Carbs or Ignition ? ? what do you think ?

long story short.

bike ran good, ran it low on fuel, started to sputter and run like crap.

pulled the carbs again to clean them. some rust dust is all I found in the float bowls....

decided to derust my old tank while I was at it.
that came out pretty good, saline solution and battery charger.

used hi temp black RTV to seal a few cracks in the carb to manifold boots. one of the cracks went all the way to the inside on #3 cly...oddly this had always been the plug that looked the best in my plug read in the last 2 months.

I should have done all three of these thing months ago, but I like to ride more than I like to wrench. it made for a fun weekend.

but it all back together and fired it up, same as before. ran rough, bogged when I gave it throttle at anything less than about 4500 rpm.

plugs look pretty much like they did before I started on it. 1,2,3 ar OK #4 is black and wet, exhaust pipe on 4 barely get hot, you can hold your hand on it.

SOOOOO I took the carbs off it again today, and I found nothing, put it back toget her and it still dosen't fire #4. I have at decent blue spark on that plug with it grounded to the head.

So should I be looking at the coil, or TCI or what ? ?
Pic of the plugs today, they look just like they did when I started this last weekend.

 

start the bike, spray ether on the carb boot for #4 and see if it picks up the skip. the pipe should get hot also. that will tell you if you have a vaccuum leak.

another thing to check would be the valves. if one of the valves ran tight it could be dumping compression on that cylinder.

its also possible compression is dumping through a scored cylinder or cracked piston. i dont think that it your problem however.

 

That Number-2 Plug looks nice.

Take a Glass Barrel Fuse and Put it in the Housing for the Number-2 Pilot Mixture Screw and let it touch the top of the Pilot Mixture Screw.

Scribe a line on the Fuse to measure how deep the top of the Mixture Screw is on Number-2.
Make sure the scribe line is right level with the Body of the Carb.

(I use an Ignition File ... but, a Razor Blade or a Fine Line Sharpie will do!)

After you get a readable "Scribe Line" on the Fuse ...

Put the Fuse into the Housing for the Number-4 Pilot Mixture Screw.
Adjust the height of the Pilot Mixture Screw too the Scribe Line on the Fuse!

See if that will bring the 4-Hole down to the same height as the 2-Hole.
Cheap trick.
Might work; might not ... worth a shot!

 

Zookie400, that was a good idea I should have thought of that. Sad to say that is not it...I just went out and started it up and gave several good sprays top and bottom on all the carb boots.

RickCoMatic, I will give that a try to even up the others. I have had #4 down to 2 out, even all the way seated a couple time in the past few days dosen't seem to have any effect.

I guess I will run a compression test tommorrow, and hope it is not some hard parts that died.

thanks for the suggestions.....we will get to the bottom of it eventually.

 

I rode the bike to work today, when I got home I had a bite to eat, then after about a hour I pulled the plugs and did a dry compression test.

Pretty even across the board 110-110-115-112
wish they were all at 140 dry, but oh well.
so I don't think it is a ring or a valve.

I remover the plug boot on #4 and had a look at the wire, looked OK, silver steel wire, but I trimmed it back maybe 1/4 inch and rethreaded the wire into the plug boot. It seemed to run a bit bettter, the pipe got hot just at idle, not as hot as the others, but too hot to hold.
I took it for a 5 mile ride and pulled the #4 plug agin, it was black, but it was dry unlike before.

So I unhooked the connectors for the coils from the wire harness and reversed them. When I tried to started the bike I got a nice big POP thru the airbox. I had the seat off of course and was kind of leaning over the air box...I nearly soiled myself..... bike did not start however.
I tried several times to start the bike, but all I got was backfire, poping, etc: never would start.

put the coil connectors back the way they were and it started right up....not sure where to look next, bike does run better than it did yesterday, about 70% as well as it ever has.

 

Did you have the Throttles WIDE OPEN for the test?

You need a fully charged battery and Wide Open Throttles!

 

well I did have WOT, but the battery may not be 100%...I was using my charger on a battery that I had just put in my truck.
Battery should have been at least 80% or so, only about 3 months old.
I could put the charger on it I guess and try again, the main thing I was looking for was a big drop off in cly #4. that would indicate a problem with rings or valves.

 

Strangely enough, this seems to be a very common problem with these bikes from what I have seen in the posts on this forum.
osage..... you are correct in looking for a big drop in the # one cylinder. They are all close enough together to get an initial assessment of the compression so you can look elsewhere.
Is the pipe for that cylinder getting hot? If not, just for the heck of it try putting the choke on a bit at a time and see if the pipe begins to get hot. Don't go so far as to make the engine start loading up, probably no more than half-way. If it starts getting hot you will know it is a fuel starvation issue.
Eliminate one thing at a time. Try changing plugs from one cylinder that you know is firing correctly and see if that cylinder begins firing. If so, could be a faulty plug. This bike has a "Wasted Spark" system. It fires at TDC and at BDC, so you should be able to reverse the plug wires between #1 and #4 cylinders and it will still run just as good if everything is OK.
I tried switching the input leads for the coils on mine a bit back because I read about it on a post. I thought it would blow that exhaust off when it back-fired and it would not start. Upon switching the input leads back, it started fine.
I have the same issue with one sitting here, except that it is #1 cylinder not firing. The plug looks sooty but I haven't had time to check into it further. The pipe starts getting hot if I put the choke on about half-way, so I know it is a fuel issue and not spark.
Keep us posted on your findings.

Ed

 

Well I think it is a spark plug wire. I swapped the coil connectors again today, backfire popping but no start. Switched the plug wires around and it started, ran just like it did, but now it was fireing #4 as the pipe got hot right away as it should.

I then put the coil connectors back the way they were and moved the plug wires back to the original position, bike started and ran as it has been.
Then I tried the quick fix I saw posted here somewhere, used 10 or so strands of copper wire twisted tightly together and forced it into the end of the plug wire where the threaded post screws into the plug wire, reattatched the plug boot and fired it up. Seems a little better than it was before, but the plug is still sooty, and the bike does not have the snap it did before the problem appeared. Exh pipe gets hot, but not as quick, and not as hot as the rest of them do.

I will be doing some surgery on my coils over the weekend to replace all 4 plug wires. Now I just have to track down some suitable wires to use.

 

Need some High-Performance Spark Plug do you?
Easy and cheap!
Just visit a Automobile Junk Yard.

Walk around and look at what some idiot did to a nice BMW, VW or Audi.
Just reach right in and take four of the longest wires there are.

Give the guy five-bucks and you're likely to get change.
Mine are out of a VW Passat.
Bosch stainless core.
Nice.

 

Sometimes the plug wire builds up resistance where it goes into the connector in the plug boot. I have had to cut off alittle of my plug wires to get good connections.

 

I can hardly wait to hear how this turns out. I have chased this problem for a while. When I get time I plan to check into it further.

Ed