Carb sync problems

Okay, so let's start with what HAS been done:

Complete carb overhaul, cleaning, soaking in carb cleaner, rinsing, replacement of ALL rubber parts inside of the carbs (except the diaphragms), all surfaces and fittings thoroughly cleaned.
Bench synced
Clunk test - passed
Float levels set WET - all at 3mm +/- 1mm
Mounted on the bike
Fresh oil, fresh filter
Fresh fuel - 87 grade
Seafoam added to oil, approx. 1.5-2oz
Remainder of 16oz can added to gas tank, topped off with 2gal premium 91 octane fuel
Idle mixture screws set to 2.5 turns out to start
Enrichment valves all set to come up evenly and return to fully closed together

Now the problem:
I can get the bike to start when warm (sitting in the sun or having previously started and engine warm to the touch), but not when cold such as in the morning.
The bike is sluggish at 2-4.5k rpms
I have attempted to sync the carbs by ear - I do not have a vacuum gauge set, nor do I have a colortune spark plug kit. I have two fresh sets of spark plugs for plug chops.
I have monitored the sound and volume output of the exhaust L-R (after market MAC 4-into-2 only sends 1+2 out the left pipe, 3+4 out the right pipe) to assist in tuning.

At this point I cannot get the idle to run smoothly when cold. I either get a hesitation to return to idle, or a hesitation when opening the throttle from idle for moderate to hard acceleration.

Is there something I am missing? Any advice from anyone?

 

Are the valves in spec?

There are several posts about building a monometer for tuning carbs. They are pretty cheap to make.

 

When the carbs were apart did you throughly clean the emulsion tubes, main and pilot jets. Then blow all the passages in the carbs with air?
A hard starting warm engine is a sign of a lean idle mixture or a bad carb sync. Try opening the mixture screws in 1/4 turns increments until it will start when warm. If you get to the 3 1/2 turns out then consider removing the carbs again and cleaning the pilot jets and circuits. Check also the jets are the correct size.

 

Valves are in spec. Carbs were thoroughly cleaned. Enrichment circuit functions properly.. even a small amount of choke and the engine begins to rev up.

Monometer is in the works. I have to pick up appropriate sized tubing.

 

I find 2 3/4 real close for the mixture and sync is impossible without a meter of some kind

 

You did not mention, but were the carbs apart??
If you soaked the carbs while together on the rack, you may have killed your throttle shaft seals, and this would be your result (I speak from sad experience). If you did replace your throttle shaft seals, then disregard.

I agree with polock - use some type of gauge on the vacuum ports.

 

Yes, the carbs were apart. They would only fit two at a time inside the carb cleaner pail. After I took them back out I thoroughly rinsed them in degreaser followed by aerosol cans of carb cleaner then allowed them to dry. When I put them back together I installed new gaskets and seals.

I also did the propane torch test around the carbs, carb boots, etc. and confirmed no air leaks.

 

I dunno... you have a whole can of seafoam in the tank before your first run and attempt tuning efforts??? I don't use the stuff, but I might point to that as a possible problem.

John if you can, here is a guage set cheap : http://www.ebay.com/itm/Vacuum-Carburet ... 05&vxp=mtr

And, colortune is invaluable IMHO especially if you have an issue... you may never hear the appropriate changes if a cylinder is dramatically out of tune for other reasons... (However, I wonder what seafoam does to the color produced by colortune??)

OK, when the bike is warm use no choke, no throttle input NOTHING. Just hit the button and see if it catches. Then pick it up with a bit of throttle, but avoid choke -- do you smell gas when cranking hot?

My GUESS is your RICH down at the low end

These are my guesses and I see you have contradictory input -- but my experience is that lean low end results in sudden drop when hitting the throttle and it comes back suddenly when letting go.

If it's rich it will "stumble, burble, stumble, burble --" then maybe catch

Wait*** SORRY I just re-rad your post -- "hard start cold"

I am not sure, but try the same recommendation - no choke at all cold just hit the button

hope this helps

 

Unless you removed the butterflies from each individual carb and replaced the throttle shaft seals, splazoid's concern is valid. By dipping the carbs, you very well could have compromised the throttle shaft seals.

Because of how "buried" they are, even an unlit propane torch won't always detect them leaking. That could very well be contributing your problem.

That being said, you cannot properly sync without some form of manometer. So that is probably your next best step; at least see if you can get them to sync up.

 

Okay, Monometer is the next step. The carbs were completely torn down, all fittings removed, throttle shafts and butterflies disassembled, everything thoroughly cleaned before being reassembled. I even took the time to count the number of pieces that compose each carb (around 53, give or take depending on which carb). I soaked the metal parts in carb cleaner, blew aerosol cleaner through all carb passages, scrubbed and scraped with toothbrushes and toothpicks, and allowed to dry before reassembly

 

Manometer:

10' 3/16" clear tubing from the hardware - $1.50
4 to 6oz. ATF fluid - $3 (a quart)
Wire staples, coax staples, or the like - $2 for a whole bunch at Wallyworld
Yardstick from Wallyworld - $2.50 OR 3' piece of 2x4 (probably have one lying around) - free

Total - $9

It will save you about $40 worth of ibuprofen when doing a carb sync.

I'm with Coach, I don't use seafoam either, but if I did I don't think I would add it until I had the tuning done. Especially 14oz. to 4 gallons of fuel.

And I sure as HECK wouldn't be adding it to the cranckcase.

 

"The bike is sluggish at 2-4.5k rpms"
no matter what you do they don't really like it down that low, 4K to 7K is fun though

 

Thanks for the replies guys! I will be tackling the bike this weekend and acquiring my parts for a monometer soon.

A rich mixture at idle sounds like it may be the case. I will reset the fuel mixture adjustment screws to 1.75 - 2 turns out and start over AFTER I get the seafoam ran through the engine and at least 1/4 tank of fresh gas through it.

 

1.75~2 turns is probably too lean.

Synchronizing is done with the sync screws changing the position of the butterflies; while mixtures can throw it off slightly, you cannot sync it with the mixture screws.

That comes AFTER the vacuum sync.

Then after you've fiddled the mixtures until you're happy;

you back and re-check the vacuum sync.

And if you dumped SeaFoam in the crankcase, change your oil before something bad happens to the clutch. Don't do that.

 

Okay so update on the carb sync:

I took the carb rack back off the bike for a final once-over. My ultimate problem was the enrichment circuits. All four carb bowl passages were not fully cleared.

I also wanted to give my enrichment clearing tool selection for reference. My brother gave me the scrap excess guitar string off of his electric guitar - those ends that get trimmed off once the guitar has been stringed. This was an electric guitar with steel strings. This is important because Nylon strings will not be stiff enough and Acoustic Steel strings would probably be too thick to fit in the enrichment circuit passages.

The THINNEST string (the high E string) is a single strand steel wire and stiff enough to work down into the carb bowl passages.

The thinnest STEEL WRAPPED string (the D string) is perfect for getting up into the siphon tube. Not only will it fit into the siphon tube, it is stiff enough to clear the tube and flexible enough to work a good way up into the carb body clearing any gunk built up farther up in the enrichment circuit.

Guitar string alone is not enough to clear these passages, I still required a generous amount of time and patience as well as the usual Carb Cleaner aerosol can.


I also re-bench synced the carbs while they were off the bike, set the idle fuel mixture screws to 2.5 turns out and viola, success!

I considered building my vacuum sync tool but decided that the set of vacuum gauges available on fleabay will be a better long-term choice.