JBM Carb Boots

[grizld1]

I just finished installing a pair of carb boots from JBM Industries. Don James claims that his boots will support the heavy OEM carbs without back support. I'd been using a pair of fresh OEM-quality Tour Max boots, but getting rid of the hanger springs I'd rigged on my (also heavy) TM36/68 pumpers seemed like a good thing to do.

Don's boots are first-rate and very robust--they offer heavier flanges, thicker walls on the boots themselves, a very positive lock on the carb spigot, and firmer support than an OEM setup with airbox in place. The only quibble I can find is that the vacuum tubes are straight, without barb ends, which will make blind plug retention a little dicey. My first thought was to sweat a fitting on the ends, but Don cautions against that, as heat may damage the adhesive; JB Weld will work just fine.

I recommend the boots highly: www.jbmindustries.com .

[tomterrific]

Griz,

You may consider a dot of Super Glue to hold on the nipple plugs. This is a trick suggested for boosted car hoses. I'm sure you can find another adhesive if Super Glue seems a bit permanent. I have used coarse sandpaper to Twist and Turn on a straight nipple to get a series of perpendicular scratches on the nipple. This gives the rubber something to key onto.

Another bit of interest is spring clamps vs. screw clamps. Replacing all my spring clamps on my cars fuel injection hose to run much higher pressure safely I found an SAE paper. It turns out the spring clamps are safer due to the elastic hose taking a set and the screw clamp staying the same. In effect, the screw clamps loosens it grip on the hose over time. A spring clamp exerts constant pressure through the life of the hose.

Tom Graham

[dogbunny]

You can use a tube flaring tool, such as are used for small copper tubing compression fittings, to make a small barb at the very end of the fitting. Only thing is, there may not be enough tubing sticking out of the carb holder to grab onto. However, this works great if you are making your own sync fittings, and you flare the end before you glue the fitting into the carb holder.

[5twins]

You might also thread the inside and plug it with a screw or thread the outside and cap it with a small acorn nut.

[grizld1]

Dogbunny, the tubes are steel and too thick-walled to flare. Good suggestions, Tom, thanks. I usually use spring clips on the blind plugs, but the straight tubes had me wondering how much good they'd do. I'll rough up the tubes as you suggest and give it a go; I always carry spare plugs, so if it doesn't work long-term it's no great loss. 5twins, I like those ideas, but I'd hesitate to put much torque to a glued-in vac tube.

It really is a minor quibble, and as you guys have pointed out there are lots of ways to skin that cat--Don's made a great product!

[dillrepair]

yeah i really wanted to buy them from him for my bs34's but he is out till a few weeks from now... he builds rubbers for rotax airplane engines etc so i trust that you have to be at least a little more hardcore to get business in that arena. Those diaphragm replacements look tight, mine were good on the rebuild but i'll use him for any future need after my tourmax and stock diaph. wear out.

[ShakerNorm]

I have a set of his diaphragms on my 79 (BS38's) and they seem to work great.

[twinfan]

Keep in mind that these caps are holding in vaccum for the most part and not pressure, I am sure they would probably stay on without any further engineering, as long as they are a tight fit to begin with.

[dogbunny]

Jul 18, 2010 6:20:15 GMT -5 twinfan said:

Keep in mind that these caps are holding in vaccum for the most part and not pressure, I am sure they would probably stay on without any further engineering, as long as they are a tight fit to begin with.

Until you have a backfire...

[scabber]

I have the jbm boots on my 750 the tubes are smaller than the originals. I used a new blind plug from mikes on one side, another one I found in my junk smaller id from auto parts. 1/8 id this fits better than the one from mikes

[grizld1]

Twinfan, did you consider that maybe my concern about blind plug retention might be based on just a little bit of experience? What you've written may make intuitive sense to you, but it's not borne out empirically. Right, scabber, I'm using 1/8" plugs and packing spares. The automotive blind plugs break down pretty fast, it's just a matter of keeping an eye on them.

[twinfan]

I'm not just trying to be a smart a$$, but I see these things get so blown up sometimes and just thought a reminder that we're not working on the space shuttle. I think the best solutions are most often the simplist, such as nice tight fitting caps, and maybe even a drop of super glue if the do tend to work themselves off.

[tomterrific]

The very first breakdown I suffered with my new SR500 was a vacuum petcock hose blown off due to a cold off idle spit. A pain in the a$$ because I had no idea what was going on with the new to me, old bike I just got running.

I can just see Griz crawling around an intersection on his hands and knees looking for the lost nipple cap. Better bring a set of reading glasses on your ride! :^)

Tom Graham (Who has lost nipple caps...No kidding!)

[grizld1]

You'll wait a long time to see that, Tom--I learned long ago to pack spare blind plugs in the tool kit.

This minor point has come to dominate the thread, so to balance things a bit I'll say it again--Don James has come up with a really fine product, and if the need arises I'll buy from him again.

[geezerman]

I have a set of JBM manifolds.
Really nice.
I did pop of a barb and replaced it, but haven't been packing some spares.
Thanks for the reminder.