Don't hurt me, I searched I promise! - 78 VM22** pilot Jetting on my GS550

[Guest]

So after looking around, and not finding anything I'm here asking for help, if anyone has been down this road I would really appreciate the info!

to start, I rebuilt the carbs last year, stuck them on, lifted the needle 1 or 2 notches (can't remember) but in the end even though the bike seems to be consistent in acceleration and pretty damn strong, it's running lean pretty much from mid-high rpms, idles good etc, but gets hot fast. so I've poured over info here, anything I can find for reference to the changes I need to make and I'm looking at 95-105 Main jets and 17.5-20 Pilot Jets. (from 80 Mains and 15 Pilots) (probably just 100-20's and use my needles and screws for adjustments.)

The problem is, the Bleeder(Pilot Jet) system in 750 carbs shows this (sourced from the VM carb rebuild tutorial on bikecliffs site)



and when I rebuilt my carbs I found this where the single Pilot Jet is in the 750's VM26's:


now the one on the left is listed everywhere as the actual Pilot Jet, my problem is that my bike is in a garage who's door is buried under 5 feet of snow, and I'm going nuts wondering if I should be ordering something for that piece on the right... someone who's taken one of these apart is bound to understand their orientation, I'm just wondering if I'm going to need to try to bore it out slightly, or replace it when I replace the Pilot Jet. I can't find any information on that piece anywhere.

TBH I Imagine the reason I can't find info is because it doesn't matter, but I have to know for sure >.< I just don't want to have to wait until spring to find out :-P

[tom203]

"....end even though the bike seems to be consistent in acceleration and pretty damn strong, it's running lean pretty much from mid-high rpms, idles good etc, but gets hot fast. "
I don't see how this a pilot jet problem? What do you have for airfilter, and exhaust? Spark plugs?

[78550GS]

I am running 15 pilots, 105 mains, and pods. Mine runs good with the stock exhaust.

[Steve]

I'm with Tom on this one. If it is not running well at mid-high RPMs, it's not a pilot circuit issue.

More important than engine speed, though, is throttle setting. Are you reaching those "mid-high" RPMs with half throttle or full?

The general rule of thumb for jetting changes usually calls for 4-6 sizes up on the mains for pods. Depending on whether you have some quality pods or EMGO crap, you will probably need something in the 90-95 range, so your current 105s are just too big. The best way to tell, though, is to do some plug chops and read the plugs. THEY are there, in the heart of the action and can tell you exactly what is going on. We can guess and get you close, but your plugs will be your definitive tuning guide.

.

[1978gs550]

K my bad for not including all relevant info, the bike currently has completely stock carb settings (80 mains and 15 slows), cheap pods, which I oiled a bit, and a cut off exhuast, I did buy NGKR plugs for it when I got it because it had a bunch of mismatched car engine plugs in it.

It's hard to see from the crappy phone pic, but this is how I bought the bike in august 2013, no air cleaner, no intake boots, and cut off/rotted off exhuast, I got it running last year, I'm putting home jobby mufflers on it in the spring, (link in the sig to see the most recent incarnation of the bike) it's still nearly stock compared to most of the cafe/brat mods I've seen on this site, It's a slow budget build. which is why I'm jetting the carbs now as opposed to when I rebuilt them the first time. I know it's never going to be one of the highly coveted full stock restorations most of the folks on this site want to see, but this is THE place to go for info when it comes to these bikes. The need for jetting is obvious in that my pipes are blueing from a 3 minute jaunt up the road and back with it. and with that much flow going I figured I should bump the idle circuit, because once my mid-high revs (couldn't tell you rpms btw still missing my tack cable) are fixed I can forsee a change in the way it's going to behave in the rpms between idle and mid, TBH I don't think I've maxxed the throttle yet because I knew it was running lean and didn't want to destroy my rings or bore.

I'm not saying I know more than you guys, I couldn't hold a candle to the vast majority on this forum, but I tried really hard to read and understand theory and practice based on the 20-30 pages of back and forth between the stocker fans and the ones who have actually done it, which is why I've boiled it down to running either 95 or 100 mains with adjusted needle height for my altitude from sea-level (which is damn near 0) and compensated for pods and semi/open exhaust and if I'm going to enrich the main circuit then the majority of what I have read from the Mikuni literature advises that the idle circuit should be enriched as well to cover any losses between high idle to mid, and inversely mid to idle so that I don't experience any hanging idle or popping due to a lean/rich issue caused by a weak spot in my fuel curve.

