Sudden issues

[godsend1]

Today riding home from the gym the bike started sputtering/stumbling at 4k-6k, it seemed to clear in the upper rpm range 6k and up. Rode into work later in the day on the freeway and it is much worse, no pull at all in the upper RPM range and still sputtering/stumbling from about 4k and up.

There is an occasional stumble from idle when throttle is applied but not everyt time.

It's a 1986 with 21k, supertrapp slipons, jetting unknown. No ther mods to my knowledge.

Any thoughts would be appreciated.

Thanks Tom

 

[Rusty McNeil]

First thing I would check would be to poke down the carb throats with a long skinny screw driver and see that the slides are not hanging up and are all returning home at about the same speed when pushed all the way open and suddenly released.

Rusty

 

[maleko89]

Check rubber intake boots too. Should be tight.

 

[davidon]

My car did the same thing recently..check dirty air filter, plugs, wires, fuel filter..change if old or clean

 

[PATMAX]

My bike did the same thing and it was my plugs but I am running horribly rich and have poor plug life. If you have not changed them recently, it is a good place to start!

 

[4gasem]

Yeah... When the max comes into Vboost it will literally blow out the spark kernel if they are toast and not creating a strong spark.

Check your plugs. Gap... Replace... Whatever it replaces.

 

[godsend1]

Thanks for the info, I'll check the slides first, then move down the list .

 

[godsend1]

I pulled the airbox cover and checked the slides , they seemed ok, while I was poking around in the box I found one of the screws that hold the box onto the carbs loose in the box. I put it back and tightened the other 2.
The box didn't feel loose before I put the screw back in so I figured this wouldn't help.

Jumped on it to ride home and back to normal.

I'll check all the boot connections tomorrow.

I'm just glad it was something simple.

 

[Robbarrie]

I'm blown away to find out if that was your problem. I never would have guessed that...wow

 

[robsplatf4]

I'd be willing to bet one of the slides was stuck and you freed it messing with it.

 

[shawn kloker]

I pulled the airbox cover and checked the slides , they seemed ok, while I was poking around in the box I found one of the screws that hold the box onto the carbs loose in the box. I put it back and tightened the other 2.
The box didn't feel loose before I put the screw back in so I figured this wouldn't help.

Jumped on it to ride home and back to normal.

I'll check all the boot connections tomorrow.

I'm just glad it was something simple.

I'm not really sure what three screws that you are talking about but sucking any air will make it not run right.Air box boots,carb boots and vboost boots.

 

[godsend1]

I'm not really sure what three screws that you are talking about but sucking any air will make it not run right.Air box boots,carb boots and vboost boots.

I'm not sure if excercising the slides or replacing and tightening the screws did it. I looked on the fiche and couldn't find the screws, I'll post a pic tomorrow showing which screws.

 

[robsplatf4]

I think he's talking about the screws that hold the breather inlet that comes off the crankcase

 

[Thevmaxrider]

Either a stuck slide or a piece of schmutz on a needle possibly. Loose airbox to carb connection shouldn't have caused that big a problem. The more I think about it the more I want to go with the consensus and say stuck slide.

 

[godsend1]

Here's a pic of the 3 screws. The top left screw was rolling around in the airbox, the other 2 screws were lose.

 

[Buster Hymen]

Here's a pic of the 3 screws. The top left screw was rolling around in the airbox, the other 2 screws were lose.

Those screws hold the lower piece of the airbox in place. I'm surprised that was the issue that was causing your problem.