octane

Hey Steve, I'm hoping you're around today. Took the bike out for the first time this season to go to work this morning. Oh, I'm keeping it. Had a lot of tire kickers, then a solid buyer who never showed back up with the money. I got tired of people hanging around my shop wasting the little bit of time I have out there, so I'm gonna ride it this season.

Anyhow, end of last season I had an intermittent problem where it felt like it was dropping a cylinder or not maybe getting fuel/vacuum. It was way underpowered, bucks like crazy, barely keeps up at 50 mph at full throttle (then kicks in and tries to chuck me), and occasionally will just stall altogether and I have to sit on the shoulder for two minutes before it'll start back up. It'll sound normal when it's at full power, but when it starts cutting out the exhaust note goes flat and it has trouble keeping rpm up.

Last summer I swapped another set of coils from a parts bike on, put new plugs in, checked all the connections and vacuum plugs, put a new fuel filter on, checked the fuel lines, and had D&D clean and synch the carbs. No dice. It was doing it a lot by the time I put the bike away, but not every time. This morning I fire the bike up to go to work and in my 15 mile commute it left me stuck on the side of 464 twice and is overall just running like shit. Any ideas? I'm going to swap a spare tank on it this weekend and see if that does anything. It's a long shot, but I was thinking this morning that it never did this before I had it painted...maybe a vent is clogged or something. If I pop the cap it doesn't help, so I don't think it's vacuum locking. When I was on the shoulder this morning I also disconnected one coil and started it, then put it back and disconnected the other coil to see if maybe a coil was dead, but it'll run on either cylinder. I'm stumped man. Any direction you could give me is appreciated...I'm not looking forward to the 15 mile ride home! Thanks man!

skr00zloose

when i first heard about your problem in your sale add i just figured it was paint clogging a vent too, but if you're popping the cap and it makes no difference, that ain't it. could be a fuel flow problem though. maybe a dirty petcock or something. there's a pre-filter in the petcock you might want to take a look at. if you pop out the petcock from the tank, you'll see exactly what i mean.
you say it doesn't do it all the time? intermitant problems like that are electrical alot of times. first things to check would have been the coils, like you did. i know you've got ALOT of work done to that bike,and it was taken apart a few times. maybe there's a bad connection somewhere. especially a ground. if there's paint on anything where a ground bolts on, it needs to be stripped where the ground attaches. including the coils. without a good ground for the coils, they won't work like they should. also check the resistance of the plug wires and caps. i don't know off the top of my head if they're replaceable or not, but i think they are. if the resistance is out of spec you could be just getting a weak spark. when you get into the fatter part of the carbs, it might not be strong enough to fire thru the mixture. i don't know your jetting, and how lean/fat it may be, but that could be part of the problem too. beyond that, i'd check the pickup coil and it's wiring, see if it's all in spec. i doubt it's a cdi problem, usually they just work, or they don't, but i guess it's possible too. i have seen a cdi that worked fine until it warmed up, then would drop a cylinder and/or completely shut down. cdi replacement is a last resort though. unfortunately there's no easy way to check a cdi other than swapping out a known good one and see if you have the same problem.

so anywho, check the petcock, check the coil's resistance, the plug wires resistance, and the plug caps resistance, the pick up coil's resistance, and check all the wiring in between. if eveything is checking out, get back to me and i'll help out in any way i can.

glad to see your keeping it too! that's a sick 500, i can't believe no one picked that up off you while it was for sale.

octane

Thanks man. I'm feeling like it's electrical too. I was planning to check the petcock screen when I swapped the tank. That screen is like 4 inches tall though and I have zero rust inside the tank, so I'd be shocked if the fuel flow was blocked at the tank. The GS vacuum petcock system is a big POS from the factory though...too many parts for such a simple purpose. I'd drop a pingel in there if they weren't so damned expensive. I may have a cdi from that old parts bike...but I may have sold it too. I hope not now!

Your ground idea just sparked something in my head. I checked all the ignition connections - but a few years ago I had some problems with the bike running and it ended up being a loose wire on the stator. I did do an ignition advance mod...I wonder if something is loose in there. Worth a look. I had sort of ruled out fuel based on the sound of the motor - what do you think of that? The exhaust goes so flat and the decibel level drops dramatically - even at high rpm. If it were fuel I'd think the sound level would be consistent, just choppy. The best I can describe it is like sitting at turn 17 at VIR - the jap fours come screaming by sounding like they're flying, then a Ducati comes by going just as fast, but it's got a flat, lazy tone. Does that make sense?

skr00zloose

lol, yeah, in a weird way, that makes sense, i know what you're talking about.

give a good once over thru the electrical system first, if you can't find anything wrong, let me know, i'll drive out and have a look (unless you want to bring it to me) and we'll go over it. some problems are hard to daignose over the internet. having the bike in front of me and being able to run it down the road makes a huge difference.

octane

Cool man, thanks.

skr00zloose

no prob mang.

and uh, since your gonna keep it.. you should let me ride it that bike is pimp.

zx636skiv

Glad you're keeping the bike...did the same with mine...now it's not as custom as yours...but getting there!!!

octane

I'll let ya ride it once it's sorted again! I still need your help with the rear suspension on the XS too. Too many friggin' projects over here!

skr00zloose

werd, just let me know.

speaking of which, you ever get that fz1 motor into that xs frame?

octane

No. Like I said, too many projects! I'm trying to finish one of the cars to make some room in the shop. I need to do some fit up on the XS though and see some progress.