KTM 550 Trike

[bikemaker]

My first post so a little back story first.

My first trike was a ATC 70; way back before 4 wheelers even existed.
Then came a LT80 after they first came out, then moved up to a 250 quadracer. My family always rode over at the Oregon dunes, but I had dreams of becoming a motocross racer. After a couple years of mangling myself and the quad at the local motocross track, I decided I wanted another trike for the dunes; but not just any trike.

At the time, drag racing was popular, and it was almost nothing except Banshee's racing. But I wanted something different. I had seen 250r's with 500's in them and then saw a Leager 500 (CR500 frame and suspension converted to a trike) and thought that was the way to go. So I sold the Quadracer and began searching for a CR500 to convert. But instead I found for sale a 92 KTM 550 MXC. Single cylinder 2-stroke, supposedly made about 10 horsepower more than a CR or KX 500. After watching the 240 pound seller practically jump off of his back porch to start the thing, I had to have it.

I ended up just throwing a paddle on the big Katoom and riding it as a bike for 2 summers. But after seeing my life flash before my eyes on numerous occasions, it was time to convert it.

Over the winter me and my dad made the conversion. Then I rode it over on the dunes for 3 or 4 years. After blowing the motor a couple of times, melting the clutch out of it, and constantly tightening all of the bolts (the vibration from a 550 single is extreme), it's final trip was to dunefest - one of the first years it moved up to the Winchester Bay area - where it blew a water pump seal. I was tired of working on it, had a wife, was starting a family, you know the story. So I rolled into the back of my Dad's barn and forgot about it.

Fast forward about 15 years - now my kids are all old enough to ride, the old man bought a fancy new Razor for him and grandma, and we're getting back into it. The old man still has 3 ATC250R's - 83,85,and 86. Got the 85 and 86 back up and running, and now it's the KTM's turn.

Here's a couple pics from after I hosed all the dust and cobwebs off.









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It shouldn't take too much to make her a runner again.

[michaelc]

Very cool? Amen

[Maico]

Very nice!! Those 550's were some evil mofo's. What would be nice is to either have a set of triple clamps made for the KTM forks or swap over an '86 Tecate or Honda R front end.

Love to see more pics of the swing arm and fender set up.

[sanchez]

Freaking sweet vintage ktm big bore trike
And your front end looks to have better rake than my leager's
but u gatta keep the slap braclet era color skeem
Can't wait for more pics

[JasonB]

Welcome! Neat machine you made there !

[bikemaker]

Thanks, ill get some more pics tomorrow.
I've been trolling around this site for a while now, and there's a lot of backyard engineering
That I've been admiring. Figured I would show off my own evil incarnation since it seems right at home here.

[bikemaker]

One of the criteria we had for this project was that it could be converted back to a motorcycle at any time. So everything is bolt on; it could be turned back into a bike in an afternoon. I originally bought this thing back in 1996 or 1997, but it was already rare, and I didn't want to chop it up.

We originally planned on building our own triple clamps to widen out the front end, but the tank on this thing has the radiator shrouds built into it, and there just wasn't a good way to make it happen without changing the fuel tank.

So after some pondering, we ran across the front tire off of a Katana 600 street bike. Whipped up a new axle in the lathe, and an adapter to mount the KTM rotor to the new front wheel using the stock caliper mounting location.
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The front tire actually worked pretty well. It floats on top of the sand way better than the stock dirt bike tire ever did; just never quite cared for the looks of it.....maybe a front fender would help it out.

[bikemaker]

Then we had to figure out a rear axle. This was kinda hard. All of the ATV swingarms we found had the chain alignment out to lunch, the closest we found was this rear axle and carrier off of a 86 250 Quadracer.
Keep in mind this was back in the late 90's; craigslist and ebay didn't exist yet so finding used parts for motorcycles was much more difficult.

