Triumph Rat Motorcycle Forums banner

Status
Not open for further replies.
1 - 20 of 103 Posts

·
Registered
Joined
·
745 Posts
Discussion Starter #1 (Edited)
I spotted cracked intake boots on a 2 yo bike and grumbled because my experience has been longer rubber life expectation in the past, so my reaction was to eliminate the offending weak link like so many others have done with those reported jubilant performance results.

so I took the air box out and opened it up out of curiosity before fabbing up the replacement parts...the more I studied it the more I come to appreciate what the design is.

I like the battery box, I like the utilization of the space, I like the wire chase on the frame spine, and I especially like the way they handle the breather huff and puff as well as the oil migration. the breather is wide open into a volume and uses the entire air filter as a breather element minus what the engine sucks. the drain tube is a sight glass to alert as to service attention needs.

eliminating the air box means a breather filter...that oil is going to migrate, so I had visions of a breather filter getting contaminated with oil within the first 5 miles, higher crankcase pressures, and breather efficiency compromised as the new norm.

I also saw the restrictor plate cross section is about equal to the air filter inlet cross section, so the stock filter inlet ID is what determines air volume...ahead of that is the snorkle that is the real restriction meter.

the purpose of the box is to scrub the intake air so grit doesn't score the cylinders and crap doesn't wedge under the valve seats...and then there's water. since I'm in SW Pa. conditions are not always perfect...I tend to be out early in the spring, late into the fall, and find iffy conditions in between...we don't get thin clean desert air here...we get mud, water, and salt on the roads, so the priority is similar to dirt bike requirements a certain part of the year.

I don't need big hp...my main concern is always getting back home, so I look at this system as a hip happenin' club called the Compression Chamber and the carbs and intake are the bouncer at the door. pods let just about anyone in, but the air box is the satin rope where some are turned away for being too ugly and un-hip for entry.

all the direction changes encourage the water to fling like a centrifuge and the restrictions act like an expansion valve on a refrigeration system with pressure differences to stretch and massage the processed air...I'm thinking that may further separate water.

so unlike many/most I ordered new rubbers and am going to put the box back in and study on it for another 2 years until the rubbers demand attention again...and I'm also leaving the snorkle and restrictor plate in place. the purpose is much like the long intake on the VW Bug engines...protect the engine from over revving...and yes there's a rev limiter to do that same job.

'70 1600 single port VW Bug was the last good one.
71 went to the dual port for higher revs/performance and began the downfall that went thru 75 FI and death throes.
the new Bug doesn't even count.

I'm good with 60hp...I don't need 75.
what I specifically don't want to do is pay $4/gal thru 145 jet orifices...yes, I know prices are currently back more reasonable, but those bastages will squeeze it up again with not much provocation, so I'm not fooling myself...the further I can separate myself from that game the better.


Say man!
I saw your wife the other day!
Yeah?
Yeah, an' she's ug-leeee!
Yeah, she's ugly, but she sure can cook!

If you wanna be happy for the rest of your life
Never make a pretty woman your wife
So for my personal point of view
Get an ugly girl to marry you
 

·
Registered
Joined
·
2,537 Posts
Hi Haggis,

I still have my airbox too, without restrictor plate and snorkel. Obviously I have looked inside th airbox . I agree with you that the airbox does a lot to protect the motor. However it is designed for very lean jets for EPA. I think they needed a lot of vacum in the box to make those very lean jets work, especially at low rpms. Have you ridden an old carb bike runing very lean? Tons of hesitation.

I am not an engineer, but I have done some piping and air duct design. From my training I know that each direction change in the airflow and each restriction adds to the static pressure or friction and hence decreases flow. People frequently talk about things like the snorkle as if any one restriction in the system can define the entire static pressure. Thats not correct. Its the cumulative static pressure that matters.For example, an engineer could tell you the equivalent length of pipe that would give the sme friction as your air box. The trick is to make the equivalent pipe length as short as possible and reduce the friction while keeping the benefits.
 

·
Moderator
Joined
·
29,948 Posts
Just a couple of quite minor points - 1) many folks have reported just as good mileage with airbox off as with it on, so I'm not convinced fuel consumption is a problem, 2) it seems from research I have done that Triumph had some bad rubber on some 07 bikes. If you still have warranty left Modre you can get your intake rubbers replaced under that, and it seems that they sorted the rubber issue out - so once replaced you should be good to go.\

Nice post. I have to say I've never been that interested in replacing the airbox before, but having found cracked inlet rubbers on mine I felt like giving it a go as it were.
 

·
Registered
Joined
·
1,043 Posts
The W650 crowd went through the airbox removal process a number of years ago, and I was one who modified the airbox on my W650 and eventually removed it completely as many have done to their Triumphs. I eventually went back to an airbox on the little Kwak and never looked back. I have kept the airbox intact on all of my T100s, only replacing the snorkels with NH bellmouth inlets and K&N filters for exactly the reasons Modre mentions - and the lessons learned from the W650 community. The airbox on the Kwak is almost identical to the Bonnevilles.

