Odd sync problem....need help!

[98Redlne]

Working on trying to get my carbs sync'd and am seeing some odd behavior.

I built a 4 port synchronizer using clear vinyl tubing and ATF (Like this one)

What I am seeing is that after getting everything balanced (all carbs within about 1" of each other), I will run the RPMs up to about 4K (all carbs seem to be level within about 2") an then back to idle. After doing that, the levels are all over the place. I realize that the vacuum needs some time to equalize, however the levels never seem to return to the same place.

If I make another run to 4K, this time the levels may be up to 6" off.
Back to idle and they are still all over the place, but not the same as they were last time.

I can continue to do this over and over and never get the same result twice (neither at idle or 4K)

A little history:
2007 with 1700 miles
Marks Exhaust
Stock motor
Factory Jetting

I have been running 1 1/2 oz of Sea Foam every tank this season and have nothing else but 10% ethanol gas available.

Any advice as to what the heck is going on :ummm:
I would assume that this is not normal.

 

[RaWarrior]

Sticky sync linkages? Only think I can think of why they'd get all messed up after revving. Maybe give a few shots of wd40 or something in there. If the differences are that dramatic I'd think you would be able to see some of the throttles not closing right. After they get all messed up, if you grab the linkages and push them as to "close" all the throttles, do they return back to in-sync?

I noticed that a bit when I sync'd mine, though I was using a Honda dealer sync tool I borrowed from work(dial gauge type). I could get them all very close(within say .5 inHg...what the gauges read in) of each other, blip the gas, and when they settled back down again only be within maybe 1inHg. No matter how many times I blipped and adjusted I couldn't seem to get them any closer, so I just let it go. They were as much as 4inHg apart when I started though.

 

[98Redlne]

I wouldn't think that a 2 year old bike with only 1700 on the clock that has never been in the rain would suffer from this issue, but hey, it's worth a look.

I will take a look tomorrow. The neighbors hate when I am constantly revving the bike when it gets this late.

 

[richwrench]

Mine was erratic as well - turns out the jet blocks were partially plugged & 1 coasting air valve was rotted & messing up the idle circuit. I know your bike is only 3 years old, but some of the fuel circuits are tiny & can plug up in just a few months if left sitting. Did you make sure your throttle linkage is not binding? I use the manometer you show in this thread (literally) & I can tell you that all circuits should even out after every blip of the throttle. I'm guessing some blockage in a carb circuit is causing the problem. Some people are nervous about rebuilding carbs, but IMHO, VMAX carbs are some of the easiest carbs to R&R & if you follow the sticky posts, not that hard to rebuild. I wouldn't even buy new parts for a bike that new (unless obviously needed) , just dis-assemble, clean & re-assemble. I also had a misfire at idle when hot because of a bad spark plug, but that wouldn't make your sync randomly go all over the place. How does the bike run? Maybe a few tanks of fresh fuel & a good kick in the ass will help. I know many here love Seafoam & back in the day it was awesome, but with ethanol gas I hate to add any more additives that contain alcohol. I'm thinking you need to clean the carbs - just my $.02...

 

[98Redlne]

Crap on a cracker! I was hoping to avoid having to tear the carbs apart this summer but is seems like that might be in the cards.

I have had the bike for a year. Stored it wet over the winter with a fresh tank of fuel treated with StaBil.

The PO bought the bike new and was not much of a wrencher. I guess this could have been an issue since I bought the bike as I think he stored the bike for 2 winters on untreated fuel and only put 600 miles on in 2 years.

 

[2stangs69-91]

does the bike run ok? can you tell a rpm change in the bike at idle when you are doing this? I would think maybe your sync tool may be missing something to get this type of reading? JMO

 

[jfeagins]

If it's idling too fast, the carbs will be harder to sync also.

I be sure my idle is @1000 +- 50 rpm's as I'm setting the sync.

This is also true as you are tweeking the A/F mixture. The slower the idle, the easier it is to tell what's happening with the A/F mixture.

You might consider doing a much simpler pea shooter routine instead of a complete removal and teardown of the carbs. If it's running mostly OK, then you may not need a teardown - (but that wouldn't reflect the condition of your coasting enrichener diaphrams.)

 

[98Redlne]

The sync tool is fine. I am using the same type as richwrench with the air restrictors in place. I would say that it is probably more sensitive than either the mercury or dial type vacuum gagues.

I haven't ridden the bike since the sync but will test it out today.

The carbs were so far out when I started that I am sure the bike will run better regardless of whether they are perfectly sinc'd or not. It took quite a number of adjustments just to get it where it wouldn't suck all of the fluid out of the manometer through one carb. #1 to #2, #3 to #4 and L to R balance were all waaaaaaay out of whack.

Possibly the shotgun and peashooter approach might clear my issues without having to tear the carbs apart.