now what's wrong?!!!

[briyenkieth]

alright I got my charging system straight and a few more buggs worked out. Went for a test lap around town and all was good. Sat and ran in the gagage checking my charging no problems while idling. Got on the road to come to work and every thing was fine at first. After a few miles I could hear it misfire here and there but nothing serious. About three miles from the shop I lost a bunch of power,scary on the freeway during rush hour. When I got off it idled fine and would rev normal but when accelerating it stumbles all over it's self past 1/3 throttle. I'm not sure where to start. Atu sticking again? Carbs? Other than the poop at 1/3 throtle it runs fine and pulls strong up to that point.
It's a 78 400 with jc whittney muffs and emgo pods mains are a bit big at 132.5 currently all else is stock.

[almarconi]

mains are a bit big at 132.5

I think you hit the nail on the head. What do the plugs look like?

[briyenkieth]

not sure yet I'm still at work. Wouldn't a fouled plug affect all revs? or is it flooding? I'd have to guess fouled since it was fine at first.

[almarconi]

Have you done the usual maintenance such as valves and carb cleaning?

[briyenkieth]

fully rebuilt the carbs with new orings inside and intake boots and orings. According to the speedo i only have around 4000 miles on the bike so I don't think it's the valves. This was a sudden occurance, bike was fine this morning.

[briyenkieth]

tried adjusting mix screws to lean it out some. Tad bit better. Plugs probably fouled. Don't know for sure yet, stuck at work for a few more hours. Noticed that when I rev it and let go of the throttle it shots a small flame out the right side. What causes that? I've had few bikes do this and never understood why.

[almarconi]

Have you checked the voltage going to your coils? When was the last time you replaced the points, plugs, plug wires? Did you check your ignition timing? I'm trying to get a sense of what's been done on the bike. Hard to diagnose problems without some maintenance history.

Is your petcock working? Does it run better if left on prime?

You said you rebuilt the carbs, did you sync them?

[briyenkieth]

you would need details like that, duh! It's been a long night sorry. New points gaped per manual, plugs new and gaped, carbs have been bench sync'd don't have a vacume guage yet, 12.29 volts to coilswhen key is on not running. Would test running but ran out of gas on the way home and had to push it the last five blocks. No close stations open. Plus noise. Charging system is good just upgraded to a reg/rec out of an "Intruder". So no problems there, this is a brand new harness I made myself. Soldered all conections and have good solid grounds. Petcock flows freely and is not Suzuki so it has no prime. Btw this whole bike is modified sans motor.
Pulled the plugs when I got home but I really dont think they are an honest read. Being how I ran out of gas. I did put half a gallon in on the way to work so I had gas when my problem started. Also it ran fine on the way home. Figures!!! But as to the plugs they read lean but again I ran out of gas so I feel like that would have an affect on the reading. Am I right? For the first time ever.... Missed a couple of your ?'s. How do I replace the plug wires? I thought they were sealed into the coils. Timing is set it usually starts up no problem. The atu was stuck shut but I think I got that freed up. Maybe I need to look in there again. Just went back to photobucket and looked at my speedo, don't know what I was looking at but the bike has 35000+km on it. That's what about 17-18000 miles right? Might be time for a valve adjust. Who knows if it was ever done. Poor bike was beat and ready for the scrap when I got it.

[briyenkieth]

since I had no gas last night I did all I could. That being the ?able atu. Disassembled and sanded it until the springs would freely swing the weights back to the center. This afternoon took it out and what a difference, snappier throttle faster acceleration easier starting even idled smother. Around town I couldn't get it to act up in any way. Wasn't until the last few miles from work that it duplicated the problem. Only difference was I could power thru the spot. About third throttle I guess and extended cruising length, say 10 miles. Let off or roll thru and it goes away. It's just a light miss now not like it was yesterday. Checked the plugs after my test ride this morning and both showed the nicest tan I've ever achieved in my own tuning. I'll post back when I can get a plug read at this throttle setting

[almarconi]

Glad you got it sorted out.

[briyenkieth]

for the most part, yeah. I think the last bit of trouble is the main jet. I've been waiting for about three weeks for new ones to come in. From what I'm feeling 130 or 127.5 would probably be better. You mentioned swaping out the plug wires. How? Do I need to replace the coils? Thanks for the help.

[almarconi]

If you have the wires that are molded into the coils then you need some NGK plug wire splicers. Cost about $4 and allow you to add new wires to your coils.

[briyenkieth]

that makes sense! Read a thread earlier about yanking out the old wire and glueing in new ones. Seemed sketchy!

[almarconi]

Read a thread earlier about yanking out the old wire and glueing in new ones. Seemed sketchy!

I think your better off with the splicers. I wouldn't trust glued in wires.