idle mixture problem / colortune issue ? / Going insane ?

[dbeardslee]

I agree with MRO on checking your jetting. You should be able to control the 'sootiness' of your plugs with the float height. If you're already at 27mm, even with the earlier model carbs, you're close to the top of the range. To get your carbs dialed in you first have to select the proper size mains (if they're not right, nothing else will be either), then slide needle adjustment, then pilots and mixture. Here's a link to an excellent page on CV carb tuning.

When is the last time your valves were adjusted?

[TDodge7]

I think I'm going to just try to set it by ear again today , with the help of a friend with better hearing than me . oseaghdha , I think that may be the case , I've tried to let the bike idle long enough (with a fan in front) and I'm still in this situation , I'll just set it and call it a day . I'm a little obsessive compulsive and will worry about things that don't need worrying about a lot . As far as the previous jetting problem goes this is the back story . When I bought the bike it hadn't been run in many years , right off the bat I could only get it to run on 2 cylinders . About 40 carb cleanings and ultrasonic cleanings later I still didn't have cylinder 3 and 4 running at idle . A member here hooked me up with a set of 79 carbs , popped em on and i had all 4 cylinders but I also had one hell of a problem with running rich everywhere . The bike would completely hit a wall at 5k under load , and 6k in neutral . My kerker had no baffle and I wanted one so that complicated things even more . Anyway I got the new baffle , and of course was still having the rich problem . So I changed the main jets one size smaller (I accidentally said larger before but it wouldn't let me edit it) from 137.5's down to 135's , put the floats to 27mm , and drilled my air box bottom . Ever since then I've been able to go wide open all the way to redline with ease , before it would start bubbling and choking out on fuel at 5-6k and would refuse to give any more at 7k .

[Pat Kelly]

I agree with sync'ing the carbs. Since the plugs were different colors that would indicate some cylinders are working harder than others.

[dbeardslee]

The pilot towers in the early model carbs had a screw plug that sealed off the towers. There's a tunnel between the pilots and the mains, and that's where the pilots get their gas from. On the later model carbs (with the exception of some bastardized '80 carbs) the pilot tunnel is open and the pilots draw their gas from there. That's why the jets are smaller on the later model carbs than the earlier ones. If you dropped down to 135 you're already below where they should be, unless you're at high altitude. If you couldn't tune through the entire color range with colortune (yellow, bunson blue, white blue), and the carbs are clean, it's an indication that the jetting isn't right - assuming they're properly synced.

When is the last time the valves were adjusted?

[TDodge7]

I can adjust thru the entire range with the mixture screws , the plugs just don't want to go tan from just idling , only the two extremes , very lean or very rich , but as oseaghdha said

"Getting your plug color right by dickin with the idle is like, I dunno, cooking based on smell.
The plugs won't color in a helpful manner until you are at speed for a period of time. Plug color is for main jets not idle. "

Which makes sense now that I think about it . As far as the jetting goes the bike was crazy rich , changing the jets to 135 still wasn't enough to make it lean out enough to be able to go wide open , it wasn't until I drilled the airbox and put the floats to 27mm (suggested by some members here as a popular change) that it started being able to throttle cleanly up to red line . I would imagine that if I had to do all of that to lean it out enough to go wide open that now it should either be dead on or maybe still slightly on the rich side . not to mention that I've been doing all my test rides in the neighborhood so I haven't really been on top end . I was saving getting it inspected for when it was tuned and ready to go so I haven't been out on the road with it .

[TDodge7]

ok , a friend and I took a stab at tuning by ear , first we synched it , then we set the idle to 800rpm , then we turned each screw until we had the highest rpm . The result was a bike that ran like absolute crap , I double checked with the colortune and it was very blue on every cylinder , the bike was sitting there popping and backfiring . Then since I had the colortune out I went ahead and adjusted them all to where you first see a very yellow ring , then turned them all a 1/4 lean from that to put me somewhere between blue and yellow on all of them . Then I re-synched them all , The throttle response is much better but idle it's self doesn't sound quite as good as it did before , it surges ever so slightly while it's sitting there idling but it's only been like this for a few minutes , I've heard it takes a bit for the tuning to settle in though . Everything else feels awesome ....my friend says run it , what do you guys think ?

[TDodge7]

here is the video , maybe I'm just crazy and it sounds great , but with all the different sounds I've been able to make this bike make over the past few months I've lost track of what it's supposed to sound like .

[bikerphil]

Dude, that sounds just fine by me, smoother than mine, lol. Just go ride some miles and enjoy. BTW, Kerkers rock.

[TDodge7]

another

[Larrym]

Full ride Cycle=warm-up, roadspeed ride, cool-down

No reason to stop the countdown clock and put the launch on hold from what I heard.

Natural "loping" or minor "hunting" through the rpms at idle is totally natural for an engine with 95 hp with no load. Especially with a low back pressure exhaust.

Put a real load on it, some real cruising at roadspeeds, and some miles on it.

Don't forget to sit at a few stoplights along the way just to round things out. Not really "preferred" to spend a lot of time sitting at idle looking cool and all that. The bike is meant to go through the whole range of performance (temperatures inside the cylinders and outside) in a ride which just might result in the plugs experiencing that range as well.

Could affect the way they look afterwards too.

[TDodge7]

That's what I was thinking , but it did seem to run a tiny bit smoother before I adjusted things . I still find it odd that the best sounding idle mixture is way too lean , but I guess these just like to be rich .

[bikerphil]

Carry an extra spark plug or 2 and a ratchet with you for the time being, just in case a plug fouls down the road, BTDT.

[mro]

then we turned each screw until we had the highest rpm

27mm float height isn’t to far out for the BS34 II's but still might be a concern.

BUT adjusting the pilots …
Turn em out till you achieve highest rpm, then turn em in (counting each turn and partial turn) till it stumbles. Turn the screw back ½ way between the two. Putting them at the highest rpm will leave em rich.

mro

[TDodge7]

putting mine to the highest rpm made them way lean , to the point of popping at idle , not rich .

[DGXSER]

Check the plug color, sometimes overly rich will also pop at idle or decel as you can get fuel build up. JAT