What's the "suction pipe" for?

That subject line sounds vaguely dirty, but 'suction pipe' is what the parts diagram calls it. It's part number 4U8-14423-00-00.

I thought it might be a trap to catch little bits of crud before they could get into the carbs (where these bits might come from, I don't know, since the suction pipe is between the air filter and the carbs), but it's open all the way through.

Is there a hose missing here? Or a filter? I'm sort of stumped, since according to the parts diagrams, my bike (XJ550RH) shouldn't even have a suction pipe at all. Just the RJ and RK's should have it.

I can attach a pic if need be.

 

The suction pipe joins the airbox to the left-side, upper-rear, shifter-case breather-pipe outlet that's connected to the interior baffle inside the cover, which vents the crankcase blow-by gases and crankcase fumes.

The vacuum (suction) -- present, within the airbox, when the engine is running, draws any crankcase gasses up into the airbox for mixing with the intake air.

 

Ah. Sounds like I have a hose missing, then.

I will look to see how I can connect the suction pipe to the spot you indicated, Rick.

Thanks for the help.

 

Well, I can't find where that suction pipe is supposed to hook up to.

There's already a hose running from the crankcase (close to and above the clutch cover) to the airbox in between the air filter and the carbs, so I'll assume that's getting rid of the crankcase gasses.

My best guess is that the PO (who I think must have been on at least one drug, probably more than one) put in an 82 or 83 airbox for some reason, but neglected to block off the suction pipe.

So for who knows how long...the bike has been run with basically no air filter. Even with a filter in the airbox, the air would have been sucked in more readily through the wide-open suction pipe. I'm amazed the carbs were as clean as they were when I went through them.

Haven't done a compression test yet...might be scary. :roll:

 

Well I can't find a good picture of an XJ550 so this will have to do (from a 750). The crankcase vent hose is about 1/2" dia or so. There is also a smaller hose about 1/4" dia which is just an air box drain hose, I believe.

If you look on the air filter parts blow up, the part number you gave is only found on the 550 Seca RJ/RK models. It comes off the air box just below the 1st carb (on the left when sitting on bike). This may be just a connection bung for the hose to connect to? If you look at the crankcase parts blow up the breather hose (key #33) comes off the back right side, which would be above the clutch housing. This should be the hose you are describing above.

 

Thanks for the pic, Nick.

That confirms what I thought...the PO put on an 82 or 83 airbox on his (and now my) 81. I have no idea why he'd do that...

The nameplate on the neck gives a manufacture date of 11/80, so I have to assume it was sold in 81.

I DO have a hose coming from above and slightly behind the clutch cover area, but there is no hose connection from the area in the picture you supplied.

Thanks for the help.

I'm going to take the airbox off and plug up the suction pipe, as soon as I figure out how to get the damn thing off without taking out the engine to make room. :x

 

If you figure-out a way to remove the whole airbox, intact ... without pulling the engine ... let us all know - will you?

Not even David Copperfield has the right MoJo-JuJu to Hocus-Pocus that Moe-foe adda dere ... few-no-wud-I'd-sane!

Have fun stormin' the Castle!

 

What the hell ...

We might as well try ... What have we got to lose? Right? Ready? OK! Say:

"BeetleJuice - BeetleJuice - BeetleJuice"

 

I took out the starter, but didn't have enough time to try to yank the airbox out. I thought maybe taking out the starter would give me enough room...high hopes, I guess.

We'll find out tomorrow. The thing is fairly pliable...maybe, just maybe.

:wink:

 

Well..awlrihteethen....
Looks like I got one over on 'ol Davey C. 8O I DID get my air box out without removing the engine (82 750 Maxim) ok..ok.. so it wasn't 100% intact, but it was 99.235% intact There was just a small 1/2 crack on the right side at the top. Of course there's no way it's going back IN the same way it came out.But I'll be going to pods when it all goes back togethe! Here's some picture proof. First pic it's definitely there (I really like what the PO did with the wiring... :roll: )

You'll notice it's gone here...

I took the starter off to get it out...but it worked

 

Floogle; I have an '81 and an '83 Seca 550 and the airboxes and piping are identical. My '81 was manufactured in Dec '80, sn 001545 and it DOES NOT match the parts fiche you are referring to. It DOES match my '83. Both bikes also match my spare airbox. There's that big tube just hanging down into space, the smaller tube from the top of the clutch housing to the front of the airbox, and a little drain tube. Considering the near impossibility of switching airboxes, it is highly doubtful that occurred. The large pipe you are referring to just hangs down about 2" or so from the bottom of the airbox, like some sort of giant drain or ??? There is a circle of "filter media" (kind of like breather filters used to be on cars) sandwiched between two "guides" where that tube sprouts from the airbox. Unless your PO removed the filter screen (called a "seal" in the "J" and "K" fiche) from in there, you haven't been running "unfiltered." Both my bikes and the spare airbox have a nice oil film around that tube, it's somehow part of the breather system too. I have found a number of things on my '81 that match the later parts fiche, don't let that surprise you.

 

>I'm amazed the carbs were as clean as they were when I went through them.


Its all that grit , sand and dirt blasting thru there, works just like a sandblaster....

 

venting your crankcase hose to the outside will save your airfilter and carbs from getting crudy

 

ah, you made me think of a question I would have had later if you had not made me think of it sooner (?) . I put those dreaded pods on, am I ok venting the crankcase to the open (with some piping to hide the vent abit from stuff falling in it like you did rdbhere)?

 

Lou; they make vent filters that look just like the pod filters but in miniature to put on the vent pipe. Here's a couple: http://www.cyclepages.com/ProductGroupD ... ID=4001237 or https://www.phatperformanceparts.com/Pr ... NT-FILTERS

 

I used to have one of those mini filters on my crankcase vent and the exhaust coming from it was overwhelming setting at red lights. I run a rubber hose down to the right side of my swingarm and i never smell it or get the fumes like i used to.