Syncing carbs R100s
-
Zombie Master
- Posts: 8821
- Joined: Sun Aug 22, 2010 12:21 am
- Location: Vancouver Island BC Canada
Re: Syncing carbs R100s
Could you describe your invention for "toolless tweaking" ...please?
Any and all disclaimers may apply
toolless tweaking mod
First off, my model bike did not come with a rubber boot cover where the 2 throttle cables exit the twistgrip housing, a lot of other models have this boot (#8)
it would have to be removed to do my mod.
I cut back the upper cable housing (#6) and I JBwelded a nut to it. I shortened the adjuster from an old throttle cable and ran my upper cable through it. This adjuster now has a total of about 3mm of usable range. That's the most I could have and still have the cable seat at about the same distance as it was in the unmodified housing. I guess I could have left the new adjuster longer if I wasn't worried about the cables looking even where they exit the housing. I probably could have made up the difference on the lower(carb end) adjuster but I wanted cable symmetry exiting the housing.
Now, I can rotate the adjuster in or out about 1.5 mm while sitting at a light, just to get that sweet spot while transitioning from throttle stop screw holding the butterfly to cable pulling the butterfly. Keep in mind that to sync 2 carbs you only need to adjust one cable.
When in the sweet spot, I get perfect sync; turning it a bit in or a bit out (as little as 1/8 turn) causes noticeable imbalance (uneven sound, slight juddering of the handlebars and windshield) that I can feel, see and hear when rolling the the throttle on.
Temperature, wear, vibration and movement (no lock nut) eventually cause the adjustment to change, but now it's so easy to fix that I don't consider it an issue. Once you try this method, and see for yourself the precision of adjustment it allows, you will understand why vacuum gauges are a total waste of time.
PS- to those of you who still believe that bench syncing carbs at higher rpm's under no load is important, I can attest that a turn in either direction creates no perceptible difference at anything over 1/8 throttle in actual use.
I might try to post a demonstration video later. You obviously will not feel a difference watching a video of it in operation, but I'm confident you will be able to hear and see the vibration I am mentioning and how easily it can be tuned out.
I could have simply left everything stock and left one adjuster nut loose at the carb for toolless adjustment, but I didn't want to have to bend down to reach said adjuster.
it would have to be removed to do my mod.
I cut back the upper cable housing (#6) and I JBwelded a nut to it. I shortened the adjuster from an old throttle cable and ran my upper cable through it. This adjuster now has a total of about 3mm of usable range. That's the most I could have and still have the cable seat at about the same distance as it was in the unmodified housing. I guess I could have left the new adjuster longer if I wasn't worried about the cables looking even where they exit the housing. I probably could have made up the difference on the lower(carb end) adjuster but I wanted cable symmetry exiting the housing.
Now, I can rotate the adjuster in or out about 1.5 mm while sitting at a light, just to get that sweet spot while transitioning from throttle stop screw holding the butterfly to cable pulling the butterfly. Keep in mind that to sync 2 carbs you only need to adjust one cable.
When in the sweet spot, I get perfect sync; turning it a bit in or a bit out (as little as 1/8 turn) causes noticeable imbalance (uneven sound, slight juddering of the handlebars and windshield) that I can feel, see and hear when rolling the the throttle on.
Temperature, wear, vibration and movement (no lock nut) eventually cause the adjustment to change, but now it's so easy to fix that I don't consider it an issue. Once you try this method, and see for yourself the precision of adjustment it allows, you will understand why vacuum gauges are a total waste of time.
PS- to those of you who still believe that bench syncing carbs at higher rpm's under no load is important, I can attest that a turn in either direction creates no perceptible difference at anything over 1/8 throttle in actual use.
I might try to post a demonstration video later. You obviously will not feel a difference watching a video of it in operation, but I'm confident you will be able to hear and see the vibration I am mentioning and how easily it can be tuned out.
I could have simply left everything stock and left one adjuster nut loose at the carb for toolless adjustment, but I didn't want to have to bend down to reach said adjuster.
Mechanic from Hell
"I remember every raging second of it...
My bike was on fire, the road was on fire, and I was on fire.
It was the best ride ever!"
"I remember every raging second of it...
My bike was on fire, the road was on fire, and I was on fire.
It was the best ride ever!"
Re: Syncing carbs R100s
I'd like some nipples soldered to my mixture screws for on the fly tweaking.
Just right for those long down hill mountain runs where the mixtures telling you where it wants to be.
Just right for those long down hill mountain runs where the mixtures telling you where it wants to be.
Lord of the Bings
Re: Syncing carbs R100s
Good idea!
A short brass T handle made from brazing rod and tacked on to the head of the screw would work.
maybe I'll do that....
A short brass T handle made from brazing rod and tacked on to the head of the screw would work.
maybe I'll do that....
Mechanic from Hell
"I remember every raging second of it...
My bike was on fire, the road was on fire, and I was on fire.
It was the best ride ever!"
"I remember every raging second of it...
My bike was on fire, the road was on fire, and I was on fire.
It was the best ride ever!"
Re: Syncing carbs R100s
June 2024 - I just wished to thank you for this procedure set out here. I had been struggling to get it right but on my 2nd attempt using this process I achieved a v smooth R100rs 1978 Motorsport. Thank you so very much. David
Re: Syncing carbs R100s
June 2024 - I just wished to thank you for this procedure set out here. I had been struggling to get it right but on my 2nd attempt using this process I achieved a v smooth R100rs 1978 Motorsport. Thank you so very much. David