5-6 speed KTM transmissions

[brian kirby]

I saw Garrett post this in the thread about PV bikes:

"There is a bolt on the side of the motor that you csn switch and change the motor from a 5 speed motorcross model to the 6 speed enduro model."

I am not familiar with this feature, how does it work and what engines have it? Do the 5 speed MC5s like the '77 400 have this feature too?

Brian

'72 Berkshire

[garrettccovington]

Phil K.  filled me on this info.  Its on page 29 of the ktm's user manuel.  I'll try to copy it and post it.  Basically, you take out and exchange 1 bolt with the other.  I'll also try to copy the difference between the gear ratio's.  I just leave it in the 6 speed mode, since that's the bolt I have.

G

72 six-day

[garrettccovington]

Sorry about the poor quality.  But its the lower left bolt thats part of the Clutch arm housing

72 six-day

[Rocket]

I have wondered about the 5 speed/6 speed conversion too.  I have been building up a couple of spare motors and one of them had the pointed bolt.  What I have found out is the shift drum has to have a pin sticking out to block out 1st gear.  I only have come across one shift drum like that and it was not in the motor with the pointed bolt.  I have a paper with some information about how you remove a pin from the drum so it can not engage 1st gear, paper is dated in the year 81 or 82, not sure without going to the garage to look.  From what I can see and measured, the pointed bolt will not hit anything unless you have a shift drum with a pin sticking out.
Rocket

[Doug Bridges]

I have a 79 175 motor and it does have the pin sticking out the end of the shift drum and if it had the longer bolt with the point on it you can see where it would block the drum from turning past the point that would engage first gear. The bolt is the one that goes though the bearing cover ( clutch actuator housing) at the lowest part of it to the rear of the housing. As far as I can see if you have a 5 speed you can remove that bolt and simply put a shorter one in and it will be a six speed. The primary gearing on the 79 motor is also much lower than on my 73 motor. I asume that is done to facilitate turning 2nd gear into 1st if it is used as a 5 speed. If the shift drum does not have the pin sticking out the end of it, it can't be made into a 5 speed.
At least that is what it looks like to me.

Doug Bridges
73 Jackpiner
74 Jackpiner/FrankenPenton
project
82 XR200R

[brian kirby]

I guess what I am asking is, is the '77 MC5 400s really a 5 speed transmission or are they blocked out 6 speeders? I've been toying with the thought of acquiring a 6 speed transmission, drum, and shift forks/shafts to convert even before I heard of this.

Brian

'72 Berkshire

[Rocket]

Brian
As far as I know, it should be a six speed.  On your clutch actuator, the lower left hand bolt, remove it and measure how long it is.  If it is 30mm long, that is probably blocking out the first gear.
Rod

[rob w]

[garrettccovington]

Keep in mind When reinstalling the longer bolt, The instructions warn about NOT having the transmisions in 1st or nuetral.

When racing last weekend, I was thinking about starting in 2nd, and trying that 5/6 speed theory that 2 is a 5 speeds 1st. but I'm not good enough and I felt that 2nd was to tall.  In the tight hairpins 2nd was definitly to tall for my skill level.

G



72 six-day

[brian kirby]

quote:Originally posted by Rocket

Brian
As far as I know, it should be a six speed.  On your clutch actuator, the lower left hand bolt, remove it and measure how long it is.  If it is 30mm long, that is probably blocking out the first gear.
Rod

That is very odd. Why would they block out a gear? I understand making a transmission with one less ratio so you can remove the gears to save weight or make the remaining gears bigger and stronger, but why just block it off? It makes no sense. That would be a pleasant surprise if that is all there was to converting to a 6 speed.

Brian

'72 Berkshire

[garrettccovington]

Brian look at the gear rations between the mc/gs 250's and 400's and top speeds it even gets stranger.

G

72 six-day

[Big Mac]

I've had 2 MC5 250s and an MC5 400, all in mx setup from out of the crate from all I could see or per original owner in the case of the 400. All had 6 speeds. Haven't run into a blocked out 1st, 2nd-6th gear only bike yet. Purpose was to avoid mistaken shift to 1st granny gear coming into mx corners when 2nd+ would do the job everywhere on most mx tracks, but to leave 1st gear option in there for woods work when needed.

[brian kirby]

The 400 I'm riding is definitely a 5 speed. The weird thing is, its got 14/52 gearing which is from what I can tell 1+ on the countershaft from stock, yet first gear is so short its almost unusable. I cant imagine having another even lower gear than the current first. I'm tempted to go to the tallest gearing I can get just so 1st is usable.

On second thought, I never actually shifted it through all the gears to verify how many it had, it may be set up with 6 and I just assumed it had 5.

Brian

'72 Berkshire

[Lloyd Boland]

I have a (very late "76)'77 250 MC5 and it is definitely a 6 speed.  I try to never use first, it is too low, even for the tight turns.  Unfortunately, sometimes going into a tight turn I actually down shift all the way to first, and you can probably hear me cursing at myself all the way to the pits.
Lloyd

[brian kirby]

I am going to have to verify its only a 5 speed, it might have 6 and I didnt even bother to check. Ernie also has a '76 MC5 that is a 6 speed.

Brian

'72 Berkshire