, it came off a parts bike that had many parts painted metallic blue and metallic green. Dang it was ugly. Piece cut off the right side is sitting on the right side of the swingarm.

Swing arm in place, front brakes (cable drums for now, disc coming) hooked up. Note the hydraulic clutch! A KTM feature for over a dozen years now. I listened to you guys and switched from twister throttle to thumb. Used the KTM cable but had to put a 40mm spacer tube (split steel fuel line) up by the handle bar to take up the length difference. Running motorbike (low) handlebars at the moment because that is all I have. The originals were broken. I typically ride standing up and at 5'11" like high bars.
Any recommendations?

Minor interference with the kickstarter. Had to grind the gusset weld and lightly massaged a flat into the frame tube to get clearance. Note the CDI box. I am looking for a place for it. Hope to have it fired up and running soon. Busy life, don't get a lot of time at it.

Better view of the swingarm and the dirty shock in place. This time caps are on the swingarm, as well as the Banshee chain guide and rollers. Not wasting time with cleaning up the shock, because I have a LTZ400 shock for when I figure out what I am going to run on the front. Want to try out the stock shocks and brakes first, since they are easily put into into good shape. Sometimes modifications are not improvements, so I want something to compare with.

Big bore flat slide ready for action. Did you know most KTMs from 125 to 380 all run the same size carb? Strange but true. Keihin PWK 38 or 39. Just change the jets and my 125 carb will work perfect on the 200, 250, 300 or 380. Go figure?

Carb comparison, KTM Keihin PWK 38 to Blaster Mikuni VM26SS. Guess which is which?

Still to come, more motor mounts. Only 2 won't do.
Rad has to be installed, as well as electrical. Also need an airbox connector.
Rear brake has to be fixed up and installed. Oh, and the pipe. That will be fun.
First job will be to get the wiring done and engine started I think.
Motivation to keep working on it. Almost 3 feet of snow outside, there is no rush!

If anyone wants any better pictures of anything along the way, say the word.

 

[99LRDblaster]

I'm interested in this project. KTM 2 strokes tend to dyno the highest HP from what little I've seen. This is what a stock KTM 250cc?....already a screamer in the quad world......and this is minus.....porting....reeds.....stroker...milling.....you name it. I get the feeling the 250 alone will be more than enough power though. I'll be excited just to see it up and moving first though......if it turns out badass, maybe you can tear it all apart again after you invest the money and gusset the frame for more strength, powdercoat and mod it all.......but hey....let's just see it in action first right?

 

[bagds101]

sweet build. youre not the only one that got ripped off. when i bought mine i thought it was a 240. lady told me her husband said it was. got it home, tore it down and realized it was only a 67mm piston.

 

[99LRDblaster]

sweet build. youre not the only one that got ripped off. when i bought mine i thought it was a 240. lady told me her husband said it was. got it home, tore it down and realized it was only a 67mm piston.

People are major bullshitters and I never trust them unless I know it to be true. I had some moron on Craigslist the other day selling his "410cc Banshee" when he himself states it's just a .050 over Wiseco pistons. 8-| I sent him a friendly email.

 

[bagds101]

yeah i always email those idiots with 250cc stock blasters. but now i know more about blasters and if i ever buy another one i know what to look for

 

[best]

I'm interested in this project. KTM 2 strokes tend to dyno the highest HP from what little I've seen. This is what a stock KTM 250cc?....already a screamer in the quad world......and this is minus.....porting....reeds.....stroker...milling.....you name it. I get the feeling the 250 alone will be more than enough power though. I'll be excited just to see it up and moving first though......if it turns out badass, maybe you can tear it all apart again after you invest the money and gusset the frame for more strength, powdercoat and mod it all.......but hey....let's just see it in action first right?

Exactly! Get it in action first.
A big mod like this cannot be "done right the first time". It is an evolution.
To powdercoat the frame at this stage would be a big waste of money.
This year (2003) was a high HP engine, but were known for peakyness.
They are about 50hp and over that with very few minor mods, much the same as the YZ250.
I may be de-tuning it with a longer pipe and flywheel weight for more low end torque and traction.
Heck, I might be lucky to get 50hp out of it. Oh well...
What was my 660 Raptor? 33-37hp? It will be bad a$$.

One thing I want to do is weigh the Blaster motor and compare it with the water cooled motor and rad.
I know the fins weigh something but I feel the watercooled motor has GOT to be at least 10 lbs heavier than
the air cooled motor. I have a 125/200 motor I can weigh too, as a more fair comparison.

Yeah, the lies about the 240 kit, broken handlebars, no brakes, no compression ("running" ha!)
really show what a persons's character is. I feel really bad that his father was pushing him to lie like that. Sad.
You lie like that and you will get caught and look like an idiot. Either stupid or crooked, that is how the world will see you.

I did not get ripped off actually.
I showed him through most of his lies, to the point his friend walked away out of embarrassment.
Stupid or crooked right? His friend wanted no part of that. He understood. We negotiated a fair price
and I am happy with it. A diamond in the rough. Real rough! Ha!

Hiding these broken bars however, that sort of thing is near criminal.

 

[99LRDblaster]

Exactly! Get it in action first.
A big mod like this cannot be "done right the first time". It is an evolution.
To powdercoat the frame at this stage would be a big waste of money.
This year (2003) was a high HP engine, but were known for peakyness.
They are about 50hp and over that with very few minor mods, much the same as the YZ250.
I may be de-tuning it with a longer pipe and flywheel weight for more low end torque and traction.
Heck, I might be lucky to get 50hp out of it. Oh well...
What was my 660 Raptor? 33-37hp? It will be bad a$$.

One thing I want to do is weigh the Blaster motor and compare it with the water cooled motor and rad.
I know the fins weigh something but I feel the watercooled motor has GOT to be at least 10 lbs heavier than
the air cooled motor. I have a 125/200 motor I can weigh too, as a more fair comparison.

Yeah, the lies about the 240 kit, broken handlebars, no brakes, no compression ("running" ha!)
really show what a persons's character is. I feel really bad that his father was pushing him to lie like that. Sad.
You lie like that and you will get caught and look like an idiot. Either stupid or crooked, that is how the world will see you.

I did not get ripped off actually.
I showed him through most of his lies, to the point his friend walked away out of embarrassment.
Stupid or crooked right? His friend wanted no part of that. He understood. We negotiated a fair price
and I am happy with it. A diamond in the rough. Real rough! Ha!

Hiding these broken bars however, that sort of thing is near criminal.

Could always looks into milling the head for a little more low end power. Maybe a slight stroker if you didn't want to run real expensive race gas. I don't know the specs of the KTM so I can't say. Pipe will need cut to fit, but with a little thought and fabbing it should work pretty well. Water cooled motors are typically always heavier with all the equipment and the excess fluids. I'll be interested in how the YFS200 compares in weight to the 125 and 250 though......I've always wondered that.

Selling a quad with broken bars or anything else is just flat out stupid......main reason being if you end up selling it and then the person ends up injured and/or dead, there is a possibility they might be held accountable for it.

 

[Paulie B]

Man shoulda done the 380.
Nice project though I'll be following it I:I