BS38 Intake Boot replacements

[RPC3]

Now that I've got my PAMCO in and running I turned back to focus on tracking down my air leak. Bike is a 78 standard, bs38's, everything stock from a carb set up aside from a jetting change. I did replace the throttle shaft seals, so that shouldn't be the issue.

My bike starts fine and once it warms up (after 10 miles of driving or so) the idle will only settle down to about 1300-1500 rpm. When cold I can get it to idle at sub 1000, so the heat from the engine must cause things to open up just enough to allow for an air leak (or further pronounce). With the Pamco my bike is idling much more reliably, so I really tried to pin-point my efforts of spraying starter fluid to find the exact leak. Turns out the leak is coming from where the carbs sit in the intake boots. I tried loosening the metal clamp a bit, as I read here that over tightening can distort the seal just a bit, but that had no change (leak still present). I'm assuming my carbs are either cracked or slightly deformed on the carb to boot seal (engine side seals fine, barb doesn't have a leak on either side). So unless anyone thinks it could be installation or user error (and I'm pretty confident my carbs are seated properly, after having them on and off the bike a few times I've learned the proper feel of seating them - and I did so with the boots greased), I think I'm due for new boots.

So anyway, on to options for new carb boots. I've read enough about the MikesXS boots to know they're probably going to break down after a bit of use due to the rubber not being suitable for ethanol. That leaves me:

1) JBM Industries - seem expensive, would be roughly $83 after shipping, but the quality seems to be decent. No barbs unfortunately

2) Ebay used - I'd prefer not, can't see a used pair holding up any better than what I have

3) Ebay new - There are a few listings for K&L carb boots along with others that just say "made in japan" that are available. More for '74-'77, but I think they'd work fine with my carbs; I just wouldn't get the benefit of the vacuum barbs. As low as $40 with free shipping

Anything else I might be missing? I'm kind of bummed that they're not making the bs38 boots with the barbs, as they'd be easy to cap off and a good feature for really any Bs38 set up. I take it I would just have to run my bike on prime full time if I switched to non-barb boots? I guess I could tap them and insert my own barbs as well, but I'd be a little nervous about ruining the new set. I know my carbs are balanced now as I just did that with my homemade manometer a few weeks back, but its a nice option to have. I don't know...just trying to cover all my bases before taking action.

Thanks

 

[5twins]

You can add the barbs to the non-barb boots. That's what I did when I got mine years ago. Mike's was out of the barbed version at the time. I think I used a 3/16" drill bit which gave a tight fit for the barb (I had to gently tap them in). I put Yamabond on them before installing and they have been fine for years now.

Eventually, I found some N.O.S. originals on eBay. They'll go on when these eventually crap out.

 

[RPC3]

Okay - ended up getting the tour max boots for $39 (shipped). (for anyone interested, ebay link is here: http://www.ebay.com/itm/NEW-74-77-X...?fits=Model:XS650&hash=item541fec75ec&vxp=mtr)

A few questions regarding the installation of the barbs, if you don't mind:

Did you use the stock location of the barbs for the drilled barbs?
Any good source for new barbs, or should I pull the old ones from my existing boots?
Any specific drill speed, drill type, or cutting oil reccomended?
Given the odd angle, did you mount the boots onto a block of wood and then then set that piece of wood in a vise (or something similar)?
Anything other than yamabond for sealing? I've got some permatex gray that is supposed to be suitable for petrolium products (I think its a competing product to yamabond).
Is this way too much hassle and should I just run the bike off prime?

I'll post pictures of the process once I get around to it - I've never really done this kind of thing before but I've got access to a drill press, so just want to make sure I've got everything figured out before I screw them up.

Thanks

 

[DogBunny]

They are kind of spendy, but if it was me, I'd probably buy the MikesXS non-vacuum replacement petcock. You only need one petcock, if the tank has two I'd remove one and blank it off, or simply cap off the one of the petcock outlet nipples. Then you blank off one of the carb inlet nipples -- you only need to supply one, the carbs already have a fuel cross-over tube which acts a tee.
All that leaves is the issue of synchronizing. If you have dual pipes, all the synchronizing you will ever need to do can be accomplished by feeling and comparing the pressure coming out of the pipes with your hand.
But, that's just me... You can make things as unnecessarily complicated as you wish.

