Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

4 carb sync question

Discussion in 'Maintenance and Servicing' at netrider.net.au started by Jackstar, Sep 25, 2013.

  1. I have had a look on google & you tube but cant quite get the answer I'm looking for, hope this is the right forum??

    Anyway, I have synced a twin before with the bottle and tube method and worked a treat but I now want to sync a four cyl.

    I cant be bothered to build a new homemade manometer with four tubes unless I have to, so....



    I get that I sync 1 & 2 first and then 3 &4 second. But when I want to sync 1&2 to 3&4 am I really just syncing 1 to 4 or 2 to 3? Do I just plug the nipples on the carbs that I'm not testing? Or am I supposed to connect 1 & 2 together and 3 & 4 with some kind of tee piece and then balance them as two pairs??
    Am I making any sense at all (n) Any input is of course always greatly appreciated. Cheers
     
     Top
  2. sync 1 & 2, sync 3 to 1 or 2 then sync 4 to 1 or 2 or 3, you are aiming at getting them all the same, common sense.
     
     Top
  3. Or....

    sync 3 & 4, sync 2 to 3 or 4 then sync 1 to 4 or 3 or 2, you are aiming at getting them all the same, common sense.
     
     Top
    • Like Like x 1
  4. Just bite the bullet and build a 4 way manometer,...and do the balance right the easy way... its not like you will only ever use it the one time.
     
     Top
  5. On mine No.1 carb is not adjustable so the other three are synced to it.
     
     Top
  6. Christ, if only I had used my common sense... how stupid of me! I'm going to get myself a library book.
     
     Top
    • Funny Funny x 1

  7. Save yourself the trouble, and get a Morgan Carbtune. No fluid, no hassle.

    cheers
    ian
     
     Top
  8. There's a bit more to it than common sense. The screw between carbs 1 and 2 adjusts the balance between those two carbs. The screw between carbs 3 and 4 adjusts the balance between those two carbs. The screw between carbs 2 and 3 adjusts the balance between carbs 1 and 2 as a pair and carbs 3 and 4 as a pair. That means that if your manometer only measures two cylinders at once and you try to sync carbs 2, 3, and 4 to carb 1 individually, as suggested earlier in this thread, you're going to spend a long time getting nowhere.

    You could try doing 1 and 2, then 3 and 4, and then 2 and 3. However, adjusting the 2-3 screw tends to have a secondary effect on the 1-2 balance and 3-4 balance, so you will end up just going back and forth and it will be hard to see what really is going on.

    You really need to come by a new manometer that measures all four cylinders at once. The home-made ones work ok, but they measure the balance in relative terms. Rather looking at where the fluid levels end up being, you watch how quickly they change - the slower the better. That's fine for a twin but can be a bit of a pain on a four. It means stopping the engine a lot to let the fluid levels settle. A commercial manometer will give you an absolute reading for each cylinder - that's going to be the quickest and most pain-free way to perform the job.
     
     Top
  9. Thanks Jack, really appreciate your positive reply and knowledge - useful input, i'll make up a four line manometer, Cheers
     
     Top


  10. These are the right answers & you have a cheap option ;)
     
     Top
  11. Got myself to Bunnings and made myself a syncing tool...
    See pics to see My Girl, My Pods, My Dog & My Man! My Girl.JPG Pods.JPG My Man!. Milie.

    Just waiting for my new powder coated engine covers before I can test my new jetted carbs and pods... can't wait!
     
     Top