building a ktm supermono with a difference......

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Thread: building a ktm supermono with a difference......

  1. #1
    Teenage Moto
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    building a ktm supermono with a difference......

    right i'll start off by saying i love my 2 strokes. i think ive owned all of them at one stage or another however ive been looking at building a supermono race bike. looking at the normal class shows its only a 4 stroke class with people using honda rs125 frames and putting in crf450 engines etc.... this was the route i was going to take aswell untill reading through the rule book and seeing a class called 'thundersport GP2' this puts sv650's, zxr400, 450 supermonos plus loads of other smaller and middleweight bikes all in one group. it also allows up to 400cc 2 strokes too. this got me thinking. .....
    honda rs125 full rolling chassis and fit a ktm300 or maybe even a 380 engine to it.

    without a doubt ktm 450 engine is easier to ride but they have quite a weight penalty over the ktm300 engine. fabrication isnt a problem (check out my cr500 motor in my ktm chassis).

    over the years ive owned both ktm300 and 380. i seem to recall the 380 vibrated alot more than the 300 which can be a real drawback on a light road bike, but if i could make it work the extra torque would be usefull. also the 300 only has a 5 speed gearbox and id really like the 6 speed. the other side of the coin is i could just use a gasgas 300 engine as i know those motors very well and have a 6 speed box too.

    ive seen these 300cc motors in supermoto's on a rolling road produce 57hp (they werent standard) and if its for race use im sure i could sqeeze more....

    any ideas on which way to go? anyone maybe already done it? ive checked the net and found yz250 engine in a rgv250 chassis but thats hardly the same.

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  3. #2
    The "Moto" Bagman's Avatar
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    Sorry, can't help you but I'm looking forward to seeing this done. PLEASE post your progress!
    "alright....i guess this is the night some bitches die!"
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  4. #3
    The "Moto" ktmben's Avatar
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    http://www.ngroadracing.org/pdf/GP45_supersingle.pdf

    in a nutshell, that definitely looks the simplest (if not cheapest) route, hope it gives you some ideas though!

    I like the idea of a road going cafe racer 450, but couldnt face the possibility of mangling my own pride and joy!!!

  5. #4
    Teenage Moto
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    haha yes im sure id never chop up my own pride and joy. if i go the fourstroke route its just going to by the same as another half a dozen bikes. im really not sure how its going to work out.
    on paper the 300 will give equal power to the 450 (except the very highly tuned ones) but weigh alot less, should turn faster and better due to less gyroscopic force and have cheaper maintenance costs.......... however.......
    from what i gather no-one has done this so far and may end up with a bike which isnt competitive which would be even worse.
    looking at lap times though between national gp 125's and the 450 supermono's there seems nowt in it. in theory the 300 2 stroke motor is only gonna weigh 5kgs or so more than the 125 engine but have a load more power and torque.
    in the next week or so i'll have secured the rs125 and will start taking pics. anyone own a 300 ktm?

  6. #5
    The "Moto" ktmben's Avatar
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    might be worthy to think about the sx250 motor? they are a really punchy engine compared to Japanese 250/2t's... im certainly no 2t nut though...

  7. #6
    Teenage Moto
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    the 300 or 380 just has that extra bit of potential. yes the chain run is on the correct side for a honda rs125 and the ktm 2 stroke engine. i think you are thinkng of the aprilia rs125 which is totally different.
    i cant use the cagiva or aprilia chassis as they arent strong or light enough for racing use.
    the engines going to be in a very different state of tune by the time the time its fitted so alot of the original punch will be taken out and tuned for top end power.

  8. #7
    My Reality Check bounced mr.tattoo's Avatar
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    380 would be the choice for me. the 300 is ok but nowhere near the 380. gasgas 300s are a nice engine ive had a couple it was only the rest of the bike that fell apart but wouldnt matter if you used the motor. have you a frame already as i may have an rs125 frame and possible forks from a project i never got off the ground.

