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VM26SS sync questions
- motomisfit
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31 Oct 2023 10:08 - 31 Oct 2023 12:11 #891155
by motomisfit
VM26SS sync questions was created by motomisfit
I’m near the end of my 76 900 LTD restoration and am waiting on the vacuum gauge kit to try and sync these carbs.
What I have right now for 1-2-3-4 respectively is 7 1/2, 9, 4, 11 inches vacuum. Warm motor, air corrector jets, K&N filters, Kerker exhaust.
As I’ve never done this before, are those numbers way off? My rebuild included cylinder honing and new rings. The bike runs great and idles pretty good. Spark plugs look pretty good. Takes a bit of cranking when cold to start but starts immediately when warm.
Thanks for any advice.
Chris
What I have right now for 1-2-3-4 respectively is 7 1/2, 9, 4, 11 inches vacuum. Warm motor, air corrector jets, K&N filters, Kerker exhaust.
As I’ve never done this before, are those numbers way off? My rebuild included cylinder honing and new rings. The bike runs great and idles pretty good. Spark plugs look pretty good. Takes a bit of cranking when cold to start but starts immediately when warm.
Thanks for any advice.
Chris
Last edit: 31 Oct 2023 12:11 by motomisfit.
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- Moose1800
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31 Oct 2023 11:20 #891159
by Moose1800
Replied by Moose1800 on topic VM26SS sync questions
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31 Oct 2023 11:42 #891161
by zed1015
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-
Replied by zed1015 on topic VM26SS sync questions
Forget the actual vac readings and just get them all pulling the same then set the idle.
These VM slide carbs don't have a register carb ( unlike most CV's ) so just start by adjusting the one that's furthest out from the rest and work from there.
Ideally you should set all the slide adjusters halfway along their threads and bench sync ( level all the slides the same) prior to install so that you are unlikely to run out of adjustment on any individual slide.
These VM slide carbs don't have a register carb ( unlike most CV's ) so just start by adjusting the one that's furthest out from the rest and work from there.
Ideally you should set all the slide adjusters halfway along their threads and bench sync ( level all the slides the same) prior to install so that you are unlikely to run out of adjustment on any individual slide.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-
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31 Oct 2023 12:16 #891165
by motomisfit
Replied by motomisfit on topic VM26SS sync questions
Oops, my bad. Yes VM26SS
I did bench sync the slides to all be the same in respect to the slide/needle positions as close as I could visually get. Zed when you say forget the vac readings, how are supposed to know what they are pulling?
I did bench sync the slides to all be the same in respect to the slide/needle positions as close as I could visually get. Zed when you say forget the vac readings, how are supposed to know what they are pulling?
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31 Oct 2023 12:56 #891166
by zed1015
Actual vac readings are an indication of engine condition and if nothing is amiss your vac readings at idle are what they are and cannot be increased or decreased to conform to a pre determined figure.
Once set the vac will only increase or decrease in line with throttle position and load conditions etc.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-
Replied by zed1015 on topic VM26SS sync questions
Just get all the gauge readings the same which means that each cylinder is doing equal work ( pulling the same as it's neighbour) then set the idle.Oops, my bad. Yes VM26SS
I did bench sync the slides to all be the same in respect to the slide/needle positions as close as I could visually get. Zed when you say forget the vac readings, how are supposed to know what they are pulling?
Actual vac readings are an indication of engine condition and if nothing is amiss your vac readings at idle are what they are and cannot be increased or decreased to conform to a pre determined figure.
Once set the vac will only increase or decrease in line with throttle position and load conditions etc.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-
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- motomisfit
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31 Oct 2023 14:47 #891167
by motomisfit
Replied by motomisfit on topic VM26SS sync questions
Before I put the holders and main jets in, I set the slides as best I could by measuring how far the needles stuck out past where the holders screw in. So getting all readings close to the same is done at a higher rpm?
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- Warren3200gt
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31 Oct 2023 15:20 - 31 Oct 2023 15:31 #891169
by Warren3200gt
Replied by Warren3200gt on topic VM26SS sync questions
Only the frequency of vacuum changes with rpm not the volume.
