air cleaner removal

Hey everyone.
I've seen some people on the forum saying that removing your air cleaner reduces the risk of vacuum leaks and can make the bike run better overall. I was wondering of I remove the cleaner, connect the carb intake vacuum nipples, and tape off the air box hole, would there be a change in the emissions that would come from the bike? My state (Virginia) is very strict on emissions and they require all registered vehicles to be checked yearly. Does anyone know if there is a change, how much of a change should I expext to see and also of the bike will still be able to pass a state inspection
Thanks

nickleo373 wrote: Hey everyone.
I've seen some people on the forum saying that removing your air cleaner reduces the risk of vacuum leaks and can make the bike run better overall. I was wondering of I remove the cleaner, connect the carb intake vacuum nipples, and tape off the air box hole, would there be a change in the emissions that would come from the bike? My state (Virginia) is very strict on emissions and they require all registered vehicles to be checked yearly. Does anyone know if there is a change, how much of a change should I expext to see and also of the bike will still be able to pass a state inspection
Thanks

I don't know who said that but they must have been smoking funny cigarettes. :laugh: :laugh: Running the bike with no air filtration is a really bad idea as it will make the bike run lean and it will let grit and other debris enter the cylinders which will cause premature engine failure. The changes you mention may in fact cause the bike to fail the emissions test.

If you have vacuum leaks (presumably at the carb holders) removing the air cleaner will do nothing at all to reduce the leaks. Air leaks at the carb holders generally are noticeable at idle, and the lower the idle the more noticeable they are. This is because at idle the carb slides are closed (or nearly so). The cylinders try to suck in the same volume of air per intake stoke regardless of the rpm and this creates low pressure (vacuum) through the intake track. So at idle, with the carb slides closed, the vacuum cannot suck very much air through the carb throats and this raises the vacuum inside the carb holders. This in turn tries to suck air through any little cracks or leaks between the carb holders and the cylinder head (or any other carb holder leaks). Because the slides are closed and very little air is being sucked through the carb throats very little air is being drawn through the air filter. So the air filter offers no real resistance to airflow at idle because it is designed to be able to accommodate huge airflow demands when the engine is running at very high rpm. This is why removing the air filter will have not reduce vacuum leaks. If in fact you have vacuum leaks at the carb holders the best remedy is to replace the carb holders.

The bike will not run better overall without an air filter. The filter is engineered to provide sufficient airflow for the engine and carbs that it came on. If you remove the filter the air/fuel mixture will be changed when you are riding at normal or higher rpm, and this will make the bike run lean and may cause the engine to overheat. The remedy would be to rejet the carbs to bring the air/fuel mixture back to the correct ratio for proper combustion, and this could be done, but with no air filter the engine will die a premature death because foreign matter will be sucked into the combustion chambers and score the cylinder walls.

If you are concerned about passing an emission test you should simply perform a full tune-up on the bike and it will pass. Ed

He's not talking about the air filter, he's asking about the emissions stuff. Not sure what the proper name for it is.

If you want to remove it, don't connect the carb vacuum ports to each other, plug them. You can connect the two ports on top of the valve cover to each other with some hose, or just plug them. And definitely plug the hole in the airbox that it runs to.

I'm guessing this will negatively affect your ability to pass emissions, but you might still be ok. Only way to know is to try it, unless someone else here has. You shouldn't be changing anything permanently by doing this, so if it fails emissions, you can always put the stuff back on.

Thanks for the replies
I was going to keep the filter and air box installed. The inserted pic was the piece I'm considering removing. I don't know the right name for it

Ah - I think that is called the clean air system or emissions system. You are correct that a lot of folks have removed that system; I think because their reed valves went bad. I don't know what affect removing it will have on the emissions test, but I'm glad to see you weren't planning to remove the air filter. Ed

Thanks Ed.
I'll give it a shot and see if it'll pass the inspection. I suppose the worst thing that can happen is they fail it and I have to put it back on.