XS650 CARBURETTOR ID AND BUTTERFLY VALVE SYNC - DONE

[@info4jon]

major help. thank you!

[@ludditeneaderthal]

Years after the fact, but the proper "bench sync" for CVs, or any multi carb set up with butterflies is to "gap match" the throttle plates. You need a thin drill bit, like a 1mm. First set that central sync screw so your right side butterfly is obviously further open than the left. Then take your drill bit, lay the shank end on the bottom of the left carb throat, so the smooth shank is sitting where the butterfly would normally travel in going fully closed. Now turn the idle speed screw so that left butterfly just barely drags on the drill shank like a feeler gauge. Now place the bit shank in the right carb throat, same exact way. Adjust the sync screw for the same feeler type drag on the shank of the bit. Hey, presto! You have now set the carbs with equal plate gap. If you open the carbs with the idle screw, or close them with it, or by twisting the throttle actuator the cables mount to, they should both open and close in sync. You then do a vac sync once they're mounted and get the engine running, because the slider springs, vac bleed drilling, and diaphragm action might not actually match perfectly, if the vac sync shows a really marked difference with equal butterfly gaps, it indicates a problem. Maybe a bad slider spring or diaphragm, maybe a blocked bleed drilling, maybe valve adjustment, maybe an intake leak, etc. Find and fix that problem, and then try again.

[@info4jon]

That doesn't makes sense, when you adjust the second side with the balance adjuster your other side is going to change again also normally there is no gap to put a drill bit under under normal circumstances... I think you have left out vital information.. also after this procedure where do you set the idle screw? Because if its miles out (which I think it will be) that bike is not going to start

[@ludditeneaderthal]

@@info4jon I think you have a reading comprehension problem. You balance the throttle blades ON THE BENCH. The throttle screw setting is immaterial, you aren't going to run the bike at that setting, you're just matching the throttle positions. You use a SMALL drillbit to do it, 0.060 inch (1.5mm) or smaller. The only thing you're doing is positioning the plates equally on each carb. That should provide an equal vac signal to each slider. You STILL have to vac balance the carbs, you STILL have to do the normal pre-start adjustments to allow starting and idling. However, the vac balancing SHOULD be minor. If it requires major adjustment, that would indicate a mechanical problem (slider springs, diaphragms, valve adjustment, clogged or oversized slider drilling, rings, etc). The ONLY object of it is to provide an equal vac signal to the slider drilling on each carb from go. An adjustment while running will undoubtedly be needed (because no 2 parts or adjustments will be exactly identical). If you don't balance the plates first, you have no frame of reference to determine if another fault is influencing the balance setting. By equalizing plate position in reference to the shaft position, you establish that frame of reference. If you doubt me, check ANY manual, they ALL list the adjustment on any multicarb setup with throttle plates

[@info4jon]

@@ludditeneaderthal No i can read perfectly, you need to explain the procedure better, of course its on the bench, you couldn't do that on the bike could you.... I'm not trying to be difficult but your procedure is lacking information and without that information its useless, at least in this video you can clearly follow what he tells watchers to do... in your comment its not enough info to do the procedure... Respect to you.

[@ludditeneaderthal]

@@info4jon what more info do you need? You use a small drill bit, the idle stop screw and the synch screw(s) to set the throttle plates to the same gap on the bore. If you want a precise step by step "turn this screw here clockwise" breakdown for a particular bike BUY A DECENT MANUAL, because it WILL be in there, provided the bike is equipped with carbs that have throttle plates.

[@info4jon]

@@ludditeneaderthal Hey no its fine, thanks for the info, its quite an easy process but my concern is after adjusting the main idle screw then the bike wont start if is way out ... do you know what the factory setting is for the idle screw? I think I read its 8 turns in? Does that sound right? Thanks for your help :)

[@gerdshed]

Thanks for the info, Always comes in handy!

[@PedroMata-pk7sb]

Donde consigo los carburadores de la xs 650 cc

[@weeverob]

very clear, tx!

[@weeverob]

hi, i've got a BS-34 mikuni that i am changing the 4 seals on the 2 butterfly shafts. in order to gain access to the 2 inside seals i had to unscrew one of the carbs from the angle iron. to make my work easier i disconnected the black, rigid T-shaped fuel pipe. since i didn't see a clip, clamp or screw locking the plastic pipe to the carb i figured it was a friction fit. when i pulled the fuel line pipe out i saw the hidden end was covered with a white substance, stuck on but dry and powdery. is this material some sort of sealer to keep the fuel line from leaking? this substance is also inside the receptacle where the line slides into the carb. tx.

[@Denis-bo8ms]

Hello I have a bank of 1983 XS650 carbs that I would like to disconnect in order to strip the paint of each carb and repaint. Is it very difficult for a novice mechanic to put them back together? Thanks

[@mattgray9699]

thank you!