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Stumble on throttle up

  • Thread starter Thread starter the_journeyman
  • Start date Start date
T

the_journeyman

Guest
Searched, but probably wasn't using the correct terminology ~

1985 GS1150ES, Pods, aftermarket exhaust, aftermarket cams, advanced ignition timing (PO's work, I don't like working with heads or timing)

When opening the throttle from closed or small openings, the bike hesitates and doesn't want to throttle up smoothly. If I come on the thottle really slow, it doesn't happen. It idles fine pulls hard from 1/3-1/2 throttle or so, but there s A LOT of popping on deceleration with a closed throttle or mostly closed thottle. By a lot of popping, it sounds like my Monster 750 on decel.

I'm thinking a the carb needles are needing an adjustment up or down. From reading on here, I'm leaning toward rich needles rather than jets or air screws being the problem ~

Thanks!

JM
 
Last edited:
First you need to check everywhere for air leaks...all connections, clamps, o-rings on the head, air box, everywhere! If, after everthings else has been ruled out (use wd-40 or starting fluid, if your me) you may try bumping the jet needles up one notch...if they're not adjustable, go to Radio shack with one of your neeldes and get a set of small washers to shim them up a bit. I had to do that on mine and the bike is bone stock and everything has been redone. :?
 
Thanks! Everything seems to seal properly, but I'll check to be sure then move/shim the needles a bit ~

JM
 
Another Stumbling Throttle!

Another Stumbling Throttle!

I just encountered a nearly identical problem this morning (suddenly, at that). The bike behaves perfectly up to 50 mph, then hesitates deeply before continuing, and again at 65 mph. I have never had this problem before. I recently adjusted my idle knob lower b/c of occasional idle RPMs of 1.5 - 2k after a good workout. Could this cause it? Could it be loosened deposits jamming the carbs? something else completely? I replaced the carb boots & O-rings last year, air filter this year, so air leaks seem unlikely to me. Many thanks for any help to this newbie!

----------------
GS650G 1982 18k
5'2" 1982 Gemini
 
Hesitating Accelleartion

Hesitating Accelleartion

Hey Journey,

I get similar problems as well after a few hundred miles of smooth riding.
Check for leaks as previously suggested then pull and look at your plugs to see if any of them are fouled out.

When mine starts doing that, I have founded that one of my cylinders has actually stopped firing due to the plug getting fouled. When I pull plug number one it is very wet and will not make spark. I clean or replace the plug and the bike runs very smooth and has plenty of power with no hesitation at any acceleration. My 750 will actually run and idle without cylinder #1 and the only way I know is that I get the symptoms you are describing.

It also sounds as though you are due for a good carb syncing.
 
Not sure as to the extent that you've checked into your bikes, but another common problem that seems to creep up on many, "have you checked your valve clearances yet"? This has caused many of problems on the fourm. If you haven't, you should. Valves that are not opening high enough will cause the symptoms that you are describing.

Also, before you tear into the carbs and try to get everything set "just right", it won't do much good if the valves are way out of adjustment.

Just a thought... :?
 
Still hunting...

Still hunting...

lunch break test results: choke and throttle cables have good action, spark plugs are clean, set the idle knob as it was when my bike was happy, boots & filter are tight... still have a serious problem. as journey described: once i try to open up the throttle past 3.7 rpm i get nothing. sometimes if i stop immediately afterward the idle takes a dive and stalls. I dont know how to check the valves, but I'll do my research (and check clymer of course). Thanks guys!
 
lafncow said:
lunch break test results: choke and throttle cables have good action, spark plugs are clean, set the idle knob as it was when my bike was happy, boots & filter are tight... still have a serious problem. as journey described: once i try to open up the throttle past 3.7 rpm i get nothing. sometimes if i stop immediately afterward the idle takes a dive and stalls. I dont know how to check the valves, but I'll do my research (and check clymer of course). Thanks guys!
Click to expand...

Have you completely cleaned the carbs ie. soak in Berrymans and check all passages with a fine wire yet?
 
Nope, i've avoided the carbs thus far for a few reasons: until today the bike has given me 5k flawless miles (occasional high idling when hot aside) and i've only ridden for just over a year now so anything beyond basic servicing of my engine is new and scary business to me. maybe it is time for that to change? :-s
at any rate it appears my weekend's work is cut out for me. I'll start with double checking for air leaks (wd40?), checking the petcock & fuel line per another post i found on this same issue, giving the plugs a cleaning for good measure, and if it persists at that point i'm not sure where to point my finger other than the carbs! many thanks for your insight!

(btw, i'm running all stock, with oil changed this year)
 
Pay special attention to the intake boots with or without the orings, this is a particularly troublesome spot. (wd-40 w/air leak=idle will drop or starting fluid w/air leak=idle will rise) Good luck and keep us posted! \\:D/
 
Just some thoughts. Maybe try running it with the gas cap loose to see if its a vapor lock/ fuel starvation issue. Or the gas tank breather hose may have a spider cocoon clogging it. Or it might also be dirty floatbowl screens.
 
:oops: Well, I feel pretty stupid, but a lot happier. cleaned the plugs, the boots passed the wd40 test, then i noticed a kinked vacuum hose to the carbs. must have bumped it when adjusting the idle knob! unkinked that and she purred like nothing had ever been wrong. sorry to bug you guys with such a silly mistake, i am new at this. thanks again & happy trails!
 
Was it the vac hose that runs to the petcock?

IF that is the case, could have not been getting enough vacuum to the petcock under hard acceleration. Since vacuum drops under WOT. May have been acting like a fuel cut off switch...
 
No, it was the right carb vent hose (sorry for the bad terminology on my last post) ....so if that works the was i think it does, that means exhaust was backing up and occasionally "burping" past the kink when the pressure built up, allowing me to eventually accelerate?
 
So you float bowls were being pressurized because they could not freely vent? Makes sense...
 
lafncow said:
No, it was the right carb vent hose (sorry for the bad terminology on my last post) ....so if that works the was i think it does, that means exhaust was backing up and occasionally "burping" past the kink when the pressure built up, allowing me to eventually accelerate?
Click to expand...

Not really how it works -- the vent hoses just open the bowls to atmosphere so that gas is able displace air in the bowls as they fill. It would never build appreciable pressure. It would starve two of four bowls of gas under hard/sustained acceleration (assuming a partial kink).
 
Don't laugh but I just had the same problem...along with an idle that went higher the longer I rode. My problem seem to have been bad gas. I was running Sunoco 93 from the station near my house for the longest time. I switched to the 93 at the Get Go a few blocks away and the problems went away. I'm guessing it was just bad gas.
 
snark said:
My problem seem to have been bad gas. I was running Sunoco 93 from the station near my house for the longest time. I switched to the 93 at the Get Go a few blocks away and the problems went away. I'm guessing it was just bad gas.
Click to expand...

In my humble opinion, you are still using "bad" gas. Not because of the brand, but the octane. :shock:

Unless your bike has been built-up with higher compression, etc., you most likely don't need high octane gas.
Octane does not equal power. Octane merely reduces the chance that heat from compression will set off the mixture before the spark. With stock engines you will burn cleaner and get more power and spend a LOT less money by using regular gas.


.
 
CA180 said:
^ I second that. Improper octane does nothing for performance.
Click to expand...

Only cures pre-ignition on highly advanced ignition and /or high compression. Alcohol will do the same thing, though you must be set up to run it. \\:D/ Nothing like the smell of a stiff drink, coming from the exhaust. 8-[
 
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