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R75/7 Carb adjustment

just my preferred method

I prefer my carbs be in sync at 3 to 4 thousand rpms. I like both carbs to lift at the same time. But how many miles do you cover at idle? Get them as close as you can at idle, but I will always do the final setting at operating speed. You will need manometer, carb tune, twin max or whatever to set them at operating speed.
 
Grounding out one cyclinder is not recommend with electronic ignition, it is ok with older models with points and condenser. I didn't see this point stressed.

What is NOT recommended for the electronic ignition is to lift the spark plug cap off the cylinder while the engine is running. And it's probably not good to do even with points/condenser. It was acceptable to do with the pre 1970 /2 bikes because most were magneto ignition and they had a safety gap which allowed the spark to find a path to ground. That is the key to any of the ignition systems...the spark must have a way to get to ground otherwise that excess energy stays in the system and can cause harm...especially to sensitive electronic ignitions.

Personally, I don't see anything wrong with plug shorting on an electronic ignition. The reason is your are providing that path to ground through the screwdriver. This does not effect the ignition. I've done it multiple times on my /7 with Dyna III ignition system.

Now, if a person has trepidations doing this and they're not crisp in the movement of the screwdriver shaft on and off the shorting extension while at the same time touching the engine fins, then maybe a different method of synching should be considered.
 
I prefer my carbs be in sync at 3 to 4 thousand rpms. I like both carbs to lift at the same time. But how many miles do you cover at idle? Get them as close as you can at idle, but I will always do the final setting at operating speed. You will need manometer, carb tune, twin max or whatever to set them at operating speed.

This is something to consider however, the point where the difference is vacuum can more easily be felt is just off idle. You could end up with some hesitation as you transition from say a stop light and pull away.

But remember there are three adjustments to the carb synch - idle mixture, vacuum just off idle, and cable tension. They each affect different aspects of the carb operation. By adjusting the carb at 3 to 4K RPMs, you're effectively only checking that you have the same cable tension and/or that the slides have been moved to a common point such that each cylinder is pulling the same. You wouldn't necessarily have affected or helped the operation off idle.
 
Kurt, we are in agreement

Didn't intend to say that idle and simultaneous lift off of the slides are not important, however I still believe that sync at the rpm the bike operates at 80%+ of the time is important, and that can only be checked with a vacuum gauge of some kind. If adjusting the sync at operating speed causes stumbling because one of the carbs is not being opened at the same time, then there is another problem to deal with.

I had a similar problem with the 90/6 with timing. If I set the points so I was perfect at idle it would start great and was good at low speed, however i was not close on timing at speed. Had new timing chain installed. New points (several of them) and still couldn't get it exactly right. My solution finally was to install the Alpha ignition. For the first time the old bike's timing is perfect at full advance. It is smoother and more powerful than I could ever get it with the points. Now the old beast is perfectly happy cruising at 80mph. A lot of my carb issues were solved. Should have said perceived carb issues.
 
The Alpha ignition can take care of a host of issues, especially if they're tied to a worn out advance unit. Since the Alpha is crank-fired (I think that's correct), that's better than the stock firings off of the camshaft. :thumb
 
Didn't intend to say that idle and simultaneous lift off of the slides are not important, however I still believe that sync at the rpm the bike operates at 80%+ of the time is important, and that can only be checked with a vacuum gauge of some kind. If adjusting the sync at operating speed causes stumbling because one of the carbs is not being opened at the same time, then there is another problem to deal with.
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Right there with you on the sync at operating speed..........What is it doing at 4K??.......Make sure you have a really good fan on in front of the cylinders, If stumbling at speed or hesitation with a roll-on, it's time to check out the diaghrams.......pardon spelling...Using a surface pro 3 and often the spell check is really hard to use......God bless.....Dennis
 
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