'96 carb sync

[dbikers]

Hello All,

I'd like to think i'm not a complete idiot (perhaps this is merely wishful thinking)...

I have a '96 RS (boulevard?) and i belive is a XVZ13A.

http://i124.photobucket.com/albums/p14/dbikers/2012-07-20_11-40-40_132.jpg

 

I have the had this bike only for a couple of weeks and have been pretty happy with it other than the pesky vibration in 4th and 5th gears. I have read (and have been told) that i need to sync my carbs, so i bought a motion pro (i've read that the glycol will stick to the tubes of the gage and sure enough they do and i already wish i had gotten a morgan carbtune). At any rate, after calibrating the tool and hooking it up to the carbs the sync looked like this.

http://i124.photobucket.com/albums/p14/dbikers/2012-07-29_14-15-33_156.jpg

So i began to sync the carbs using this page from my clymer manual

http://i124.photobucket.com/albums/p14/dbikers/2012-07-29_20-14-38_307.jpg

However, this page is very different than the carb sync in some of the tchnical lbraries here as well as on Venturers http://www.venturers.org/Tech_Library/index.php?action=article&cat_id=002010&id=311

Well, to say the least i never got the carbs sync'd correctly and it's now worse. The screw to sync 1-2 worked perfect but the others adjustments didn't work correctly. Though i haven't ridden it, it backfires and pops and smells "hot" (lean) after adjusting the "A" screw to sync 4-3 and then the "B" screw to sync 2-4.

Can anyone with a '96 tell me if the page from the book that i have attached is correct? If not can anyone tell me what the "A" and the "B" screws do on my bike so i can get them back to what they should be?

Thanks in advance all.

John

Edited July 30, 2012 by dbikers

[Marcarl]

Guess you are are going to have to answer some questions:

The carb sync tool you are showing, were all synced before you hooked it up to the bike?

Which screws were you turning on?

 

The page from your manual doesn't show up so good, so maybe we'd better start from square one to keep things simple. Take some pictures of the screws.

[dug050]

Hi John and welcome to the forum. I had the identical bike as yours but sold it a week ago. They are a great bike so don't get discouraged.

The Royal Stars are different from both the first and second generation RSV. They are similar in appearance but the carb setup is different. The page you show is correct for your bike, the screw on the left side under the choke lever syncs carb #1 to #2 and is adjusted first, screw A syncs carb #4 to #3 and is adjusted second, screw B syncs carb #2 to #4 and is adjusted last.

I had a set of mercury tubes that I believe are similar to the Motion Pro but use mercury instead of the glycol. Things I might suggest are :

1. be sure the hoses fit tightly on the vacuum port nipples

2. be sure to adjust the screws in the correct order

3. turn the screws in small increments, it only usually takes small adjustments

4. rev the engine between adjustments to make sure there is no binding in the linkage

5. check the idle speed after each adjustment, as you sync the carbs the engine may change rpm's

I never had any problems when following this procedure. Synchronizing will only be entirely successful if your engine timing and valves are within spec and the carbs are clean with no restictions. If you have no luck following the procedure in the manual it may be time for a valve check and adjustment and check to be sure there are no other vacuum leaks. There are good articles on this site on doing this. The pilot screws also have an impact on synchronizing since you are doing the adjustments at idle speed. Some people do the sync at engine speeds closer to highway operating rpm's, you could try this. One thing I would stress is that you record all current settings before you make changes so you can at least get it back to where it was before you started if it gets worse.

A good dose of Seafoam will help clean your carbs if they are not too bad.

Synchronizing should be the last operation after checking all the other things.

 

Good luck, there is a wealth of information on this site and very knowledgeable owners that will assist.

 

Doug

[dug050]

Something I forgot to mention, I don't know exactly what the calibration marks on your Motiom Pro represent but it appears from your photo that the sync between #1 and#2 and between #3 and#4 don't look too bad and may be within spec. The sync between #2 and #4 which is adjusted by screw B may be the issue. If I remember correctly when you turn that screw columns 1 and 2 should come down and columns 3 and 4 should rise up until all four match.

If this isn't happening check the linkages for binding.

