Stuttering while accelerating?

[3Phase]

Cap'n, it's too bad my laptop died in a tragic coffee incident on a cross-country trip, all I have is the desktop machine and it's not going anywhere near the garage.

That's a nifty little gadget but where would I keep it?

The space under the right-hand cover has the spare TCI, the left has the registration, tire removal cable tool and the toolbox but I guess I could ditch the bar of soap.

.

[CaptonZap]

Now Scott, you are supposed to have learned by now that you fix the bike AT HOME. Where storage space is not an issue. (Or maybe not, as I look at my garage)
I mean, the Nano is no larger than some cell phones, and can be recharged from a USB port.
And can you really use a laptop as an O-scope?
What won't they think of next?


CZ

[bkham1972]

stuttering

I have the same bike, same pipes, it does the same thing, what did you find? I think its jetting, wondering where you ended up with jet sizes.

[bkham1972]

new to site, not very good on the computer, trying to find out what Gramin ended up doing, any help is appreciated.

[Graman]

Hi bkham. Welcome aboard.
I changed the main jets from the stock 137.5 size to 142.5. 2 sizes bigger. I probably should of increased the pilot jet 1 size at the same time but didn't. To be honest I noticed really no difference in the performance of the bike and it made no difference to the crap out at 4500 rpm. Right now I am just waiting until I have time to adjust the valve clearances before I try anything else. I will probably pull the carbs again and try increasing the float height a touch. I may just put the stock jets back in or up the pilot jets 1 size. Not sure yet. The battle goes on. You are going to find this site a wealth of information. I advise reading this thread from the beginning. I know it has wondered off topic a few times since I started it but there is some very sound advise from a few of the gurus on the site. Checking coil pick up wires and such. Mine were good but you never know.
I did however solve my bouncing idle problem. It turned out that 1 of the new Dyna coils I installed a few years ago was bad. I managed to get a set of old Honda CB750 coils from a local shop for $40 and put those in as a test. Problem solved. Bike now idles @ 1100 rpm solid as a rock.
Please stay in touch with any solution to the crap out. I will never surrender.

[bkham1972]

graman, just being lazy, not wanting to r&i the carbs any more than needed.after I put the mac 4into2 set on mine crapped out about 3600rpm.got a jet kit from sigma, put in 140.5 on1&4 cyl 142.5 on 2&3, put 45 pilots in &raised the needles 1 notch, now it craps out about 4300, it will stutter to about 6000 then smooth out, but it does not pull as hard as it used too. not sure if rich or lean, plugs look ok to me. I will post the results of my next try, but I am sure it is in the carbs. tks, bkh

[Graman]

It sounds like we have almost identical problems. What did you adjust your float height too? I am curious about the jet sizes you used. I have never heard of using different size jets for the carbs. Not that it isn't a good idea but what made you use different jets in 1 and 4 than in 2 and 3?

[bkham1972]

left the floats alone because it ran fine before the new exhaust system. as for the jet size diff. I had read that our model xs tended to run lean on 2&3, after checking my plugs I had to agree, 2&3 were always light gray, 1&4 much darker. also when I removed my old pipes 2&3 were white inside, 1&4 were black. Also the instruction from the place where I bought the jet kits from recommended one size bigger for 2&3. I am going to try lowering my needles 1 ring lower than they were at the start. I think if it makes an improvement I'll have a better idea which way to go. Believe me, I have considered many options.

[Graman]

Very interesting and I tend to concur. My #1 in particular has always run richer than the others. The #1 plug will always be a little fouled when the others are clean even though the idle mixture is set the same on all 4. Where do you have your mixture screws set? Mine are about 2 turns out. I was also considering raising the needle height. I actually had this problem before I changed the pipes although it did become much more pronounced after. I originally had an ugly black 4 into 1 header on it that was installed by the original owner.
It's nice to have a partner in the battle.

[bkham1972]

mine are about the same,2 out or so. From what I can gather the needle jet is controlling the fuel mix at about the 4 to 6k rpm range, by raising my needles it should lean it a bit. Just a guess on my part, but I'm gonna try it. I also enjoy having you to chat with, also if any other members have additional input PLEASE jump in

[TopCatGr58]

Hey there Bkham and Graman,

It's around this time that Motoman would probably chime in with many pearls of wisdom, but he's a bit pre-occupied at the time being!

SO...I'll chime in a bit. First off, the early years of the XS11's were jetted with richer jets for the 2-3 because they didn't cool as well as the outer cylinders 1-4, and so Yamaha thought that a slightly richer setting would help those to not run as hot, but they abandoned that scheme later on, it really wasn't necessary to stagger them.

Raising the slide needle RICHENS the mixture because it opens the pathway thru the main jet needle/emulsion tube sooner with less vacuum and lifting of the slide.

Putting aftermarket pipes should NOT prevent you from being able rev the bike under load to redline, at least in the lower gears. I have the 81SH, it was jetted quite lean from Yamaha for EPA by then, 110's across all 4. Remember these are the later style that used smaller mains because the pilots get their own supply from the bowl, not shared thru the mains, so they don't need to be ~137+. In my foolish youth, I took off the OEM pipes and put on a 4-1 set to get "more power" ! I did NOT rejet the carbs, rode it for 8 years that way, and could still run it to redline in all but 5th gear.

I can't see the signatures now, so can't recall exactly, but one of you has the OEM airbox with drilled bottom, don't know what the other one has...OEM or pods?

I haven't re-read the whole thread, don't remember if it was one of you who actually started the thread, or if you just joined in later? But as Brant would say, make sure you've checked the ignition components first. The 79 has mechanical centrifugal and vac. advance, have you taken apart the timing parts and cleaned and lubed everything to make sure the timing plate moves easily without hanging up? Have you checked the timing while running with a timing light to ensure that it's advancing to the proper amounts at the different rpms?

T.C.

[bkham1972]

hey T. C.

I meant to say lower the needles....senior moment I guess. I also have drilled air box on my '79, like Gman. My problem started with the install of the MAC 4 into 2 set up,but I will check out the timing. I guess it's possible that the MAC has more back pressure than the stock. At any rate, just trying to get it to run better or worse, then hopefully I will have a better idea which way to go. Your input is apprrciated. thanks a bunch.....

[bkham1972]

stutter gone

runs great now, only tested about 20 miles,but I am happy with the way it runs. Needles are now at the groove one below the top,thus lowering the needles 2 positions from previous position, floats 25mm, pilot screws out 2 turns,have nice idle at 1050rpm,stutter is gone! pulls nicely to about 6,000rpm then pulls even harder to red line. good luck with yours G man.

[Graman]

Congrats! That's great news. So by adjusting the needle clip up 2 positions you actually leaned the mixture a fair bit. You have possibly saved me from going the other way. Thanks. Did you adjust your floats to 25mm or were they set there to begin with?

[bkham1972]

most of the floats were off by an 1/8th'' or so,adjusting to 25mm lowered the fuel level in the bowls a tad bit. Haven't had a chance to ride any more since my last post, but I was sure tickled with that first test ride, good luck with yours, look forward to reading a post from you telling me yours runs better !!!!