Ktm 50 Clutch, Exhaust and Jackshaft

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kksbunny

New Member
Hey guys I recently placed an order of ktm 50, so i will be getting it in a week!!!!! Cant wait!!.

This is the bike i got http://www.ironhorsebikes.com/hard-tail/2012-yakuza-5-1

Some info about the bike....
1) Engine type: single-cylinder, 2-stroke, air-cooled
2) Piston displacement: 49cc
3) Bore x stroke: 39.5 x 40 mm
4) Max. power: 9HP/9500RPM xct2
5) Max. torque: 7NM/11000RPM
6) Compression ratio: 11:1
7) Ignition: CDI
8) Spark plug: NGK BP7HS
9) Carburetor: 19mm Plunger type carburetor
10) Air filter: polyurethane foam(built on the KTM50 bike)
11) Start mode: KICK start
12) Clutch style: centrifugal automatic
13) Average fuel consumption: 610g/kWh
14) Dimensions: 250x205x290 mm





So my question ....
1. can i use the expansion chamber from sbp as an exhaust
2. What is with the clutch mods...... ( https://www.youtube.com/watch?v=aJ1SYC9aLPY ).
3. mounting suggestion, might use the jack shaft kit!!!! If the engine fits.
4. any other things i need to worry about.



Thanks.
 
For your pipe, you'll need a different header pipe. The header pipe slips over the exhaust port. Your best bet is to buy a ktm pipe and retwist it to fit. That's what Headtrama and Nashmoto did. Also you'll probably need to off set your motor mounts because the exhaust comes straight out in the middle of the cylinder or either mount the motor back as far as possible bad have the header pipe bend right after the exhaust port.
Keep us posted on your build.
 
kksbunny said:
Hey guys I recently placed an order of ktm 50, so i will be getting it in a week!!!!! Cant wait!!.

This is the bike i got http://www.ironhorsebikes.com/hard-tail/2012-yakuza-5-1

Some info about the bike....
11) Start mode: KICK start
12) Clutch style: centrifugal automatic
13) Average fuel consumption: 610g/kWh
14) Dimensions: 250x205x290 mm
Click to expand...
You would be hard pressed just to fit a small standard 2-stroke in this bike frame.

i_2012_IH7080WM_blk_4.jpg


I doubt you'll fit that big kick start cent. clutch engine in that frame.
So my question ....
1. can i use the expansion chamber from sbp as an exhaust
2. What is with the clutch mods...... ( https://www.youtube.com/watch?v=aJ1SYC9aLPY ).
3. mounting suggestion, might use the jack shaft kit!!!! If the engine fits.
4. any other things i need to worry about.
Thanks.
Click to expand...
I haven't seen the KTM 50 engine you bought and there are tons of versions but none look like they would bolt to a SBP 2-stroke jackshaft kit which is really going to leave you screwed unless you loose your back disc brake for a sprocket and go direct drive.

In short it looks to me like you have set yourself up for a project destined for heartbreak.
 
I have a buddy that did it 6 years ago (w/o the jackshaft) so any things possible but you should consider using a different bike. If I remember, the biggest hurdle he had was making a set of cranks to clear the motor. You should look at Wild Bill, Headtrama and Nashmoto's builds to get some ideas.
 
KCvale said:
I haven't seen the KTM 50 engine you bought and there are tons of versions but none look like they would bolt to a SBP 2-stroke jackshaft kit which is really going to leave you screwed unless you loose your back disc brake for a sprocket and go direct drive.

In short it looks to me like you have set yourself up for a project destined for heartbreak.
Click to expand...
Wild Bill has quite successfully raced a KTM 50 mated to a Sick Bike Parts shift kit.

Sent from my SCH-R720 using Forum Runner
 
I have one of those KTM clone engines.

I don't know of any mounting kits to fit one in to a bicycle frame. Depending on your fabricating skills & equipment you may be able to get the engine in that 29'er. It is not a drop-in like the China Girl.

You would need to fabricate a mount set to clamp on to the shaped tubes, or you could fabricate aluminum mounts from 6061 aluminum and weld them on to the frame.

I never had enough patience to sort out that clutch with the spring washers. Be prepared to have the cover off a dozen times, with oil all over the place. I had trouble with the springs binding in the counter bores, and re-machined all of the shoes...

I gave up and installed a Tomar clutch. Problem solved.
http://www.tomarengineering.com/to/holeshot-clutch-for-ktm-pro-jr-pro-sr-mx-bikeshtml/

As Neil said, Wild Bill runs that engine on a shift kit at the races. He shifts it gently. I suspect some WOT shifts would be hard on bicycle chain & parts.
 
FFV8 said:
I have one of those KTM clone engines.



