more VM26 questions!

[Agemax]

ok, carbs are rebuilt now, just gotta get a couple of new screws that got rounded off during dismantling.
i have 2 queeries:-

1. on the bracket that the cables connect to on top of the assembly, what is the purpose of the spring which goes between the steel bracket and the ali mounting bracket? is it just to prevent vibration loosening the screws as it seems to serve no other purpose.

2. when bench synching carbs from a complete strip down do you have to back the main idle adjustment screw right off first or adjust it so it just lifts the slides slightly?

cheers,

Age

 

[tas850g]

1. I don't recall what the purpose of the spring is but it seems that you do need it.

2. the main idle screw should be backed off all the way but the way it affects all 4 slides simultaneously i don't think it really matters. I would back it off though.

 

[hampshirehog]

As far as I know that spring is for anti-vibe.

It doesn't matter where the idle knob is set for synch, though it helps to have the slides very nearly completely shut so that the differences in slide height are more noticeable.

If you've got vernier calipers you can bench synch from the top of the carbs (tops off) down to the top of the slides. I've started doing this now and was really surprised how accurately Mikuni made the heights of those slides / height of the carb bodies. As long as you make the measurement in the same place on each carb, chances are you won't have to do a running synch - it really is that close.

 

[sam78gs750]

2. when bench synching carbs from a complete strip down do you have to back the main idle adjustment screw right off first or adjust it so it just lifts the slides slightly?

back the idle screw off completely and adjust slides so they are all completely closed. Then adjust the idle screw so that it lifts the slides slightly. if you bench sync with the screw in already you could be ok, but you might also find that when you put everything together and start up the bike you run out of room on the screw and still are idling too high or too low....

 

[Agemax]

thanks guys, and cheers Wally for the vernier guage trick, sounds like a good idea

 

[Sandy]

When I bench sync I start with the slides bottomed out (idle screw all the way out) and get them as close as I can. Then I turn in the idle screw so the slides are open a bit and fine adjust them using the shank of a drill bit as a gauge to fine tune the initial bench sync. I think I use about 3/16" bit or smaller, you don't want the slides open too far. You'll get the feel for a slight drag on the bit and this I think is far more accurate than anything you can do visually (IMHO). My bench syncs usually then require only some minor adjust with the vacuum gauges. Oh yeah, that little spring, I have no idea what it does, but I do put it back.

 

[SqDancerLynn1]

Everything is based on the #3 carb, so back the idle screw out completely and make sure #3 carb is completely closed. Turn idle screw in until your drill will just slip in, then adjust 1,2,4 and your all set. Don't forget to back the idle screw back out until the slide is just barley open

 

[Agemax]

Everything is based on the #3 carb, so back the idle screw out completely and make sure #3 carb is completely closed. Turn idle screw in until your drill will just slip in, then adjust 1,2,4 and your all set. Don't forget to back the idle screw back out until the slide is just barley open

why is everything based on #3 carb, if you dont mind me asking?

 

[hampshirehog]

Everything is based on the #3 carb, so back the idle screw out completely and make sure #3 carb is completely closed. Turn idle screw in until your drill will just slip in, then adjust 1,2,4 and your all set. Don't forget to back the idle screw back out until the slide is just barley open

They're VMs Lynn - doesn't have a base carb.

BTW - measure the carbs while they're off. I bet they're VM28s (will measure 28.9mm or thereabouts on the head side, internal).

 

[Agemax]

They're VMs Lynn - doesn't have a base carb.

BTW - measure the carbs while they're off. I bet they're VM28s (will measure 28.9mm or thereabouts on the head side, internal).

i will do tomorrow Wally but i thought only the 28's were on S models

 

[hampshirehog]

i will do tomorrow Wally but i thought only the 28's were on S models

Loads of UK E models also came with the 28s as well (far more than came with 26s). The Yanks only got the 26s on all their bikes, including the S.

 

[Agemax]

Loads of UK E models also came with the 28s as well (far more than came with 26s). The Yanks only got the 26s on all their bikes, including the S.

ooh im intrigued now. will check tomorrow when i dig out my digi verniers to synch the carbs. too late and too much wine to do it now

 

[tas850g]

They're VMs Lynn - doesn't have a base carb.

BTW - measure the carbs while they're off. I bet they're VM28s (will measure 28.9mm or thereabouts on the head side, internal).

It seems like i have iread n the Morgan Carbtuner and the tuturial on Basscliff's website that states you start with #3 then work out from there. I forgetting if you go to #1 then 2 and 4 so i would have to reread that.

 

[Sandy]

It seems like i have iread n the Morgan Carbtuner and the tuturial on Basscliff's website that states you start with #3 then work out from there. I forgetting if you go to #1 then 2 and 4 so i would have to reread that.

VMs are mechanical slides are all pulled from a common solid shaft so it really shouldn't matter what order you do them in. The BS carbs adjust from the throttle butterfly shafts and the adjustment is dependant on the carb beside it. So you would start with the carb controlled by the cable (#3) and work out from there. When you start just make sure none of the slides are bottomed out and holding the throttle shaft open a bit.

 

[sam78gs750]

the drill bit is a good idea...never thought of that. I usually just eyeball them with the ruler on the side of my float caliper...but it doesn't really get in there next to the slide too close. measuring from the top isn't a bad idea either....

 

[Agemax]

They're VMs Lynn - doesn't have a base carb.

BTW - measure the carbs while they're off. I bet they're VM28s (will measure 28.9mm or thereabouts on the head side, internal).

measured them today and they all measure 26.5mm so they must indeed be VM26's

 

[hampshirehog]

Yep, 26s. You're in a minority over here then. 28s are noticeably better suited, though the power figures were always listed the same regardless of size. Very unusual for Zook not to claim some massive power hike in the adverts.

Plenty come up on Ebay - you could get a set, swap over your good bits (the bits that deteriorate all swap) and then sell the 26's on Ebay for the same money (I've sold a few sets of both sizes but no one ever asked the size). If yours are all polished and clean you'll even make a bit.

Did you see those VM29s that sold on Sunday? The seller thought they were originals. I was going to chuck ?150 at them thinking I'd get them for a lot less; someone else must have spotted them as well though for ?155.