One for the UBER GURUS!!!!

[Cobia]

I have problems with #3 cylinder not performing as it should.
This is on my 79F. It had a Jardine 4X2 SS turnout exhaust which I want to keep for my 80G. So, I found a set of original replacement Yamaha exhausts which I installed. Shortly after that #3 cylinder started acting up as evidenced by the lack of heat on the exhaust pipe (spraying the manifold with water) and rough performance. So, here is what I did and the results:

1. Suspecting the spark plug wire, I nipped off 1/4" and re-installed the cap.
2. This made it run better for about 5 min but the problem returned.
3. Suspecting the plug, I replaced it without success.
4. the plug always comes out wet.
5. Suspecting the coil, I replaced it with a known good one, no luck.
6. Suspecting the cap, replaced it with a known good one, same deal.
7. And here's the clincher.. switched the cables 3 to 2 and 2 to 3, #3 manifold still cold.
8. Took #3 plug out and cranked engine and observed orange spark between the electrodes. Isn't it supposed to be blue??

I'm kind of at wits end with this.
In the spirit of full disclosure...
When I installed the new exhaust I had to shim the flange nuts with washers and didn't notice that #2 and #3 weren't tight against the head. That's been corrected and the problem still persists.
WTF - Does anybody have any ideas about what may be going on????
Any and all ideas are appreciated. Picked a few Guru brains already and we are all kind of scratching out exessive skulls on this.
Thanks,
Robert

[DGXSER]

Not a guru, but here is my half a cent worth

Stick with fuel from what you described. If 2 is good and three bad, and switchign the plu wires makes no difference, then it is not in the coil and most likely not in the wire.

Of course it is possible that the wire has a break that connects better when you twist it over to two than in the position it is in to three.

Still think fuel is your primary suspect. have you switched to prime on your petcocks and watch for flooding fuel bowl?

Again, just my thoughts.

[Cobia]

Fuel

That's what a guru said, but wouldn't a wet plug indicate that it's getting enough fuel?? Maybe too much, and not getting enough fire?? Don't know, just wondering!!

[trbig]

When's the last time you checked you valve clearance? Have you done a compression check?

Also.. have had a pilot jet back out before and run like crap.

Tod

[Cobia]

Re: valve clearance and CT...

Well TR,
The valves do not sound as if they are out of tolerances, and we adjusted the chain.
And yes, the compression test is #1 on the "to do list" for tomorrow. I'm just hoping that it doesn't go that far...... denial???

[trbig]

It's either not making enough compression to burn the fuel, or it's dumping in too much. Electrical stuff usually comes in twos on these and it sounds like you've covered that part of it well.

If it's not compression, you may have a stuck or sinking float in that carb. Basically a needle valve not seating for some reason due to that or trash.

Tod

[Cobia]

BTW - I went through the carbs thoroughly and she was purring like a kitten, but the pilot jet may be a point of consideration. I put 200 miles on it w/out issues before we did the 2nd gear fix, and she was running just great until I replaced the exhaust. It's probably not related to this issue but it just makes you wonder. That's why I'll be checking the compression tomorrow..... too much back pressure??

[oldyam80sg]

I 2nd the fuel thing.Ran into a similar thing back when my screen where the float valve goes into-you know where at the bottom the fine wire mesh screen.It was plugged almost solid because i had a hard time getting the float pin out and i checked all the rest and said the hell with it! Pipe would get lukewarm at best.Tried changing the coils,TCI,cut the spark plug wire and changed the plug.No good.With the screen plugged,it was obvious that a little would drip out and then stop.Plug was wet but not enough to keep things going.Bike also idled fine and didn't stumble while driving it at low speeds.

[xs11lover]

I'm no guru for sure, but those pick up coil wires made a few of my bikes do all sorts of crazy things. I changed alot of parts around, scratched my head, wrung my hands, talked to myself,ect. It seems it always came back to that.

