5-B Race Motor

[gooddirt]

Have a 5b with- stuffed crank -straight cut gears -crank has been polished as well as the inside of the center cases and inside the crank area also-looks like GS porting all of that has been polished-even the upper area of the center cases were the cyld.liner drops in has been stuffed - looks like it has a 100 head- The head and barrel have been cut to look like a 1977-78 175 KTM motor! Would the 6 speed be any better than the 5 speed or let her run as it is?  What kind of gearing for the 5-SPD. Any Help or past lessons you could share. Forgot to say that I got this motor right off the back room rack at a old penton ktm dealership. Had been there from 1972. It was a great find!

[john durrill]

gooddirt,
 Check the # of teeth on the gears in the tranny. There was a close ratio 5 speed tranny that was listed in some of the old parts manuals.
 You could have one. The engine power band , track and rider skill would be the only way to know if a 5 speed or a 6 would be better for you. 1St in a stock Sachs gear box is a stump puller gear. Dont know you would ever need it in MX. CC events i would opt for a 6 speed on a 125.
John D.

[gooddirt]

Found out from the dealer that the motor is out of a 72-73 wassell. Would that make it a wide or close tranny ? The shop only ran the motor once and they don't know.

[sixdazed]

If it's out of a Tyran (made by Wassell) it's probably an E.C.Birt modded motor.He did the Tryans motors in 3 stages...
                                                       Ric

ric emmal

[Gavin Housh]

Larry, just put that motor in a frame and lets go racing! I have some parts books that list the 5B motor gear tooth specs. I would run a 13t counter shaft sprocket and a 60t or custom 61t rear sprocket. The five speed with that big crank is good. you should leave the motor the way it is. All you need is the two bolt top Bing 28mm carb or even a 30mm from a Jackpiner can be adapted to fit. You know that I raced a big crank 5 speed A motor for three seasons with great success. I like the five speed. I did give up a bit on the top compared to the small crank 6B motor, but I think most times that if your a better rider than another guy the bike isn't going to win the race for you. I missed Taft but I'll be at Sand Hill, are you coming down for that? Gavin

[john durrill]

gooddirt,
 If Mr. Birt did the engine it could have anything in it. He is about as good as they get with Sachs ,and Hodaka engines.
 The Jump from 4th to 5th is big in a stock 5 speed box. From what you describe in the engine you have it probably would slow you down on an MX track.
 Thats why i suggested checking the # of teeth on the gear set. I like the 5 speed on a stock B engine and its my favorite on an alloy barrel A engine for the woods.
John D.

[gooddirt]

Got the motor apart and counted the gear teeth ,looks to be a close ratio . 1st-42t-- 2nd-38t--3rd-35t--4th-33t--5th-31t . Its has the -B- motor  small crank. The Sachs list of spares book shows a 5-speed as 1-46 /2-41 /3-37 /4-33 /5-31  looks wide. The motor was out of a 73 penton { wassell] trails bike,it was set up for flat track or dirt track..   Should the Layshaft Bearing have tension on it from the Profile Washer that is behind it?  If I press on the washer the bearing will spin  alot easier.The motor is low hour is this common with this bearing?[?][:0]

[Ron]

I have a 6b small crank, ported, 30mm Mikuni and a Circle F pipe.
I run 13 x 60 on the MX tracks.
I found 1st to low and 2nd to high when I was running 14 x 57.
Now I don't even use 1st and almost never even get into 6th. I like it much better.
RonW

[Lew Mayer]

Here I can fix that motor for ya. 'Course ya may not get it back.[}:)]

Lew Mayer

[VICTOR MONZ]

Larry:

Barb wants a 5B motor for her slimmed down frame...she wants you to install it though !

Her machine is quite fast you know she is an expert rider.

Or just give it to me, I have a "super secret item you need".

Victor

[Doug Wilford]

The profile washer behind the layshaft is supposed to put tension
on the layshaft.  It was designed that way to eliminate back lash
of the gears.
Have Fun!