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supasamurai · 04-23-2009, 02:06 PM

So I just got my first ever motorcycle. It's great, I love it, but it doesn't run. It's a 2000 Vulcan 750 and with just a little rust on the chrome, I paid $400 for it! Unfortunately the carburetor came in a hundred pieces in a box. The guy that sold it to me pulled it from the shop because he didn't want to sink anymore money into it and I get to rebuild the carb in order to get the bike going.

So the long and the short of it is that while I've got no problem figuring out how to put a carb together, I realize that there are a few things I need to know. I have most of the parts, missing a few hoses and such and those aren't free, but that's ok. The the box held two keihin cvk34 carbs.

There's a light layer of varnish which I know I need to clean, and the jets look good. I need to replace the air cut valve diaphragms on both sides and I think that was why the carb had to get worked on. Also the vacuum valve diaphragms don't seem to fit in there right and there's a layer of fine rust particles on it in places like the guy that took it apart left it out in the rain for a minute and just let the water evaporate out of it. It seems to wipe right off though.

My questions are:

1.) Do I really have to pay $45 apiece for air cut valve diaphragms and $95 apiece for vacuum diaphragms or is there a cheaper way? Seems like I could mosey down to the junkyard and buy a new set of carbs for cheaper than $300, you know?

2.) Why can't I find a dang carb rebuild kit? The o-rings for this thing are gonna run me like $28 per carb if I buy them separate. Whats up with that?

3.) Barring buying new o-rings, how can I tell if the old ones are still good? Should I just assume that they aren't? Could I use rtv sealant or something like that instead of o-rings? Could I just go down to the hardware store and fine some rings that seem to fit right? It it that big of a deal?

3.) Whats with the screw thats attached to a cable and has a knurled nob one the end of the cable, is that the idle stop screw? Which screw do I use to "set the idle"? How do I tune these bad boys?

4.) Finally, like a good puzzle, the pieces seem to go together easily, but I have no clue as to how much to torque things. Which screws are the ones I use to adjust things? Do I screw every screw/jet/bolt etc in till they stop? I learned from rebuilding cars that for small aluminum pieces you should screw until you see the tendons stand out on your hand (which I take to mean a normal person, as I'm a big manual labor type I do it till just before that point), but is that right?

Also, why in the heck did the guy tear the whole carb apart? Maybe there is a rebuild kit and I'm just not finding it. I partially rebuilt a carb on a 65 ford big block and it seemed to have all kinds of fun stuff in it.

Sorry for the length but thanks for the help!

04-23-2009, 02:06 PM	#1
supasamurai Join Date: Mar 2009 Posts: 4	Carb rebuild questions: So I just got my first ever motorcycle. It's great, I love it, but it doesn't run. It's a 2000 Vulcan 750 and with just a little rust on the chrome, I paid $400 for it! Unfortunately the carburetor came in a hundred pieces in a box. The guy that sold it to me pulled it from the shop because he didn't want to sink anymore money into it and I get to rebuild the carb in order to get the bike going. So the long and the short of it is that while I've got no problem figuring out how to put a carb together, I realize that there are a few things I need to know. I have most of the parts, missing a few hoses and such and those aren't free, but that's ok. The the box held two keihin cvk34 carbs. There's a light layer of varnish which I know I need to clean, and the jets look good. I need to replace the air cut valve diaphragms on both sides and I think that was why the carb had to get worked on. Also the vacuum valve diaphragms don't seem to fit in there right and there's a layer of fine rust particles on it in places like the guy that took it apart left it out in the rain for a minute and just let the water evaporate out of it. It seems to wipe right off though. My questions are: 1.) Do I really have to pay $45 apiece for air cut valve diaphragms and $95 apiece for vacuum diaphragms or is there a cheaper way? Seems like I could mosey down to the junkyard and buy a new set of carbs for cheaper than $300, you know? 2.) Why can't I find a dang carb rebuild kit? The o-rings for this thing are gonna run me like $28 per carb if I buy them separate. Whats up with that? 3.) Barring buying new o-rings, how can I tell if the old ones are still good? Should I just assume that they aren't? Could I use rtv sealant or something like that instead of o-rings? Could I just go down to the hardware store and fine some rings that seem to fit right? It it that big of a deal? 3.) Whats with the screw thats attached to a cable and has a knurled nob one the end of the cable, is that the idle stop screw? Which screw do I use to "set the idle"? How do I tune these bad boys? 4.) Finally, like a good puzzle, the pieces seem to go together easily, but I have no clue as to how much to torque things. Which screws are the ones I use to adjust things? Do I screw every screw/jet/bolt etc in till they stop? I learned from rebuilding cars that for small aluminum pieces you should screw until you see the tendons stand out on your hand (which I take to mean a normal person, as I'm a big manual labor type I do it till just before that point), but is that right? Also, why in the heck did the guy tear the whole carb apart? Maybe there is a rebuild kit and I'm just not finding it. I partially rebuilt a carb on a 65 ford big block and it seemed to have all kinds of fun stuff in it. Sorry for the length but thanks for the help!
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