Dick
 

·
Registered
Joined
·
33 Posts
I have been having this arguement for a couple of weeks...K&N filter, stock airbox, D&D race pipes that go under the frame. I live in Central Pennsylvania...so I need to keep my filter protected. My argument has been air injection removal due to my black pipes getting messed up like stock would and possibly putting vent holes in the air box. Thoughts???
 

·
Registered
Joined
·
395 Posts
If transportation was the primary purpose of my bike I would keep the airbox and maybe add a K&N filter , a bellmouth, and rejet . However , I bought my bike to have fun and ride like a hooligan so the airbox had to go!! As far as gas mileage goes , when I ride like a sane person ,it's just as good if not better than it was with the airbox.
 

·
Registered
Joined
·
493 Posts
Modre's observations regarding the airbox sound well reasoned to me. We have made design improvements on our gas valves to add chambers on the inlet side which trap moisture and sediments to keep them from contaminating the valve seats. So Modre's observations seems well reasoned to me.
But mainly I'm chiming in regarding the rubber boots. I do not know enough about rubber to add proper scientific information but I've been close enough to the manufacturing processes here at work to maybe know more than most. And here is all I am going to say:
The ingredients, molding, curing and finishing processes have everything in the world to do with the longevity of rubber products similar to those boots. From my observation point it really only looks like a case of a bad batch or maybe several bad batches. I say that because after seeing photos of some of the boots they look like they have been setting out in the sun for the past 15 years yet they are two years old or less. It seems to mostly affect the 2007 model year (I could be wrong about that). But I can see from my son's 2007 T100 that it does not affect ALL of the 2007 model year. His will be 2 years old in April and the boots look like they are brand new. My 2005 T100's boots look fairly new still too. I think there is every chance in the world that when you replace your crappy boots with new boots that they will last much longer than two years.
 

·
Registered
Joined
·
8,872 Posts
I ride my bike in all kinds of weather doing away with the air box does not make the filters get wet or dirty .What you are not looking at is with 2 filters there is 2x the filter area so the air going in is just as clean maybe cleaner.The next thing is the breather if its in the air box and you get oil in the line it puts it your motor thats not good for anything.If you have much blow by to the point your dripping oil you got something wrong any way.If your motor is right about all you get is water out of the breather.The air box is not doing you any favors.You can get as good or better mpg with out it.The truth is the stock carbs wont flow what the stock head will and the air box wont even flow what the stock carbs will.
When you do the air box kit its not like the filters are out in the open they are behind the side covers they dont get as wet as you might think.I look at it this way ether leave the bike stock and ride it or pull the air box and be done with it,dont waste work or money changeing the air box its a waste of time.
 

·
Registered
Joined
·
147 Posts
If one does not like to tinker with bike and power is not a factor in riding pleasure let it be as engineers planned it to be.

Some of us are anyhow different, we cannot leave it like it is but to try to make it run better, faster, louder...because the pleasure is there.

I have thought to run the bike in future without filters, only nice looking and sounding trumpets on carbs. I know that engine will eat dirt but who really cares? Bike was made to give pleasure, not to last forever!
My next engine tuning idea makes me to open it anyhow long before it has worn out and propably I will change the parts long before they are worn out even without filters.
 

·
Registered
Joined
·
3,588 Posts
I've only put 20,000 miles on my '03 sans airbox. It idles better and is less trouble carb-wise. I have only cleaned the air filters one time--they are due cleaning now, and I will do this while doing the 24K maintenance. I have not needed to balance the carbs once since removing the airbox--I have checked the balance every 6K and it is spot on.

I have averaged 50+ mpg over the 20,000 miles without the airbox, and I am not a mild mannered rider. I do spool it up through the first three gears to the rev limit of 8100 at least once each ride.:D

I have ridden all day in the rain with no problems. As Mike said, the side covers protect the K&N cone filters a lot.

If I were going to leave the bike stock, I would leave it stock--no need to rationalize or explain to anyone. The only person you have to please is yourself and maybe your significant other.:) If rationalizing your decisions makes you and others feel better, great! I just have a hard time understanding why some think my bike should look a certain way or within certain "accepted" change guidelines. Same goes for performance mods. I've done some...some have done less and some more.
 

·
Registered
Joined
·
72 Posts
My scrambler travels on gravel, and occasionally across low level creeks. It has gone down in a creek once, and the snorkel was under water for about 10-20sec with the engine off. Only about 1/2 an egg cup of water entered the box.
A very good design in deed.

The people who believe pod filters work as well as a still air box are deluding themselves. Microscopic particles do get past pod filters much easier than with a proper air box, and more so if the engine is in a higher state of tune.
But don't believe me, lets just compare engine internals at 100 00km mark.:cool:
 

·
Registered
Joined
·
284 Posts
I have no interest in modding my bonnie for extra power. If I wanted that I would have brought a different model or brand.

