Black Tar/Sticky in Intake

[Marxman61]

What's up guys. I'm having an issue with my motor. Let me give you a small breakdown of the backstory.

I was the one that changed their hawk into the Brat Bike (can be seen in "Videos and Pics." As you can see in the pictures, I put a pod air filter on the carb and removed the muffler from the exhaust. Now here's the problem I'm currently facing. Keep in mind, before the project, the motor ran fine with no issues.

I changed the head gasket seal because the stock one was leaking. No big deal, easy swap. But ever since I put the pod and removed the muffler, I've been getting black buildup in the intake that ends up sticking to the inside of the carburetor and, after it sits a while, will seize the throttle up.

Now my first thought was that I did not jet the carburetor and am running a Mikuni. To be honest, the bike runs great with no back fire and is very smooth. If the carb needed to be jetted, (which I know it probably still should), the bike would run like crap and very lean. Keep in mind this is the first bike I learned to work on and am still new to various variables when customizing. My first thought was that the gas was evaporating in the intake because the engine ran hot and the gas was too lean, thus creating an ethanol buildup in the intake. I don't believe this is the case.

I believe that it is a valve adjustment. I think the valve either pre maturely opens or does not close all the way, so the explosion is getting into the intake, thus causing the black sticky tar in the intake and on the throttle. I did not have a tool to measure the space to ensure an accurate adjustment, but I did try to adjustment the valve as, (if this is the right way to say it), the highest setting, thinking that it will fully close and fully open. That did not work, and am buying a proper measuring kit. Does this diagnosis of the valve sound like the problem?

I am pulling the motor off to:
1. Clean it, and
2. Inspect the valve.

I'm hoping I did not do damage to the valve for whatever reason, but to be honest I might just buy a new hawk motor. Keep in mind that the valve might have been bad for 1000 miles (thats when the gasket started leaking), and now that the gasket is nice and sealed, all the extra pressure had to go somewhere, which was out of the bad valve. Thoughts?

[Badluck]

So copy paper is about .005" thick. I'm not telling you setting the valve lash with copy paper is acceptable, but it'll get you in the ballpark better than eye or feel. Set it light enough to be able to drag the paper out without tearing.

It could be the oil used in the pod filter.

[rpshawk250]

I think you main issue is using ethanol fuel. That shit will gum up any carb. What does the spark plug look like? That will give you an idea on if its lean or not.

[Marxman61]

Originally Posted by Badluck

So copy paper is about .005" thick. I'm not telling you setting the valve lash with copy paper is acceptable, but it'll get you in the ballpark better than eye or feel. Set it light enough to be able to drag the paper out without tearing.

It could be the oil used in the pod filter.

So I did not put any oil on the pod filter and the carb is clean from the intake/pod side. I also put on a fuel filter which is clean as a whistle as well. The black tar is coming from the motor itself, not dirt from the pod. It is only sticky on the motor side of the carb on the throttle.

[Marxman61]

Originally Posted by rpshawk250

I think you main issue is using ethanol fuel. That shit will gum up any carb. What does the spark plug look like? That will give you an idea on if its lean or not.

Have not checked the spark plug, but I use 93 premium. The throttle in the carb is not gummed up on all sides, just the side that faces the motor. Inside the motor as well in the intake is all black and tarry when a finger goes down there. If its running lean, could that create the black gum? I was under the impression it only makes the bike run bad -- which when it runs, it runs great with no back fire and tops out at 70 mph.

[TxTaoRider]

By chance is your catalytic converter still on?

[Marxman61]

Originally Posted by TxTaoRider

By chance is your catalytic converter still on?

Yea its probably still in the exhaust. Do you think that is the cause of the issue?

[XLsior]

Out of curiosity does you PCV hose connect to inlet manifold by any chance? Is the gummy residue building up before or after the carb...

Is there an EGR system? if so the build up could be a combination of exhaust gas and crank case oil forming a black shmutz.

[Mudflap]

It's likely oil from over oiling the pod filter. It can also form carbon on the back of the intake valve. I've seen it before.

[Chris_Top_Her]

Sludge in engine, sounds like dino oil.

[TxTaoRider]

Originally Posted by Marxman61

Yea its probably still in the exhaust. Do you think that is the cause of the issue?

Maybe. If you open up the intake flow and the exhaust is still choked off, you could be getting reversion into the intake system. Since it takes a couple hundred miles for the rings to seat some of that oil may also be carried back into the intake as well. It may get better as the engine breaks in.

On a car, if you run a rich air/fuel mixture or oily mixture for very long, it will eventually plug up a catalytic converter. Then you get severe back pressure and reversion.

[Marxman61]

Originally Posted by TxTaoRider

Maybe. If you open up the intake flow and the exhaust is still choked off, you could be getting reversion into the intake system. Since it takes a couple hundred miles for the rings to seat some of that oil may also be carried back into the intake as well. It may get better as the engine breaks in.

On a car, if you run a rich air/fuel mixture or oily mixture for very long, it will eventually plug up a catalytic converter. Then you get severe back pressure and reversion.

Not sure if anyone still follows this thread, but I figured out the issue for a while now and have not ofund the time / keep forgetting to post on the thread. The issue was that the "catalytic converter" was still in the exhaust and choking it, as expressed above. After removing that garbage AND rejetting the carb (which the carb ran well even without the rejett, but I did it anyway), the problem was fixed. So if anyone is experiencing the same issue, its because of the exhaust.