Cleaning Throttle Bodies

[SkooterG]

The PAIR air injection port is located in the cylinder head exhaust port right at the exhaust valve and should not be the culprit causing dirty intake tracks.

There is a phenomena known as 'back-streaming' which is likely to be related. Air is viscous and elastic, engine designers use this property to improve volumetric efficiency. During the induction phase the intake valves are open, a mass of air is moving quite rapidly from the air box into the cylinder. At some point the ECU fires the fuel injector misting the air flow with mostly atomized gas. On or about the time the intake valves slam close the fuel injectors are closed. If there is any velocity left to the intake air mass, it will strike the back of the intake valves and get reflected back along the intake tract. If there is any trace of atomized fuel left, it is dragged along with the rebounding air mass. The fine traces of fuel will coat the intake track when the air mass becomes still. Any traces of dust that made it past the pores of the air filter will stick to the fuel traces. The design of the cam (timing, overlap and ramp speed), intake runner shape and runner length can make back-streaming much worse or almost non-existent.

Another good theory that I discussed with others and considered. In the end, I am not too worried as my motor lasted a loooong time. I think Constant Mesh may be right in that it is a 'if it ain't broke, don't fix it' kind of thing. Oh, and off the forum I had an FJR owner say his TBs looked the same with only 15k on his odometer.

 

[Crash Cash]

I feel like I just got smarter.

Every time I read an Ionbeam post, both my brain cells jump up and down and go "OH BOY!"

 

[ionbeam]

The PAIR air injection port is located in the cylinder head exhaust port right at the exhaust valve and should not be the culprit causing dirty intake tracks.

True, but the other side of the PAIR valve goes to the clean air side of the Air box. If the PAIR reeds were allowing some back-flow it would be possible for some exhaust gas to be pushed back past the solenoid valve into the airbox... itself.

Since your Air Injection Solenoid is sitting on a shelf someplace, take a gander into the hose that couples the AIS to the air box and see how dirty it is inside. Just saying, it would be a long path to get from the exhaust port, past the reed valves, into the air box and back out to the throttle bodies. Were it exhaust, I would have expected the coating to look more exhaustish -- kinda carbon black.

I do agree that if the throttle plates ain't a stickin' and you aren't racing and need every 0.000001 HP, I wouldn't worry about the film on the intake throttle plates.

FWIW, if you were sitting on a piston top and look up at the ceiling, this is what you would see. Note that the Air Injection has only one port, behind one of the exhaust valves.

Exhaust valves removed for a dramatic view

 

[HaulinAshe]

Lots of good theories about where the gunk is originating. I've not taken the time to study the phenomenon carefully enough to add much. What I do know is that bikes with the PAIR system capped early in life (< 5,000 miles) DO NOT have as much crud accumulated on the butterflies as others. My '07 butterflies looked good at roughly 97,000 miles, after the PAIRectomy was performed at 67,000 odo. I suspect it's a combination of malfunctioning PAIR backwash, back-streaming or "intake bounce" as us rednecks call it, and in my particular case... oil from a re-usable air filter (which will NEVER happen again!).

It is surprising how stiff the throttle gets over time as that crud builds up. It's one of those things that slowly degrades to a point where you don't notice it until you twist someone else's throttle. IMHO that throttle body buildup is one of the major causes of so many off-idle, jerky throttle complaints.

 

[HaulinAshe]

Jeff, are you talking about GenIIs specifically?

When I changed my starter I had to do all this. Yep, it was somewhat of a pain, but not that bad. And my TBs were DIRTY!!! Have no idea why. Carver's were the same with a lot less miles.

No, not specifically. I think the same rules of dis-assembly apply for both Gen-I and Gen-II in this case. ABS always makes life more complex than non-ABS, if for no other reason there's more **** to stare at.

I can understand Carver's being crudded early. He rides a dirty/dusty environment. Filtration just doesn't get everything.

 

[HaulinAshe]

I'm not sure how healthy sea-foam fogging the intake like that would be. Any flushed junk that passes through (hopefully) may very well get hung up in your cats (assuming that you still have them).

I mean, isn't the whole concept of one cleaning the intakes to prevent the accumulated grit and junk from getting sucked into the engine?

Seems like you'd just be precipitating the occurrence.

edit - I guess I'm in the camp that is happy when the grit is stuck in the intake beacause that stuff didn't get in the engine. If I felt compelled to clean it I'd want to disassemble and wipe or rinse it away, not in.

I get where you are coming from. I'm a big believer in SeaFoam for de-carboning the exhaust valve system, but luckily most of that gunk is already on it's way OUT of the engine.

