Old Japaneese motorbike transmissions 1970s to 1980s

[acr]

Im posting this as a last resort i have asked this other places but no one has any ideas at all i am trying to find out what did/do japaneese motorbike gears have 14.5 or 20 Degree pressure angle on the teeth and how did they one year have 12/45 and the next year they had 12/44 ratio on their first gear but still keep 43mm between the drive and counter shafts. I expect some one has done some transmission work on this forum and can point me in the right direction :confused:

[jato]

what model bike is it? i have quite a few gear cutters here and one or two old kawasaki triple gearboxes i could see how they match. i would expect 20 degree pa but you never know how far british influence went... another option is a tooth profile gauge. re the centre distance v tooth count i have seen 3 different 1st driven gears used with the same drive gear achieved by a custom profile in a suzuki race bike.

[Grumph]

The definition of a clever gear cutting engineer has always been the ability to cut gears to suit small ratio changes without changing both gears.

Suzuki probably did more of this in period. Nova in the UK seem to be doing it now with close ratio conversions for Hondas

As Jato says, what make and model are you asking about ?

[husaberg]

Im posting this as a last resort i have asked this other places but no one has any ideas at all i am trying to find out what did/do japaneese motorbike gears have 14.5 or 20 Degree pressure angle on the teeth and how did they one year have 12/43 and the next year they had 12/44 ratio on their first gear but still keep 43mm between the drive and counter shafts. I exspect some one has done some transmission work on this forum and can point me in the right direction :confused:

Bradleys first book explains it all.
https://pictures.abebooks.com/isbn/9780951292921-us.jpg
from memory it says there are 6 different modules used in one kawasaki transmision (KR250 i think.)
i gives great real life examples.

[acr]

what model bike is it? i have quite a few gear cutters here and one or two old kawasaki triple gearboxes i could see how they match. i would expect 20 degree pa but you never know how far british influence went... another option is a tooth profile gauge. re the centre distance v tooth count i have seen 3 different 1st driven gears used with the same drive gear achieved by a custom profile in a suzuki race bike.

The engine is the 1969-1979 suzuki 50cc used in the A50 AC50 AS50 bikes the drop between 1st and 2nd gear is from 3.67 to 2.17 (far to much) they did a R/T racing/Track transmission in 1970 and the first gear was 2.8 15/42 i have managed to find /buy the 15 tooth drive shaft but i need to make the 42 tooth driven sprocket and when i try to measure and calculate the modul i dont end up with a good number the first year had a total of 57 teeth and the later years had 56 teeth and the R/T hopup kit had 57 teeth again the distance between the shafts is 43mm making a sprocket i dont see as a problem its finding out what im dealing with :sweatdrop

[acr]

Bradleys first book explains it all.
https://pictures.abebooks.com/isbn/9780951292921-us.jpg
from memory it says there are 6 different modules used in one kawasaki transmision (KR250 i think.)
i gives great real life examples.

Well I had a look for the book but they are asking over 300 USD :crazy:

[acr]

what model bike is it? i have quite a few gear cutters here and one or two old kawasaki triple gearboxes i could see how they match. i would expect 20 degree pa but you never know how far british influence went... another option is a tooth profile gauge. re the centre distance v tooth count i have seen 3 different 1st driven gears used with the same drive gear achieved by a custom profile in a suzuki race bike.

The engine is the 1969-1979 suzuki 50cc used in the A50 AC50 AS50 bikes the drop between 1st and 2nd gear is from 3.67 to 2.17 (far to much) they did a R/T racing/Track transmission in 1970 and the first gear was 2.8 15/42 i have managed to find /buy the 15 tooth drive shaft but i need to make the 42 tooth driven sprocket and when i try to measure and calculate the modul i dont end up with a good number the first year had a total of 57 teeth and the later years had 56 teeth and the R/T hopup kit had 57 teeth again the distance between the shafts is 43mm making a sprocket i dont see as a problem its finding out what im dealing with :sweatdrop

[acr]

The definition of a clever gear cutting engineer has always been the ability to cut gears to suit small ratio changes without changing both gears.

