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Discussion Starter #1
Hi All,

Seems to be a few 2 stroke supermoto builds underway... looks like I have caught the bug!

I always wanted a 2T bike, but I figured that it would be something like an RS250 that I would use on track days. Well that never happened, and I am having to cut back on my track days budget so I figured a nice road registered 2T supermoto would fit the bill. So for a couple of weeks I was hunting around, just missed out on a Husky WR360, then spotted this 1998 KTM 380 EXC and jumped on it before I missed out on another bike!

This build is all on a fairly tight budget, I negotiated a price I'm really happy with and just got home last night after a 3,400km round trip to pick up the bike. I had organized to look at a set of supermoto wheels on my way back home, so I stopped in and initially only the guys wife was home. I got out the measuring tape and was scratching my head trying to work out if the rear wheel would fit... I wanted to believe, but I really didn't think it would. I unloaded the bike and the guy I was buying the wheels from was kind enough to fit up the rear wheel to make sure it was all okay. :thumbup: And it does fit, and I am stoked! :D But that is why it has the dirt front wheel still on...

If anyone is interested, I believe the wheels are from a KTM 625 SMC, and the rear slotted right into the 380! Disc and sprocket alignment look to be perfect as well. I will just be checking the chain with a string line to be 100% sure, but looks like the rear wheel is all set. That was the one thing that I was worrying about, if a 5" rim would fit. As a bonus the rear hub has cush drive, so I'm happy about that as well.

I took some quick photos so here is what it looks like at the moment:





Showing the front SM wheel:




160 rear tyre on a 5" rim. Bolted right in like it was made for it! Currently using a little spacer on the right hand side between the axle spacer and the brake caliper carrier. It was being a bit of a pain to get it centred while the axle nut was tight.


A tight fit is to be expected.




The chain guide will need a little modification. The sprocket is rubbing a bit on the plastic of the chain guide. Or I could just let it clearance itself I suppose...








Now the jobs list is going to grow... need to get the lights sorted. There is also a fork seal kit that came with it, which is well overdue so I'll be learning about fork internals as well. A few other bits & pieces I can spot that I know will be needed for road reg, needs a sidestand etc. Will need another speedo, time to go all electronic & modern.

Then onto the engine... a question for any 2T guys, would you work on it while still in the frame? Or is it just a whole bunch easier if you take the engine out? From what I understand, the bare minimum is to remove the cylinder head and check out the piston & rings, and also for free play at the crank? I am guessing that you can look down once the cylinder is removed and see if there's any gunk or other stuff sitting in there?

For the radiator - is changing the coolant the same as on a road bike, or are there any special tricks that you can do on a dirt bike? I am thinking it will need a clean out with a bit of the old vinegar & water mix. Bike has been sitting for about 2-3 months I'm told. Rear axle was bone dry and hard to remove, it wouldn't surprise me if 3 months is being very optimistic... I hope the engine was looked after better than the rear axle. They guy I bought it off said that he had it started on Monday and also the week before. I have not started it yet or seen it running myself, never had a kick start bike so that will be an adventure for me... only the guys wife was there when I picked up the bike so I didn't want to flounder around and potentially snap my shin up while she was watching!

The other thing is whether or not I tear it all down and paint the frame, new bodywork etc. or just do the basics to get riding. I have to admit that I am very keen to get riding now... Maybe I will put off the painting & bodywork until stage 2... Then again there are some dodgy things that but me, like the rear brake light wires are soldered on top of the banjo bolt with nothing covering them. I still think I will ride for at least a couple of months before I move to stage 2...

What about an exhaust protector? Would you guys use something like the exhaust protectors that attach with hose clamps? Or does something like a little lowside not damage them much, would you even bother for road use?

Well that's enough posting for now, I've gotta get up in the garage and find a place for this bike & all it's bits & pieces. Been ages since I have worked on any kind of project so my work area is one heck of a mess, I've got a very good reason to clean up now!
 

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Discussion Starter #2
First bit of progress - got the front wheel off. That's only really notable because there was a rounded pinch bolt that needed to be dealt with. I learnt that Vise Grips will be able to remove most rounded bolts, you've just gotta put them on tight! I also just had to Dremel two flat spots on the bolt head, all good.

Anyway, I got in and had a look at the spacers and how the wheel would line up, looks like I might just luck out with this one! The guy I bought the wheels off had a 260mm disc fitted on the front, and that lines up with the caliper just fine. Dare I say "perfectly"... Sweet. :D

Took the spacers out of the wheel and had a measure up, I think they are pretty much perfect as well!! This is the distance they would sit if they were in the wheel, which is pretty much spot on! :thumbup:



So I just need to take the spacers and have duplicates made to the same specs, just with a smaller inner diameter to fit the axle. Or maybe even just use these spacers with a sleeve inside? Too easy!!

