Intake boots - again !

[Redman]

Started getting the high hanging idle (after warmed up) last few rides last year. And then worse on first few rides this spring.

THis also happened about 9 years ago. I found the intake orings were hard and shrunk. I found the boots were so hard that I replaced them all. Did something of a carb clean and replaced all the carb orings that I could without breaking the carbs out of the rack. That all, took care of most of the problems, but not all. A couple months later it came back. So then I got another set of orings, and broke carbs all the way down, did carb dip, andreplaced all the carb orings including the choke enricher mechnism oring..... and That took care of the problem. Untill last fall.


So, now I got replacement intake orings and carb orings. I didnt really suspect the intake orings. I more suspected the choke enricher orings. So I set forth in doing a carb breakdown and cleaning and replace all carb orings.

But, look what I found.

One carb boot comming loose from its flange, and another looking like not too far behind that.

So, you folks think this where my problem lays......?

 

[gustovh]

I would start there.

V

 

[Guest]

Dave, you are saying those are new(er) boots? yowza. Wondering if 9 years ends up being the average time a gs ran till it was parked when new...

 

[Redman]

Dave, you are saying those are new(er) boots? .,... ... ...

Yep, those are boots that were new in 2010 ($27 each, BikeBandit). One is coming apart from the flange and the inner throat, and another one looks like it is about to. Are still flexible some after 9 years. But I figure that is enough to be causing the high-hanging idle (after warms up).

The original boots on the bike were hard and stiff. Not cracked. But were so hard it was difficult to remove the carbs and harder to replace the carbs, such that I thought they would soon crack, or I would break them trying to get the carbs back on. Oh, and the orings were so brittle that they broke into pieces. Yah, so those original boots were 28 years old, and stayed together, but were rock hard. Could have reused them, but thought since so hard they were about to crack or maybe not making good seal to the carbs.

New replacement boots are now $37 each at some places.
Babbitts listed them for $29 each. (I will avoid the $20 shipping by picking them up.)
Man, I wasnt expecting this expense, but am glad they are available.

 

[Nessism]

When installing the carbs did the airbox fit nicely and bolt up nicely to the carbs and frame without a lot of stress? A lot of the time the airbox boots shrink and then you have to really force everything to line up, in which case there will be a lot of stress added to the carb boots.

 

[Redman]

When installing the carbs .............

Have yet to get carbs orings replaced, have yet to get the replacement intake boots, so havent reinstalled anything yet.

Air box boots were also replaced 9 years ago. They seem pliable yet.

.

 

[bwringer]

I replaced the boots on my GS850 about 20 years and at least 100,000 miles ago. They're still in good shape so far.

I think the 1100 runs higher temperatures back there behind the cylinder head. And bikes with fairings can get even hotter.

Every so often I wake up in a cold sweat in the middle of the night thinking "what if they run out?" and get an urge to order another set of these boots just in case.

Dave's were physically separated, so beyond rescue. However, I have successfully softened and restored intact carb boots (just hardened and shrunk, not cracked or separated) with a wintergreen oil (methyl salicylate) and xylene potion.

There are also folks over on ADVrider who are exploring 3D printing unobtanium carb boots, which is showing promise. It might be a good idea to try and arrange a good scanning or measurement while these are still available.

 

[Burque73]

So, you folks think this where my problem lays......?

Looking at the rust that formed after that relatively short time, part of your problem is living in MI! LOL You can look under original 30+ year old boots here and not see near as much rust, if any!

 

[bwringer]

Is that rust or something else? The bases of the boots I've seen are cast aluminum, and they're bolted to an aluminum cylinder head, so I'm rather puzzled as to where that rust (corroded iron) could be coming from. It doesn't look like oil or gasoline residue, but maybe it's not rust either.

Or do the 1100G boots have steel bases? Not sure what's up here.

O-rings look pretty good, FWIW.

 

[Redman]

Roger,
Oh, yah, rainy for weeks at a time here. And attached garage is cold for months during winter, but just enough warmth from house to melt snow and slop off the cars.
Oh, and 1/2 of summer is humid.

Brian,
Ah, that got my interest. Went out to garage with a magnet. Yep, ferrous metal.
Yah, these boots on 1100G are different than others, in that use the larger orings (40mm) and the shorter screws (16mm).
Or, I suppose, maybe these are steel because I got them in 2010.

Yah, these 9 year old orings were still pliable and extended up above the groove (but I got a new set). The ones I replaced in 2010 were probably original, they were so hard and shrunk that I thought they were plastic not rubber, and they broke into pieces.

 

[Burque73]

So, you got me wondering about the boots I installed a couple of years ago, whether they're aluminum or steel at the base. The magnet stuck to the band clamp, the bolt in the vacuum port but not to the base.


Yeah, Dave, you guys get real weather up there. We have something like eight inch annual rainfall. Last weekend I pulled the rear wheel to replace a leaky tire valve and it was 65 degrees F in the garage. So nice outside in fact that I layed the tire in the sun for twenty minutes and mounting it was a breeze.

 

[Redman]

Got my new intake boots the other day. They have steel bases.

I have noticed that the boots for the 1100G seem to be different than 850G.
THE ones for 1100G are shorter. Are about 3/4th inch on short side and 1 1/8th on other. Maybe that has some relation to why are steel bases, just a guess.
Maybe they are shorter just so the engine and the carbs and the airbox fits in the bike frame.

