Right Cylinder Backfire - Engine Tuning

[marcmiller001]

Hi gang,

Since I am still waiting on a tank and seat - and the valves have been adjusted, I wanted to start up my bike today to warm it up, check my Gen light wiring and gauges (installed Acewells) and check my oil temp sensor I installed.

I also selfishly just wanted to hear it run. It fired up but I noticed that the right cylinder didn't fire. I assume this is from the fuel flow and the right side cylinder not getting the fuel it needed right away so I primed it more and started to get strong exhaust pulse in the right cylinder bank.

I let it run a bit, but I noticed a misfire (exhaust pop) out the right exhaust as it purred at 1500 rpms.... and I also notice the right cylinder and valve cover noticeably cooler than the left. I let it run and the exhaust pop never went away and I am wondering if this could be a timing or fuel flow issue and how would the best course to diagnose it?

Thanks in advance!

[wilcom]

best course to diagnose it?

You've just had the carbs all apart as I remember....I'd start by fiddling with the mixture adjustment on the faulty side.

Shade tree Joe............

[marcmiller001]

best course to diagnose it?

You've just had the carbs all apart as I remember....I'd start by fiddling with the mixture adjustment on the faulty side.

Shade tree Joe............

So you don't think it could be timing? I pulled the plugs and one looked good, the other was black and wet (right cylinder). I swapped plugs just so I can read them better when I tried tuning again.

[Bob_Roller]

Have you replaced the fuel lines ??

I had a right cylinder issue, that I finally troubleshot, to a kinked fuel line when it came out of the airbox .

I have installed a .25 inch steel line through the airbox and bent at 90 degrees as it comes out of the airbox, then place the fuel lines on the steel tube .

I also had issues with idle jets being clogged the metered orifice at the end is almost impossible to tell if it is clear or not .

[marcmiller001]

Have you replaced the fuel lines ??

I had a right cylinder issue, that I finally troubleshot, to a kinked fuel line when it came out of the airbox .

I have installed a .25 inch steel line through the airbox and bent at 90 degrees as it comes out of the airbox, then place the fuel lines on the steel tube .

I also had issues with idle jets being clogged the metered orifice at the end is almost impossible to tell if it is clear or not .

Yes - all new fuel lines... but zero kinks and both carbs completely rebuilt. I assume it is either a carb tuning issue (both carbs are set back to factory spec) or a timing issue (I have not set any timing, only done valve clearance/adjustment). I replaced spark plugs and wires over winter as well, and I checked both plugs have spark, but obviously the right cylinder is running much cooler and misfiring.

[Justin B.]

Have you swapped in a new plug for the fouled one?

[marcmiller001]

Have you swapped in a new plug for the fouled one?

I swapped the left side plug with right one but haven't tried firing it up. Think it could be fouled plug?

[Justin B.]

If it's wet and black that's a good recipe for getting it to not fire correctly!

[marcmiller001]

If it's wet and black that's a good recipe for getting it to not fire correctly!

OK - swapped plugs - clean plug to the right cylinder, dirty plug to left - fired right up - but same issue of right side cylinder having a misfire and running much much cooler than the left side.

Here are some facts:
[list bull-blackball]

• The left side carb (which seems to be running smoother - I was able to turn the mixture screw out to about 1 turn and hear the idle increase. I seem to be able to adjust this carb.

[list bull-blackball]

The right side carb, the mixture has no effect on the idle whatsoever.
[/list]

[list bull-blackball]

• On the right exhaust, I notice during idle that the exhaust wrap starts to smoke, it goes away as engine warms up, but seems like that might be a by-product of un-burnt fuel being pushed into exhaust? (see photos)

[list bull-blackball]

• Right side cylinder still misfires periodically, especially as the rpm comes down from a rev.

[list bull-blackball]

• Pulling the spark plugs shows that the right side cylinder has a black spark plug (fairly wet) but not necessariliy fouled - putting that plug in the left side and swapping them, firing the engine, it does the same thing and once you remove the plugs, the same result happens - left plug gets cleaned up and right side gets black. (see photo)

Anyone have some thoughts??

[Justin B.]

Well, it's seems that side has very weak spark or is flooding that cylinder.  When you pull the plugs, attach the plug wires, ground the plugs and crank the engine do both plugs have nice fat blue sparks? 

I'm leaning toward carb since adjusting the mixture screw has no affect on idle speed.  Turned all the way in idle should drop drastically and when turned out should increase until idle starts dropping again.

[Bob_Roller]

What ignition coil do you have, a black nd ray, red and black ??

[marcmiller001]

Well, it's seems that side has very weak spark or is flooding that cylinder.  When you pull the plugs, attach the plug wires, ground the plugs and crank the engine do both plugs have nice fat blue sparks? 

I'm leaning toward carb since adjusting the mixture screw has no affect on idle speed.  Turned all the way in idle should drop drastically and when turned out should increase until idle starts dropping again.

Last night, I went through a carb tuning procedure. This time, I started with the left cylinder, adjusted air screw until I felt like I got a good tune - and then went to the right carb and adjusted the air screw down and that the idle went down.... opened it up and now I was getting a responsive change in idle. Eureka! The miss-fire went away, idle seems smooth now and throttle response is great. I think I ended up about 1-1/2 turns on the left and 1-1/4 ish on the right and it seems to run fine for now.

Now I have a pesky neutral switch leak and/or pan gasket leak... Already have a neutral switch I ordered when I got the bike, went through Snowburns site and read it twice and curse there are no photos. LOL. I'm more a YouTube University type guy than reading print.

Turns out I believe the smoking is just residual oil from my oil filter change that likely won't burn off until my first decently long ride.... but given the issues with the missfire, it had me more worried than I should have been.

[marcmiller001]

What ignition coil do you have, a black nd ray, red and black ??

Ignition coil looks all black to me. You can see it in this photo.

[Justin B.]

The stock BMW coil was problematic, developing cracks which wreaked havoc with ignition.  The only bad one I've had (knock, knock) produced no spark at all and had very visible cracks which was an easy diagnosis.  I have read where others have had small cracks where it would run OK but act up when it was damp.

Probably the most fool-proof thing to do, if you plan on keeping the bike for a long time, would be to put in the Dyna "brown" coil.  Very robust coil and much cheaper than the stocker.

On the neutral switch they are like the coil - not if they fail but when!  The switch is a notorious leaker and fairly easy to get at with the rear engine mount stud driven out and the aluminum spacer removed - you'll see what I mean when you take a good look at it.  I changed one, once, without removing the tube and from then on I learned it was much quicker to remove thew stud and spacer.

[marcmiller001]

The stock BMW coil was problematic, developing cracks which wreaked havoc with ignition.  The only bad one I've had (knock, knock) produced no spark at all and had very visible cracks which was an easy diagnosis.  I have read where others have had small cracks where it would run OK but act up when it was damp.

Probably the most fool-proof thing to do, if you plan on keeping the bike for a long time, would be to put in the Dyna "brown" coil.  Very robust coil and much cheaper than the stocker.

On the neutral switch they are like the coil - not if they fail but when!  The switch is a notorious leaker and fairly easy to get at with the rear engine mount stud driven out and the aluminum spacer removed - you'll see what I mean when you take a good look at it.  I changed one, once, without removing the tube and from then on I learned it was much quicker to remove thew stud and spacer.

This one? http://www.euromotoelectrics.com/product-p/dyna-coildc2-1x1.htm

Is this a direct bolt-on replacement?