Help. Running carb sync w/ homemade manometer

I need some help doing a running sync.

I've read multiple threads watch multiple videos of how to do this. But i still can't get this right.

Carb 2 & 3 are synced.
But when I try 1 &2. Or 3& 4. There's such a huge different in the vacuum I've tried turning the sync screw and it doesn't change the vacuum in the bottles. Just changes the sound of the bike.



I'm struggling a lot with this any help is greatly appreciated.

Thanks timmy

 

Timmy, you might want to post pictures of your nanometer, so folks can see if that might be causing the issue. However, when I synced mine the I found it needed a lot of adjustment before all four lined up. Also, sync 1&2, then 3&4, then 2&3 (other folks will correct me if I am wrong, but I am fairly certain this is the right order).

 

Just to clarify, which screw are you turning in the picture? I see a lot of tool marks around the idle mixture screws.

 

@JHM thanks for commenting I'm adjusting the sync screw not idle mixture. Is that correct?
the Phillip head one between the carbs. Not the flat head one with tool marks

 

@Lightcs1776 thanks for commenting

From what I read about xj650 and watched your suppose to synchronize 2 and 3. Because 3 is the main vacuum for fuel.

This isn't mine. I'm not by my bike now. But this is very similar

If you need anymore info just ask
Thanks tim

 

I'll point out that this will be difficult if there are vacuum leaks. In your photo, I notice a missing bolt for #1 carb boot. There seems to be copper RTV used to seal the boots. I would start by testing for leaks by either spraying carb spray or using an un-lit propane torch to introduce flammable gas that could be sucked into any vacuum leak. That would cause the engine to race or at least run faster till that gas is consumed.

 

Thanks @dkavanagh. I've done vacuum leak checks already with the unlit propane torch. I didn't find any leaks or higher rpms from doing that. But I will double check that again.

 

the order that you do them in is important. do 1/2 then 3/4 then 2/3 last.
you have a little too much liquid in the bottles, each one should be 1/4 to 1/3 full

 

The missing bolt head is worring. If there's not a vacuum leak at that intake boot now, there will be in the future.

 

Thank you @Polock. For telling me the correct Sequence for tuning I will adjust the amount of liquid as well

 

Thanks @kmoe for replying and informing me on this.

I bought the bike like this. If the bolt are snapped in the intake. What's the best way to extract the snapped bolt?

I would like to fix this before it becomes a issue.

Thanks again
Tim

 

Heh, we should probably have a pinned thread, or how-to (if there isn't already) about extracting broken bolts. It's been discussed probably 4 times in the past week and a half!

 

@Polock
Could you help me understand the syncing. I would like to know more information about the screw. Does screwing the screw IN increase or decrease the vacuum ?

 

I just tweaked each screw till the vacuum registered was about equal (as it jumped around). You find out which way it has to go quickly enough.

 

Ok

ok. Thank you @dkavanagh for the advice. It's my first bike. So I'm learning as I go

Thanks Tim

 

This was mine as well. You'll get more confidence as you go. These forums are a wealth of information.

 

Thanks again @dkavanagh

 

I believe that turning the screw in raises the vacuum on the carb(s) to the right (right as you are facing forward/ riding position).

 

Ok. Thanks you @Stumplifter for the information

 

that screw will close one throttle plate (throttle butterfly) and at the same time open the other one. then when the pairs 1/2 and 3/4 are balanced, the last one 2/3 balances the 1/2, 3/4 pairs to each other
the whole time you're doing this, make sure that the idle knob will control the idle speed

 

And remember to blip the throttle after making small adjustments.

 

Ok I was playing with my homemade manometer and this is what I believe to be true. (Either that or I have something truly screwed up with my Manometer or carbs!). I am using a smaller diameter tube connecting the two bottles, this seems to make the fluid flow very slowly (no bouncing) but it takes a llloooonnnggg time for the levels to 'settle in'.

2 bottles - the left bottle:
A) goes to 1 (when synching 1 - 2)
B) then goes to 3 (when synching 3 - 4)
C) then to 2 (when synching 1/2 - 3/4).

Turning synch screws in (clockwise) results in the following:
A) = raises vacuum to 2
B) = raises vacuum to 3
C) = raise vacuum to 3/4

 

that did it, now i'm confused. afraid to ask, where's the other hose go

 

Have you seen the simple manometer I made? Worked nicely.. scroll down on this post: http://www.xjbikes.com/forums/threads/dirt-cheap-manometer.98613/#post-536408

 

Where's Matti when you really need him?

