Replacing BS 38 carb holders...

TeeCat · Posted: November 17, 2009, 8:50 am Post subject: Replacing BS 38 carb holders...

'morning, guys...

I just received these BS 38-compatible replacement intake manifolds from Old Bike Barn. They're nice and supple. I plan to replace mine this weekend, time permitting. Mike Morse at 650 Central told me that they should be fine because I'm running pods and don't have to worry about airbox alignment.

I have two questions, though:

- If you look at the enlarged pic at the linked page, you'll see that the carb-side face of the holders have what appears to be an alignment notch of some kind. Offhand, I'm not sure if the existing ones have that or not. Do I need those and, if not, can I gently shave them flush?

- My early carbs ('73) are not mechanically conjoined - they have two throttle cables - but have a single (what appears to be) rubber transfer tube/hose that runs between them, friction fitted to a brass fitting on each carb. If the carbs end up at a slightly different angle after I replace the holders, I may need to replace this tube. Is any kind of fuel line okay? Also, I have noticed that the brass fitting in the right carb will come right out of the carb body when I separate the carbs. Do I need to worry about that? It doesn't ever leak.

Thanks!

TC

Yamahopper

They look Identical to the ones I got from MikesXS.com. Which worked perfectly!

Yamahopper

No, I got the barbed ones, but other than that...

TeeCat

Thanks, YC!

pumps

The barbed ones are to make it easy to sync , yes?

TeeCat

Thoughts on my other questions still welcome.

Also, is there a concern with ethanol fuels with these, guys?

tacoswild

TC, that tube carries the choke mixture (when you have the choke on). Maybe not so bad as straight gas but if you can find a fuel line that fits tight that would be ideal.

The other question, I think you mean that sort of rib or ring inside the holder? My carbs have a grove that mates with, I would think they all do.

TeeCat

taco, thanks very much!

As to the "notch", it's not the groove, but it's like two little raised spots on the carb-side face of the rubber part. It has me wondering if there's a designated left and a right holder or something. I don't have my bike in front of me atm.

gordo

Tee Cat,when you take off your carbs, see if there is a 'notch' for the carb boot's.If not, you can, of course, shave the little nub's off if you like, but I don't think it will matter either way. I can't remember if there is a spot on the carbs or not.And as far as a right & left side, again I'm not sure. Just hold each one on the head before bolting it on & see if there is any difference as far as coming off the head straight or crocked. I would go for the straightest of the comparison. Don't forget to hold them on tight & also turn them upside down. You want the carbs to sit as level & straight as possible.
On the fuel line, only fuel line should be used. I think it's 1/4" id.Other line will deteriorate & gunk up the carbs.

TeeCat

gordo, thanks much for the tips! I'll employ them for sure, especially the leveling part. I'd imagine there are only so may ways, but I'll do as you suggest, compare old to new, and try to see what works best.

TC

gordo

Glad you finally found some, and for a resonable price.

TeeCat

I replaced these today with ones from Old Bike Barn. While they seem to fit, it's correct that the airboxes would be a problem. I'm not running them so it's not an issue. However, the angle of the carbs is changed just enough so that my stock side covers do not fit properly any more, so I have to figure out a way to mount them without using the bottom pivots. I might have to try to get a longer top bolt and just let them hang from it. I'd love custom ones but I have neither the skills nor the equipment.

It's too early to tell yet whether they will have an impact on my idle and decel pop on the left side. The old ones were not visibly damaged, but they had a kerfed metal sleeve over the rubber, right beneath the clamps, that might have impeded closure a bit.

Will test on a dry day... another variable eliminated.

TC

tacoswild

Cool, that's really good info TC. You're the first person I've heard from that tried these on an older xs.

TeeCat

Thanks, taco. At least another variable is eliminated, but the side cover solution has not knocked at my cerebral door yet. Sad

jayel

the stock intakes have a left and right (makes a difference on air box line-up) on your fitting that pulls out, a little jb weld then give it a light tap to seat it

TeeCat

I tried both ways, jayel. One way had the carbs too far in toward center. These replacements are canted, whereas my original ones were not, so I had to play with them and try to get the carbs in roughly the same alignment as stock. Left to right I'm good... but the intake bells are a little higher, I think. They are not a "direct replacement" on a '73. This is why I asked lots of questions on this topic earlier, but there were no definitive answers, so I guess I'm the first, as taco said.

JeffM

Thanks for posting this Teecat, great info.

TeeCat

My pleasure, Jeff.

Well, the side covers will work... they mount in approximately the stock location... but I won't be able to use the lower mount points. I'll just use the top bolt. I had to get two longer ones, and I need two rubber spacers to snug up the mounting so they don't move or vibrate. Shouldn't be too hard.

TC

What Happened to 650rider.com?

Yamaha xs650