I prefer to wipe/brush/scrub the intakes directly. But once they are a "known clean", SeaFoam might not be a bad way to maintain the condition.

 

[Fred W]

Sounds like we are on the same page. :thumbsup:

 

[road runner]

Lots of good points in this thread.

I would agree with Fred about not fogging the engine with anything, because of the cats. They are actually very delicate, and can be overworked and burned up pretty easy. In the auto world they have before and after O2 sensors that can see if the cat is doing it's job, and if not you get a code "cat efficiency". We don't have that on the Feeg so if it's not working no one will now, but still I'd rather not burn it up.

I'd also agree with Alan that part of the dirty intake track could be from cam timing & overlap. On the intake stroke the piston is going down and the intake valve (IV) is open. The piston gets to bottom dead center (BDC) then starts to go back up on the compression stroke a certain # of degrees before the IV closes. This will push a very small amount of the mix back toward the intake. On the Ex stroke the piston is going up, the EV opens, before the piston gets to TDC the IV also opens, so there is a certain # of degrees that the IV and EV are open at the same time (overlap). This can also push a very small amount of dirty mix toward the intake.

If you've ever taken a 4 stroke engine apart, you've seen the back of the intake valves dirty. I think it's from cam timing and overlap.

 

[charismaticmegafauna]

I'm not sure how healthy sea-foam fogging the intake like that would be.

...I'm a big believer in SeaFoam ...

SeaFoam might not be a bad way to maintain ...

Quidado...!

Your engine can get "hooked" on SeaFoam...

(happened to a friend's BMW... )

 

[Crash Cash]

Exhaust valves removed for a dramatic view

So that's Hungry RadioHowie's bike, then?

 

[RadioHowie]

Exhaust valves removed for a dramatic view

So that's Hungry RadioHowie's bike, then?

Nope....STILL haven't yanked the head off my dead motor.

Got a stripped head bolt that I haven't bothered to grind out yet...I keep telling myself "There's Always Tomorrow!"



Oh, and the "Hungry" remark??? :finger:

(Hungry Howies -- the WORST pizza in the universe!)

 

[dcarver]

Check out the pattern of mine..

 

[ionbeam]

Check out the pattern of mine..

Say, you don't happen to live off of a long dirt road do you?

 

[dcarver]

Check out the pattern of mine..

Say, you don't happen to live off of a long dirt road do you?

I DO! But that weren't dirt!

 

[beemerdons]

I feel like I just got smarter.

Every time I read an Ionbeam post, both my brain cells jump up and down and go "OH BOY!"

+1, Gunny! And besides that, Alan's posts always make me want a drink; ionbeam enables my alcoholism!

 

[Fred W]

I feel like I just got smarter.

Every time I read an Ionbeam post, both my brain cells jump up and down and go "OH BOY!"

+1, Gunny! And besides that, Alan's posts always make me want a drink; ionbeam enables my alcoholism!

Oh geeze. I think you just helped me realize why I like the guy so much...

 

[beemerdons]

I feel like I just got smarter.

Every time I read an Ionbeam post, both my brain cells jump up and down and go "OH BOY!"

+1, Gunny! And besides that, Alan's posts always make me want a drink; ionbeam enables my alcoholism!

Oh geeze. I think you just helped me realize why I like the guy so much...

+10, Tenfold Gunny! Alan's a great guy, got a chance to meet and converse with Mr. and Mrs. ionbeam at Mont-Tremblant last June for CFR 2010 Quebec!

 

[road runner]

I don't know if someone mentioned it already, but were does the crankcase breather go ? If it goes to the air box then that would put an oily film on the TB's. Then any fine particles that get threw the filter would stick to it.

Never mind. I see wfooshee already mentioned it.

 

[wfooshee]

Not only that, but the breather goes in behind the filter. The filter only sees outside air coming in.

Start a trend: On a Mustang forum a bunch of guys were putting fuel filters on the PCV hose, the plastic kind you could see into, and when they turned really bad they put a new one in. The "thinking" (if there actually was any) was to keep oil out of the intake.

So who's gonna be the first to filter their breather pipe?

 

[mattster31]

i just cleaned my TB yesterday before reinstalling. I have to say I hadn't touched them since I bought the bike and I've put 35k(miles)on them and they looked nothing like the photos posted thus far. I just used a bit of carb cleaner and looked brand new. I do like the baking soda tool, and i'll use that next time. Bike purrs like a kitten now. Obviously I dont live in a very dusty area and I rarely travel dirt roads.