um, newbie here, mixture screw?

[fredintoon]

- - - I love the "roto-tiller" description - I thought the bars were very weird, but after riding they kind of work - after all you're leaning and not steering - but I'm sure I'll change them out soon - any suggestions on which brand/style has best looks/feel? I don't want to sit too far forward - - -

Hi Bigibee,
the problem with the rototiller bars ain't their height, which is about the same as the CB750 bars that several riders have replaced them with, it's their wrist angle.
The rototiller's grips point just about straight back at you and that ain't right.
Just sit there in your chair and shove your hands out like you were gripping a handlebar.
With your wrists horizontal the grips should be straight across.
Now turn your wrists vertical to suit the rototillers "straight back at you" grip position.
See how the rototiller grips should also be just about vertical so you can hold them without straining?
My best advice on 'bars is you gotta try 'em on for size, just like when you are buying shoes.
Go to a bike shop that's got a whole rack of different 'bars on display. Or find the handlebar guy at a local swapmeet.
Grab up different 'bars and hold them out in your preferred riding stance.
Pick one that feels right. It may take you more than one purchase to get it right but at least you'll have some extra 'bars in your swap pile.

 

[peanut]

thats odd. the stock bars on my 79 special are generally called 'ape hangers ' I take it that these are not the same pattern as the 'roto tiller' bars ?

I find that if I extend both my arms and clench my fists lightly my hands fall comfortably to a 45 degree angle !

If my grips were both vertical then you would need to actually grip the grips all the time in order that your hands don't slide down off the grips by gravity.

That would surely put a hell of a strain on your wrists maintaining that grip?

I find the high bars on my 79 are set about 40 degrees from the horizontal if memory serves . http://www.ebay.co.uk/itm/1979-yamaha-xs650-special-y395-handlebars-bars-/291323101859?hash=item43d435c2a3:g:5cYAAOSwuMFUe8bT

 

[5twins]

I just mentioned the replacement adjustable needles in passing. In most cases, for the normal "pods and pipes" type mods most do to these bikes, just changing mains and pilots is enough. Yes, the needle is fixed and rather lean, but the new larger mains and pilots will bleed over into the midrange and in most cases just make it right.

4 turns out on the mix screws is a bit much. Most likely your carbs require a cleaning and maybe some replacement o-rings. The mix screws have an o-ring on them and if it's bad, they won't function properly. There is also an o-ring on the float needle seat. If it's bad, fuel can leak past the outside of the seat instead of just flowing through it like it should. The original gaskets (float bowl, choke housing) are very good and I recommend just re-using them if they're not damaged during the tear-down. But, having rebuild kits on hand is good just in case. I recommend these because besides the gaskets and a couple o-rings, you get not one but two different adjustable needles you can play with .....

http://www.ebay.com/itm/161720238856?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

None of the rebuild kits I've seen have the mix screw o-ring but the size is 1mm x 3mm if you need to replace that.

Yes, the sync screw is on the linkage between the carbs. It adjusts the opening of the right carb butterfly so you can match it to the left one .....

 

[Hightower-Ash98]

It seems your '78 is not quite a virgin (that dirty slut, lol) because you appear to have BS34 carbs. They didn't happen until 1980. But ..... there was no Special II in 1978. You may be mistaken about the year of your bike.

Yes, you have mix screws but they're capped so you can't fool with them. You have to drill the metal caps out and extract them to gain access to the screws. You must take care when drilling because the screws are just below the caps. If you go too deep, you'll ruin the screwdriver slot on the screw top, making adjustment or removal very difficult. Note the small "vent" hole in the metal plug .....



Using a 1/8" drill bit, start drilling into the plug. Drill a little and check the hole, drill a little more and check again. Watch that little "vent" hole in the center. As soon as it begins to get larger, stop drilling, you're almost all the way through the plug. Get a small sheet metal screw and blunt the point on it .....

Screw it into the plug until it bottoms and the plug starts turning. Yank it out with vice grips .....

Twisting as you pull it out helps.

The BS34s were pretty E.P.A. strangled. They usually run best with the mix screws set somewhere in the 3 to 3.5 turns out range. You may find the factory setting down near 2.

Hey Five, can you repost the images, I'm personally at a loss here as well

 

[5twins]

OK, done and done.