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BS34 Bench Sync
- nicksorg
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29 Aug 2010 18:40 #394867
by nicksorg
1982 Kawasaki KZ1000-K2
BS34 Bench Sync was created by nicksorg
I have my rack of BS34s on the bench to clean and replace pilot jets. I'm going to check the fuel levels doing the clear tube test. Last time I had them out, I changed the butterflies to be open by letting a little sliver of light in. I'm not sure this was a good change. I have a couple questions:
1.) Can someone give me the steps needed to bench sync these CV carbs?
2.) Should the butterflies be set to be slightly open or closed at rest.
Thanks
Nick
1.) Can someone give me the steps needed to bench sync these CV carbs?
2.) Should the butterflies be set to be slightly open or closed at rest.
Thanks
Nick
1982 Kawasaki KZ1000-K2
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- Rickman
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03 Sep 2010 07:53 #395811
by Rickman
1983 KZ1100-L1 "LTD Shaft"
Wiseco 10.5:1 1171 piston kit, bored by APE
Dyna 2000, Dyna S, Dyna grey coils, WG coil power mod, CB900 starter
Replied by Rickman on topic BS34 Bench Sync
Hi, Nick; I've been staring at the same thing this week! While I know that the BS34's on the XS11 may be slightly different than the ones on a KZ, (Google will lead one to Jamaha forums, as well as other places muahahaha) I'm thinking the baseline bench sync may be similar enough. in the carb outlet, up over the butterfly there are three little holes; position the butterflies with the set screws so that half of the innermost hole is visible. This will leave the b-flies open a crack, yes.
Another bench sync procedure I've seen in the FSM and on this forum is to use a particular something small (drill bit? bread tie?) as a feeler gauge to measure the gap when setting the b-flies, but I'm sorry to say I can't recall what size measuring stick you might use. The idle circuit holes idea just seems more logical for some reason.
You then do the vacuum sync on the bike, and it seems it is best to baseline the idle mixuture, sync, check the idle mixture again, check the sync again, repeat 3rd time if still sober. Bench sync is just for a solid starting point for vacuum sync, it can't replace it..
hope this helps,
Rick
Another bench sync procedure I've seen in the FSM and on this forum is to use a particular something small (drill bit? bread tie?) as a feeler gauge to measure the gap when setting the b-flies, but I'm sorry to say I can't recall what size measuring stick you might use. The idle circuit holes idea just seems more logical for some reason.
You then do the vacuum sync on the bike, and it seems it is best to baseline the idle mixuture, sync, check the idle mixture again, check the sync again, repeat 3rd time if still sober. Bench sync is just for a solid starting point for vacuum sync, it can't replace it..
hope this helps,
Rick
1983 KZ1100-L1 "LTD Shaft"
Wiseco 10.5:1 1171 piston kit, bored by APE
Dyna 2000, Dyna S, Dyna grey coils, WG coil power mod, CB900 starter
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- Grantl
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- KZRider is Da Bomb!!!
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03 Sep 2010 08:20 #395817
by Grantl
1981 KZ1000 CSR
1983 KZ750 Project Bike
1990 550 Zephyr
1994 KZ1000 P
Replied by Grantl on topic BS34 Bench Sync
The way I have done mine is: I set the adjustment screws to allow the butterflies to appear shut at rest but the key is that when you turn the throttle rod, they all open the same amount at the same time.
So, you sync as usual by syncing 3 to 4, then 1 to 2, then 3-4 to 1-2.
This method usually gets me pretty close.
So, you sync as usual by syncing 3 to 4, then 1 to 2, then 3-4 to 1-2.
This method usually gets me pretty close.
1981 KZ1000 CSR
1983 KZ750 Project Bike
1990 550 Zephyr
1994 KZ1000 P
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- TeK9iNe
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- What did you do!?!
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03 Sep 2010 12:34 - 03 Sep 2010 12:35 #395874
by TeK9iNe
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
Replied by TeK9iNe on topic BS34 Bench Sync
All good info provided above...
After a good vacuum sync on a healthy engine, the butterfly's will be exposing about half the first pilot mixture jet hole at the top of barrels.
Sync is exactly in the order Grant has described.
You dont need to use a drill bit/wire/etc IF YOU ARE GOING TO VACUUM SYNC. If you arent going to vacuum sync, then 1: Your nuts, cause cv carbs really require proper vacuum sync, and 2: Do as accurate as possible a bench sync, and although it will still be fairly off, it will work OK.
When Vacuum Syncing with manometer, remember that low vacuum means the butterfly is open more, higher vacuum means the butterfly is closed more. If one or more cylinders has very low vac and requires alot of adjustment to get up to vac of others, then it most likely has an air leak.
Get the cylinders vac synced, then turn the idle down as low as it can go. Wait a minute idling, then check the pipes by spraying water mist on them and make sure they are all still vaporizing/steaming water (still firing correctly), check sync again. If one isnt firing, then there is likely an air leak, and the butterfly is closed completely to achieve equal vacuum.
Good Luck!
After a good vacuum sync on a healthy engine, the butterfly's will be exposing about half the first pilot mixture jet hole at the top of barrels.
Sync is exactly in the order Grant has described.
You dont need to use a drill bit/wire/etc IF YOU ARE GOING TO VACUUM SYNC. If you arent going to vacuum sync, then 1: Your nuts, cause cv carbs really require proper vacuum sync, and 2: Do as accurate as possible a bench sync, and although it will still be fairly off, it will work OK.
When Vacuum Syncing with manometer, remember that low vacuum means the butterfly is open more, higher vacuum means the butterfly is closed more. If one or more cylinders has very low vac and requires alot of adjustment to get up to vac of others, then it most likely has an air leak.
Get the cylinders vac synced, then turn the idle down as low as it can go. Wait a minute idling, then check the pipes by spraying water mist on them and make sure they are all still vaporizing/steaming water (still firing correctly), check sync again. If one isnt firing, then there is likely an air leak, and the butterfly is closed completely to achieve equal vacuum.
Good Luck!
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
Last edit: 03 Sep 2010 12:35 by TeK9iNe.
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- nicksorg
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04 Sep 2010 07:14 #396026
by nicksorg
1982 Kawasaki KZ1000-K2
Replied by nicksorg on topic BS34 Bench Sync
I put the carbs back in after installing the remainder of my carb rebuild kits (main, pilot, and needle). Of course she cranks but won't start. I'm going to pull the rack again and put the old needles and pilots back in and see if I can't get her running again. One of these days I'd really like to go riding...
1982 Kawasaki KZ1000-K2
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