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Old 08-24-2012, 05:10 PM   #1
scout18 OP
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airhead noob

Hey there folks I got this cool 1974 r75/6. It has dual plug heads and 900 jugs with high compression pistons and runs great, rides great. It just doesn't like to idle smoothly I know that there is a ton of information here covering this. BUT. Are there any inmates in the Portland Oregon area that wouldn't mind meeting up and showing me just what I need to do to sort this out? please pm me or email me jaredscout18@gmail.com. Thanks.
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Old 08-24-2012, 05:27 PM   #2
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What carbs do you have? Bings? Yes, many inmates can help you. Bings (if that's what you are running) are easy to sort out.
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Old 08-24-2012, 06:29 PM   #3
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Yes Bings. I'm pretty handy. I have the Bings one turn out on the idle air screw and it starts easy but it's very lumpy at idle hot or cold. While I'm riding it runs well and pulls hard from all gears. Between 4000 and 6000 rpms it's smooth as glass.
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Old 08-24-2012, 06:59 PM   #4
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You running points or an electronic ignition with the dual plug setup?


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Old 08-24-2012, 07:01 PM   #5
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Sounds like a balance and fine tune is in order.

Plenty here can help with that; Portland? Dunno.

Do you have a carb balancer of some sort or access to one (buying one wouldn't hurt).
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Old 08-24-2012, 10:39 PM   #6
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Sounds like your points need looking at, they are a pain in the arse to do and end up being neglected as well as badly adjusted. Fitting a boyer is a good move, just don't buy the cheaper Boyer black box, buy a Microdigital. The cheaper unit has an analogue curve that doesn't match the engine.

If you don't want the expense of an electronic ignition then theres a tool available cheaply to take the pain out of adjusting them --> Linky
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Old 08-25-2012, 06:27 AM   #7
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I prefer the booster box instead of an electronic advance. You keep the mechanical advance OEM unit and you keep the points. If stuck somewhere because of box failure the stock points can be rewired in a mater of minutes. This is the one I have;

http://www.dynaonline.com/skins/prod...ikes/boosters/

As long as the stock ignition works fine and fires evenly this unit will take the higher voltage off the points so they last a long, long time.
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Old 08-25-2012, 06:57 AM   #8
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Quote:
Originally Posted by scout18 View Post
Yes Bings. I'm pretty handy. I have the Bings one turn out on the idle air screw and it starts easy but it's very lumpy at idle hot or cold. While I'm riding it runs well and pulls hard from all gears. Between 4000 and 6000 rpms it's smooth as glass.
Do all the tuning things as recommended by these fabulous inmates. Old gas, water, and corrosion can easily mess up the idle circuit. I would take the Bings off, disassemble and thoroughly clean 'em. After installing and adjusting, check for vacuum leaks - that will affect idle. Points work fine; they are simple. I have the Boyer system and it has been reliable for many years.
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Old 08-25-2012, 07:25 AM   #9
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I second Disston the dyna booster. It's just the best Bang for the Buck as far as ignition systems on the points style engines (especially the 70-78 models)
If you're running Dyna Red coils because of the dual plugging you shouls already have some kind of boosting system, if not that may be the problem.
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Old 08-25-2012, 07:42 AM   #10
Bill Harris
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And if it is an R75/6 with "900 jugs with high compression pistons" lordy knows what has been done to it. Start out with a complete major service, check everything including the carbs and jetting. That will be a starting point unless you can get feedback from the PO.
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Old 08-25-2012, 12:12 PM   #11
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Dual plugged points HAVE to have a Dyna booster. They cook otherwise. The advance needs to be modified in order to time dual points correctly. Where is the timing at idle? OT? That could be your problem right there.

One turn out? That is NOT the way to adjust mixture screws. Find the lean stumble point and the rich stumble point and adjust half way between. The screws are very often adjusted differently.

Mixture screws adjusted thusly and still stumbles? Leak down test and listen for leaking valves. They will not idle right with leaking valves and I find them leaking often.

Good luck!

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Old 08-25-2012, 12:51 PM   #12
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So I still need to short out one side then the other to find the stumble points then tune the idle screws for air flow I guess.
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Old 08-25-2012, 12:54 PM   #13
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Is there a special tool for snorting the plugs other than a spoke nipple adaptor.
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Old 08-25-2012, 01:26 PM   #14
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Quote:
Originally Posted by scout18 View Post
Is there a special tool for snorting the plugs other than a spoke nipple adaptor.
Jeff Trapp makes a plug-shorting tool for carb balancing, and includes instructions; http://www.northwoodsairheads.com/Tools.html
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Old 08-25-2012, 02:54 PM   #15
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There is no need whatsoever to short out the plugs while adjusting the mixture screws. Just do one at a time while they are both idling. It is as simple as that. If the engine dies at the lean point, keep track of where it was and start the engine back up. Keep track of your turns as if the screw slot was a clock hour hand and set it half way between the stumble points while both cylinders are running. It could be 12 hours from stumble point to stumble point on one cylinder and and six hours on the other, for instance. It varies.

Personally, I wouldn't short a cylinder out for any carb adjustment. There is absolutely no need to be chasing a setting while the bike is constantly getting over a flooded and fowled cylinder. That is what is happening to the cylinder that is shorted out. It takes our engines quite some time to completely get over being on the side stand. Same story with shorting out a plug. Oil and gas build up. Go figure. Good luck!

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