Fouling #2 plugs and carb "coughing"

Still trying to figure this thing out...

I've replaced all 4 spark plugs, bike seems to perform much better, #2 is firing but still not up to par. I've noticed now that the bike is making a coughing sound and air is coming out of the hose that goes to the petcock out of carb #2. I wonder if this has anything to do with it?

Took the new plug out to check today and it is black and damp. I just changed the oil today after that as well because its level was to high.

As far as the bike's performance... it starts out "coughing" at lower RPMs when the bike is first being run, but once I get it up over 55 it usually does not do it again even when I slow down.

Also... can someone help me find where I can buy a coil mod? I'm not competant(sp?) enough to make my own. haha

I'm also waiting on getting my petcock bolt out of my tank... it snapped off when I was installing my new petcock today.

it sounds like you have float valve problem with no.2 carb probably why your oil level was high as well take the carbs off and remove the float on no2 and take out the float needle and check for grooving on it.

Adidas120mi wrote:

I've noticed now that the bike is making a coughing sound and air is coming out of the hose that goes to the petcock out of carb #2. (

you probably answered your own question with this statement. On a carb, any time you have air going in or out where it is not supposed to you will probably have problems. A tiny leak can sometime cause alot of problems. Replace that hose and see what happens from there.

Edit:

Other things to check,

Compression & spark
Carbs clean?
Carbs synched
Air/fuel mixture screw adjusted correctly
no air leaks on your boot
timing advancer working

telefunkin wrote:

Adidas120mi wrote:

I've noticed now that the bike is making a coughing sound and air is coming out of the hose that goes to the petcock out of carb #2. (

you probably answered your own question with this statement. On a carb, any time you have air going in or out where it is not supposed to you will probably have problems. A tiny leak can sometime cause alot of problems. Replace that hose and see what happens from there.

Edit:

Other things to check,

Compression & spark
Carbs clean?
Carbs synched
Air/fuel mixture screw adjusted correctly
no air leaks on your boot
timing advancer working

I guess to clarify, I noticed it was coming out of the hose because I was running the bike without the gas tank on it so the hose was detatched from the petcock when I made that discovery.

I'll check the other things you've listed... I think it might be a few days though I have to wait to get that bolt out of my tank and get the petcock on and working.

Here's an update... While I was waiting to get the tools to repair the snapped off bolt in the gas tank so I could get the petcock on... I changed the oil, made sure it is at the correct level and put a new plug in the #2 cylinder.

Got the tank fixed and on the bike... it smoked and backfired a lot at first, I only took it out for about a mile drive or so but when I got back all 4 pipes were hot enough for me to spray water on them and it all scold off and evaporated instead of running down the #2 pipe and onto the ground.

What I'm thinking is the oil level being too high was saturating and fouling the plug, and causeing compression issues because it wasn't allowing the #2 cylinder to fire. The backfiring and smoke at first start upon changing the oil makes sense if the oil level is corrected and what's left is burning out of the cylinder. I'm going to take it out tomorrow for a thorough ride to see how it runs.

Did your oil smell like gas when you changed it?

Sounds to me like you have petcock failure and it's leaking gas down the vacuum line into #2, then your crankcase.

Also, does your bike have VM carbs? Doesn't that vacuum line from the petcock go to #3?

The oil didn't smell like gas when I changed it. I just couldn't see through the oil window on the crank case until I washed it... and by then I had added oil, too much oil. haha

Yes, I have Mikuni VM carbs, the vacuum hose connects to my #2 on the #1/#2 side.