First Ride - Post Restoration - Mixture Settings

[Mike V]

Took the first ride today after the initial break-in procedure (3500 rpm 2-3 minutes). I had a hell of a time getting the thing to run at all in the low to mid range. I had set the idle and mixture screws at the static settings specified; idle stop screws at 1/2 turn and mixture screws at 3/4 turn. Drove me nuts, I had no idea it would be so far off.  Basically starved for fuel, ran great at full and 1/2 choke and ran beautifully except at idle. I immediately dropped the bowls, rechecked the floats wet and dry, blew the pickup jet clear and ran a copper strand through it. Checked the main jet, removed the mixture screws and cleared everything I could with the carbs assembled and on the bike.  Checked fuel flow and the plugs. Checked the spark - violent spark at both grounded plugs. Plugs were moist but couldn't rely on that since the bike was running for such a short period of time and on choke most of the time. Checked the valves...good. Damn, everything was good! Except it was rough as a cob below 2250 rpm. So, put fresh plugs in it and decided I would try (quickly) to turn the mixture screws out (ccw = enrichen). Half turn, 3/4 turn, and it came to life. Didn't want the new motor to idle any longer than necessary so quickly jumped around to the other side and did a quick balance by ear and dropped the idle down.  Running pretty damn good now. Did a quick 5 mile loop and the thing runs so sweet, quick responsive and pulls hard in all the gears. Brakes are 10 times better than I ever imagined an airhead to ever be.  Still a little rough in the low & mid but I'll work that out later.  Gotta get some miles on it first.  Well, gotta get the title cleared first - then the rides will come.

I'm just curious where you guys idle mixture settings are? I'm sure the motor is going to change often until I get a few hundred miles on it.  It really threw me for a loop for a while today.  Feeling much better at this point. I'll get the bugs worked out soon. What a sweet bike!

[nhmaf]

I think that my mixture screws are around 2/3 or a turn or so.  Depending on your jet size and exhaust and air filter (all stock?) this might still result in lean running, or be perfectly fine.   It is an adjustment on almost every bike is slightly different.

[Mike V]

Ooooohhhhhhhh. The Keihan exhaust?  I doubt the removal of the pulse air would have anything to do with it. You guys are good. I'm probably at 1 1/4 turn.  But this is all by ear and when I get a balance device on it I'm sure it's going to change still. It has some settling-in to do.  I'm just happy I got it to idle well and respond off of idle through the low and mid range. It already has some spunk to it.

I love these 650's!  This thing is like a cat.

Thanks nhmaf.

[Barry]

As nhmaf said every bike can be different. Glad you got it running well Mike

What interests me is that your experience seems to confirm my own view that idle mixture settings effect running in the low/mid rpm range above idle to far greater extent than many people think and it is important to get them set right for good performance and economy.

[Mike V]

Barry,
Couldn't agree with you more. I know this is a highly debated subject. I can only comment on my personal experience. I've found idle mixture, balance, and cable settings to be key to an efficient and smooth accelerating motor. I've done all the procedures and what I've found is one of the most important; is finding that critical balance just off idle and in the 2k range. When I can achieve that - it makes for a happy motor. I'm a little persnickety when it comes to cable free play which makes the process a little more difficult to obtain. I'll get her dialed in with time and some miles. Everything is newly rebuilt on this bike and I'll have to be patient with letting her tell me when she's ready.

[ukzknos]

Mike

You may recall a similar post that I started a few weeks ago, ref. Mixture?

I had the same symptoms. I set the mixture with a colortune so was pretty confident on mixture but still had your issues.

The fix for me was retarding the ignition advance by 2 degrees. Runs like a dream through the full range now!

Steve

[Mike V]

Thanks Steve,
Just got back from a 20 mile ride and stopped at an Airhead friends house to have a look on the manometer.  Tweaked her a little since after the first good run the idle creeped up too high.  Did a quick balance and she's running damned well.  Can't remember the last time I've had so much fun. I've noticed a very slight flat spot in 4th or 5th gear when rolling the throttle slightly - very minor and I'm confident the small issues will get worked out in time.  Lots of small changes going on right now but I'm keeping the screwdriver away from her and will let her air it out for a while.  I haven't even checked the timing. I will but I'm having too much fun riding her right now.  I'll keep you all in the loop when the critical tuning happens.

[Semper Gumby]

Colourtune Plug will help you set your mixtures right.

[montmil]

Mike, be very sure the engine is well warmed before attempting carb tuning and playing with the manometer. I usually ride 15-20 miles in mild weather and up to twice that when it's "Texas Chili" prior to hooking up the famous $4.00 manometer.

BYW, the manometer is the bomb for adjusting throttle cables for idle and higher revs.

Monte

[Bengt_Phorqs]

Just for the record, were valves adjusted and timing spot on?  I presume so since you just did a rebuild, but just asking.

[Mike V]

Yes, the timing was checked today and it was spot on.  The valves were set fat initially at 0.006" & 0.010" for break in.  I reset the valves at 0.004" & 0.008" tonight and retorqued heads. I've spoken to Oak and he's mentioned the Bing manual may be a little stingy in their published static settings.  And these bikes normally are happiest when at the rich side of things.  I'll continue my tuning in the near future. The bike is running exceptionally well, better all the time.  I'll richen things up and hopefully that will help cure the flat spot in the mid range.