Putting Carbs On

brasco18 · Posted: June 29, 2007, 2:17 pm Post subject: Putting Carbs On

Is there a trick or special tool that will make putting the carbs back on my '77 easier than just using brute force? The amount of energy and time required to remove and reinstall the carbs actually stops me from doing any work on them. I'm getting about 28MPG right now (unless my odometer is incorrect) and need to get my carbs in shape. Also there has been mention of a jet size of 170 up to 200... what jet is this? Mikesxs has mainjets that go up to 160 but not higher and the pilot jet stays down in the double digits. What would be one main/major thing I could do to increase my MPG, without having to fine-tune each jet in my carbs?

Xumi · Posted: June 29, 2007, 3:11 pm Post subject: Re: Putting Carbs On

A little bit of soap and water on the boots would help get them in a little easier.. And practice.

I'll let someone else make jet recommendations.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Tune it up completely (valves, points, timing). Check your carb jet sizes as there's no telling what the last owner put in. You should be getting around 50 mpg. Also check your float levels - they may be too high. Those 170 to 200 mains are for aftermarket VM slide carbs, not the original CV diaphram type. Those sizes would be way too big for the stock carbs. Here's a chart of the correct sizes for the various years .....

xs650temp.proboards29....1170448810

To remove/install the carbs, I lube the boots with WD40 or CRC556 (my fave) then rock them up and down as I pull/push. They pop right in/out pretty easy that way, for me anyway. Most jet changing can be done with them in place. Drop the bowls with a stubby phillips to change pilots, change mains through the drain plug (bowls still installed), and the tops can be removed to access the needle by just pulling the tank and breather hoses.

78xs · Posted: June 29, 2007, 4:56 pm Post subject: Re: Putting Carbs On

hi,

first thing i would check is the air cleaners (dirty?)

if you decide to dig into the carbs, here's a link to some info that i found helpful dealing with them. there is one (at the bottom of the page) that covers remove and replace carbs. it takes a little while for the pics to load, though.

the other thing that i found helpful was taking the bike out for a 5-10 minute ride before taking them out. it warmed up the holders and made it a little easier to get them out and back in!

650wiki.org/index.php/...arburetors

i have '77 carbs on my bike and just spent a bunch of time (and patience) getting them straightened out. there are many folks on this board that are real experts on carbs and they will need to know what (if any) modifications have been made to the bike. (airboxes removed, non stock exhaust, etc)

here's a link to a chart on jetting sizes that you may find helpful. (courtesy of 5twins)

xs650temp.proboards29....1170448810

here's a link to constant velocity carb basics that i found useful: (courtesy of pamcopete)

www.geocities.com/moto...basics.htm

here's one on disassembling & cleaning: (not sure who gave me this one)

users.rcn.com/kochc/mo.../carb.html

having never seen the inside of a carb before this year, i was a bit intimidated. don't feel alone!!!

bob

78xs · Posted: June 29, 2007, 5:07 pm Post subject: Re: Putting Carbs On

looks like while i was typing, 5twins was already on the job.

you're in good hands, brasco18!!!!

78xs · Posted: June 29, 2007, 5:09 pm Post subject: Re: Putting Carbs On

looks like while i was typing, 5twins was already on the job.

you're in good hands, brasco18!!!!

INXS650 · 650Rider Supporter Joined: Mar 22, 2007 Posts: 645

Wow, glad to see I am not alone. I am getting about 33 MPG with mine, but I have the 36mm VM's. Carbs are a fun proposition on these things. If you have the money, get a set of 34mm VM's set up for you, and you won't believe the difference.

brasco18 · Posted: July 2, 2007, 2:11 pm Post subject: Re: Putting Carbs On

Thanks for all the info! Carbs seem to be a hot topic always. I will check those links out and try to educate myself.

As for the build of my carbs, there are no modifications. I recently rebuilt them with a kit from MikesXS so the jets are stock (122.5 and 25). I cleaned them with carb dip, scrubbed everything so they should be super clean at this point. I have stock air filters, boxes. I know one airbox has a foam muffler while the other doesn't.

I recently attempted to lean the mixture out a bit. I learned that the info I got from my Clymer's guide was wrong (I had been enriching the mixture instead of leaning it with the mixture screw). After leaning out the mix, I believe, the bike now does an odd thing... After having the bike up at around 3500rpms for a minute, I pop the clutch and come to a stop. The engine comes to an idle at 1450rpms (can't get it lower than that now) and after about 5-10 seconds, the engine revs up to about 4500rpms for about three seconds. I believe I leaned it out too much. I will enrich it a bit and see if it clears up.

I never thought of the WD40 idea to lube up the manifolds. That's a really good idea. Thus far I have been using brute force and a rubber mallot to get those buggers back in.

Thanks again for the info! I will try to post updates. INXS650, if you get your MPG up let me know and help me out!

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Are your carbs synced? If the right carb is turned up higher than the left one (via the linkage) you'll never get the idle down. You also need to blow compressed air through all the small passageways to insure they're clear. Just dipping and scrubbing isn't good enough sometimes.

brasco18 · Posted: July 2, 2007, 6:47 pm Post subject: Re: Putting Carbs On

I synced a couple weeks ago but it was running super rich at that point. I believe I have leaned it out and shold probably sync them again. I will do that one of these days here and post an update.I think I need to run through a tank and see what my mileage is now that I leaned it out. Should be getting 40-50mpg right?

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