Newbie reporting in with rough low-speed acceleration

[Oompa_Loompa]

Hey all...

I just bought an 81 XS1100 with 20K on the clock. It runs beautifully except for one little thing...

Even after having been well warmed up, when I take off from a stop light (around 1500 RPM) the engine kind of sputters and then recovers once I get to 2000 RPM and then is fine. This is a consistant thing and I have two theories (which may be completely off-base): 1. my fuel mixture is off and my carbs need to be adjusted. Or 2. The rubber hoses that go from the carb to the engine have cracks in them which allows extra air into the engine, therefore messing up the fuel/air ratio.

You input is very much appreciated. This is my first 'real' street-bike and I have been having a blast on it. I rode dual-sports for years and this is a whole new level of motorsporting. The wealth of information on this site is staggering and I already did a search on the subject to no avail.

Russ

Anybody else on here from San Luis Obispo, CA or elsewhere on the central coast?

[strom]

Mine does that too...
Have a 4in2 stock headers on and open exhausts, no cross-pipe.
I dont worry about it much, since it has a gorgeus sound from 4-5k rpm onwards (sounds like an old VW below 3k)

LP

[John]

Re: Newbie reporting in with rough low-speed acceleration

[QUOTE]Originally posted by Oompa_Loompa
[B]Hey all...

1. my fuel mixture is off and my carbs need to be adjusted. Or 2. The rubber hoses that go from the carb to the engine have cracks in them which allows extra air into the engine, therefore messing up the fuel/air ratio.

Russ

You said the hose from the carbs to the engine? Do you mean the intake boots/manifolds? Crack sthere are common, but usually not cracked all the way through. There should be only one vacuum line, on the carbs, coming from the carb body of #2 carb, and it goes into the left side engine cover for the vacuum advance (retard) mechanism. The should also be a vacuum line to each petcock from #1 & 4 intake boot if the bike is a Standard, or if it is a Special, then just one vacuum line from #1 intake boot to the fuel distribution/shut off valve (octopus).

[Pat Kelly]

It could also be a sticky timing advance/retard mechanism.

[mro]

What John say's.
Have the carbs been synchronized?
Then adjust fuel/air.

81 special or standard??
Stock or got mods???

Could post a pic too



mro

[80mdnt11]

Golden Ticket?

You guys are all pointing him in the right direction, however I think he might have a Wonka Bar with a Golden Ticket stuck in there somewhere! Sorry Oompa_Loompa, couldn't resist. Stick around, this web-site is Great!

[TADracer]

I think I put my foot down in a Wonka Bar once when I stoped at an intersection.

Ommpa Loompa, if she has 20K on her when you got her, might be wise to do a full tune up (unless you know the previous owner kept the service routine up) it could be something as little as float level and carb syncronizing. Or if the previous owner did some mods, could need some low circuit rejetting.

My 79 special did this after I put on aftermarket exhaust several years ago. I made necessary main and pilot jet changes and the problem vanished.

[TopCatGr58]

I liked the Original Movie Music better!

Oompa-Loompa oopidy do,
Why do you think this happens to you?

Running the engine below K 2,
Will cause it to sputter and shudder, too!

A thumper it's not, pistons a four,
So twist the throttle, the power you'll adore.

Below 3 K, I never run,
The torque is great, and lots of fun!

The lesson is here, and yours to learn,
Open it up, and let the fuel burn!

The pistons and plugs will stay nice and clean,
That's the way to treat this wonderful machine!

T.C.

[80mdnt11]

WOW!

You Da Man T.C. !

[strom]

This thread got me (s)thinking...

I got me a stock set of carbs, stock guts in them.
Got 4 in 2 original headers and a homemade exhaust, a bit more free-flowing for now. Will close it up some. Got a stock airbox with a tad more unrestrictive air filter. Ignition system is stock.
Carbs are synced.
Low rev range there is nothing... remotely.... 1100 like.
I can putter along from idle, it accelerates, but slowly. No misfiring, jerking or anything... just a slow acceleration till I hit 3-4krpm. After that, its a different story, but below... it sucks. Anyway, I will resync the carbs... again...
As different main jets go.... got none for testing.

LP

[pggg]

Misbehaving at low revs there's a chance it's a spark plug/spark lead/spark plug cap problem, those resistor plug caps can get grungy inside - there's springs and resistors in there that might want stripping and cleaning, trouble is the inner plug caps CAN'T be stripped sometimes. I ditched my plastic resistor caps and use auto-type rubber non-resistor caps and that aggravating low rev stumble has never returned since!

[Oompa_Loompa]

Thanks for all the help guys... I'll let you know what I do to fix the problem.

In the meantime, here are some pics of my new beast:

These were taken in the hills above San Luis Obispo a week ago.





BTW...
TC, that was freakin' awesome

[TopCatGr58]

Hey Russ,

Thanks, but so is your machine!! The Pilot circuit may be a little clogged, go out and get some SEAFOAM, and put at least a 1/4 can in the tank and drive it thru, you'll probably see an improvement before the tank is empty!

Have you tried keeping the revs a little higher? You'll find that the throttle response is much brisker as well, makes pulling out, passing, etc. much quicker!!
T.C.

[Oompa_Loompa]

I would love to keep her in the high RPMs but up there I feel bad shifting because the transmission feel is a little clunky. I'm trying to make this bike last by avoiding future tranny issues because we all know what a pain in the ass those are.

I have a bottle of seafoam I'm going to pour in there tonight (a quarter-bottle, like you said). Then i'm going to take her on a "brisk" ride up the coast. It's always fun when that smoke starts pouring out. I feel like a stunt plane with those colored smoke trails.

[TopCatGr58]

Russ,

I'm not talking about running all the time at 6k rpm!! Just keeping it a bit above the 2k "lugging" range!! And as for the shifting, it actually shifts easier when you rev it a bit, depending on what you are needing to do, but then you blip it dropping the throttle for a split second as you shift using the clutch, and these things shift quite easily and smoothly!

The tranny's weakness is in 1st and second gears mostly. Many techniques to reduce the wear when stopping, or starting in traffic, like holding the clutch lever in for a few seconds before shifting into 1st from neutral. Also, when first starting cold bike, running it a minute or so till it's slightly warmed up. Then turning off, shifting into 1st, and then restarting it to take off already in 1st gear. And use the clutch, that's what it's for, don't shift without it.

Enjoy your smoke, er...I mean ride!
T.C.