Black tar in intake

[vbmike]

Hi guys. Just wonder if someone can tell me what the black tar crystals are in the intake manifold. Is this cause for concern? All four intake ports were like this. Some worse than others. I had to remove the carbs to clean them and notice this after removing them.

 

[DakRatFink]

It looks like carbon, but why it would be up in the intake and not further downstream where combustion is happening is beyond me.

 

[KJShover]

It does look like carbon.
It could be oil leaking past the intake valve guide/seal as well.
Improper overlap of the cams or bent valves would also cause a similar scenario.

I would do a leak down test of the motor, This will tell you alot. A great engine will leak about 5-10%. Good is about 20%, you have issues if its 30% or greater.

• If you hear air coming out of the pipe, more than likely you have a leaky exhaust valve.
• Air coming out of the carburetor, leaky intake valve.
• Air coming out of the breather vent, its possible the rings and/or cylinders are worn.

You can also use a compression test with a leak down test to find out more info for troubleshooting.

• A cylinder that has poor compression, but hardly any leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, etc.
• If all the cylinders have low compression, but show littlel leakage, the most likely cause is incorrect valve timing.
• If compression is good and very little leakage, but a cylinder is misfiring, This could be a fuel issue or ignition problem.

Harbor freight carries leak down testers for about $40 and compression testers starting at $10 depending on the model. $50 is pretty cheap for a couple of tests that spit out good info.

Hopefully you have no real issue and a little seafoam in the fuel and oil will help clear that up.

 

[MaxMidnight]

Could be oil mist fed in from the breather?

 

[satariel666]

Looks normal to me.

 

[one2dmax]

Agreed. Does look normal for the most part. BUT, the heads are normally black painted in there (not paint but not sure what it is). When one gets ported then the bare aluminum is exposed. Not sure i'd worry too much about it though.

Sean

 

[vbmike]

Ok, after having another look that black stuff is inside the head not the intake. If they have that black coating on the head from the factory I'm assuming that it's just flaking off and going through the motor and out the exhuast. Some ports only have a little another others are completly covered. The heads have never been ported. The bike as been runing great until the carbs started giving me trouble so I guess I won't worry about it then.

The compression and bleed down test sound like a good idea. I might do them but with 6000 miles on the engine I wouldn't think there would be anything wrong.

 

[SpecOps13]

Wow, only 6k on a 93 ??????

 

[vbmike]

Yep. I'm the second owner and the guy I bought it from just didn't have the time to ride it. It's been a good bike till this spring when I fired it up and it was dumping fuel out the exhaust from a stuck float.

 

[Rollie]

Wow, only 6k on a 93 ??????

Low mileage like that usually means it has been stored or broke down for long periods of time. I bought my '90 in '04 with 3,745 miles on it. It only had a Kerker and stage 7 carbs for mods done but it ran a straight line really well . I bought it from a scooter dealer who used to be a Yamaha dealer as well . His son can build a motor and tune a set of carbs . He gets most of my carb business .

 

[maleko89]

BG44K will take that carbon right off.

 

[Redbone]

BG44K will take that carbon right off.

Is it added to the fuel or is there also a spray cleaner type of BG44K?

 

[maleko89]

Brian, I should've been more clear. You add it to the fuel tank. I split one can into 3 treatments and then add each when filling up a tank of gas.

 

[Redbone]

Thanks Mark, I think I'll pickup a bottle of it because I noticed the same issue when I had my engine out last winter.
I remember Danny saying that he ran a bottle a season on his bikes but I didn't think I needed it. I should have listened and now that Mark backs him up I'm doubly sold on running some through Redbone now.:worthy:

 

[maleko89]

LoL. I buy a can once a year. Another additive I like is Rislone engine treatment. You add it to the oil and it clean everything including valve seals, bearings, etc.

 

[Redbone]

LoL. I buy a can once a year. Another additive I like is Rislone engine treatment. You add it to the oil and it clean everything including valve seals, bearings, etc.

Check, I'll add some of the Rislone too and run a few hundred miles before I change out the winter oil.
Damn, Ima agonna halfta write all this stuff down, this har Vmax maintenance 'sho be technical!:hihi:

 

[satariel666]

Agreed. Does look normal for the most part. BUT, the heads are normally black painted in there (not paint but not sure what it is). When one gets ported then the bare aluminum is exposed. Not sure i'd worry too much about it though.

Sean

Thats what I ment to say...its a PAINT.