The only thing I'm not too sure about is how much the fork bottoms should close up when the axle is tightened? I think maybe the outside of the spacer on left of picture may need to be shaved down a touch depending on this, but I guess I'll find that out as I go.

Once I get the front wheel sorted and have had my maiden test ride I will be satisfied and start pulling things apart to get ready for road reg. Getting a bit desperate for that first ride though!
 

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Discussion Starter #3
Got a call this morning from the tooling shop, they already had the new spacers ready. Super quick, $30 for the two front spacers, good stuff!!


New spacers hot off the lathe! by mugget, on Flickr

Got home eager to get the front wheel fitted up and out for the first ride, found that I had messed up the measurements. :headshake

I think it was tricky before because the wheel was just floating around on the axle, couldn't get a proper measurement. Now that the wheel is solid on the axle I could see the problem clearly. Easy fix, gonna take a spacer back to the shop tomorrow and ask them to take 5mm off one end. I calculated from my highly technical "paddel pop stick width" measurements that the cut down spacer should yield a 7mm gap on each side from the edge of the tyre to the fork tube. Just a brief delay... I will be out for the maiden ride soon enough!

I figure I will just use washers to space out the remainder, then once the spacing is all set I may get new ones made up, or just use some type of super-adhesive to glue the washers and spacer into one piece.

I also had a random thought about the ignition... I figure I won't be riding/parking anywhere that I leave it unattended (can always use a disc lock or great big chain anyway), so why not just ditch the key and use a push button ignition? I am guessing that would be easily do-able since it looks like a very simply ignition system, nothing tricky like immobilisers etc. Does anyone have thoughts on this?
 

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looks like fun. nice pictures.

i hope the bike starts for you. that'd make me nervous :hmmm:

keep us updated.
 

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Discussion Starter #5
Cheers Cozmo! I am sure it will be more fun than any bike I've ever owned! :thumbup: But now just to get it started...

I finally got the front wheel sorted - had to shave a bit of material off the back of the caliper mounting bracket, rotor bolts were rubbing on it. Painted it quickly just so I could easily spot if it was still rubbing.



Got one of the spacers modified to remove 5mm, to make up for my measurement mess up:



Major milestone I thought! :D So I figured, "okay, time for the maiden ride!"

Well... after about 20 minutes of kicking I think I may have got the hang of it, but was too tired to give it any more of a proper go. :hmmm: The only thing I've ever had to kick start before this is a 50cc 2T scooter! So I wouldn't be surprised if I have a bit to learn about this... any tips appreciated. A few times that it seemed promising... I was told that there was plenty of blue smoke, dunno if that means anything.

After kick starting didn't work, figured I'd try a bump start. Then I found that the clutch was not even dis-engaging properly... bugger! :headshake Still tried a few times to bump it, tried 3rd & 5th gear, just ended up making a hell of a clattering noise and locking the rear wheel. Again, sounded a couple of times like it was gonna go, but didn't get there. Should you have to play with the throttle to get it going? I wouldn't have thought so, tried it with choke on/off as well.

So, what to do now? I had a quick look at the spark plug, didn't take it out, but it looked brand new. Fuel tap was off, so there shouldn't be any gunk in the carb? Bike was running a couple of times in the last week before I picked it up, or so I was told... Now I tured the fuel tap off again, but it hadn't been running so probably stuff sitting in the carb now? :hmmm:

I also noticed some oil dripping down on my stand, seems to be coming out of the countershaft seal. Starting to think I should just tear down the engine and replace all bearings and seals to start fresh.



I think I'm going to look at getting this clutch sorted first. I adjusted the lever to be sure it wasn't stopping on the grip. To make it even more interesting, looks like a hydraulic clutch... which I was under the impression didn't come until the 1999 model? And here I was thinking I had a 1998 model, or maybe the clutch has been changed to hydraulic? Anyway, I wanted a project bike, starting to look like I sure landed myself with a project bike!
 

