Getting to know my new Super hawk. It's running really great, but as these things are so cold blooded, and I've only really brought it up to good engine temp on a couple longer rides, I'm still finding its happiest idle setting.
I just have a simple question about syncing the idle speed screws. Ed's guide says to back them out until the slides bottom out, then "turn slide screws in a couple of turns" and "Adjust slide screws to even cylinder speeds."
This is my first multi-cylinder bike so I'm not sure how precise this has to be and I'm also a little foggy on the fundamentals.
1. If the pistons are always moving at the same time (180 offset) wouldn't adjusting the idle on one carb also raise the speed of the other cylinder?
2. Can you just set them via sight, so if one is turned 3 1/4 turn out, turn the other 3 1/4 turns out?
Just looking for some general guidance. On my S90 you just turn the screw out until it idles nice and low. This is a bit more complicated.
I'm very careful and pay really close attention to sounds and feelings of my bikes, so I'm still learning what's normal and what isn't, and what the bike likes. We're still getting to know one another, hahaha. Having a blast so far though.
Thanks.
Syncing Idle Speed
Setting idle speed can be tough.
You'll have to also work with the pilot screw. I've had my best luck using my finger to feel contact with the screw. Then start turning them evenly till you find about 1000rpm. Then turn your pilot screws for peek rpm (maybe smooth would be a better description) Then reset idle screws if needed.Just over 1k is good when warm. I would not advice trying to find the lowest idle.As lugging the motor is hard on it. My understand of twins is sparse, as is my knowledge of the superhawk, but it seems like the left cylinder is not performing as well as the right cylinder in some way...... although I may just not have it warmed up enough, especially if these bikes are as cold-blooded as they say.
Seems to run just great as far as I can tell, but at idle, the left carb idle screw is not nearly as responsive as the right side idle screw. Also (and maybe you're not supposed to do this) but I was so baffled I ran each cylinder by itself for a moment. The right side cylinder kept idling when I pulled the left plug cap off, the left side went out immediately when i pulled the right plug cap. It got a little better when I twisted the left idle screw in more than the right, but again, aren't they supposed to be synced? Do you sync the setting, or sync the rpm of each? Shouldn't the setting be the same? Confused here.
You should first make absolutely sure your valves are correctly set, then check the plugs (gap & condition; new = better), after that check/adjust the points gap for both sides; folowed by timing. When that is accomplished, remove and clean the carburetors. When all the basics are in order, then you can start tuning.
Don't expect to tune the motor without establishing a reliable and correct baseline! There are many methods to balance the carbs - which is a critical performance item for any multi-carb motor - but you will need tools. I've used Colortune on some of my bikes to set the mixture, followed by Carbtune to balance the RPM. Where a vacuum port is not available, an electronic tachometer switched from side to side may be used. A procedure of taking alternating cylinders out (shorting the plug lead) is in wide use in the BMW Airhead twin world, to great effect. The 305 motors are just as capable of running on either cylinder at a time (which you've discovered already). The goal in that approach is to attain identical RPM, at least at idle (better across idle + the power range) with either of the cylinders under power. None of this is relevant, however, unless your baseline is in order. Don't skip the basics. -- Michael Stoic The engine is rebuilt and was tuned by the seller, it has about 500 miles on it since rebuild. He made it very clear to me that it is properly tuned in terms of valves, point gap, timing, etc, and it seems to show when you get it up to speed, the idle and warm-up is mainly what i'm curious about.
I realize idle is one of the last things you look at after the baseline. The idle screws aren't responding at the same setting, left side you hafta screw in further to get the rpms to go up, right side responds when it's further out. Is that normal? If I just get the rpms the same does it matter that the left screw is turned in, or out differently than the right side?
Did the seller install new points?
If so after 500 miles ya will need to adjust them as they wear to the shape of the points cam and don't open as wide as before and it changes the time of plug fire. ..........lm
Ed,
Andy bought the bike from me, and I set the points and timing before delivery. They do have close to 500 miles on them, as does the entire resto. I also changed the oil, and cleaned the slinger before delivery. The bike runs extremely well, and Andy needs to learn the quirks of these old bikes. Some time spent learing all of the basic functions will serve him well. Davo
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