1981 Yamaha Virago questions

mymomsspace DeleteThis @gmail.com wrote:
>My husband asked me to post these questions regarding his 1981 Yamaha
>Virago. Thanks for your help!
>1. Starter sounds like jet engine winding up before engine turns over.
>It's always been wierd, but is there something I should be ready for?
>It does start.

Starting researching what the minimum length of the starter brushes is.

http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=651328

The dual function starter solenoid is like the one in my pickup truck.

It has large contacts inside to carry the heavy current needed by the starter.


But...

The starter solenoid ALSO pulls on the core #10 that has the fork on it.

The solenoid has to develop enough power to overcome spring #15. Arm #14
moves collar #12, sliding #1 GEAR,STARTING MTR into contact with the
reduction gearing that cranks the engine over.

If the brushes are worn out or the brush springs are weak or the starter
commutator is corroded, the solenoid cannot get a good ground and the starter
spins without engaging the #1 GEAR,STARTING MTR, which is like a Bendix drive.


http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=648541

9: FRONT BRACKET ASY shows the infamous epicyclic gear reduction unit that is
inside the starter itself. You and see the two small planetary gears attached
to the output shaft. The stubby gear right next to the commutator turns the
planetary gears and they have to follow the outer ring gear around.

The epicyclic gear reduction unit is known for breaking internal welds.


>2. Hitachi made carbs in '81 and can't find parts (diaphrams). Which
>year carbs after '81 will bolt on?

Before buying used carbs that may also need work, look at
www.oldbikebarn.com for rebuild kits. And, google for diaphragms in this
group. There's a company in England that will make them and won't charge you
$100 each.


>3. Will 920 barrels work on 750 bottom end? Is 920 bottom end
>different gearing-wise?

I wouldn't be surprised if the 920 barrels would fit.

Check the bore and stroke specifications for 920 versus 750 Viragos. If the
920 used a longer stroke, the 750 rods will probably be too short to bring
them all the way up in the barrel and you'd wind up with a low compression
engine that was just a little larger in displacement and didn't run any
better.

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