 

Doug

[dbikers]

Something I forgot to mention, I don't know exactly what the calibration marks on your Motiom Pro represent but it appears from your photo that the sync between #1 and#2 and between #3 and#4 don't look too bad and may be within spec. The sync between #2 and #4 which is adjusted by screw B may be the issue. If I remember correctly when you turn that screw columns 1 and 2 should come down and columns 3 and 4 should rise up until all four match.

If this isn't happening check the linkages for binding.

 

Doug

Hello Doug,

i calibrated the tool before attaching to the carbs and attempting the sync.

Screw number 1 seamed to complete the sync for 1-2 with no problem

Screw A seemed to sync 3-4 but ( i think)

Screw B seemed to sync left bank to right side.

i would blip the throttle 3 times between checking. at one point i had them all synced ...then i shut the bike off and when started it again it was no longer synced. that's where it seemed to go wrong

in trying to sync 3-4 with the A screw i got carried away (actually, i tried to adjust both cw and ccw and it just got worse....

right now the right side is backfiring bad (lean i believe)....cyl 3 is pulling the glycol all the way up if i leave at idle.

i think i need to richen the A screw but not sure which direction (cw or ccw) i need to turn it to do so.....

am kicking myself (as i should) as i didn't note exactly what adjustments i made (i know better than that)..

any further help would be greatly appreciated.

 

john.

[dug050]

Hi John

I am at a bit of a disadvantage since I don't have the bike anymore to go out and check it but I will try to recall what I did. As you turn screw 1 you should see the levels in column 1 and 2 come closer together or farther apart depending on what direction you turn it. Once you have them equal move to screw A and do the same thing to equalize the levels in columns 3 and 4. You now have carb 1 sync'd to carb 2 and carb 3 sync'd to carb 4. Now as you adjust screw B you should see both columns 1 and 2 move together and columns 3 and 4 move together to sync the two banks.

If you had them all sync'd at one time and turned off the bike and found that they were out of sync when you restarted it I would guess that you have some binding or excessive wear in your linkage that results in the throttle plates not returning to the same position every after you blip the throttle. When you are syncing carbs you are not leaning or enrichening mixtures in the same way as adjusting a mixture screw, you are making slight adjustments to the position of the throttle plates so they are all drawing fuel the same.

If you can get 1 sync'd to 2 and 3 sync'd to 4 but can't get the two banks equalized my guess would be a linkage issue, if you can't get anything to stay in sync you may have to systematically look for vacuum leaks from loose clamps, cracked intake boots, holes in diaphrams..etc.

You didn't mention how many kilometres on your bike, has it had a valve check done?

I don't know if this will help you but keep posting on your progress and others will also help resolve your problem

[wes0778]

Hello All,

I'd like to think i'm not a complete idiot (perhaps this is merely wishful thinking)...

I have a '96 RS (boulevard?) and i belive is a XVZ13A.

http://i124.photobucket.com/albums/p14/dbikers/2012-07-20_11-40-40_132.jpg

 

I have the had this bike only for a couple of weeks and have been pretty happy with it other than the pesky vibration in 4th and 5th gears. I have read (and have been told) that i need to sync my carbs, so i bought a motion pro (i've read that the glycol will stick to the tubes of the gage and sure enough they do and i already wish i had gotten a morgan carbtune). At any rate, after calibrating the tool and hooking it up to the carbs the sync looked like this.

http://i124.photobucket.com/albums/p14/dbikers/2012-07-29_14-15-33_156.jpg

So i began to sync the carbs using this page from my clymer manual

http://i124.photobucket.com/albums/p14/dbikers/2012-07-29_20-14-38_307.jpg

However, this page is very different than the carb sync in some of the tchnical lbraries here as well as on Venturers http://www.venturers.org/Tech_Library/index.php?action=article&cat_id=002010&id=311

Well, to say the least i never got the carbs sync'd correctly and it's now worse. The screw to sync 1-2 worked perfect but the others adjustments didn't work correctly. Though i haven't ridden it, it backfires and pops and smells "hot" (lean) after adjusting the "A" screw to sync 4-3 and then the "B" screw to sync 2-4.