[skids]

Compression should be checked. You know, I had a set of pipes that I could never get my carbs adjust for. My stock Yahmaha pipes lost the baffles and started causing excessive fuel consumption. Then I put on the JC Whipme mufflers and I swear the carbs could not be adjusted for them. It was probably my own ineptitude...

BTW - I went through the carbs thoroughly and she was purring like a kitten, but the pilot jet may be a point of consideration. I put 200 miles on it w/out issues before we did the 2nd gear fix, and she was running just great until I replaced the exhaust. It's probably not related to this issue but it just makes you wonder. That's why I'll be checking the compression tomorrow..... too much back pressure??

[Cobia]

[B]Peter:[B]You may have a point there, because these carbs were absolutely trashed when I got the bike. I even had to replace the mains because they were so corroded. Although I made sure that everything was totally clean when I reassembled, and ran over 200 miles w/out issues. And I did clean the screens...
I wrote a string on this, with pics and all....
The other factor that makes me suspect the carbs is that although the tank had been Kreem'd and I added in-line filters after re-building the carbs, when I drained the bowls recently, in the hunt for a solution this issue, I was astounded at the ammount of sediment that got past the filters and came out of the bowls. And these were top-of -the-line filters. Makes me wonder what the standard is, in microns, for filtration?
XS11Lover - I checked, and this one already has the pick up coil fix done to it!!

[fredintoon]

I have problems with #3 cylinder not performing as it should.
This is on my 79F. It had a Jardine 4X2 SS turnout exhaust which I want to keep for my 80G. So, I found a set of original replacement Yamaha exhausts which I installed. Shortly after that #3 cylinder started acting up as evidenced by the lack of heat on the exhaust pipe (spraying the manifold with water) and rough performance. - - - -
Robert

Hi Robert,
looks like you tried all the obvious things. Going for the weird:-
Could the #3 side of the #3/#4 fuel Tee be plugged?
Is it possible that the #3 exhaust is plugged?
How about you swap the Jardine system back on and see what happens?
You said the carbs were clean. I fought with my iggy for a week when my #4 cylinder quit. Turns out that my two weeks before carb clean was only a temporary thing on #4 carb.

[Ivan]

Orange spark and a wet plug. Fuel can foul a plug. Swap the plugs and see if ti follows the plug. If that's the case, new plugs are in order. They are cheap and easy. Also, switch the spark plug cap.

One other thing to look for is carbon tracking on the plug. On the outside of the plug a very thin black line can form. Almost looks like dust, but won't wipe off. This lets the spark travel outside the plug to ground. Easiest way to find that is run the engine with no lights on in the dark. You'll see the spark. This would definitely create a wet plug scenario

Compression check would be a good idea. Loose exhaust runner could possibly have burnt a valve. Usually (on cars) they need to run quite a while with the leak for that to happen. On an air cooled engine that may be exacerbated.

Last thought. Do you listen to Country Western music while you work on the bike? That stuff will make anything go tango uniform.

[Cobia]

List for today.

Thanks for all the suggestions. Today I'll start by doing a compression test and then pulling the carbs for another cleaning.
I'll keep you posted.
Thanks.

[Cobia]

Update....

Warmed up the engine and did a compression test.
Results:
#1 - 155 psi
#2 - 170 psi
#3 - 175 psi
#4 - 160 psi
I know, I know, the compression on these engines is factory rated at 140 to 145 psi. I can only attribute the discrepancy to an uncalibrated tester. I was mainly confirming that I didn't have other major problems, and I also wonder if some PO had installed an overbore kit. BikerPhil and I discovered that apparently the case had been split previously as evidenced by the non-YamahaBond sealant that is still visible. We found this out when we did the 2nd gear fix and installed the secondary gear shaft.
Would an overbore kit increase the compression to these levels, or is my tester just off? I've tested outboards with it and it has been right about where it should be!!??

Well, I've just removed the carbs and will be digging in to #3 first.
Eventhough this is a '79F it does have the series 3 carbs and unlike my 80G and my 82J, it has the pilot jet rubber plugs!!! Do some series 3 carbs have plugs and others don't??? Should they even be in there??
I'll keep you posted,
Thanks