Yamaha CS3-200 Scrambler sometimes won't shift from 1st to 2nd - should I buy it?

Question

I've gotten the motorcycle bug, and have been looking for a vintage 2 stroke 1 cyl bike as a project, and to learn to ride on. I found a 1970 Yamaha CS3-200 locally for $500. It looks great, new tires, starts right up and sounds good. The owner said sometimes it misses the shift between first and second. He said you can start it in second with a lot of gas or when you shift, you sometimes have to hit the shifter a couple times to get it to go in to second gear. Should I buy the bike with the intention of trying to fix this? The following site: http://www.mrcycles.com/fiche_section_detail.asp shows exploded views of all major systems, and has most parts for the shift mech. and tranny. I think it might be part of the shift mech. - parts #9, #10 on the diagram or thereabouts. Put in Yamaha, 1970, CS3 and go to SHIFTER to see exploded view. I'm very mechanically adept, but have never worked on a motorcycle, and can't find much on the CS3-200. Thanks in advance!

I'm going to look at the bike today. VERY good explanation. There's just one thing I'm not clear on, which I suspect will be much clearer when I get things opened up.. But - when you refer to the 'roller' what part exactly is that, #10? Not #21, that's the 'stopper lever'... Right?

Answer 1

Common problem of that era.

Item #21 wears out

And Item # 27 is an "eccentric cam" bolt which functions as an Adjustment.
What it Adjusts is both the Orientation and Travel of Item #24

If ya look at 24 almost directly where the Part Number is pointing,,,there's a Large Slot to the Left.

#27 Adj Screw is Straddled by that Slot
The Adj Screw sets how far the FootLever>Shaft can travel in each direction.

It's a adjustable "STOP".

Those boxes do NOT shift by being pulled fully into gear by foot.
In fact ya cannot.

You can only INITIATE a Shift.

Foot pressure turns shift drum until the Stopper Lever #21 has just Passed Center of Pin #9.
Thats as Far as Foot can Pull the Shift Drum into next gear.

Roller Action of #21 on "Downhill Side" of Pin #9 Takes Over at that point and completes the Shift Drum Rotation fully into gear.

If you look at those Pins end-on view,,,they form a "STAR".
Each pin is a Point on the star.
The Star Spins while Roller #21 rides on it's O.D.,,,hopping in/out ~~Up /Down between the Points of the star.

You Foot Pulls the Shift Drum to rotate it.
Roller Rides "Uphill" to Point of Star,,then BARELY,BARELY Past Center/Peak.

At that point Foot Travel is Stopped by Adjuster /Stop Screw #27.....
But the Spring Tension on the Roller begins to push on the Star(Pins #9 actually" on the Beginning edge of it's Downhill run.
That completes the rotation of the shift drum.

Reason You cannot Consistently get 2nd Gear is due to Wear on the Roller's Center.
The Wheel part wears on it's axis.

Which allows Roller flop around back and forth SIDEWAYS across the lever.

That messes up the Orientation and Relationship geometry of all the parts involved.

So when Your Foot Tries to rotate Drum and position Roller Just BARELY past Center,,,
Slop in the Roller's axis may allow the Roller to LAG Behind a small bit and IT never reaches center.

So 1-2Shift is INITIATED as Normal,,,
But is never Completed,,,cuz Roller never reaches PAST the Peak,,,where it can then apply Spring/Roller pressure to finish rotating drum fully into gear.

SOMETIMES it's possible to used the Adjustment to allow OverTravel of FootLever,,,which pulls drum around Far enough to get past center in relation to the Roller.

But it's BEST to replace the Roller.

Makes them shift Very Slick,Crisp,and Certain.

Parts are Cheap and can be replace without Removing Clutch.

Parts Needed
* the Roller"Stopper Lever" #21
*and Clutch CoverGasket
*and some replacemt Trans Oil

Only very rarely do any of the springs fail

Adjustment>>
The Roller establishes "Fully In Gear" when it is snuggled at bottom between 2 adjacent #9 Pins.
That indexes the Shift Drum in Proper position.
It happens "automatically" so to speak,,,same as any spring loaded detent.

To Ajust,,,turn screw #27 to allow Shift Shaft enough Travel to pull Shift Drum Pins #9 around Just Past the Roller's Center.

Try it in Both Direction,,,,,Upshifting and Downshifting.
Split the Difference.
But in Both Directions the #9 Pin must be pulled Barely Past the Center of the Roller21.

All you're trying to do is pull it around till Roller is on "Downhill Side of Star's Point" so it's spring tension can finish rotating shift drum fully into selected gear.

Look at it when ya get it opened up.

YOUR Foot and That Roller are PARTNERS.
Foot STARTS the Shift,,Roller Finishes it.

Also,,Tans must be Turning to fully go into gear.
Put it on center stand and turn back wheel as you shift it,,,or turn Clutch assy by hand.

Note the Roller's action as it hops in/out between the pins.
And Foot Levers action as it Pulls on the pins to rotate shift drum.
If Shifter does not pull drum around far enough to get Roller PAST the Pin Center,,,use the adjuster screw to get more travel.
Ya MUST check it in Both Shift Directions,,,and the adjustment does NOT offer a very wide range INTENTIONALLY.

The point is to LIMIT the Rider from Cramming Gears' engagement dogs when they are not aligned with their reciever holes.

Really Simple and easy to see,,,,,Lots easier than to explain.

Function and adjustment procedure is almost "Generic" among all Yamaha's of 70's~80's,,and Most Jap Bikes in general.

A 125 Dirt Bike or 350 twin street bike,,etc,etc service manual would show you "How To" just as well as an actual CS3book.
BEST to get a Proper Service Manual,,obviously.
But if by chance you have access to a Different one,,,,It'll show you what ya need to know about the mechanism.

You'll make more sense outa it by Just LOOKING and "trial shifting " a few times as you watch,,,than this answer does,lol.

MAYBE trans is Blown Up,,,it's a possibility.
I've replaced Several 1,000's of "Shift Drum Stopper Levers" and done 1,000's of adjustments.
Probably in the 7~8,000 range.

Actual Box Destruction is RARE,especially on Yam's street bikes.
And when Internal Parts are Trashed,,,,there's NO "sometimes" to Missing Gear Teeth,Gears cracked into 2 pieces,,Gears galled to shafts,,Burnt/Bent Shift Forks,,or "Missing" gear Dogs sheared off the gears.

They are Fun Bikes to ride,,and run really good.
You oughta get a kick outa scooting around on it.

Be Careful,have fun,,and Good Luck with it.

Answer 2

The most likely problem will be the shift forks - worn or bent - the most common of transmission problems on all Jap bikes.
#2-3-4
Possibly - the shift drum "also" #1
#s 9&10 have nothing to do with the symptoms you're describing.
Since the owner has known about the problem, he's probably been riding the bike like that for a while - expect to purchase at least 2 transmission gears.
Double & tripple check to see if you can get all the parts.
Including gaskets - head,base,clutch cover.
The entire engine has to be dis-assembled.
Purchase a shop manual for that kind of work.
http://www.motocom.com/motorcycles/

The most common "of" transmission problems.

Answer 3

Don't buy it. And it's not a common problem with Japanese bikes,it's a problem with people that don't know how to shift.