On the road and stumped: hesitation/lurching during acceleration (among other things)

[azr]

I don't see how the carbs could be effecting the petcock. If your petcock is not flowing fuel to the carbs on prime then there is something wrong with your petcock. If there is something wrong with your petcock it could be the reason behind all your problems. it's pretty simple to test your petcock when it's not hooked up to the carbs. Suck on the vacuum line a bit while the petcock is in the "on" position and fuel should flow, the same when it's in the "reserve" position and fuel should flow when it's in the "prime" position with no vacuum being applied to the vacuum line. But really if it wouldn't flow when hooked up there's like an issue.

[klylor10]

Alright, this is getting weird.

I filled up the gas tank to full, and the petcock is flowing, seems to be running about the same as with the fuel bottle, although I don't see much fuel in the clear fuel line, just a dribble down to the carbs. I checked the petcock off the carbs, and res+on deliver fuel when I sucked on the vacuum line, and prime caused fuel to flow freely. I still have a hunch that this is a problem, but I'm hesitant to spend $70 to replace it if it's not an issue.

I took it for a ride with the full tank and it ran okay for a bit then gave me some of the old lurching problem I had and one of the cylinders went out (either 1 or 4, I can't remember). I came back and did more troubleshooting, and found that one of the wires from my 1+4 coil is firing intermittently or not at all, as the pipe doesn't get hot and the problem seems to follow the wire.

I checked the voltage on both coils, ranging from 11-19 (the meter jumped a lot), and the signal generator resistance measured slightly over (spec is 140-180, I got 185-188).

This is exhausting! Seems like new problems pop up every time I make some headway.

[klylor10]

The (hopefully) final update:

I finally got my bike running at midnight tonight. After 3 weeks and countless hours of work I think I've finally made it. I'll go on some long rides tomorrow to be sure while I'm near the safety of a workspace, but it feels and sounds amazing, better than it ever has.

From what I can gather, aside from all the necessary maintenance, the issue was twofold: ignition and fuel. When I installed the Dynatek coils, the mounting was a challenge, and at some point after installing them one of the primary wires got disconnected enough to make intermittent contact. For those using Dynatek coils in the future, careful, because they are not at all a good fit for the GS850GZ although they work very well. The wire problem I mention in my previous update was what tipped me off, and I dismantled the coils and put them back together carefully.

The fuel issue existed somewhere in the carbs, and the long dip (thanks for the push, oldvet) ensured that they were sparkly clean. I am still concerned about the petcock, but it seems to be delivering fuel at a fast enough rate. I'll have to run the tank low and see if I lose fuel flow.

I can't express how grateful I am for all the advice and the folks who stuck with me through this process. If any of you are between Arizona and Florida, let me know and I'll buy you a coffee/beer. I am continually blown away by the support on this forum, and am thrilled to be a part of it, even though I'm not at a level where I can offer out much advice.

I'm sure I'll be back. There's about 8,000 miles between me and home.

-Loren

[fastbysuzuki]

Hi been watching this with interest,t hope everything goes ok from herein let us know as you progress? Good luck.

[azr]

Fingers crossed

[klylor10]

Any thoughts on the petcock conundrum? Maybe I should buy a new one and have it shipped to my next big destination. I know it's recommended that they be replaced...

[azr]

If you tested it as described and it's not dripping out any fuel while it is in the 'on' position then it should be fine. But...it is 33 yrs old and will go eventually. I would have to guess you were tired and possibly not seeing thing right or something like that. Anyways....hows the bike running??? I keep meaning to ask as well, where are you staying while you've been stuck for weeks??

[OldVet66]

Petcocks can stuff up like carburetors but are not dip friendly, get a new one. Look up the stock number for Suzuki fuel line and use that after you are satisfied with fuel flow, it may just come in black now. If you need some PM me an address and I'll send you some on the way, I have enough to give some away and still have too much. Clamps are not necessary with this line, but I can send some tie locks.

[Gorminrider]

Petcocks come apart, but there are subleties in vacuum petcocks -it's easier to tell you that Turning the tap to prime will bypass these, while still allowing you to turn the fuel off (by turning to res or on) when the bike is parked.
There are screens to check if you remove it from the tank,

[OldVet66]

Petcocks come apart, but there are subleties in vacuum petcocks -it's easier to tell you that Turning the tap to prime will bypass these, while still allowing you to turn the fuel off (by turning to res or on) when the bike is parked.
There are screens to check if you remove it from the tank,

From all the rebuild failure stories with petcocks, I would just replace it if that is where you think the flow problem might be. I have seen the petcocks completely blocked up so it's not impossible that there might be a partial blockage. With the proper rebuild kits come the failure stories. I'm sure some have luck with it.

[klylor10]

Update: Sorry it's been so long since I updated y'all, but take that as a good sign. I'm currently in western Arkansas headed to Memphis soon. Everything has been great! No problems yet, fingers crossed. I've gone almost 2,000 miles since all this, and things seem to be all in order. I'll have to stop at some point before I get home to do valve adjustments again/syncs carbs, as I'll hit the 4,000 mile maintenance mark and will probably be another 3,000 from home at that point.

I keep meaning to ask as well, where are you staying while you've been stuck for weeks??

I was sleeping on someone's lawn in my tent the whole time. It was quite nice, actually.

[azr]

If the bikes running fine I wouldn't bother with the valves until you get home. There's lots of people that ride these bikes wayyyy past the service time and they're just fine. As long as there's not a lot of top end noise your fine.