I really hope that all makes sense, because I literally spent 3 straight days reading up, as well as countless throne sessions reading up on this stuff to try to get a grasp on it.

but to get back on track.... does anyone know if I need to do anything with that short bleeder jet that goes in over the actual pilot jet?

[tkent02]

Lose the cheap pods and cutoff pipes. It will never run right with that crap. Get good pods and a good pipe. The 550 is different from the 750, it is supposed to have that second part shown in your second picture.

[greg78gs750]

I think most here will agree that you will be best served by starting in a bone stock configuration (airbox and a real exhaust) and moving out from there. unless you really know what you are doing, it is going to be a long road to get things right with cut off pipes (pretty much universally viewed as obnoxious) and cheap pods.

[OldVet66]

FYI, even with the GS1000, Pilot jets are recommended to stay stock size when re-jetting VM carburetors for high flow pipes and pods. Mains jets, needles and needle position are the only changes along with finding the right air and Pilot fuel screw settings. I agree that wide opened pipes and cheap pods are going to cause you headaches. Re-jetting for quality high flow pipes and pods is not exactly a walk in the park. What you are working with is a nightmare or impossible.

[1978gs550]

well this is all great and useful information, but what I'm gleaning from it is basically this: no one knows if I should try to find something to size up the unknown piece. Else-wise the majority of people refuse to read, see what they want to see and make assumptions without research. I won't get new pilots, *bonus* it is a LOW BUDGET build of a previously doomed half useful parts bike. so that's less money, AND I don't have to worry about the piece I was asking about in the first place and got a half answer about. for anyone interested in the future of my bike link in my sig, and to be clear, yes I've been sarcastic a little bit, but after asking the question, explaining that I'm not just pulling numbers and logic from a dark smelly place, and pointing to my build thread for further consideration of my point, this thread has turned into a PPP thread. --- which would be fine if I was asking for advice about jetting in general, and ignoring the millions of other posts asking the generalized what jets should I use nightmare question. but thats not what this started out as, was not my question, and as I said before I'm not captain GS of the S.S. resource knowledgebase, I know how to read, and interpret information, I know how my bike runs as is, and also that without a dyno with a fuel air sensor and a bunch of tools I can't afford I can't get it exactly right ever. and if I had that kind of money, I would have spent it restoring the bike to original and sold it because that's not what I'm interested in. I love my bike, I love being able to do what I want to do to it because that's how I do things, I would also love to eventually have a fully stock 750 or 850, because after some short riding time I feel like my 550 is actually probably a little small for me. but it's good to learn on, riding and mechanically. ok, so maybe thats just one hell of a rant... but I'm kind of annoyed that this thread turned into something far from what it was intended.

[chuck hahn]

Go to the CARB OEM SPECS STICKY at the top of the carb forum...550 is like the very first bike listed.

[chuck hahn]

Save this chart somewhere..

[1978gs550]

Also, I've renamed my project, as of today, it is titled "The Impossible Nightmare"

[1978gs550]

chuck, I've seen this chart and have it bookmarked, please refer to post #9

[SVSooke]

Also, I've renamed my project, as of today, it is titled "The Impossible Nightmare"

Until you spend some $$ on decent pods and a proper pipe that's what it will be.I get the not having the bucks to do stuff.

[OldVet66]

I wouldn't get an attitude about it. Enough people have "been there and done that" to tell you the way it is and no one is refusing to read what you said. Your project will not work unless you get either quality pods on the bike and mufflers or revert to stock. There are lots of cheap stock Harley mufflers out there. That part doesn't have to cost much but quality pods are necessary. Stock jetting, cheap pods and open pipes will trash your motor in short order. I have a motor in the garage that is damaged from running too lean (future big bore project). Your bike can be jetted for high flow intake and exhaust, but it is not an exact science, every motor is different and what works on one may not work on another. We are just trying to nudge you in a direction where the variables are in a controllable range and you have a better chance of success. Your bike isn't a great candidate for modifying (not much return for effort and money spent) so there isn't a lot of people who have done it. It will work, it's a mini version of my motor, same type carburetors and similar design. Things like cheap pods have failed enough times that they are known to make the job near impossible. The same goes for open pipes.