WTF is this stuff?! Help?

[lukeinorbit]

FZR 400 1WG 1986 : Basically today i pulled the carbs off for a good cleaning as it was a job i hadnt done with it yet. So i pulled them off and cleaned the jets, 2 of the idle jets were completely blocked... Then i noticed down the 4 inlet ports is a thick crusty black residue of sorts and its absolutely caked in it! im sure it has something to do with that stupid hose from crank case to air box! i was wondering if anyone knew any tips on how to remove this crud as i know it cant be good for the performance of the bike! I tried to take photo but was too dark! i hope someone can shed some light on this! cheers yal!!

[Evilchicken0]

OK - the hose from the crank case to the airbox is a breather hose. As the pistons get pushed down from the detonation they move the air in the crank cases, if this doesn't vent you get a pressure build up which will push out past a gasket. The air from the cases has an oil mist to it because it comes from an oily place

What I think has happened is some oil has vented into the airbox (don't worry it's meant to do that), then some dust has mixed with it. The heat from the engine gradually dries the oil and it forms this crusty layer.

So what's to be done .... well clean the carbs as you're doing wash out the airbox and renew / clean the air filter (if you have a K+N type). Make sure the breather is clean inside and doesn't have any kinks. Put it all back together.

It would be good if you can balance the carbs and then reset the idle speed.

[willandrip]

Try to have the inlet vales closed on the cylinder you are cleaning and perhaps a very small rag inserted to help prevent debris entering the cylinder.What about misting the caked on material with a solvent to soften it prior to removal ? A blow gun on a air line would be handy to finish off with.
Are the valves coated also ?

[lukeinorbit]

Thanks guys for the quick response! you have enlightened me as to what has happened! i think im going to just drop the lump out all together and give a good clean of the valve inlets and paint it up ! and yes the valves are also slightly coated, i was wondering why it was hesitant to start! been bumping it for the past month!!!

[Evilchicken0]

Usually when the get hard to start its the valve clearances, add it to the list