 

[DogBunny]

...but if you are going to drill a hole for a barb, yes you use the original position because the metal carb holder shroud that goes around the boot has a slot for the barb.

 

[5twins]

Yes, slip the metal shroud over the boot and start your hole. They drill easy, it's only aluminum under the rubber. I used my old barbs. One was easy because it had pulled right out of the original manifold (that's why I replaced them). The other wasn't too difficult to remove. Press or tap it in a bit to break the sealer or goop Yamaha used to install it, pry it back out from the inside. Work it in/out like this with some penetrating oil for a bit and it will loosen up enough to pull out.

I think the key here is a slightly smaller hole than the barb so you get a nice interference fit. I think I used a 3/16" bit but it was several years ago so don't hold me to that. Test drill some holes on some scrap aluminum to check the fit. Just the Yamabond was all I put on them. I put a light coat on like the bottom 3/8" of the barb and tapped it in until it was flush with the inside wall.

 

[jamesgs4]

+1 for the JBM

 

[RPC3]

quick question - will popping the new boots in the freezer prior to drilling:

1) make the drilling easier or 2) shrink the rubber so that the size of the bore ends up expending and being too big?

Just a thought before I try this out.

Thanks

 

[TwoManyXS1Bs]

Old machinist's trick was to deep-freeze rubber just before machining. Cuts are more precise, don't get that gouging problem. Gotta be quick though, before it warms up and softens...

 

[RPC3]

For anyone pondering this same topic, here is what I ended up doing:

As discussed, I bought some after market boots off e-bay for $40, made it japan, Tour Max brand. Look and felt good, could tell where the new ones had worn over the years.

I was surprised at how easy the barbs pulled out of the old boots. I did have some cracking around one of my barbs, and the other boot had noticeable cracks when flexed. I don't think they went all the way through, but it was safe to say that the boots were worn.

I first cut a square block of wood and then marked holes for each boot on the wood so I could mount the boot to the block while in a vise, oriented so the hole to be drilled was facing exactly up. With one of the old boots mounted to the wood, I set it up in the vise and aligned everything perfectly so my drill bit (3/16ths, as 5Twins suggested) passed perfectly through the hole in the old boots.

I had stuck my boots in the freezer the night before, so I unmounted the old boot (leaving the block of wood in the vise), got the new boot for the appropriate side out - mounted it up, and drilled through. Rinse and repeat for the other side.

I was happy with the results, but a bit nervous as the new bores did look noticeably smaller than the old (perhaps part of the issue). I was able to get the barbs into the new holes without too much pressure, so I figured I was good to try installing them. I put yamabond on the bottom 1/2 inch of the barb, pressed it in with my finger, and then seated it with a plastic mallet. I didn't get the barb 100% of the way through, but it was a tight fit and all but a few millimeters from passing through, so I called it good and mounted everything back up. I'll fire it up tomorrow, but all in all it took about an hour (not counting disassembly/assembly) and went smoothly.

 

[TwoManyXS1Bs]

I would've used a brad-point wood boring bit, to avoid bit gouging/clawing and get the hole walls straight, but your job looks to have come out just fine.

 

[gggGary]

Nice write up and photo spread. Thanks for sharing!

 

[hard_y_rd]

Can this be done with any barbless boots like the earlier ones that didn't have them?

 

[RPC3]

Can this be done with any barbless boots like the earlier ones that didn't have them?

The boots I drilled were esentially manufactured for the '74-'77 models, so I think the quick answer is yes. The exact spot to measure/drill is going to be a little more of a guess, and I'm not sure if the metal bracket that sits over the boot and under the hose clamp has the barb cut outs on the pre-78 boots, but just keep that in mind and it can probably be done very similarly.