I gave up and installed a Tomar clutch. Problem solved.
http://www.tomarengineering.com/to/holeshot-clutch-for-ktm-pro-jr-pro-sr-mx-bikeshtml/

As Neil said, Wild Bill runs that engine on a shift kit at the races. He shifts it gently. I suspect some WOT shifts would be hard on bicycle chain & parts.
Click to expand...
Tomar clutches for these engines should come mandatory from the factory!! Just got no use ''lowls'' After farting with the stock one. Gave it a go too. Tomar Baby!
 
Goat Herder said:
Tomar clutches for these engines should come mandatory from the factory!! Just got no use ''lowls'' After farting with the stock one. Gave it a go too. Tomar Baby!
Click to expand...

Yes, Tomar clutches are awesome because you can adjust the engagement. I have mine set high @ 8k rpm for racing. I took my bike around the block for a cruise the other day and it was fun to ride but it was also turning heads because the neighbors thought I was racing around so I didn't ride it that long.
 
As a couple others have said I am running a KTM 50 with an SBP shift kit. Make sure you are very familiar with setup and adjusting a rear derailleur. Also don't hammer the gears when you shift, be sure to lt off the throttle for each upshift and roll the throttle back on kinda smoothly. You will also want to be good at retensioning and trueing rear wheels, the shifting works the spokes a little. To be honest I was surprised that the 8 speed chain/freewheels have been holding up, I have had minor problems but they were few and were really self inflicted. The biggest problem was a bent rear sprocket caused by shifting at full throttle in the heat of an on track battle, the sprocket bent because it was a very lightweight rear cassette, there wasn't enuff metal and the sprocket folded over on an upshift. I have long since switched to a Shimano Megarange rear cassette that is much more beefy!

Some [posted a link to my bulid so that may help.

I welded some flat bar tabs to the jackshaft bracket for the engine mounts and that worked pretty well.The frame that you posted pics of look like it will be a tight fit if it does fit at all. I wouldnt worry about the aluminum frame, I have seen a few KTM engines on aluminum frames without problems.
 
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Oh ya I forgot to add that you want the clutch RPM to start to grab right above idle to keep the power from yanking on the chain and freewheels. I removed a spring washer from each shoe so theres no spring preload on the shoe and I used shims to keep any play out. That got me to where the clutch starts to grab just above idle. On the very first couple test rides when the engine was cold the clutch had very slight drag when I first fired up the engine and after the engine ran about 30 seconds the drag went away. Then after a few test rides there was no drag at all at idle.


On a single speed setup you need a high clutch rpm to get you into the power band since you run a higher gear ratio on a single speed and you need the power to get rolling, on a shifter setup you have a much lower first gear and you don't need or want that kinda power or you will tear stuff up.

And I wouldn't use an SBP pipe, that's too small for this kind of RPM, you really need to use a 50cc dirt bike pipe, I found a new KTM 50 pipe w/silencer on Ebay for $70 w/free shipping. Good luck on your build and keep us up to date.

Heres a vid of the bike..... https://www.youtube.com/watch?v=m_j5y9XDyKw


.
 
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Hey Bill I've been kind of following you on your builds and racing gt the last couple of yrs and am only mentioning this because I know you are interested in and quite educated on the ktm's...
Well as it is I have a complete 2006 liquid cooled bike that has such low run time that you can almost call it new...plus has the aftermarket fatty pipe and silencer which my brother in law was told his 5 yr old daughter would have to have...whatever??? LOL!! He paid $310 for it too.Anyway like I say everything is there rad is perfect shape... **** it's ALL perfect.
Interested ??
Whole bike ?
Motor & rad ?
Motor and pipe ?
Whatever works for you or anyone else who might want it I am open to any serious offers as it is a very serious little motor/package.
Let me know.
Ron.
 
I thought the point of using a 11k rpm motor was to use the rpm. wouldn't it make a faster setup, esp. for racing? by using a hub mounted sprocket adapter. then 2 sprockets on the rear left. That would give you acceleration and speed.a upside by having no jack shaft.that whole jack shaft setup leaves a lot to be desired. With just a 80cc jug, nt carb, angle plug head an a tuned pipe that worked I would flex that stuff out of shape all the time. taking the whole drive system down and a hour of frustration getting all back in alignment. It wouldn't be that hard to make a derailleur to shift the left side drive chain just be able to hit 2 gears. with 11k rpm range and over 9 hp it would be all the gear spread you would need and far more dependable. also providing the tensioner too. maybe a uhmw chain guide at the motor to keep the chain feeding straight. (uhmw is the high density usually white plastic lots of cutting boards get made from.) (ultra high molecular weight )

It is tough the chain could rub it for hundreds of miles with little wear. Heck you can tap threads into it. GL
 
You might have to use 3 just to get the chain to jump reliably from the smaller back to the bigger low speed one.
 
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