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Good thing winter is coming
Lol you got yourself a project but will have one of the sickest 2 stroke sumos around when complete
I notice your not getting many responses Engine wise and Im certainly not going to give you advice when the last 2 stroke I rebuilt was my Yamaha blaster 200 :Funny:lol but I'd say before you go tearing the engine down pull the carb off and check it out and check out Ktmtalk (don't mean to promote other sites) I've found it very helpful and there are some ktm geniuses there (not saying there not here)
Good luck and once again sick build :thumbup:
 

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N btw pull off those frame gaurds and check for rust under them, there rust magnets:headscrat
 

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trick to starting i had an '99 300exc slowly kick it a few times get the cylinder primed then bring it to TDC and just give it one big kick all the way to the peg and it should fire right up every time. Just make sure you have good spark, your carb is clean and jetted correctly
 

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My '00 300 EXC supermoto starting procedure: Turn on gas, pull up (open) choke, lean bike over to the left side at 45 degree angle and wait for gas to run out of the carb over flow, put bike back up straight, one kick and she starts. Once it fires brap the throttle to keep it running until warn.

2T's want a lot of gas at start up.
 

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Discussion Starter #10
Imar - winter isn't coming for me... It's early spring here in Australia!
No matter, I ride all year around anyway. It never gets cold enough for me to park the bikes in the shed!
Thanks for the tip on the frame guards. Everything is coming off now, I think I will paint the frame and look for any rust/problem spots. What do you think about frame guards for regular supermoto use? Don't bother? Or just use some type of adhesive padding directly adhered to the frame? I'd rather not use regular guards if they're going to cause rust problems down the track...

Thanks guys for those starting tips! I needed them! I think my mistake on the first attempt was that I didn't use any throttle at all. I tried again this morning with some throttle, and it fired up after a few kicks! :bannana:

Very excited about that. Went for the first ride as well. Just a quick one around the block on the gearing it came with (14/50), and DAAAAAMNNN!!! This bike is mental!!! It scared me (a little bit), and I would say that I was well under half throttle! It's crazy-fast... makes my GSX-R1000 feel like a learners bike. Makes my XR400 feel like a BMX... Very stoked on this bike now that I've ridden it! Not that I expected any less... but now having actually ridden it... WOW! Just WOW!! :D

So this is how it looks now. Basically nothing has changed from when it was in dirt mode, I just have the motard wheels sorted:













Some video here, including a n00b kick start mistake. :lol:
http://www.youtube.com/watch?v=66VWeLpxI2o

Now I'm tossing up whether or not I just do a quick check over and get it on the road ASAP, or go ahead with plans to paint the frame and do new bodywork etc...? Well, I'll see how it pans out.
 

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My recommendation from (up until recently) NOTHING BUT 2t experience and builds-

Pull the motor.
Do a leak down test to make sure your crank seals are good. If they're not it'll cause a lean condition from sucking too much air, and you'll blow the top end anyhow.

If your crank seals are good, replace every seal and gasket you can get to without splitting the cases.

New piston, bore, and associated.

While the motor is out of the bike, go ahead and have the frame powder coated. (Might as well)

Now that the aforementioned is done.... go ride! You'll be chomping at the bit for new bodywork soon enough but at least then you have a solid platform to build.on.

PS (this is uber important)

The bike looks just shy of ragged. DO THE LEAK DOWN TEST. it'll not only tell you if your crank seals are bad, but also your base gasket, intake gasket, and head gasket are bod too.

2 strokes have a sealed crankcase. The fresh air/fuel is actually drawn into the motor UNDERNEATH the piston. (Hence having good crank seals) as the piston travels downwards the pressure is increased, forcing the charge through little tunnels in the cylinder wall called up-draft exchange ports, so the charge is now on top of the piston. The piston travels back upwards compressing the first air/fuel mixture (while drawing ANOTHER charge in underneath it, and boom!
 

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Discussion Starter #12
Cheers for that thrill-billy85. I am definitely going to do the leak down/compression test. I am betting that there will be some seals that need replacing... looks like the countershaft seal is leaking for one...

On the subject of powder coating frames - I have read different opinions on that, some people say that it will chip easily, and then peel and it's hard to patch up? I was just thinking of a rattle can job. I believe that preparation is the most important thing. I have a set of BMX forks that I did a rattle can job on... maybe 10+ years ago, and they are still absolutely perfect.
 

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First time I seen anyone kicking it over in first gear.
Yep it runs pull it down and do a good job. Sell the xr and use it to do the ktm. Top end off and go from there. Your old man looks a bit worried
 

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Couple things....

The compression test won't tell you about air leaks. Just if your piston/rings/bore are good. Google "2 stroke leak-down test. It'll tell you a lot of info on what you need to buy. I built mine. I used a bolt in freeze plug to seal the exhaust port, and a PVC y fitting with a bolt in valve stem in one leg of the y, and a psi dial guage in the other. Leave the spark plug in to seal that hole. Needs to hold 6 psi for 6 minutes.