 

[bwringer]

Yep, they're definitely different boots than the eight fiddy. Why they're steel and the 850 uses aluminum I can't begin to imagine. The boots are certainly shorter; the 850 and 1100 frames are the same part number, so they had to make up little bits of space somewhere to stuff in bigger jugs.

And as I mentioned earlier, I think bikes with a fairing definitely retain a lot more heat behind the engine; the rubber bits, hoses, wiring, etc. all seem to get a little more roasted. Or maybe that's just the bigger engines.

 

[Dogma]

...

There are also folks over on ADVrider who are exploring 3D printing unobtanium carb boots, which is showing promise. It might be a good idea to try and arrange a good scanning or measurement while these are still available.

This thought has crossed my mind as well. I can handle the scanning now, but I'm not sure what material to use to make the clones. I'm thinking some kind of silicone in a printed and smoothed mold. I'm sure the folks at Smooth-On can sort me out. I'd like to attempt airbox gaskets and snorkels too. Maybe a filter cage seal too, but I don't know what those originally looked like. The boots are still available, so I wouldn't feel right about producing them.

 

[bwringer]

In this thread over on ADVrider, the OP printed a dirtbike intake in TPU.

I had no idea you could 3D print in a flexible material.

https://advrider.com/f/threads/3d-printing-an-intake-boot.1374386/

Of course, the next question is whether TPU (3D printed TPU) will hold up to heat and gasoline vapor. The chemical resistance charts for TPU say that it should, so this is promising.

How this might apply to GS intake boots is a little murky, too; our bikes have rubber intake boots bonded to an aluminum or steel flange. So we'd need to figure out a substitute mounting method, or find a way to bond or clamp new rubber bits to the old flanges. Urethanes are darn near impossible to bond, so this could get very tricky.

This is the dirtbike part being printed, just before printing was done. Looks pretty good.

Seems appropriately squishalicious, too...

 

[Burque73]

...............

And as I mentioned earlier, I think bikes with a fairing definitely retain a lot more heat behind the engine; the rubber bits, hoses, wiring, etc. all seem to get a little more roasted. Or maybe that's just the bigger engines.

Do you think this heat issue applies mostly to fairings with lowers? Ive been thinking about getting lowers but havent been able to as of yet. Maybe its a good thing to keep as much air flow down there as possible.

 

[Dogma]

Very interesting. I never would have guessed TPU is fuel resistant. So, I should be able to attempt some air box gaskets. Eeeeinteresting.

 

[bwringer]

Do you think this heat issue applies mostly to fairings with lowers? Ive been thinking about getting lowers but havent been able to as of yet. Maybe its a good thing to keep as much air flow down there as possible.

I'd say it's a very, VERY good idea to keep as much airflow as possible around the cylinders and cylinder heads. I can't say I have any actual behind-the-engine temperature data on naked vs. fairing, or on how much more heat the bigger engines put out vs. the smaller versions, but it makes sense.

Very interesting. I never would have guessed TPU is fuel resistant. So, I should be able to attempt some air box gaskets. Eeeeinteresting.

According to the material charts I can find, TPU is supposed to be gasoline resistant. Whether that also applies to at least some of the flavors of TPU used for filament printing I dunno. Some do specify petroleum resistance.

I can't really find any data on the heat resistance of finished parts, but from what I can find, TPU is not thermosetting. So I think that means it can re-melt. Recommended nozzle temps start at 225c, so it's quite possible TPU parts could start to weaken well below that temperature. And of course, this all varies wildly with the exact material used.

3D printing also brings another challenge to mind, porosity. I don't think the parts will leak air or anything, but there's definitely a certain texture to the structure and surface finish, and you wonder whether that might give gasoline vapor a place to condense. And of course with intake boots, you also need to resist high temperatures. For that matter, gasoline vapor is very "active" compared to liquid gasoline. It's a challenging environment for the material.

Anyway, back in the airbox temps are much more reasonable, so this could be a great place for TPU gaskets. Then again, extremely cheap foam weather stripping also works perfectly well...

 

[Dogma]

...
According to the material charts I can find, TPU is supposed to be gasoline resistant. Whether that also applies to at least some of the flavors of TPU used for filament printing I dunno. Some do specify petroleum resistance.

I can't really find any data on the heat resistance of finished parts, but from what I can find, TPU is not thermosetting. So I think that means it can re-melt. Recommended nozzle temps start at 225c, so it's quite possible TPU parts could start to weaken well below that temperature. And of course, this all varies wildly with the exact material used.

3D printing also brings another challenge to mind, porosity. I don't think the parts will leak air or anything, but there's definitely a certain texture to the structure and surface finish, and you wonder whether that might give gasoline vapor a place to condense. And of course with intake boots, you also need to resist high temperatures. For that matter, gasoline vapor is very "active" compared to liquid gasoline. It's a challenging environment for the material.

Anyway, back in the airbox temps are much more reasonable, so this could be a great place for TPU gaskets. Then again, extremely cheap foam weather stripping also works perfectly well...

Well, I ordered up a spool of TPU from FormFutura to experiment with. They have lot of interesting engineering grade filaments. It turns out, the "U" is for urethane. No wonder it has good chemical resistance. Formfutura claims their TPU is heat resistant up to 135?C. So, not so good near the head.

It is definitely true that weatherstripping is cheap. I'm interested in the technical challenge, and having airbox seals that don't fall apart every time I open it. If I can replicate a working snorkel, I think that could be genuinely useful.

 

[bwringer]

It would be super-neato to be able to produce snorkels for shaftie airboxes.

They can't run right without the snorkel, but so many have mysteriously gone missing.