Needle clip location different in each carb

plane_ben

XS650 Junkie
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Here are my thoughts. First a little back ground on my set up. I'm running the BS34 carbs(I think), they came off a 1970/71 engine. Pod filters and freeflowing exhaust. When I first stated running this engine setup, I was lean both idle and full throttle. So in my tinkering I opened both my idle jet, main jet, and raised the needle to its highest setting(clip on bottom notch). Runs great, first kick starter.

I did the XSJohn top end oil cooler, and it's working great. Altough I reported some bogus cyl head temps initailly(lower than actual), my temps now, after purchasing an IR thermometer are right cyl 230/235, left cyl 200/210. Pretty par for the course according to all my reading here on this site.

Yesterday I'm out for another ride when the bike started running irratic. I thought I had a plugged up fuel passage. Limped home. Today I took carbs apart. Nothing looked plugged. One overflow drain(right carb) was stopped up but that was it. Charging output and battery right where they should be. So I pull the plugs. Left cyl looks fouled, to rich. Right cyl looks perfect. I need to mention that these plugs are an unkown age and where replaced. New plugs cured the miss, and although old plugs were mostly to blame, I was wondering about the difference in plug readings. Wondered if doing kind of a reverse XSJohn mod makes any sense. Since the left cyl looks rich, what if I dropped the needle one clip. Would that make it slightly leaner and balance the head temps? Or am I totally nuts?:shrug:
 
I think your old plug just wore out or went bad. You don't compensate for a rich running cylinder by jetting it's carb differently than the other carb on this or any bike. That "suddenly rich" condition indicates you have a problem either with the carb or some of the ignition components for that cylinder. If you're still running the old points ignition, they're tough on plugs, wearing them out in as little as 2 or 3K miles.

If you have an adjustable needle in your carbs, they're not 34s, they're the older 38s. And no one I've ever heard of runs the needles in the richest slot. You generally change jets (mains and/or pilots) before resorting to that and if you need to run like that, it's telling you to change jets. I wouldn't say you're nuts, just not very good at carb tuning, lol.
 
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You're not very good at doing your homework, either: www.amckayltd.com/carbguide.pdf . Not very good at troubleshooting, either, so here it is, one more time: Do not screw around with the carbies until everything else, and particularly IGNITION, has been inspected and set right.
 
plane_ben,
Don't take it personally . Dick isn't Dick if he isn't being a dick on occasion . It could be worse . I am a dick and somewhat more harsh on newbs . In fact I just had one for breakfast .

~kop
 
Oh dear....both Pow and Kapow from both the carb guru's!

Hey 'plane Ben' good morning, how about we start at the beginning? Can you post a good picture of those carbs? Preferably, off the bike, with a decent view of the intake throat side. It's rare that someone could have/did put a linked set of Mikuni CV BS 34's on a 70/71 engine.

Jack Webb Dragnet style.....What are these carbs.....really? linked set? single or dual throttle control cables? Good pics will establish the facts, then the needles, jets and
settings follow.....sound reasonable? Best, Blue
 
That "suddenly rich" condition indicates you have a problem either with the carb or some of the ignition components for that cylinder. If you're still running the old points ignition, they're tough on plugs, wearing them out in as little as 2 or 3K miles.

5twins, My ignition is a pamco. My plugs in this instance were of unknown vintage, dumb I know. But they worked and I never got around to purchasing new ones until yesterday. Also, I'm running the BS38s. Thought they were the newer carb. My bad.

You're not very good at doing your homework, either: www.amckayltd.com/carbguide.pdf . Not very good at troubleshooting, either, so here it is, one more time: Do not screw around with the carbies until everything else, and particularly IGNITION, has been inspected and set right.

grixld1, Thanks for the link. Aside from the needles at the leanest setting, I'm right in line with your procedures. I've been doing this a long time on motorcycles and VWs. This is only the second time I've played with a set of CV carbs. All my other variables(timing, camchain tension, and valve lash) are spot on and were checked again after my little problem occured. As mentioned above, spark plugs were the problem. I think the sootyness I saw on the left plug was just a result of an old plug that had finally fouled out. I will keep an eye on the new one.

One of my concerns though, and I was just throwing out an idea, is the differential cyl head temps between left and right cyls. It bugs me and saw that XS john spent many years and developed his own needles to make the right cyl run cooler. Since my current 235 right cyl HT is not detramental to my engine operation. I was thinking of a way to raise the temp of the left cyl HT to balance out the two. I think I remember reading Kawaski triple tuners used to run a richer mixture on the middle cyl to make the top end last longer. Fouled a lot of plugs, but it was cheaper than topend siezures.

I used to fly with a friend in his Cessna 172. Four cyl aircooled engine. Sitting in the right seat, I'm right in front of the cyl head temp guages. I don't think I can ever remember all temps even, so maybe I worrying about nothing. On another note, VW engines for years had the oil cooler in the fan shroud, and would have higher cyl temps on cyls 3/4. When they went to the 1600 DP motor, they offset the cooler outside the fan shroud to give more air to 3/4.
 
In his 8-1 compression bike, xsjohn was tinkering again and this time it was plugs. He was running Autolite 65 on the left with the end (non twist off) ground down to fit in the cap and 64 on the right. Last post was he had 500 miles down on them and he could richen the left side and the color was the same on the plugs.
 
In his 8-1 compression bike, xsjohn was tinkering again and this time it was plugs. He was running Autolite 65 on the left with the end (non twist off) ground down to fit in the cap and 64 on the right. Last post was he had 500 miles down on them and he could richen the left side and the color was the same on the plugs

Any more details on this. Doesn't make sense to richen the left side. That's the cool side already.
 
John would adjust the carbs for color....what was set for one side wouldn't neccesarily be the same for the other.
He was running autolite64's on both sides and then went to the 65 in the left and said he could richen that side up a bit......that's all I know- what he said. This is for the 8-1 compression set up.
 
Just want to clarify you say the plugs are the problem but aren't they the indicator? What fuel tank / petcocks are you running?
 
Plugs were the problem. One started to foul out(left cyl). These plugs were in the engine when I pulled it out of the junk yard. Can't give you a reason I didn't chuck them and put new ones in.:eek: Just lazy I guess.

My tank is an old Honda 305 scrambler tank with two relocated petcocks. Lined with POR-15 tank sealent after I did the electralisis(sp?)deal on it.

tank24.jpg


pinstripe2.jpg
 
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