Sputtering under load? (long)

[sdinino]

I did a ton of work on the V over the long weekend:

 - fixed the oil leak on the left case cover
 - replaced steering stem bearings w/ tapered roller bearings
 - installed the new tires
 - fixed my neutral indicator switch
 - re-tested the charging system
 - dipped the carbs

My first impression once I got everything put back together was that it was a LOT more stable. The tires are one size larger in front ( 100/90-18 ) and two in back ( 120/90-18 ). I'm sure there's a larger patch of rubber hitting the road now. That plus the new steering bearings makes it feel like its glued to the road. Just what I was hoping for.

The little fixes (neutral light, oil leak, check the charging system) were things I'd put off, knowing I had big jobs pending but its still nice to finally get them done. The bike really looked like hell with all that road grime stuck to the oil residue underneath.

Finally, the point of this thread ?:D :
For quite a while now I've been living with a bad sputter when I jump on the gas. I can't say it's the "stumble" really, because I interpret a stumble as a momentary hesitation, after which the bike surges and never looks back. Mine will.... well, sputter. This will go on as long as you keep on the gas. If you back off and 'feather' the throttle, it will accellerate smoothly. It's just at a certain amount of load and above that you'll get this phenomenon.

I just always assumed it was carbs, and when my idle deteriorated to the point where it wouldn't idle at all below 3k my suspicion seemed confirmed.

Boy was I right! The back carb had a thick build up of slime in the bottom of the bowl - I think it was water. Not sure. Anyway, they soaked overnight and then got blown out w/ compressed air afterwards. Float levels were checked and reset to spec and then everything was reassembled. I had real hope that not only would my idle come back, but that maybe the sputter would go away.

No such luck. After syncing and adjusting the mixture my idle is better than it ever was. As an added bonus, my choke works better as well - it's not all or nothing anymore. But the sputter remains.

I'm wondering now - my carbs are as clean and as adjusted as they ever have been, but the sputter hasn't changed an iota. Could I have an ignition problem? Lousy valve adjustment? Could it be fuel related, as in pump or petcock? Or has my exhaust system deteriorated to the point where I need to adjust jets in the carbs? Not sure where to start trying to eliminate possiblilites.

[Lucky]

Couple of thoughts here.
How old are the plugs? they can look fine & shoot a nice blue spark when they're out of the bike with no compression, but putting a load on them is the real test.  cheap enough to replace them to find out.

It also sounds like a fuel starvation/lean situation.  Check for vaccume leaks in all the usual places, fuel pump, petcock, YICS!, and also around the throttle shafts. (use a can of Gumout with the straw on it to give short bursts of cleaner around where you'r leak testing to see if the idle changes.  if so, you've found a leak.)

is the flapper door working freely?

The seals around the throttle shafts end up getting dipped because to remove them, the butterflies must be removed, and the screws are staked on.  Often these screws will break if you try to take them out. Also, the butterflies have to go back in EXACTLY as they were or they can bind, and a stuck throttle is not something anyone wants to experience.  For this reason, I usually only dip the bodies an hour or so, not overnight. Also, did you flush them well with water after you dipped them? this is importaint because the acid in the dip needs to be nuetraized before their blown dry...

--Lucky

[sdinino]

I can answer a couple of your questions:

 - the YICS is off the bike being repaired, so the nipples in the heads are sealed off

 - I did take out the throttle shaft seals before dipping (I did this last time too) and I believe I got the butterfly valves back together properly - they only go in one way as far as I can tell. At least, they don't bind and they close all the way. I still need to check for vacuum leaks.

 - I did NOT flush the carbs with water ?:o. I DID flush them out with Gumout. According to the instructions on the can of dip, it's not supposed to be harmful or corrosive to metal, so I figured Gumout was all I needed to get rid of the residue. Hopefully I won't end up with a handful of powedered carb!

I hadn't thought about the plugs. That is cheap to check, as you said. (I think I'm using the plugs you sent with those heads! ?;D So that may well be the problem.)

[Lucky]

I don't think there were plugs in those heads...

[sdinino]

There you go! Not having any plugs would certainly affect performance!

[Blake]

hehe..  yeah..plugs are kinda important...because we all know if this bike was run off of hopes and dreams like we'd like....none of us would ever be here..hehehe ;D




Blake

[scootertramp]

mine was sputtering under load. lurching kinda. up and down like it was kinda runnin' out of gase a little.
So I synced the carbs(with the four dollar and eight cents vac gauge) and set the fuel air scwoos.(thanks dudes for helping me find them. !)
now mine has a definate LAG/BOG at four thousand rpms.
The sputter is GONE man. so now I'm adjusting the little rod under the carbs as I sync to allow both carbs to pull the same UNDER LOAD.
I have them the same at idle and at 2500 rpms.
I still have the lag/bog. dang..
The lag/bog WAS GONE for a time and it came back with a VENGENCE.
my bike MAY HAVE been hot (messed up readings)so I will try it again soon.
it cranks and starts and idles at ONE TOUCH. two twists of the throttle first before crankin'. VROOM!
If I get the LAG to go away I will tell you.
A wrench haid tole me :"it purrs like a kitten")
NO SPUTTER.
GOODE LUCKE!