Rattle can paint jobs. Yes! I'm a fan..... use spraymax 2k urethane clear coat after you let the base coat dry for a few days, and you'll have an automotive like finish that'll never damage from gas and chemicals. The 2k part is important because it is a chemically hardened finish, and that's what keeps it from getting messed up when gas touches it. The spray Max is the only.one I know of that offers it in an aerosol can. It has a separate chamber with the hardner that you "activate" before use.





Both pics are rattle can paint jobs
 

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PS.

On the leak down tester the y fitting clamps in the intake boots. Looks like you've got either a 33 or 35 mm keihin pwk. If memory serves it'll be an 1.5" FITTING that has the outer diameter that'll work for you.
 

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Discussion Starter #16
First time I seen anyone kicking it over in first gear.
Yep it runs pull it down and do a good job. Sell the xr and use it to do the ktm. Top end off and go from there. Your old man looks a bit worried
Funnily enough, I posted this on another forum and almost straight away someone said that they also try and start their bike in gear all the time. :lol:
But hey - it was the first every time I'd kick started a bike... I'm sure I won't try in gear too many more times! :laughings
You know I was wondering if I should just sell the XR... it's kind of lost it's appeal now that I have this bike! But it's still handy just for quick trips around town. I couldn't bring myself to abuse the 380 with short trips like that...

Thanks thrill-billy for that extra info. And here I was thinking that leak down and compression tests were kind of the same thing... Shows what I know. :hammer:
Anyway I'll take the engine out and head down to the hardware store to get that all sorted!
Those painted parts look good! Cheers for the tip on Spray Max 2k, I have just looked up some info quickly - seems like great stuff. I was wondering what type of paint to use for the frame as well... looked up their Auto-K paints... I am thinking the frame will look good in Neon Orange. :D Now just need to find a dealer in Australia... Something tells me that I may need to use different paints...
 

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The spraymax 2k I always buy online. In fact, I've never seem it in ANY store. Listen, if you use it (and I hope you do) WEAR SOME TYPE OF RESPIRATOR!!! The stuff in 2k (2 part) paint can and will kill you. Even if you spray outdoors, with some wind, wear some kind of respirator.

For the black frame base coat, I used rustoleum engine enamel. For the yellow tank I used dupli-color paint shop finish system- chrome yellow. The tank graphics are actually underneath the clear....

For a primer I recommend some kind of self-etching primer. Ideally you wanna use the primer from the same line of base coat color.... hence I use the rustoleum engine enamel. And their sandable self etching primer over sand blasted bare metal. Since your frame is already powder coated from the factory, you can brought that up with 400 sand paper and that should provide a good primed surface for paint to stick to.

If you use aerosol enamel for the paint, let it dry for like 4 days. Or more. I sprayed the base coat on Sunday, and the clear on the following Saturday. The enamel dries via the thinner in the paint evaporating out of the paint. This actually takes a couple days. Just because you can touch it and I feels dry, doesn't mean it is. As its drying its actually shrinking. If you clear with a chemically hardened paint before its dry, it'll crack. :(

If and when you do a leak down test, make sure to have pulled the clutch cover, and ignition cover. This way, if it leaks, you can see the crank seals and spray soapy water on them to see if it bubbles. Thats
 

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Discussion Starter #18
All good info. I appreciate that. :thumbup:
I definitely plan on buying a respirator... definitely. Also some fully body covering and gloves. I took a look at the data sheet - nasty stuff!

Speaking about the clutch and ignition cover - I meant to ask about re-painting the engine case covers. What kind of process would you recommend for those? Since they are already partly worn down to the metal, I guess maybe stripping it back to bare, then starting out fresh with the right surface prep, primer, etc.? Would paint stripper be alright to do that, or would you recommend taking it somewhere to get sand blasted? I have a friend with a bead blaster at their work, he has said that he uses it to clean parts all the time, maybe I will ask nicely and see if he can do that for me... Seems like the easy way. But what paint should I be looking to use on them? High temp. engine paint I'm guessing, 300ºC, 600ºC?
 

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Yeah... I powder coat those. Whether you paint or have them powder coated they'll need to be sand blasted.

My process.... use a wire wheel in a drill to get all the old powder coat off. (They're pd'd from the factory.)
Sand blast after I wire wheel them. (The wire wheel just makes the whole process faster as I don't have a big air compressor)
Then I powder coat them.
I bought a powder coat system for around $100 from harbor freight tools. (Online)

After I bake them in my.oven at 400* f

Yeah I know they say not to do but its just polyester powder... if its a small part I've got a small toaster oven that works pretty well :)

Those parts don't get THAT hot. Regular paint would probably work, but I've got the stuff to powder coat, so that's what I do.
After 4 builds its saved me thousands
 
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