Sachs primary drive gear ratio/teeth

[Mike Lenz]

Could anyone supply me with this info?
Thanks!
Mike Lenz

[Mike Lenz]

I will need the tranny gear ratios or teeth also.
Thanks Again
Mike

[john durrill]

Mike,
 This is what we counted up last week.
Primary gear small 31 teeth
P Gear large 65 teeth
1st gear 10 /46
2nd gear 14 /41
3rd gear 18 /39
4th gear 21 /36
5th gear 23 /33
6th gear 25 /31
hope this is right? My eyes are not what they once were. chuckle chuckle!
john d.

[Gavin Housh]

John, I have kept your yahoo link to your sachs 175 project in my favorites for a few years now. Once in a while I go back to it to look at it again, until yesterday. It has been taken down. Or at least I am unable to get to your photos. It does ask me to join Flicker. Do I need to join to get back to you pics. I'm interested in the dimensions you posted for the small rectangular cut away on the cyclinder side of the bottom of the Bing carb slide. I have one with this cut away and one without. What is the difference. Thanks for all your help over the years. You have been an invaluable part of this site. Gavin

[john durrill]

Gavin,
 Yahoo. deleted all my Flick a photos.
Don't know why.
 The info was something we got from Speedy years ago to help clean up the bottom range on some engines, carb combos


hope this is what you were looking for.
 I have some things on a Photobucket account now that you can get to.
( http://s439.photobucket.com/home/sachs175/index )

john d.

[Mike Lenz]

Thanks John. I really appreaciate it.
Mike

[Mike Lenz]

Found out some interesting stuff from John's numbers using the gear ratio site I have previously mentioned at //www.nightrider.com.
The Sachs engine final drive ratio to the rear wheel is as following:
13/60 sprockets=28.35 2nd gear overall ratio
11/54 sprockets=30.16 2nd
75 RM 125 1st gear with stock gearing 31.08
76 RM 125 1st with stock gearing 35.15
98 SX 125 1st with stock gearing 30.04
07 SX 144 1st with stock gearing 30.03
Interesting. Around 30 seems to be the magic number for MX low gear for a 125. However, the post I read about Mettco probebly is the most accurate.  Gear it down as much as possible just not to run out of top gear on the fastest straight...unless your like me and will shift down to far if 1st is too low. FYI, all the newer 250's are around 20 for first.

Some other interesting things are that the gear spacing on a Sachs and KTM are very similer 2nd thru 5th.  Sixth is spaced out more on the 125 KTM, but not 250/400? Even more amazing is this ratio seems to work ok for 125 thru 400! However, these ratios are wider than a more modern close ratio 125, and even a modern close ratio 250 a bit. Also, first to second is wider on the Sachs! Second to third is much closer together than first to second, and from second to fifth the ratios get closer together.  As stated, some trannys do space out sixth quite abit for top speed.

Verdict: For a Sachs and 70's KTM engine 2nd thru 5th gearing is what you want to focus getting the correct overall gearing ratio on for MX. For me this also means I have to block out first on mine or I will inevitably shift down too far, inevitably at just the wrong time in the race!

[Gavin Housh]

Yes John this helps. I am having trouble reading the figure for the depth of the cut. Mike I have read your post and believe that you are correct in focusing on the top gears 2nd thru 6th. I have been running a 13/61 on y 125 Sachs engine. Seems to work well for me, but I too will sometimes drop into first by accident. With as low a gearing as I have it can be dangerous to shift into that low of a gear unexpectedly. How would you block out 1st gear? On the selector rod?

[john durrill]

Gavin,
 It looks like 1.2 mm but it is fuzzy. It is wider than deep from the drawing.
Post Speedy a note , he has the original not a copy of a copy like we are looking at.
sorry but its the best we can do for now.
john d.

[OUCWBOY]

I have never seen this, but back in the early 70's there was a wrench at Stan's Honda in Duncan OK, who also sold Monarks, that told me he took a 6 sp Sachs engine for a Monark he was building and used the Gear Lock selector assy from a 5 sp and adjusted it so that 2nd gear in the engine was actually 1st gear on the Gear Lock, thus 6th gear was 5th on the Gear Lock. This effect make the 6 sp gearbox a 5 sp gear box without the use of 1st gear. Like I said, I've never seen this or attempted it, but he swore it worked well for his rider. I will do some research and see if I can even track the guy down.

Donny Smith
Paragould, AR

[brian kirby]

I run 12/54 on my 100 for MX and CC. With that gearing I can start an MX race in 2nd and never have to use 1st, but I still have 1st if I need a bailout gear in CC. I guess I might have accidentally dropped into 1st during an MX race, but I dont recall it being an issue.

Brian

[brian kirby]

Upon further inspection, my gearing is 12/57 not 12/54.

Brian

[Mike Lenz]

I brought up this discussion again because I may build a Penton/sachs 100 for mx, and if so would like to block out first making it a 5 speed to be able to properly gear it for mx without the opportunity to downshift into first by mistake, and also take advantage of the closer ratios between 2nd thru 5th, as I have done with my 125 KTM motors. Donny Smith mentioned what sounds like a relatively simple way to do that below.  My question is if doing that mod would you not have a neutral? Or would neutral be at the bottom, below what would now be first? I dont know much about Sachs trannys, so please inform.
If I can do this I plan on running 13/66 or 12/61 gearing to get "first" gear about at a 31 overall ratio. If a 30 ratio is right for a 125 (13/64 or 12/59), then I would expect a 100 needs geared a little lower?
TY

[Mike Lenz]

Another thing on the subject immediately below.  The 006 100/125 parts manual shows a different Sachs gear selector boss and a bracket, etc that says its "for gear lock". Alan Buehner has this gear selector boss on his web parts Sachs engine parts.  Al/anybody know what this is for?

[Mike Lenz]

Make that the subject immediately above.  This page changes order after you post!