Sync them at slightly above idle speed to damp guage needle bounce.
Job done.
Bench set all the slides the same by using a 1mm ish drill bit under the slide on the engine side of the slide. If the drill is trapped by the slide adjust the height of the slide until the bit will just fall out under gravity. Do all four the same and they are bench set. Do this with the idle screw a few turns past touching to allow you to adjust the slides further closed if needs be to get the right idle speed when fitted.
Sync them at slightly above idle speed to damp guage needle bounce.
Job done.
Bench set all the slides the same by using a 1mm ish drill bit under the slide on the engine side of the slide. If the drill is trapped by the slide adjust the height of the slide until the bit will just fall out under gravity. Do all four the same and they are bench set. Do this with the idle screw a few turns past touching to allow you to adjust the slides further closed if needs be to get the right idle speed when fitted.
Last edit: 31 Oct 2023 15:31 by Warren3200gt.
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- Mikaw
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31 Oct 2023 15:26 - 31 Oct 2023 15:28 #891170
by Mikaw
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Replied by Mikaw on topic VM26SS sync questions
A bench sync is done using small gauge wire about .07mm but this size isn’t that important. First set the air gap of the idle adjustment screw to about 2mm. Adjusting the slides with the adjustment screw on the pivot arm inside the top chamber. Till the wire has same drag on each slide. Follow the procedure below
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Last edit: 31 Oct 2023 15:28 by Mikaw.
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31 Oct 2023 19:31 #891175
by motomisfit
Replied by motomisfit on topic VM26SS sync questions
Thanks for that Mikaw. That’s pretty much what I did but I used how much the needles were protruding out inside the carbs as reference. I only needed to adjust two of them and at that very little.
I took it for a good ride today and it blasted thru the rpm range. Just a little blubbery at idle and off idle and oddly not all the time. Took the plugs out tonight and the #1 plug was very black and sooty. I was having this same issue the last time it ran 13 yrs ago. Cylinders honed, rings new, valves and seats new, valve clearances and ignition timing spot on. Float bowl levels spot on. Scratching my head a little on this one. Will post a pic of the choke plunger for #1 carb. It looks ok to me but…..that could very well be the issue.
I took it for a good ride today and it blasted thru the rpm range. Just a little blubbery at idle and off idle and oddly not all the time. Took the plugs out tonight and the #1 plug was very black and sooty. I was having this same issue the last time it ran 13 yrs ago. Cylinders honed, rings new, valves and seats new, valve clearances and ignition timing spot on. Float bowl levels spot on. Scratching my head a little on this one. Will post a pic of the choke plunger for #1 carb. It looks ok to me but…..that could very well be the issue.
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- motomisfit
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31 Oct 2023 19:46 - 01 Nov 2023 15:49 #891176
by motomisfit
Replied by motomisfit on topic VM26SS sync questions
Last edit: 01 Nov 2023 15:49 by motomisfit.
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31 Oct 2023 21:29 - 31 Oct 2023 21:43 #891178
by Mikaw
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Replied by Mikaw on topic VM26SS sync questions
Zed1015 can rebuilt your choke plungers, it’s good to eliminate that from the mix. When the carb were apart did you check the needle jets for oblong wear? If #1 is oval or the jet needle is worn it could also cause the rich condition.
EDIT, when the carbs were apart did you verify all of the brass were the same, in 40+ years anything can happen. You need to verify consistency.
EDIT, when the carbs were apart did you verify all of the brass were the same, in 40+ years anything can happen. You need to verify consistency.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Last edit: 31 Oct 2023 21:43 by Mikaw.
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01 Nov 2023 08:34 - 01 Nov 2023 14:28 #891190
by motomisfit
Replied by motomisfit on topic VM26SS sync questions
Yeah, something is going on in that #1 carb. I’m pretty sure it’s not anything in the ignition because #4 plug is fine. It’s looking like I’ll have to pull the carbs and go thru them again. I never thought to check the needles out of round. Thx
Last edit: 01 Nov 2023 14:28 by motomisfit.
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