Can anyone with a '96 tell me if the page from the book that i have attached is correct? If not can anyone tell me what the "A" and the "B" screws do on my bike so i can get them back to what they should be?

Thanks in advance all.

John

If you are new to this/these bikes I would caution you that in most instances 5th gear is for 65mph plus on an open level highway. Anything under that you will be lugging and the bike WILL vibrate in protest. Around town in stop and go traffic I rarely get my '98 any higher than 3rd. BTW 3rd is good to about 96mph, indicated on your speedometer. That's where the rev limiter will catch it. Don't be afraid to hit the rev limiter in 1st, 2nd or 3rd, as it will not hurt this almost bulletproof V4. Now as for what the local LEOs will think about 96mph,THAT is at your own risk!!!

[tazmocycle]

does the sync tubes jump around a lot when you put the screwdriver on the screws to adjust them?if they do you may has some looseness in the springs or levers that holds the carb shafts together. if you screw them ccw too much the springs can come out. the single screw syncs the 1 &2 carbs together, the #2 screw which is the screw towards the back of motor, syncs the 3&4 carbs together and screw #3 towards the front of motor, syncs the 2 banks of carbs(1&2 to3&4) together. if you have them wayout of sync you can pull the carbs off so you can see the threaded ends of the #1 & #2, screw the screws ccw till the end of the screw is even with the bracket it's screwed in, then turn them back in 3 full turns cw. the #3 screw is around 1 turn cw from even with bracket. i've got this off a set of carbs that was synced just before taking them off, i think this will get you back close enough to start over.

[dbikers]

well.....i got it

 

i took the motion pro back and was refunded (the glycol sticking in the columns really made it impossible). i promptly went to harbor freight and bought two fuel pressure/vacuum gages, made a couple of chokes (i need to re-do 'em with some smaller orifices) and got 'er done!

http://i124.photobucket.com/albums/p14/dbikers/hfvacgage.jpg

 

i honestly can't tell whether or not the vibes are gone (feels a l'il worse in 4th and a l'il better in 5th ). i think i'm gonna monitor the mpg and maybe with some smaller chokes go back and re-sync one more time and call 'er good.

 

thanks all for your help in this matter. your input really helps. one more payin' member about to join.

 

john

Edited August 13, 2012 by dbikers

[Seaking]

a little note about synching carbs that make a little bit of difference for some folks.. when you put the screw driver to the adjustment screws, be careful not to push hard against the screws as you turn it as it chugs down the engine (I'm not technically savvy enough to explain why, just know that it does..).. So when you make your adjustments, place the screwdriver up against the screws and gentle turn the screw driver just a little.. if you press against the screws, the revs drop and gives you an erroneous reading when synching.. when you smoothly and gently blip the throttle, they reset themselves and you'll find your synch is way off.

 

Just a note about the synch tools; I have all three manometers, the Carb tune, the needle dial one and the Pro Motion liquid one and the pro motion manometer is by far my favourite one to use as it's more precise and allows you to really get the synch done properly.. As far as the fluid creeping up the tubes, I find that getting the revs up a bit and holding it allows the fluid to settle itself properly down the tubes when calibrating the tool before synching the carbs. I used the carb tune to adjust the synch and after a test ride, put the pro motion to it and wow, a world of difference.. so smooth I haven't gotten any hand buzz at all since the last synch.. I put the motion pro to the bike again after that test ride and found the synch spot on again..

 

yes, I would admit its a more finicky tool to use but its well worth the effort..

[tazmocycle]

the reason the idle goes up and down while you are adjusting the screws is that you are pushng on the throttle shafts that the throttle cables pulls. it's best to wiggle the throttle after you adjust the screws so it sets back down after pushing on them, some problems i think is caused by getting in a hurry. i put josh's set back together after the bike shop warped them all up. put them on sunday and got his back running good, may need to recheck them after he runs them a few weeks. i shot a little video of checking the float heights after setting them a little over 9mms, itried to show my calipher and the reading but the camera wouldn't folcus on it. i'll try and put it on here, haven't put a video on here yet, see what i can do.