Bike Finally Running - Header Pipe #2 Warm Not Hot - Cylinder Firing?

[Guest]

All,

I took my time and finally got the new-to-me bike running. Carbs were removed and dipped and reassembled with new rings about a month ago and didn't sit with fuel in them at all. I must admit - I didn't adjust float levels, though. Bike starts up and idles (what I though was) great. Revs freely, no popping, missing (that I perceived) or backfiring. I noticed a couple of the plugs looked very untouched when reading them (only at idle - bike needs brake work to be ride-able) so I took a temperature gun to the headers. I am running the bike from a temporary plastic gas tank with a filter set up in between. Plugs are brand new. Here is my trail of breadcrumbs:

• At idle (with a fan in front of the bike), temps at the header pipe for cylinders 1, 3 and 4 are in the high 300's (hopefully due to single-wall construction and possibly a tad lean). Temp, however for cylinder 2 is never more than 150 - so much so that you can touch the header pipe with your hand and live to tell the tale.
• When checking for spark, I guess the carbs still had a little fuel in them (even though I ran it till it cut out) and the bike fired up with the #2 plug laying across the cylinder head. The bike ran as well as it had been running (which shows my noobness), but what was strange to me is that as I stood there and felt the compression coming out of the plug hole and looked at the spark, I expected mist to be elected from the spark plug hole and nothing came out but air. Should I have seen/smelled/been covered in a gas-air mixture?
• I replaced the plug, started it again and then grabbed the plug wire for that cylinder and pulled it off with no affect in performance. I replaced it, and when I grabbed the #1 plug lead, not only did I get a nice little jolt in my hand, but the idle definitely changed.

So there you have it. Everything I know about the issue. Would your money be on a coil issue, a carb issue or both? Proud to say this isn't another pod-thread. Hopefully. I just populated my signature, but just-in-case: this is an 83 650GL, running pods and a 4 into 1 header. According to the PO, it hasn't run in a long time as evidenced by the stripped, balled-up, rats-nest of a harness handed to me in a box...
Thanks in advance,
Geoff

[allojohn]

You said already...... float level in #2 is off. They're probably all off to some degree.

[Fjbj40]

Does the vacuum for the fuel Petcock come from that dead cylinder? You said you were running it from a small tank, so if it gets its vacuum from that dead cylinder did you plug the vacuum port on the carb?

Massive unmetered air leak will cause it to be too lean to run, increase the revs and it will get hot!

[UKPR1]

Got it. I'll check and go through the float adjust procedure. In my many pulling-the-carb sessions (for other reasons) I would always open the bowl screws to drain them and they all appeared to contain approximately the same amount of fuel, so my suspicions never went to the float levels...
That being said...I'll check and adjust them.
Thanks for responding.

Geoff

[UKPR1]

FJBJ,

Funny...I ran to take a look as soon as I saw your post and the port to the petcock is still open on the carb. Would it affect only that carb to the point it negates any fuel it may want to ingest?
Good call.

Geoff

[Big T]

That is correct. Plug the vacuum port and try running your bike again

[UKPR1]

Wife came home and she's sick of hearing it run/losing me in the garage. It'll have to be in the morning...I'll check in with what happens.

With Thanks,

Geoff

[chuck hahn]

For what its worth, last week my 78 1000 stopped firing on #4. Cleaned the plug with the sand blaster style plug cleaner and held it to the engine and it sparked. Put it in and still a dead cylinder. went and got a new one and problem solved. Would spark holding it to the block but wouldnt fire IN the head...

[Fjbj40]

FJBJ,

Funny...I ran to take a look as soon as I saw your post and the port to the petcock is still open on the carb. Would it affect only that carb to the point it negates any fuel it may want to ingest?
Good call.

Geoff

yup, I made that mistake myself!

[UKPR1]

Well done, FJBJ! That was most certainly it. I capped the vacuum port on carb #2, and now the header temps are where the others are...until today. Yep - the rabbit-hole goes a little deeper... Here's what's going on:

1. There seems to be no combustion going on in the #4 cylinder - header temp is barely 130 (most likely from the adjacent header) and the #4 header can be held.
2. Pulling the plug, it is definitely wet and smells of gas.
3. In pulling the lead off the #4 plug with the bike running yields no difference in running. Doing so with the other plugs either drops the RPMs or stalls the bike (pulling the wires off of #1 and #3 stalls the bike. #2 drops the RPMs).
4. Laying the plug across the valve cover, a definite spark is observed - appears to be strong but it's all relative with nothing to compare it to at the time.
5. In swapping out the plugs, there are no changes. In other words, #4 cylinder still does not fire even with a different plug.
6. Some blue smoke from the exhaust on deceleration with unburned gas smell.
7. Definite air-gas mix ejected from the cylinder #4 when running with the plug out.

One has to ask - what changed? #4 was functioning yesterday when #2 was not. Now #2 is up and running, #4 has decided to take the day off. I recognize that the closer I get the bike to running condition, the smaller gremlins will replace the larger ones. I'm hoping this is the case. Coil? Coil wire?

Thanks in advance for your collective advice.

Geoff

[John Park]

For what its worth, last week my 78 1000 stopped firing on #4. Cleaned the plug with the sand blaster style plug cleaner and held it to the engine and it sparked. Put it in and still a dead cylinder. went and got a new one and problem solved. Would spark holding it to the block but wouldnt fire IN the head...

Once in a while you find one that's afraid of the dark.

[UKPR1]

That's why I tried another plug. Maybe its the wire. #1 and #4 fire at the same time, correct? If they reach, perhaps I'll try swapping the #1 and #4 plug leads and see what happens...

[londonboards]

I wouldn't get too carried away with testing a static bike with a temporary fuel tank.

Get it all together and go for a blast down the highway.

You'll probably find they all chime in and work perfectly.

Don't chase your tail testing in unrealistic conditions (a stationary bike at idle).

[Kiwi Canuck]

I had a similar problem on my newly rebuilt GS650E, cylinder #1 was barely warm after running the engine for 2-3 mins.

I removed carbs and cleaned carb #1 in the ultrasonic cleaner, but didn't find anything obvious that could cause the issue, I could blow air through all the passages and all the jets looked good.

When I was installing the fuel bowl, i thought to double check the little hole that the brass tube goes into and when blowing air through it's hard to tell if it's going through so I filled the bowl with water and blew air in from the top, and it didn't bubble out.

The carb bowl had been in the ultrasonic for at least 1 hour at 50 degrees celsius and hadn't dissolved whatever was blocking this passage.

I used a very fine wire and carb gunk cleaner and sprayed it in, let it soak for 30 mins, worked it then another 30 mins, finally started to get little bits out and then it cleared.

Long shot, but double check this as your symptoms sound similar as mine.

Good luck

David.

[UKPR1]

So...I swapped the #4 plug with other plugs (including an old set) with no change. I then put the #1 wire on the #4 cylinder and vice versa also with no change - header is not getting hot and I can pull off the #4 plug lead with no change in idle. Before I pull the carbs off yet again to check and also check for compression, is there anything I've missed electrically? Through swapping things out and the cylinder still not firing, I think I've rule out the ignition - or have I?

Thanks again,

Geoff