Dirty Throttle Bodies

dcarver · May 12, 2009

~65k 2006, in for wiring harness replacement. Service manager says 'you got to come see this'. "RuhRoh Rollie", it starts, I think.

The airfilter box has been removed, so can directly eyeball the butterfly valves of each intake.

And they are nasty. Each of the 4 are covered with a gooey layer of splooge that looks like oil and fine dirt/dust. Took a finger and 'wiped' it clean. Thickness of the goo was about like 3 or 4 sheets of 20 bond paper, maybe .003" or so? Opend the butterflies and looked down the intakes, and they too are covered, but much less than the backside of the butterflies.

I don't get it, and the SM/Tech say they haven't seen this on other FJR's they worked on.

For the record:

I've run only OEM air filters, changed out about every 6,000 miles or so
I do live at the end of a dusty dirt road, 6 miles daily, but normally I'm not behind someone e.g. eating their dust
I do NOT take an air compressor set at 120 psi to blow the dirt out - tap filter on concrete to remove dust
There are no visible signs of leakage past the filter - the air box is tight, the clamps looked good, and all 4 intakes look similary dirty.
CrZy8 still seems to run good, gas mileage hasn't dropped, does not burn any oil between changes (3k normal change, 5k max)

Questions -

I seem to recall someone mentioned that the clean air system could possible breathe 'dirty' air into the airbox under decel or something? I tried searching but didn't find the thread.
I wonder how good the stock air paper filter is.. Maybe a Uni is in order?
Could the crankcase breather be the culprit?
Has anyone else seen similar intake grunge when you've lifted the airbox?

Hope to have pix later, SM is calling Yamaha.

wfooshee · May 12, 2009

I had the air box off of mine a month or so ago, and the throttle plates were oily but not dusty. I do no unpaved riding, though. Oily coat would be from a crankcase breather, I'm sure, but of course any dust getting in would collect on the oily surfaces.

The air injection to the exhaust would not put oil into the airbox, as it's a one-way street from the airbox to the exhaust ports, and it has no source of oil, anyway.

Maybe with the dirt road you need a shorter interval on your air cleaner.

There may also be an issue with the particle size on the air filter, enough really fine dust in your road maybe still getting through. That's just a guess.

Patriot · May 12, 2009

I have been tempted to go with K&N as I have with all my other bikes, but Walter da WFooshee checked mine when doing AVCC install and all was fine.

rushes · May 12, 2009

Yur ridin' like a candy butt. She's all stopped up...

Wring her neck, get the juices flowin...

It's a self cleanin' machine...

I'm jus' sayin...

BTW, how long since you checked valve clearance?

dcarver · May 12, 2009

wfooshee said:
I had the air box off of mine a month or so ago, and the throttle plates were oily but not dusty. I do no unpaved riding, though. Oily coat would be from a crankcase breather, I'm sure, but of course any dust getting in would collect on the oily surfaces.

Was it 'gooey'? Mine is. It's not like loose dust sitting on a surface, e.g. dust on a rim that's easily blown off. This is more tarry, gooey, black colored.

Patriot said:
I have been tempted to go with K&N as I have with all my other bikes, but Walter da WFooshee checked mine when doing AVCC install and all was fine.

I've read that K&N's actually allow larger particles to pass than paper (OEM) or foam (Uni) filters.

rushes said:
BTW, how long since you checked valve clearance?

Valves adjusted last summer, before NAFO, or about 20 - 25k ago? No discernable performance loss and no oil use.
Thanks everyone, and I'll post pix when the SM emails them to me.

Bungie · May 12, 2009

Well without having seen it, I can't really say, but its a pretty common thing to get some crap build up on the air cleaner side of the throttle bodies. Buddy bought a bike that we couldn't to a TBS worth a damn on it. 10 minutes with some carb cleaner on the backside of the butterflies and it was purring like a happy kitten.

Now if its _dirt_ thats something else entirely.

PA1195 · May 12, 2009

One air filter test. Others can be found by Google. I've used both Factory and K&N as have many. I like the K&N's performance on my old airplane which is worth about 75-100 RPM static increase (only maybe 95 HP), but it will pass more dirt.

