cross country carb question

[rowdyrandy]

Tax time is here and I was thinking about looking into some different carbs for the bike. Right now I have the stock Bs38's and they've been fine, no real complaints, I'm running Uni's as well. The only I will say is that anytime I crack the throttle open from idle, I get a breathy kind of gasp and then it starts to go, not very snappy but I'm assuming thats not far off from normal.. My question is how forgiving are the Bs38's over say Vm's, Tm's, etc..for changes in elevation, humidity, etc..? I'm planning a cross country trip this summer and If the Bs38's are the best bet, I'll stick with those. But if I could get something a little more responsive and still be ok, cool. I'm in denver and we're going to be going over some passes for sure - this summer I was up and down from ~11,000ft, saw a bit of a drop off in power but wasn't all that bad. Motor is 4th over and I'm going to have a set of gordon scotts on the way with his mufflers.

 

[retiredgentleman]

I find the BS38's work great where I drive. I live at 3400' ASL and take trips into the mountains.................7200' ASL at times. I don't feel any difference in power at all.

In Denver you're already down in power compared to the lads at sea level. For every 1000 feet ASL you lose about 3% power.

 

[XSLeo]

The BS38 carbs being vacuum operated are much less effected by elevation changes than carbs that have a direct linkage from cable to slide.
The direct connected carbs will respond faster to drastic throttle changes quicker than vacuum carbs.
On vacuum carbs it takes time for the carbs to sense the change in vacuum and respond. Just turn the throttle a bit slower and the carbs respond fine.
Leo

 

[rowdyrandy]

I find the BS38's work great where I drive. I live at 3400' ASL and take trips into the mountains.................7200' ASL at times. I don't feel any difference in power at all.

In Denver you're already down in power compared to the lads at sea level. For every 1000 feet ASL you lose about 3% power.

I know, tell me about it.. Its was a bummer to do the rebuild and just not get the full potential out of it. On foggy cool days here though it's like a different bike, pulls a whole lot better. Sounds like i'll hold on on to the 38's a little longer and put the money elsewhere, thanks guys.

 

[5twins]

Sounds like you haven't re-jetted and tuned them properly for your mods and/or elevation. I have several sets of the 38s and all respond well, pretty much instantaneously, to throttle inputs at all speeds. But then again, I took the time to jet and tune them correctly. I went above what was ideal to the point that carb functions started degrading, then stepped back down to what jets worked best. This is the proper and time proven way to tune carbs but most can't be bothered. To them I say it is what it is and I guess you'll just have to live with the way it runs. Certainly, it can be made to run better, just not by you.

 

[rowdyrandy]

Sounds like you haven't re-jetted and tuned them properly for your mods and/or elevation. I have several sets of the 38s and all respond well, pretty much instantaneously, to throttle inputs at all speeds. But then again, I took the time to jet and tune them correctly. I went above what was ideal to the point that carb functions started degrading, then stepped back down to what jets worked best. This is the proper and time proven way to tune carbs but most can't be bothered. To them I say it is what it is and I guess you'll just have to live with the way it runs. Certainly, it can be made to run better, just not by you.

Its funny, on my last post you made an uneducated comment on my jetting because you didn't take the time to read that I was at elevation...Now here you are again offering nothing but a crap attitude towards my perceived aptitude. You've obviously lost sight of what this forum is for. Please stay off my threads unless you plan to offer help. We're all learning something new everyday in one way or another - I'll get it sorted, always have, always will.

 

[5twins]

OK, good luck then. Buy some VMs, then you'll really be in for a treat, lol. You're supposed to include info in your posts like what year carb set you have and what jetting changes you've made. That is, if you expect really helpful responses. You think we'll dig through all your old posts to find out? LOL You're getting as much help and advice as you deserve.

 

[rowdyrandy]

OK, good luck then. Buy some VMs, then you'll really be in for a treat, lol. You're supposed to include info in your posts like what year carb set you have and what jetting changes you've made. That is, if you expect really helpful responses. You think we'll dig through all your old posts to find out? LOL You're getting as much help and advice as you deserve.

“Never argue with a fool, onlookers may not be able to tell the difference.”

- Twain

Jetting specs are irrelevant concerning my original question... and this is the most you're gonna get out of me from here on out - Man, I remember when you were useful too...shame, but sounds like it's time to retire boss.

 

[scabber]

The CVK carb off the EX500 is a good choice. Vacuum operated flat slides modern design . Read the thread.

 

[rbjenterprises]

I am going to be interested in what you end up with. I plan on replacing my filter box and filters with a pair of unit's. Stock XS650B.

 

[rowdyrandy]

Hmmmm read up on the ex500 carb swap last night...really intriguing. Seems like the best of both worlds and with their availability I think I can score a pair for not too much. thanks for the tip