how to tell if D engine 74 125

[ktmkirk]

I ran across a 1974 125, Frame number  408.76547 which makes it a 74 125 and the Sachs engine has the KTM tuned stickers on the cases, Does this make it a D style engine? is there anyhting else to look for to see if this is the special D engine . The motor is locked up at the moment.

Thanks, any info wuld be aprciated...Kirk

[firstturn]

Kirk,
  Look at the side fins on the cylinder and if they are "V" shaped horizontal fins as opposed to one horizontal fin.  If it is "V"  it is a "D" cylinder.  Did it have a engine number plate on the ignition cover.  You can send me pictures and I will try and help you.

firstturn at hotmail .com

Ron Carbaugh

[ktmkirk]

The bike is at a friends house so when he gets back from work I will go and look at the fins and try to get a picture as well...Thanks...Kirk

[joe novak]

Hello,  The most obvious external method to determine a Sachs D cylinder is by either the bolt-on intake manifold, and the "V" shaped cylinder fin webs.   Joe  p.s. or you can just send it to me and I will tell you

[ktmkirk]

Engine number is 1251/6D  7747961

The cylinder fins look like a V where they are  Reinforced from the side, I guess now I have to see if the owner  wants to sell it and for how much since I can tell it is missng the end cap ( part held on by springs ) of the exhaust pipe and the Idle screw is missing out of the carb and I think that is why we think  the motor is locked up from just looking at it in his garage last night.  It could be another saved penton  who know's

[checkcrew]

This is another fool proof way to tell a "D" cyl.

D cyls. are 6 fin
A & B's are 7 fin

some times it is hard to see the V in the webbing from the photo angle,
but you can almost always count the fins !!

hope this helps,

regards,

Mike Gallagher, NJ.

[ktmkirk]

Thanks about the number of fins that is good info, I'll call and see what it has...Kirk

[firstturn]

Mike,
  You have to be sure the person you are talking to can count....and Joe, as one person told me the cylinder has a manifold, what more do you want to know?  It turned out to be a B.  All great answers and I appreciate my Brothers adding to the discussion.  []

Ron Carbaugh

[joe novak]

OK, I am a little confused now.  According to the POG site information, to distinguish a Sachs D cylinder one needs to look for these characteristics: 6 fins, bolt-on intake manifold, and V-shaped fin webs.  Obviously, one cannot fake the 6 fins or the V-web, but it is possible that someone might retrofit a bolt-on manifold.  The frame no. 408XXXXX designates a late 1974 model.  My understanding is that there where some 1974 1/2 Penton models which came stock with the D engine. But it was only in 1975 when the frame was changed to the layed-down shock position and all 125 Pentons had the D engine.  I believe the D engine has a special head which is designated by a boss near the spark plug area.  I have a D cylinder, but not the matching head, so I do not know as a fact.  Only hear-say from Paul Danik.  Oh, that does make it fact!  Also, did D engines come with an internal Moto-Plat?  Joe  p.s. just trying to sort out what's what re: D and this engine...

[Larry Perkins]

I am constantly amazed at the stuff that gets discussed again and again when a search would bring up the info.  I will give a quick synopsis as this "D" motor misconception happens about every 6 months.

THERE IS VERY LITTLE THAT IS SPECIAL ABOUT A "D" Sachs motor.  Except for the rubber bolt on intake and some cosmetic differences it performs NO DIFFERENT than a "B" motor.  The "D" motors that went on the 1975 Penton 125 was this plain old "D" engine.  

A "D GS" motor is a different story.  A few of these were in Monarks and a very few were sold as "Specials" that went to fast guys to help make them faster.  The "D GS" motor had a stuffed crank, high compression head, internal rotor motoplat, and cylinder porting that could not really be duplicated in a regular Sachs motor.  They also ran a different piston with a shorter skirt and different ring location.  

If you have a "D" motor rest assured it is HIGHLY UNLIKELY it is the "D GS" one but a plain old "D" that is only better from the bigger carb mounting problem standpoint.  So, build it, ride it, and don't think you have the ultimate secret weapon.  Hey the Penton is a weapon secret or not.  LOL!

Larry P

[firstturn]

OK, I am a little confused now. According to the POG site information, to distinguish a Sachs D cylinder one needs to look for these characteristics: 6 fins, bolt-on intake manifold, and V-shaped fin webs. Obviously, one cannot fake the 6 fins or the V-web, but it is possible that someone might retrofit a bolt-on manifold. The frame no. 408XXXXX designates a late 1974 model. My understanding is that there where some 1974 1/2 Penton models which came stock with the D engine. But it was only in 1975 when the frame was changed to the layed-down shock position and all 125 Pentons had the D engine. I believe the D engine has a special head which is designated by a boss near the spark plug area. I have a D cylinder, but not the matching head, so I do not know as a fact. Only hear-say from Paul Danik. Oh, that does make it fact! Also, did D engines come with an internal Moto-Plat? Joe p.s. just trying to sort out what's what re: D and this engine...

Answers to the above questions;
1.  You can machine the intake area to accept a D or aftermarket manifold.
2.  Yes some 74 1/2 did have D engines as I have owned one, but most had B engines.
3.  I have owned several 75 Sachs powered  125 Pentons and they all had D engines.
4.  The D engines I own have the boss on the head.
5.  The D engine Pentons I have owned had external flywheel.

Hope this helps.

Ron Carbaugh

[Paul Danik]

Larry,

   I would like to respectfully ask you to look at these questions from a different point of view.

   The search feature to me is an "option" for folks to use, not a required path to be used before posting a question on the message board.

   Fortunately for us there are always new folks being registered to use this message board, and many more new folks who do not register who just like to read the posts to gain knowledge of all things Penton. Questions such as Kirk's provide the catalyst for some great discussions that help to fill the newer interested persons with knowledge and hopefully feeds their Penton enthusiasm, as well as helping to fill in the knowledge gaps of long time readers.

   I personally feel that comments such as yours can have a negative effect on folks who would like to ask a question, but feel that they might get chastised for doing so.  Any and all questions are not only welcomed here but are greatly encouraged.

Respectfully,
Paul

[Larry Perkins]

Paul,

I sure don't want people to stop seeking knowledge I just wish sometimes they would search it first and the answer would be there.  Most of the time it is not that big of a deal but there are some things like the "D" motor and oil preference that have come up 20 times in the last 10 years and the debate starts all over again.  Also on the "D" motor all the misconceptions are thrashed out once again which makes me feel the need to try and set the record straight.  Perhaps we need a FAQ section and that would help.  If nothing else perhaps it could contain oil quanities and weights and such.  

I was not trying to be negative but just expressing my frustration and opinion.  One could say that your saying I am being negative has a negative effect on me to want to express my opinion so that I give input less and less.  Had I not brought it up the debate over how to ID a "D" motor would have gone on and perhaps no one would point out that "D" motors are not the wizbang that LOTS of people still think they are.  

Sorry I expressed MY opinion on a pet peeve and hope all that have questions will still ask.  Just wanted to push the SEARCH feature as there is much info already out there on many subjects.  I feel properly chastised and will be less expressive of my opinions if that is possible.  

Larry P

[Paul Danik]

Larry,

   Thank you for the positive response on my comments

Have a great day,
Paul

[Dale Fisher]

I think the easy answer here is a picture saves a considerable amount of conjecture.
Attached is a picture of my "B" cylinder with an aftermarket kit modification.  Somewhere I have the flyer for it.



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