I'd be tempted to use a Uni-Filter next time around on the FJR to stop the fine stuff and maybe add some flow. The gunge is likely a combo of oil fumes, mainly from the breather both after shutdown and while running, and very fine dirt. Check the intake valves for deposits and use elixir to clean.

Gary in Fairbanks

wfooshee · May 13, 2009

dcarver said:
wfooshee said:

I had the air box off of mine a month or so ago, and the throttle plates were oily but not dusty. I do no unpaved riding, though. Oily coat would be from a crankcase breather, I'm sure, but of course any dust getting in would collect on the oily surfaces.

Click to expand...

Was it 'gooey'? Mine is. It's not like loose dust sitting on a surface, e.g. dust on a rim that's easily blown off. This is more tarry, gooey, black colored.

I would call it gooey. You could smear it with your finger, and it wasn't hard to clean with a WD-40 spray and some rags, but it was thicker than just an oil smear. Kind of cooked oil.

Fred W · May 13, 2009

Maybe one of the reed valves in the PAIR system is back-flowing (leaking) allowing exhaust back into the intake?

wfooshee · May 13, 2009

It would also have to get past the ECU-controlled PAIR valve, which is shut nearly all of the time. And unless something really bad is happening, there's not a whole lot of oil up there.

It's normal to have some oil from the crankcase breather (or PCV valve in a car) in the intake system. I've never seen a throttle plate on any vehicle with any miles at all that didn't have a little slimy gunk on there. Dust and sand, that's a bit of a bother, though.

wheatonFJR · May 13, 2009

Are you sure you didn't take the air filter off so you could hear more "intake growl"?

I hear that's all the rage.

Jes messin widcha. Hope you get to the bottom of it soon.

SkooterG · May 13, 2009

So you are saying they looked like these?: Clicky HERE and scroll down for TB photo

How did yours compare to my photo?

My guru mechanic, without seeing the photo but based on my description told me it's most likely normal for my high mileage and caused by 'normal 'backwards pulses' of air through the intake.

I also wondered about the crankcase breather hose? Bringing oily vapored air into the airbox from the crankcase?

Edit: Here's just the photos from the link above. My 'gunk' was gooey too.

PA1195 · May 13, 2009

SkooterG said:
So you are saying they looked like these?: Clicky HERE and scroll down for TB photo
How did yours compare to my photo?

My guru mechanic, without seeing the photo but based on my description told me it's most likely normal for my high mileage and caused by 'normal 'backwards pulses' of air through the intake.

I also wondered about the crankcase breather hose? Bringing oily vapored air into the airbox from the crankcase?

Some of the "dirt" may actually be carbon from the cylinder blown back as your mechanic described. The exhaust system can, under certain conditions and design, flow a reverse pressure wave that inhibits filling of the cylinder on the intake stroke during valve overlap at TDC between the exhaust and intake strokes. That's what can cause the torque curve "dips and bumps" we see, and may move some carbon that can then stick to any oil residue. See Kevin Cameron's explanation in Chapter 7 - "Exhaust Pipes", among others.

Gary in Fairbanks

Fred W · May 13, 2009

Looking at Skooter's pictures you can definitely see that the dirt (or whatever it is) is deposited only on the lower half of the butterfly plate, and on the lower edge of the shaft, but not the upper. Since the plate tips away from the view, with the top going toward the engine, that would suggest the deposit is coming from the filter side, not backward through the body.

charismaticmegafauna · May 13, 2009

PA1195 said:
SkooterG said:

My guru mechanic, without seeing the photo but based on my description told me it's most likely normal for my high mileage and caused by 'normal 'backwards pulses' of air through the intake.

Click to expand...

Some of the "dirt" may actually be carbon from the cylinder blown back as your mechanic described. The exhaust system can, under certain conditions and design, flow a reverse pressure wave that inhibits filling of the cylinder on the intake stroke during valve overlap at TDC between the exhaust and intake strokes. That's what can cause the torque curve "dips and bumps" we see, and may move some carbon that can then stick to any oil residue. See Kevin Cameron's explanation in Chapter 7 - "Exhaust Pipes", among others.

