#1 cylinder intermittently back fires.

[peanut]

sorry I thought that you said it was not firing at all on one cylinder ?? now it fires ??
I think you need to be a lot clearer and more precise in your description.

Does it fire on No 1 cylinder ?
Is it backfiring out of the exhaust ? or is it out of the carburettor ?

You say the engine is not running properly yet you know that you have poor inlet joints ?

You still haven't responded to the question about whether you get a spark on No 1 spark plug or not . Come on give us a chance to help you by responding to our questions

 

[paulson_shawn]

Its only firing on 1 cylinder now but just before I changed the orings it was idling good on both.

 

[peanut]

Its only firing on 1 cylinder now but just before I changed the orings it was idling good on both.

well if that was all you did and No 1 cylinder stopped firing after that I would guess that the problem lies with the air screw or the O ring or the air screw setting .

 

[paulson_shawn]

I was thinking I might have caused an itake leak when I pulled the carbs since they're pretty bad looking. I also set the floats and adjusted the sync screw by sight when I had the carbs off.

 

[Orion61]

On the other hand he said the plug was wet? That means it is NOT firing.
I think we need to get to basics here. Also it is hard to eyeball the sync screws. As you are sitting on the bike is it the cylinder on YOUR Left hand side or the Right hand Cyl, that is not firing?
I think you need to pull the plugs and lay them still connected to the plug wire ON the cyl, turn the motor over with the switch on, and see if you are getting spark.
Do it to EACH plug. IF you get spark on just one side, try swapping sides with the plugs, if the problem follows the plug you have your problem.
But from now on so we are sure, use Left Cyl, that is the cylinder on YOUR left while you are sitting on the bike. Same for Right cyl.. This using cyl 1, and "ONE cyl" is confusing.
It is possible to short out a plug if it is wet, I have had them go dead even after they are dry again.
This should be fairly simple, if the bikes pipe is not getting hot while running it either has No Fuel, OR too Much Fuel. OR no Spark. So test for Spark first and go from there, and lets keep this SIMPLE, make sure you try each step, and we will get you through this.
Larry

 

[paulson_shawn]

It's running on the right side cylinder. The left side only backfires. I swaped the plugs from one side to the other and it still did the same thing then I swaped the plug wires and it did the same thing again.

 

[paulson_shawn]

It's kick start only (starter delete) so it's kind of hard to check for spark with the plug out.

 

[Orion61]

It's kick start only (starter delete) so it's kind of hard to check for spark with the plug out.

If you pull both plugs you can easily turn it over, Amazing how easy they turn without compression!
I just thought of something, if you pulled the float, you may have put it back in upside down. It is actually pretty easy to do (believe me) lol!
It may not even be letting gas in the bowel. If you pull the bottom plug on the left carb do you get gas?

 

[peanut]

On the other hand he said the plug was wet? That means it is NOT firing.

yes I was well aware of that Larry..
It was me that asked that specific question in post #12 ...........
In post #6 I already suggested he swop the HT leads over

 

[peanut]

I should have warned you .

Its very important not to test for a spark with the spark plug removed when you have an electronic ignition system fitted unless you are very careful to maintain a ground from the spark plug to the chassis at all times .
If either of the spark plugs slip or you lose the ground connection for even a second you risk frying your very expensive Boyer electronic ignition system.

 

[paulson_shawn]

I had to replace my coil in the past because I started it with a lead off the plug so I'm conscious of that now. I will check if I put the float in upside down. Thanks for the tips guys.

 

[weekendrider]

There are cyl1 and cly 2 designations.

 

[paulson_shawn]

I pulled the float bowl plug and the gas drained out so that's not it.

 

[weekendrider]

I would guess that the problem lies with the air screw or the O ring or the air screw setting

There aren't any "air" screws on the stock cv's.

 

[paulson_shawn]

Correct. The pilot screws regulate fuel instead of air on my bs38's

 

[5twins]

They do that on all the 650 CV carbs. But actually, they regulate the fuel air mix from the pilot jet, not just straight fuel. And only a small portion of it, about 25%. The other 75% flows directly into the carb's main bore. The only way to alter the strength of that is by changing pilot jet size.

 

[peanut]

There aren't any "air" screws on the stock cv's.

I must have had my Lambretta Dellorto carburettor head on

 

[Orion61]

I should have warned you .

Its very important not to test for a spark with the spark plug removed when you have an electronic ignition system fitted unless you are very careful to maintain a ground from the spark plug to the chassis at all times .
If either of the spark plugs slip or you lose the ground connection for even a second you risk frying your very expensive Boyer electronic ignition system.

GREAT INFO! Thanks for posting that! I am betting I am not the only one to learn that today.. I have a couple spring clamps I use anyway. I have had enough zaps holding plugs down by the wires with my fingers in the past. lol, It isn't a huge shock but it gets your attention!

 

[peanut]

I have had enough zaps holding plugs down by the wires with my fingers in the past. lol, It isn't a huge shock but it gets your attention!

it certainly does doesn't it

 

[robinc]

Had a High School Auto shop teacher who said if you squeeze the plug wire really hard you won't get a shock. Was never brave enough to see if he was right. Lol.