Suzuki probably did more of this in period. Nova in the UK seem to be doing it now with close ratio conversions for Hondas

As Jato says, what make and model are you asking about ?


The engine is the 1969-1979 suzuki 50cc used in the A50 AC50 AS50 bikes the drop between 1st and 2nd gear is from 3.67 to 2.17 (far to much) they did a R/T racing/Track transmission in 1970 and the first gear was 2.8 15/42 i have managed to find /buy the 15 tooth drive shaft but i need to make the 42 tooth driven sprocket and when i try to measure and calculate the modul i dont end up with a good number the first year had a total of 57 teeth and the later years had 56 teeth and the R/T hopup kit had 57 teeth again the distance between the shafts is 43mm making a sprocket i dont see as a problem its finding out what im dealing with :sweatdrop

does there exsist metric and imperial types of modul ?

[jato]

i just went to my favourite gear calculator (otvinta gear calculator) and entered module 1.5 also 15T - ref diameter is 22.5, a 42T has a ref diameter of 63mm so giving a calculated shaft centre of (22.5 + 63 ) divided by 2 = 42.75mm (are you certain the shaft centres are 43?) - if it were me, considering its going to have 10 hp or so i would make a test gear out of plastic or aluminium and see how it looks for contact pattern and if it feels smooth turning by hand under a bit of load, then either go ahead and make one out of case hardening steel or if need be possibly decrease the depth of cut on another test piece by 0.2mm or so depending on backlash and the contact pattern.

[husaberg]

Well I had a look for the book but they are asking over 300 USD :crazy:

HI $145 NZD on trademe and worth every cent.
Suzuki made a race kit for either the a50 or 100. Edit you have seen this...
You can modify the gear so a different number tooth gear will still correctly mesh Dyson who formed nova and barry hart made a living doing this.
The definition of a clever gear cutting engineer has always been the ability to cut gears to suit small ratio changes without changing both gears.

Suzuki probably did more of this in period. Nova in the UK seem to be doing it now with close ratio conversions for Hondas

As Jato says, what make and model are you asking about ?

Sorry missed your post Greg.

[acr]

i just went to my favourite gear calculator (otvinta gear calculator) and entered module 1.5 also 15T - ref diameter is 22.5, a 42T has a ref diameter of 63mm so giving a calculated shaft centre of (22.5 + 63 ) divided by 2 = 42.75mm (are you certain the shaft centres are 43?) - if it were me, considering its going to have 10 hp or so i would make a test gear out of plastic or aluminium and see how it looks for contact pattern and if it feels smooth turning by hand under a bit of load, then either go ahead and make one out of case hardening steel or if need be possibly decrease the depth of cut on another test piece by 0.2mm or so depending on backlash and the contact pattern.

Sorry Jato i dubbled checked my info and its 43.5mm c-c do you think they used DP on one ratio and Modul on another ? some one must know if the Japanese used DP or Mod on the early transmissions on bikes ?

[jato]

It appears your gears may be custom profiles , but to be sure a visit to a gear cutting company would verify that. i've mostly made standard profile gears and go and visit a very experienced old gearcutter for situations like yours - invariably he'll study the gear with a tooth profile gauge before announcing the next step. as a footnote is this type job something that you are quite comfortable doing? if so then the earlier suggestion of a test piece would give plenty of clues...

[Vannik]

In all the special ratios we made for the TZ250's from the 90's the gears used standard cutters as a first cut and then turned at a different angle to relieve the tips more and to do root correction etc. So very far away from a standard profile or contact angle but who cared, the life expectancy was not very high so a bit of wear and rubbing and efficiency loss was of no consequence.

My friend did all the gear designs and he had a gear manufacturer as a friend.

[speedpro]

Suzuki made a race kit for either the a50 or 100.

We managed to buy race kit A100 cylinders with bridged exhaust port from Suzuki NZ in about 1985. There were 5 I think at $15 each. An army mate bought a full race-kitted A100 2nd hand. I got the wheels for my AC50. They were a bit wider, still 18", and had a bit bigger drum brakes.