One thing I would do tho is list out all of the design criteria that are resolved by the particular deisgn and what effect any mods would have on them. For myself, there is nothing worse than looking at a design where someone has achieved 5bhp gain, but messed up so many other factors.
 

·
Registered
Joined
·
745 Posts
Discussion Starter #15 (Edited)
every time the pistons go down, 865cc is displaced out the breather while 1/2 that is sucked into one chamber or the other...as the pistons go up 865cc is sucked back in.

the breather is using twice the air box as the intake, yet everyone sees the air box as a dedicated intake device...doesn't anyone love their breather?

I like the air box for the way it handles the breather.

a comment like "If one does not like to tinker with bike" doesn't really apply here.

if you've been following there was the bus, the log house, kit cars, the bike history,
...and more recently racks
http://img.photobucket.com/albums/v107/modre/Bonneville/rackdown1.jpg[IMG]

seats
[IMG]http://img.photobucket.com/albums/v107/modre/Bonneville/rhs2oclock.jpg[IMG]

look carefully for stuff you haven't seen anywhere else...
[IMG]http://img.photobucket.com/albums/v107/modre/Bonneville/Tmud.jpg[IMG]

then there was the lowsets and tools that showed in public and a whole lot I never let you see in between...I like to tinker just fine...so it's not that...it has to do with the breather and practical intake protection...you imply that's a limited perspective.
 

·
Registered
Joined
·
1,408 Posts
The design of the airbox does more than flow filtered air and keep out water (and create a place for the battery and filter the crankcase air, etc). It is a twin plenum design that manages intake length and air velocity, too. Admittedly, the design is based on a lowish maximum rpm, but the stock airbox sans snorkle delivers great throttle response from idle to redline once the carbs are jetted for a better mixture rather than low emissions. Individual air filters can be made to mix well too, but do best at the upper end of the rpm scale. Its like the difference between open headers and a megaphone equipped exhaust; the airbox being like the megaphone. Scavenging will work more effectively over a variety of rpms with a megaphone and with a twin plenum airbox as well. The cost is peak revs, but if (like me...) you spend most of your time in the 3k to 5k zone...what's the point of the cost and trouble of installing Pods? We all have different priorities with our bikes. I dealt with handling, brakes, and ergos first. Retuning the engine was done in the interest of improved starting, cooler running, and better throttle response. The extra horses were just a coincidental extra for me...
 

·
Premium Member
Joined
·
1,908 Posts
The only ones that say there so great have never taken theres off so they dont know how good the bike runs with out them.WALK THE WALK BEFORE YOU TALK THE TALK.
Actually, I have been talking to someone that wished he hadn't mutilated the airbox, then removed it. His comments are:

- yes, more power
- on-off feel to the throttle
- feathering clutch at low speeds

The bike goes like hell, but its not exactly a daily rider anymore. Its not "easy" to ride.

The comments about the breather are interesting. I've never really thought about how much air gets pumped out of the crankcase by the pistons going up and down. Because of the staggered firing order on auto engines, its not much of an issue, but two cylinders going up and down together is a different beast. I'm glad I have a Scrambler (staggered firing order).
 

·
Registered
Joined
·
3,588 Posts
PokeyJoe...please recommend to the someone that he/she get their bike jetted properly on a dyno, and the problem you mention should be solved.

Sheepdog...those statements are pure BS as far as my bike (790cc) is concerned. It has better throttle response at all rpms, and it produced more torque on the dyno with the max torque being produced at 3800 rpm. I have NO knowledge of what happens to the 865cc bikes since they have different cams and timing.

I am NOT trying to convince anyone to ditch the airbox--that is their choice to make, and if they make the decision based on opinion, data from dyno runs, or whatever...that is their business and theirs alone. I run a 17 tooth counter sprocket on the 790 and have many opinions about counter sprocket size on these bikes--but they are just my opinions, because if I ever change to a different size counter sprocket it will be to a 16 tooth and not an 18 or a 19 tooth counter sprocket.:D
 

·
Registered
Joined
·
8,872 Posts
you might be shocked to know how little air comes out the breather as pistons go down air goes down the breather tube but when they go up it sucks air in.You can hardly feel much air at the end of the hose.Whats real strange is most any water or oil stays in the tube till you stop the motor then drains out of the hose.I put a catch can on my bike.rideing in warm weather i dont get much in the can at all,since it turned cold it gets alot of water in it because the water comes out of the air as it cools in the can.I took the can off and just put a big breather filter on it, I have yet to even see it drip a drop .Strange isnt it.Think of this to haveing the breather in the air box lets waste oil and water get on your filter and down your carbs and thats not a real good thing ether.
 
1 - 20 of 103 Posts
Status
Not open for further replies.
Top