Intake boots - again !

[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.

[Steve]

I have noticed that the boots for the 1100G seem to be different than 850G.
THE ones for 1100G are shorter.

Not only are they shorter, they also lack the sync screw ports.

On the 1000 and 1100, the sync screw ports are in the cylinder head, not the boots.

.

[2BRacing]

…...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.

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....

From my recent work on a GS1000G fitted with a Vetter Windjammer fairing plus the full lowers, compared to my GS850G fitted with a more "open" Honda replica fairing, I can report that my observations support the "retained heat" theory.

On the GS1000G the fuel hose, vacuum hose and airbox drain hose were all rock hard and had to be replaced, compared to those hoses which are still "normal" on my 850. I strongly suspect that this was caused by the fairing lowers with the extended "side covers" resulting in higher temperatures in that area.

GS1000G with fairing lowers and extended "side covers"


GS850G with more "open" fairing

[Grimly]

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.

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.

From my recent work on a GS1000G fitted with a Vetter Windjammer fairing plus the full lowers, compared to my GS850G fitted with a more "open" Honda replica fairing, I can report that my observations support the "retained heat" theory.

This exact topic has been bugging me recently and I'm pursuing a method of addressing it in my peculiar circumstance.
As some know, I run a single carb (and full fairing with lowers) and the air filter is right bang in the exit line of the engine cooling air, which does not make for a happy idle when the engine is fully warmed up. As part of doing the final tuning on my SU (along with springing the bunce for a proper wideband AFR gauge) I'll be modifying the air intake and remoting the filter to a cooler area.
I've just sprung for a heatshield that guards the carb from manifold heat, and I'll get an upward-facing intake trumpet that will allow me to attach a cool air hose. When I thought about it, I realised the original snorkel was collecting relatively cool air from the tunnel under the tank. The presence of the fairing blocks cool air entry to that, but that can be addressed.
It's not that it runs badly, it's just that it could be better and now that I've rebuilt the top end I want to have it running as best it can under the circumstances.