Yamaha DT125 model ? old induction box under tank how to do major clutch adjustment?

Question

has screw and locknut on pressure plate. vertical shaft below actuating arm has a srew to it. this appears to have a wear mark that appears like there was a ball bearing there but a bearing doesn't fit there . there is no bearing between the clutch rods also

Answer 1

It sounds like the ball bearing is missing.

Answer 2

-Always give year, make, engine size and model # when asking questions. I can't give you an accurate answer without knowing the year of your bike.
-Most Yamaha's have a ball bearing between the push rods.
-Yamaha's with lock nut's and adjuster screws on the pressure plate, usually have the clutch actuator on the opposite side of the engine. So I'm unsure of what you mean by "vertical shaft actuating arm".
-Which ever side the adjustment screw is - Loosen the lock nut, turn the adjustment screw in until it just touches the push rod.
-Then back it out 1/4 turn and tighten the lock nut.
-Check that the adjuster didn't move when you tightened the lock nut - there should be a little free play on the actuating arm.
If none of this is doing it for you, look up your bike on Bikebandit. -Send me the bikes info, picture you're looking at and the # your confused about.
Good luck
http://www.bikebandit.com/partsbandit/OEM-Parts.asp

Answer 3

Hey Steve,
It IS supposed to have a ball between the 2 pushrods,,wont work without it.
If you need to get one,,try to get a genuine Yamaha part.
Otherwise,,if you get one from a hardware store make certain it's not too small,, or it wont intersect the Rods at their center.
Not a good thing.
"ROD SIZED" is Right Size

The screw on the L/h side simply retains the shaft in the case.
It intersects a groove in the shaft.
There is NO ball there.
The wear pattern is from the set screw rubbing on the shaft as the shaft rotates during operation.
If the screw is removed the shaft will slide straight out,which you dont need to do.

That throwout mechanism works fine when "all is right".
But they are quirky in the sense that they're unusually sensitive to small details and to adjustment.

That characteristic is due to a very short leverage radius on the actual "throwout cam" which is merely a Flat cut on the end of that shaft.

The Flat creates a sort of "D-shape" which the pushrod intersects Off-Center of the shaft

Something like this,viewed from top:

..Rod........D<

As the shaft rotates,,the flat on the D comes around and pushes on the rod,,,which lifts the pressure plate to release the clutch

You can see the diameter of the shaft is small,
Half that diameter is the effective leverage radius.
Which produces Very small motion available to drive pushrod.

That also makes them sensitive to "Lost Motion" anywhere in the system.

Imagine that the Flat's full operational range was 1/8 turn of the shaft.
Correlate that to the Actuator Arm,,and the Straight-Line distance the cable must pull it to rotate the shaft the necesssary 1/8 turn.

That's quite a distance.
Barely within the capability of the hand lever to produce.

Adjustment Procedure:
* Loosen Cable at engine substantially,,and screw Hand Lever adjuster all the way IN to loosen cable further

*Actuator arm should be Fully Back with plenty slack in the cable
(that screw on the side of the arm MIGHT constitute an "arm position stop" by virtue of Shaft Groove being cut only partially around the shaft??? I simply cannot recall,,but I "Think" thats right)
No matter,,,as long as Shaft is Fully Back & cable has slack

*Screw Pressure Plate Adjuster IN untill it's snug

* To Adjust the working clearance,,,
You'll monitor the Actuator Arm as you Screw the adjustor OUT.
Hold the Arm Forward with moderate hand pressure,,,
as you Unscrew the Adjuster the Arm will be allowed to move Further Forward.
When Arm has moved about 3/16~1/4" Forward,,
Tighten the Adjuster's LockNut.
You should be able to move the arm by hand about 1/4" at it's end.

That's the "distance" between the Arm's rearward Stop,,,and it's forward movement taking up the slack in the Push Rod assy.

If tightenenig the LockNut happens to disturb the setting,,Try again.

The FreePlay Movement measured at end of the actuator arm
is what you are "adjusting".
Too Tight, Arm's Free-Travel will be Short,and clutch rod wont have proper working clearance.
Too Loose,Arm's Travel will be Too Great,,and Hand Lever will not have the range to cleanly disengage the clutch

*Take up as much cable slack as possible at engine end of Cable

*Make fine adjustment at Hand Lever

* When Final Adjustment is done,,,Actuator Arm should have a small amount of "wiggle".
You should be able to push it forward a small amount,,maybe 1/8" or so at arm's end.

*TEST for a Full Clean Disengagement
--get back wheel off the ground
--shift to neutral>spin back wheel and note the resistance
--shift to 1st>>Squeeze Hand Lever,spin wheel and note resistance

--It Will be higher resistance than neutral,but should clearly be "Free Wheeling"

_Gradually Release clutch while turning wheel,,,
and Note Engagement Threshold>>>IN TERMS OF Lever Distance from Handlebar.

It "Should be" a Minimum of approx 1/4 of the Total Lever Travel

What you Don't Want is engagement beginning "right off the handlebar".
That signifies Not enough throw-out travel.

It will probably be fine.

If by chance the clutch is not disengaging cleanly,,and You're confident the adjustment is close enough....
Here's some things to check;
*Bent Hand lever can limit lever travel
*Loose HandLever pivot can cause a larger loss of motion than it seems it could
*Any kink or bend in the cable can also cause a loss of motion,,on either inner cable or outer cable sheath
* "Oversize" handgrips can limit Lever Travel
*aftermarket levers can have insufficient ratio or travel to produce a clean,full disengage

Have a Good Weekend