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1978 GS 1000 VM carbs

earlfor

earlfor

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OK Y'all. I would like to know how many inches of mercury you're pulling on those VM's at an idle rpm of 1200.

Earl :-)
 
Around 8 to 10 ft on my vacuum guages (I just get the carbs to be on the same settings!), but I have a non-standard motor with bumpy cams, high compression etc so may not be much of a guide to standard motors.

An article I have says a Z9 would be around 8 inches.
 
Earl, I have used both the "GT" mercury tuner and the "Motion Pro" mercury tuner. The lines on both tools are spaced 2cm. The first line on the scale represents 6 cm. At 1200 rpm, typical levels are about 6-8 lines up (16-20 cm) but they are commonly unstable. At 3500 rpm, they typically rise another 5 lines for a total of about 30 cm. 2 cm is about 3/4".
So I have about 7" of mercury at 1200 rpm, give or take. I have found with a very good manual sinc', the initial start up always shows the levels somewhere in this range. If not, then it's a poor manual sinc' or there's a mechanical problem/intake leak.
 
thanks Keith, thats what I was looking for. :-)

Earl

KEITH KRAUSE said:
Earl, I have used both the "GT" mercury tuner and the "Motion Pro" mercury tuner. The lines on both tools are spaced 2cm. The first line on the scale represents 6 cm. At 1200 rpm, typical levels are about 6-8 lines up (16-20 cm) but they are commonly unstable. At 3500 rpm, they typically rise another 5 lines for a total of about 30 cm. 2 cm is about 3/4".
So I have about 7" of mercury at 1200 rpm, give or take. I have found with a very good manual sinc', the initial start up always shows the levels somewhere in this range. If not, then it's a poor manual sinc' or there's a mechanical problem/intake leak.
Click to expand...
 
Hoomgar, I'm not really sure but I would guess the "V" stands for Vacuum or Velocity. I would guess the "M" stands for Mechanical.
 
Earl, if by chance your very moody carbs are showing levels that keep changing, I have a tip that you may not be aware of.
If you think you may have sticking slides, take some Semi-chrome or Blue Magic polishing paste and smooth up the entire slide area inside the carb body. Obviously, just a little paste/pressure is enough. I put just a small dab and work it into the cloth first and then with my index finger, lightly rub up and down doing about 1/4 circle of the slide area. I re-apply a dab of paste and repeat for the next 1/4...I rub up and down maybe 20-25 times per 1/4. Remove the residue with a clean cloth and you'll see how mirror smooth the slide area is. Carb cleaner can get off any varnish spots on the slides. The slides have more tendency to stick when they heat up. I've found this helps remove any oxidation film and the slides operate more smoothly.
 
Thanks again Keith. I'll give'er a go. :-) I'm having a bitch of a time gettin a smooth and progressive vacuum response whilechanging throttle settings. It may well be some slightly "sticky" slides. Although, after soaking and assembling them, they did seem to move easily with a light finger touch. Drat! :-)

Earl

KEITH KRAUSE said:
Earl, if by chance your very moody carbs are showing levels that keep changing, I have a tip that you may not be aware of.
If you think you may have sticking slides, take some Semi-chrome or Blue Magic polishing paste and smooth up the entire slide area inside the carb body. Obviously, just a little paste/pressure is enough. I put just a small dab and work it into the cloth first and then with my index finger, lightly rub up and down doing about 1/4 circle of the slide area. I re-apply a dab of paste and repeat for the next 1/4...I rub up and down maybe 20-25 times per 1/4. Remove the residue with a clean cloth and you'll see how mirror smooth the slide area is. Carb cleaner can get off any varnish spots on the slides. The slides have more tendency to stick when they heat up. I've found this helps remove any oxidation film and the slides operate more smoothly.
Click to expand...
 
I've found that even after a polishing inside I still needed to apply a very very very light coating of grease on the slide but not the needle, the needle I only polished. I used brasso on my brass needles.
 
Won't the vaporized gasoline remove the grease from the slides?
 
Now that you mention it, youre probably correct that gasoline will remove grease. I doubt that grit will evaporate or be removed though. :-) :-)

Earl

knelson said:
Won't the vaporized gasoline remove the grease from the slides?
Click to expand...
 
Yes, the gas will remove most of or maybe all of the grease. I'm not certain because I've never greased the outer slides. I do know that white lithium grease will stay on the inside of the slide, at the swivel points of the linkage. Gas vapors are present there too. I just would'nt use grease on the outer part of the slides. If your slides are sticking, then you need to replace them or clean them up and the carb body. If you try to make them work smoothly with grease and the gas DOES dissolve the grease, then you just wasted your time and possibly attracted grit to the slides at least temporarily. But any damage done by the grit will not be temporary.
 
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