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  9. #8
    Teenage Moto
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    thanks for the offer but im going to buy a full bike and spares kit. saying that mind if the frame and forks are cheap i still might have them coz you can guarantee im going to smash my bike to pieces lol

    the ktm 380 has a 6 speed box right? can you make these motors rev? any idea for hp output after some work mr tatoo??? i seem to remember that my old one vibrated alot. whats it like back to back with a 300 model

  10. #9

    Join Date
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    KTM Supermono

    Hi all,

    Im new to the forum as of taday as I have just come across the thread about Supermono's.
    Over the past year or so, I have built an Aprilia RS125 framed KTM LC4 640 in my spare time. The bike is very near completion as a working dry build as I intend to ride it and set it up extensively before tearing it all down to give it its paint job.

    The spec of the bike is as follows:
    1999 Aprilia RS125 frame & swing arm.
    New 2009 Yamaha R6 complete front end.
    Custom built race spec & fully adjustable Nitron rear shock.
    Marchesini wheels with Michelin Pilot One Competition tyres.
    Carbon fibre mudguards, chain guard, heel plates & undertray.
    Custom designed quickly detachable subframe incorporating the fuel tank cover & fuel cell, QD fuel line.
    Custom CNC 6061 T6 engine plates, footrest assemblies, front sprocket cover/crankcase saver, shift rod, captive wheel spacers, rear caliper hanger, dished bodywork washers etc. All parts hard anodized.
    Numerous 6061 T6 spacers, fittings, brackets etc.
    Custom SS top fairing bracket/instrument hanger, adjustable steering stops, silencer hanger & top rear engine brace.
    Laser cut SS battery cradle mounted on left side of crankcase.
    Custom designed and built thin wall SS full race exhaust system with oval Titaniun silencer.
    Brembo brakes on custom built Goodridge hoses with polished SS fittings.
    Quickly detachable Tyga Suzuki RGV 250 fairing & seat unit.
    Custom machined Delron stand bobbins.
    Individual custom built racing & road wiring harnesses.
    Dynojet Quickshifter, coil & rev limiter.
    Aprilia RS125 instruments & lap timer.
    Heavily modified (enhanced) rear suspension rocker & linkage.
    All new SKF C3 bearings throughout.
    All new SS hardware throughout.
    Balanced crankshaft & reciprocating assembly.
    Highly modified & ported cylinder head.
    Custom designed performance camshaft, valves, springs & retainers.
    Modified Keihin FCR41 carb with K&N filter.
    Custom built engine breather system.
    RGV250 radiator.
    Setrab oil cooler.
    Talon sprockets on Regina 520 O-ring chain.
    Custom CNC chain adjusters.

    The bike is nearly finished now with just the harness and fuel tank & cooling system to be completed. It is my intention to dyno tune the motor as quickly as possible and then get the suspension dialed in. The angine should produce 64-68BHP when dyno'd with the chassis now weighing in at 298lbs dry weight and 53-47% weight bias.
    I expect to need & spec new front fork springs as the R6 springs will likely be too heavy for the little Aprilia chassis.
    Any teething problems will be addressed quickly before tearing it all down to have it painted.
    Pending the high speed stability with the shallower R6 fork yokes, I will probably CNC a set of custom adjustable yokes to suit the chassis.
    The only unfinished piece of the project is that I have so far given little thought to the paint scheme of the finished bodywork. Perhaps someone might wish to submit some suggestions.
    Looking forward to being part of your forum & discussion groups in the future.

    Sincerely,
    Slash

  11. #10
    Teenage Moto
    Join Date
    Jan 2009
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    259
    dont lynch me but ive started the the thread here so i'll continue it lol

    unfortunately theres going to be no ktm parts on it...... may just paint the wheels orange so it looks a little ktm-ish.

    ive just bought a gasgas300 and a full complete honda rs125 so the project is off the ground. however im in the middle of moving house so progress will be slow for a while.
    whilst the rs125 is complete ive applied for a cert of newness from honda.
    im going to try get a legal plate for it as a 125 for the time being (fingers crossed). then once the 300 motor is in i could either be a bit naughty and use it as it is or even declare the engine change. it will all be alot easier whilst its complete and original when they ask to have a look at it.

    ive chosen the gasgas 300 motor as its just so smooth and it has a six speed box. i was going to use one of the electric start ktm 300's but the extra weight put me off. all in im aiming for 55hp (definately acheivable) and no more than 75 kgs.

    shes gonna be an animal lol

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