Then we constructed our swingarm. The Quadracer rear axle was flipped upside down (KTM chain is on the right side of the bike). The swingarm is only 4" longer than the stock motorcycle unit, even though it looks longer because of the ergonomics of the bike (more on that later). And the Quadracer axle was close, but didn't quite line up correctly with the front sprocket on the KTM. The entire rear axle is shifted over slightly to the left. IIRC, the sprocket was off by 1/4", resulting in the left rear tire hanging out 1/2" more than the right side. Enough to matter? Yes. Rode it couple times with the offset, was not noticeable for the most part, but a high speed run through the sand whoops had the rear of the bike swapping back and forth pretty hard. So the half assed fix was a set of wheel spacers; chucked one up in the lathe and knocked 1/2" off of it. Now it went nice and straight through the whoops.
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[bikemaker]

And then came the rear fenders.
The ergonomics of the dirt bike put the seat and gas tank way forward compared to a quad or trike. The only fenders we found that fit very well were from a banshee, so on they went.
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What are the rivets and lynch pins for?
The kicker on the KTM is on the left, is really long, and goes to the rear. All of the 500 powered machines I had sen required removing the seat and rear fenders to start. My approach was different. The seat stays in place, and only the fenders flip up for starting. Still a pain? Yes. But at least you can start the bike (by jumping off of the left rear tire due to the left side kicker) , then just flip the fenders down and secure them with the lynch pins.175401

[bikemaker]

So overall, this thing worked really well for a bigger guy.
I'm almost 6'4" so a 250R feels kinda like a kids bike for me. The KTM fits me way better; but it is huge. It's probably 4" taller, 4" wider, and a foot longer than a ATC250R. At some point I'll have to get a picture of the 2 of them parked next to each other. Sitting on it, it seems like it would be unstable because your higher off of the ground, but after riding it, it's just as stable as my 86 ATC250R, just not as nimble in the tighter stuff. And the suspension is WAY better. It has about 12" of front travel, and 14" of rear travel and is plush. This thing would be nearly impossible to beat in a long sand whoop section.

The other point of interest, it only weighs about 10 pounds more than the ATC; but with roughly twice the power.:naughty:

I've contemplated many times doing another similar conversion, but with a more common bike. Maybe even a aluminum framed CR250. For riding in the dunes, it's a pretty awesome setup.

[Tri z250]

Nice trike

[R.J.M.]

That thing looks nuts!! Welcome to the board

[oldskool83]

you need a nice front end on that bike and it would be way nicer. prob just walla get with jason hall and have some tripples made to run all you oem stuff and just stuff a new atv front tire on there and your set.

[bikemaker]

Still thinking about doing that. My dad has a nice mill and lathe, so it's something we could make ourselves.
The initial plan is to get it up and running, take it out for a day to make sure everything still works. If all is well, I may just
Tear it down this winter and redo some things. This bike was put together when I was about 19, and after spending the
Following 15 or so years working with metal as a machinist, fabricator, and welder, my standards for fit and finish are a little
Higher now.

[bikemaker]

Started checking things out this morning.

The only thing I remember being wrong with it was a bad water pump seal. Tore the water pump housing and clutch cover off, and the seal was in fact toast, but the clutch and everything else looks to be in good shape.
There was a bunch of gunk in the water pump; the housing is magnesium and I'm guessing using regular tap water was causing some kind of chemical reaction with the magnesium. The crap that infiltrated the cooling system took out the water pump seal and dumped water into the crank case. Luckily I drained the crank case before the bike went into storage.
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The clutch is huge, but still known not to be very strong. They hold up fine as long as you don't slip the clutch very much - and this thing makes enough power there's never any reason to slip the clutch.

It's looking like a new seal, some fresh fluids, and cleaning out the carb might just get this thing back up and running...

[bikemaker]

Just a reference pic of an old 550 piston sitting next to one out of the 86 ATC250R
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The bore is somewhere around 92mm, or about 3-5/8"; about the size of a piston from a Chevy 305.
And here's one of the blown up cylinders
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This was the first meltdown. Turns out there are multiple thicknesses of base gaskets that can be used. We wanted more power, so we used the thinnest one. That produced enough compression to result in severe detonation. Funny thing about a 550 single; it's so dang loud at high RPM that you can't hear it.
Rattled the wrist pin clip out, got sucked up a transfer port and wedged itself between the piston and cylinder wall. Broke the sleeve and the cylinder. You can still see a chunk of the clip imbedded in the cylinder wall.
So we got another cylinder and piston and proceeded to do the same thing again, just not as catastrophic; this time the cylinder was saveable with a new sleeve, but we found a used one and ran that with a new piston. Back then, pistons were only available from KTM, only in standard bore size, and were just under $400. Pistons have been obsolete now for years. Luckily, this piston / cylinder only has a handful of hours on it - even though it was over a decade ago.

