Carb boot life expectancy?

[foxox]

1989 GSX600F (note this model has different carbs from the 90+ Kats, which is why the vacuum ports are on the boots, as you will see below)

About a month ago after doing some work on the bike I went to sync the carbs and upon trying to pull off the vacuum port rubber plug, the vacuum port nipple itself on the #4 cylinder / carb boot pulled right out of the boot! o_o

So, I used some silicone on it for the time being and ordered a new boot. When installing the new boot, I put some dielectric grease on all 4 nipples so the rubber plugs would pull off smoother to avoid having the same thing happen on the other 3 cylinders. The grease has worked quite well for the past month or so... makes it much easier to install/remove the plugs.

Fast forward to last weekend... did more work on the bike, bike ran super duper amazing for one day, let it sit overnight, then it's all crappy. I'll spare you most of my incredible 2-day-long troubleshooting saga (and I don't know if it's over), but I just found a showstopper for today...

http://imgur.com/e0z4Pmk

The rubber is cracking on the #1 cylinder / carb boot, like on a tire with dry rot. Also, there is a gap forming around the vacuum port nipple (like what happened with #4, but it hasn't entirely come apart... yet). I discovered these while spraying some starter fluid around to try to identify vacuum leaks. I noticed that the RPMs would go up for a moment if I sprayed exactly where the cracks are. If I sprayed anywhere else, even half an inch away from there (even directly onto where the carb fits into the boot), nothing changed... so I think these cracks actually go all of the way through the rubber (though I can't see where on the inside).

So I have some silicone goop setting up now on that boot to hold me over until a replacement comes in. The middle of the night's probably a good time to call it quits working on the bike for the day anyway...

[EDIT: REMOVED BECAUSE I AM PROBABLY AN IDIOT. I made this post thinking I had replaced these boots in 2011 but it turns out I might have only wanted to replace them then but skipped out and just changed the o-rings instead, so these boots are probably ancient and it's no surprise they're falling apart]

I have been riding without fairings... the bike is parked in a dark garage most of the time but could UV light while riding have deteriorated the rubber? It IS the upper/outer portion of the #1 boot where the cracks appeared, where light would hit it most.

What about things like starter fluid causing the deterioration? When checking for vacuum leaks, I spray it around there, but obviously this is not a regular occurrence so the boots should not have been exposed to too much of the stuff.

[92xjunker]

Mine lasted 20+, the 88' were original. Those look thin. Both bikes were about 3/8" thick at the carb side. Maybe they were cheap after markets. Since you have 90+ carbs use 90+ boots.

[foxox]

Mine lasted 20+, the 88' were original. Those look thin. Both bikes were about 3/8" thick at the carb side. Maybe they were cheap after markets. Since you have 90+ carbs use 90+ boots.

Okay, hmm... maybe I'm an idiot haha. I just went through my entire receipt collection and could not find where I purchased new boots (except new airbox boots I purchased recently).

Maybe I never did replace them! I might only have replaced the o-rings (which I definitely did do). In my service log I have 3/20/2011: "Vacuum leaks, replaced boot o-rings (fixed the problem)"... no mention of new boots :3

So... perhaps these are ancient 1989 carb boots, or like you suggest, maybe a PO put on aftermarket ones. The OEM #4 boot which I replaced recently looks pretty much identical to the one it replaced so if size is the primary determinant, then the old ones should be OEM too... probably original.

I've been avoiding posting about my troubles this week because I figured I would post and then figure out what the problem was right after posting here asking for help... looks like that happened just as expected...

Also, these are the 1989 carbs so it's right that I have the 1989 boots.


I'm still curious about whether UV light and chemicals like starter fluid would cause this sort of deterioration, if anyone knows

[steves]

If the bike has been mostly stored inside, they'll last a long time. But any prolonged storage outdoors is going to make those fall apart after a few years...

[foxox]

This morning I checked the #2 and #3 boots and they're cracking too! Moreover, I did a more thorough check for vac leaks and it looks like the throttle/butterfly valve seals on the sides of the carbs are going bad too. This stuff was all fine 4 years ago when I first rebuilt everything, so if it's all original (and it probably is... the butterfly valve bolts look like they're factory peened), I guess around 25 years is how long this stuff lasts. New OEM parts on order... boots, seals, and float bowl gaskets for good measure. After this, the only wear-prone part I will not have replaced (since they're not available) is the emulsion tubes.

The butterfly valve seals on the 2/3/4 carbs are leaking but even so, those carbs seem to be operating well. #1 is still giving me trouble; perhaps its seals are just much more busted than the others or I've still missed something in the pilot circuit (though I've cleaned and examined them thoroughly multiple times to be sure over the past few days). I considered it could be an electrical problem but the #1 plug is making beautiful blue sparks and the voltage and resistances at the coil is fine. I think it's strange how quickly this problem started... bike was running great, then cylinder #1 completely crapped itself overnight while sitting in my garage. It feels like a pilot circuit problem but I've checked everything so carefully I am at wit's end here. Fingers crossed it's just this vac leak stuff and everything will work in a few days when the parts come in...