| Author | Message | ||
     Vortec57 |
Working on an 82 Yam XJ550R (seca). It runs great on the top end, but lower RPM it stumbles and bogs like it's about to die. Haven't gotten into the carbs just yet, but looking for someone to help me narrow it down, or confirm my theory. The way it bogs at low rpm but then comes alive HARD at mid to upper RPM I get the feeling that it's trying to say either the pilot jet or needle are too rich. The girl it belongs to says she never needs the choke to start it, and the time I rode it the bog wasn't as obvious right after starting it up, got worse as it warmed up. (continuing to lead me to believe it's rich at bottom) Anyone care to enlighten me or agree with me? | ||
| Mortarmanmike120 |
I'm not an expert but I'd check the needles first. If it's a stock bike with stock jets then it's probably just gummed up or something. A little debris or varnish could hold the needle higher then it should be, ie too much fuel. Plugs should tell you if it's running rich. | ||
| Vortec57 |
Thats a good point. I'm intending to check the plugs here in a bit. Just figured I'd go for some moral support first. Back with plug reading... | ||
| Mnbueller |
Disclaimer: I know little about bikes, but a lot about cars. Sounds like the timing is too far advanced, or stuck at full advance....does the bike have progressive timing like a car? | ||
| Strokizator |
I gotta believe that after 17 - 18 years, the carbs are due for an overhaul. Since they are stock, a simple clean-up should get you back to running good. I'm with mortarman in thinking its the needle. I've never seen pilot jets suddenly go too rich. Bike Bandit is showing parts are still available. | ||
| Mortarmanmike120 |
I definitely know my limitations when it comes to carbs. I suck. If you fail to get much help here in the quick board, I'd suggest posting carb questions in the Old School Buell or Thumper forums. Those bikes have carbs and the riders may be better able to help. I'm sure there's also forums for UJM bikes that may be of assistance. Good luck. | ||
| Mortarmanmike120 |
Good point Mnbueller. I'd guess the 82 seca has progressive timing. My 79 Kaw does. If stock, it seems to me though that a timing failure would cause high rpm problems not low/idle rpm problems? The idle timing is the fixed value is it not. The adjustment happens as rpms climb. Something else to check, is there an inline fuel filter? If not, I'd add one. Particles in the gas will end up plugging something important in the carb. Vortec, you will probably find that there are many things on an older bike that cause it to go loopy. The fix is rarely as obvious as hoped. But in the spirit of KISS, id clean the carbs first. Fixing a girls bike should definitely put you in her good graces. Good luck. | ||
| Etennuly |
I would agree with the gummy carb assessment if it spent much time parked. Needle and or float sticking. | ||
| Vortec57 |
We have a winner on gummy needles! Plugs were pretty black, but when I met her we flooded it trying to get it started (side of road with keys and knife for tools) cant get carbs out without doing some major disasembly (wonderful design on airbox) needles are cleaned up, seafoam in bowls, going to get new plugs and oil change. I know it's gotta be simple, these things are FAR from rocket science! Oh yeah, and she's super cute  | ||
| Fast1075 |
Couple of words of wisdom Vortec...no matter how big a pain in the ass the stock airbox is to remove...remove it carefully and undamaged...resist the temptation to leave it off and stick on a set of pod filters...if you do, you will open a can of worms with the low speed jetting...put it all back stock. Also...spring for a new set of pilot jets..they are easily gummed and not easily cleaned...save some grief...they should be common mikuni parts... | ||
| Mortarmanmike120 |
Oh yeah, and she's super cute Awesome! You're her hero. How come that shit never happens to me? x2 on keeping stock airbox. You do NOT wanna go pods. The airbox sucks to work around but performs far better then pods. | ||
| Vortec57 |
Looking for service manual to find out how to remove airbox and carbs. no worries, I wont pod this one. I already have pods on my cafe project, the factory airbox will never go back on. Its sold a long time ago, and the mounts are gone from the frame, other parts now in its place. Hoping for NOT having tons of trouble on that one, but its another story for another time How come that shit never happens to me? It never happened to me until a few days ago, had to make a detour home and just happened upon a cute girl broke down on the side of the road. Moral of story: make detours, keep an eye out for cute girls! | ||
| Aptbldr |
CV carbs: diaphragms are delicate expensive to replace. Diaphragms can be salvaged with light and flexible patching. |