Well, what exactly does K.C. say (those pages can't be read for free)?

When the engine's running, there's a strong positive pressure at the exhaust ports and a, pretty constant, negative pressure (vacuum) on the intake side. There's pressure in the intake with forced induction and 2-strokes (which is a form of forced induction) -- but a, standard, 4-stroke intake sucks (when running).

Oil fumes from the crankcase are ever-present, more-or-less.

dcarver · May 13, 2009

SkooterG said:
So you are saying they looked like these?: Clicky HERE and scroll down for TB photo
How did yours compare to my photo?

My guru mechanic, without seeing the photo but based on my description told me it's most likely normal for my high mileage and caused by 'normal 'backwards pulses' of air through the intake.

I also wondered about the crankcase breather hose? Bringing oily vapored air into the airbox from the crankcase?

Edit: Here's just the photos from the link above. My 'gunk' was gooey too.

GREAT post, thanks SkooterG! Yeah, that's what mine look like, only mine had no 'brass' showing at all on the bottom halves - they are entirely black and gooey. From your pix, it looks like someone has already 'cleaned' the top half and portions of the lower half as well?

The crankcase breather tube injects dirty air downstream of the air filter, and I consider it suspect too. Take a careful look at the inside of the cc breather tube in your pix - do I see crap in there?

When I get CrZy8 back I'll do a compression check, and maybe get all inspired and put a k&n filter on the cc breather tube, block of the hole in the air box caused by removing the hose, and install a Uni air filter. Of course, it all might just have to wait until after CFR.

PA1195 · May 13, 2009

Fred W said:
Looking at Skooter's pictures you can definitely see that the dirt (or whatever it is) is deposited only on the lower half of the butterfly plate, and on the lower edge of the shaft, but not the upper. Since the plate tips away from the view, with the top going toward the engine, that would suggest the deposit is coming from the filter side, not backward through the body.

Does make perfect sense to me Fred that the deposits could be comprised of some carbon. Any reverse flow would be more apt to exit the throttle plate backwards in the area of lowest intake flow = the dirty bottom, and be deposited there on oily residue. That's only my speculation of course.

charismaticmegafauna, regarding the exhaust pressure wave backflow and potential carbon blow-back, Kevin's material is copyrighted, but permits a reviewer to quote brief passages for the purposes of review. As a review of his book, here's a quote from p.57, ch.7, Fig.3. "Here is the dreaded flat-spot, the rpm zone in which it is a positive wave that hits the cylinder during valve overlap, pushing exhaust back into the cylinder and even right back through the carb to the airbox" Well written indeed, and there's further explanation in the chapter text.

Read away with your copy of his book, and please don't shoot the messenger. Both M/C books he's written so far are worth owning, and a third's (TDC II) on the way in November just in time for a Christmas stocking stuffer.

EDIT: The above explanation of cylinder backflow during valve overlap is also described in the on-line review in ch. 3, p. 12 here.

I just missed it in my earlier post, so the above "book review" is a dupe from a later chapter not shown that covers the same subject.

Gary in Fairbanks

mattster31 · May 13, 2009

dcarver said:
~65k 2006, in for wiring harness replacement. Service manager says 'you got to come see this'. "RuhRoh Rollie", it starts, I think.
The airfilter box has been removed, so can directly eyeball the butterfly valves of each intake.

And they are nasty. Each of the 4 are covered with a gooey layer of splooge that looks like oil and fine dirt/dust. Took a finger and 'wiped' it clean. Thickness of the goo was about like 3 or 4 sheets of 20 bond paper, maybe .003" or so? Opend the butterflies and looked down the intakes, and they too are covered, but much less than the backside of the butterflies.

I don't get it, and the SM/Tech say they haven't seen this on other FJR's they worked on.

It was FRONT tire rubber you maniac!!!!!!!!

dcarver · May 13, 2009

Ok, here are the pix, taken with a BlackBerry..

The one smudge in the middle pix is where I used my finger to wipe through the goo...

What do ya'll think? Normal or a problem?

Dirty Throttle Bodies

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