I ass-u-me that it would be understood the other tube (from the right bottle) would go to the 'matched set' whilst synching (1 to 2; 2 to 3 and 1/2 to 3/4).


Shame on me.

 

Whn you are at the point of matching the pairs, you hook up to 2 and 3.

The fluid levels don't have to be at a specific point; thy just need to be equalized.

 

No! -

Wait -

Really? -

I know with the Morgan Carbtune you want all 4 readings equal regardless of the gauge value.

I was playing with my homemade Manometer yesterday and had a dickens of a time getting both bottles at the same level/ height.
Tweak synch screw, rev throttle, blip-blip throttle, let idle and watch as 3 minutes tick by and the fluid level slowly changes.

In regards to a two-bottle Manometer and your statement above which of the following are you saying?
Equalized - like both bottles fluid levels are static and not fluctuating? (regardless of height)
Equalized - like both bottles fluid levels are the same level/ height?

 

This one, how high/low the levels are doesn't matter.
Host so their not moving

 

Ok - dang!

Some lessons are learned the hard way.
I really spent waaaay too much time fiddle f*={ing around yesterday.

 

Thank you everyone for responding. I took your information and have been using it. I've been working on my bike every night trying to do a running sync I have carb #1&2 synced together but I cannkt get #3&4 to sync. I've been struggling with it. I've spent hours doing this do you guys have any suggestions ?

 

Have you checked for vacuum leaks?

 

Thanks @kmoe. I have checked for vacuum leaks with a unlit propane torch. I haven't seen any spikes in rpm from checking Is there a better way to check for a vacuum leak. I've heard of people using sprays.

Thanks again any suggestions is greatly appreciated.

 

Spray carb cleaner works better for me.

 

Ok. I'll will pick up a can and try checking for vacuum leaks with that. Thanks. Tim

 

Timmy, have you had your carbs apart lately?
You are saying there is no rpm increase yet when trying to synch 3/4 you can hear an idle change?
A vacuum leak should cause an increase in RPM's and/ or a hanging high idle when you twist the throttle.

 

what might have happened is, as you sync 3/4 one of the butterflys might be going completely closed. Reason: #3 carb is controlled by the idle knob, it's possible to get #4 butterfly closed more than #3 then the idle knob isn't controlling the idle.
Solution: turn the idle knob in until the idle goes up to about 18-2000 rpm, now try to sync them, when they get pretty good do 2/3 and keep the rpm at 2000 with the idle knob.
now lower the idle to 1500 with the knob and do the 1/2, 3/4, 2/3 again. finally go to 1100 and start again on 1/2.........

 

I usually do 3/4 first, because of the idle screw. Then, I go to 1/2. The 2/3 screw is only to balance the left half and the right half.

 

That's how the book has it too. Funny that.

 

And usually I have bike synced within a few minutes. I doesn't take long. It takes more time to remove the tank and hook the carbtune up

 

Wait,...... There's a BOOK?!?!

 

Well I found that I in fact do have a vacuum leak. So I need to remove that snapped bolt out of the intake. I'm having a hard time getting it out. What's the best way for removing the bolt? Drilling it and using a left turn drill?

 

I didn't hear any change when I was using propane while checking for vacuum leaks. I did hear changes when trying to sync the carbs. I did find that i do have a vacuum leak.

 

There is enough of the screw still sticking out I'm gonna try welding a nut onto the end

 

That is a good plan. If if fails get yourself some modling clay, and Alum (spice rack at the grocery store). Form a cup around the brokn bolt with the clay. Mix the alum in warm water (ratio isn't terribly important, but don't go so far as to saturate the solution). Pour the mixture into the clay cup and wait a fw days for the broken bolt to dissolve, leaving behind a nice, undamaged threaded hole.

 

Thank you @k-moe i would of never thought of that. I will defiantly keep that as plan b

 

Oh, degrease the head so the clay can stick.

 

NOw that's weird, my book says to start with 1 and 2, then 3 and 4, and then match the two pairs together.

 

Which book?

 

I think it is a copy of the service book from Yamaha. I don't copy the first page, so I'm not 100% sure.

 

The FSM for the Seca 750 does not cover synchronizing the carbs, though the 900 manual may have. The Haynes has the order that you list, but most manuals I've read call for the baseline carb (the one with the idle speed screw) to be synched to first. Either way can work so long as the pairs of carbs (1&2, 3&4) are synched last.