[bikemaker]

Only thing I've found to be junk is the front brake is completely seized up; that's OK, I never used it anyway.
While I'm messing around with the front end, what do you guys think about flipping the forks around so the front axle is to the rear of the forks? Should handle a little better (in theory), but it might just expose the front tires inability to float on top of the sand like a regular ATV tire would.

[bikemaker]

Been putting the memories together in my head; the last time this bike ran was in 2000 at dune fest. One of the things that killed it was the noise restrictions at the Oregon Dunes, IIRC they went into affect in 1999. The year prior to that I was riding the bike still as a motorcycle and the Staters were doing free noise tests in preparation for the upcoming noise restriction. I don't remember the exact db reading, but lets just say there was no way in hell the 550 was going to be that quiet. Readings taken 12" away from the side of the cylinder (instead of off the exhaust like there supposed to be), was something like 102db - coming from the cylinder:wondering

[bikemaker]

Took a bunch of stuff apart over the weekend; flushed the cooling system out, new brake fluid, got front brake working again, cleaned the carb out (float level was set WAY too low), adjusted the rear shock (I'm about 40 pounds heavier than I used to be). Also has to weld a tab back onto the subframe, and rebuild a couple of brackets that weren't up to par. It's kind of fun to study my fab skills from back when I was just out of high school; although my current standards for fit and finish are considerably higher.
Should have a new water pump seal in the next day or two, and I'll be ready to see if she will run again.

[Bird76Mojo]

Awesome fab work OP. A sweet wheeler for sure..

[bikemaker]

Had a test fire tonight. Rolled it over a couple times, then gave her one he- man kick and it started right up for the first time in over a decade.
One problem though, the clutch drags really bad. I remember it happening before due to the clutch plates digging grooves in the basket. But it now has a new clutch basket. I can see the top of the clutch through the fill plug, and with the clutch lever in their nice and loose.
I tried to click it into gear at an idle, and it killed the motor, then I tried to put it in gear with some throttle and the front tire left a 10 foot skid mark up my driveway before I got it shut off.
Anyone have any ideas why its dragging so much?

[big specht]

Hey bikemaker you want to sell those wheels on that ford crew cab?
Are those weld wheels ??? If so are they 16's or 16.5's?

[D-dub]

OMG That thing is awesome! and begging for a Jason Hall front end! .....Wonder what Camexican will think of this one??

[bikemaker]

I need to put a bigger pilot jet in it, and go through the clutch. After that, I'll fire it again and try to get a video of it running.
I don't think I can widen the front end without changing the tank and maybe even relocating the radiators; I'd like to widen it, but I'll save that project for this winter. This thing needs to visit the dunes first.
The wheels on my truck are 16.5 x 10 Welds. Not for sale for now, but they might be in the future: it's getting hard to find 16.5" tires these days.

[fallguy666]

The clutch is dragging because it sat dry for so long.take the plates out and unstick them and oil em up real good and you shouldn't have a problem

[bikemaker]

That's pretty much what I figured, I just didn't want to open it up again.

[Tstatic1]

That's a sweet trike. Bet it'd be fun on the dunes.:cool:

[bikemaker]

Got the clutch feed up, changed the pilot out, and spent the last 3 mornings kicking the snot out of this thing; can't get it to fire.
My ankle hurts, my thigh is sore, and I have a bruise on the arch of my foot.

I think I have the crankcase loaded full of fuel at this point, so I'm going to take it out to my dad's this weekend and try to pull start it.

Hopefully that does the trick. This thing has always been temperamental to start; as of today it's got me walking around in a circle.

[fallguy666]

Did you go to big on the pilot?

[bikemaker]

Oh yeah.
I've since come to learn that the stock jettings specs in my manual are nothing to go off of.

[markmelvin]

Nice trike!! I think all of us who started off on the old atc 70 have a love for three wheels that no one else will ever understand.

[88RGuy]

what a handful!!! holy moly ya better hang on.. lol.. great build.. both of u guys..