Slider springs

[Ivan]

What are the symptoms of carbs with the slider springs (under the cap on the top of the carb, pushes the needle down) too soft?

 

Does it cause any adverse running problems?

 

Thanks in advance.

[pegscraper]

Do you mean the cap on the side of the carb? On our Ventures these are on the sides. If the springs get soft, the slides will open earlier than usual. That translates into quicker throttle response and possibly but not necessarily reduced gas mileage.

[Bob Myers]

If only one of the springs gets soft that could cause a feeling of missing or surging on acceleration too.

[MiCarl]

What the slides do is keep the airflow more or less constant through the throat of the carburetor (constant velocity). As they open they also let extra fuel in through the needle jet.

 

If the springs are too light the slides will open prematurely, resulting in slower air flow and a lean condition - particularly on acceleration.

 

Whatever problem you're having, it's not likely the slide springs are the culprits (unless somebody damaged them).

[Ivan]

What the slides do is keep the airflow more or less constant through the throat of the carburetor (constant velocity). As they open they also let extra fuel in through the needle jet.

 

If the springs are too light the slides will open prematurely, resulting in slower air flow and a lean condition - particularly on acceleration.

 

Whatever problem you're having, it's not likely the slide springs are the culprits (unless somebody damaged them).

 

This is what I was thinking as well. reduced air velocity.

 

FWIW, my XS 1100 has a pretty bad stumble at off idle. No power up to about 2500 rpm. I have tried new idle jets, synced it nicely and set the idle mix. I was thinking that maybe the springs have been relaxed a bit from 27 years of service. I guess its easy enough to stretch them a bit, and see if it makes a difference.

[Bob Myers]

If you decide to stretch them, take some measures to assure that the spring rate is close on all four. Something as simple as a single weight placed on each individual spring, and measure the weighted height to equalize their rate. Doesn't mean spring rate will be right, just more equal.

Back years ago I made parts for a moto-gp racer and he did that on every carb setup. Claimed it smoothed out the acceleration,and took out flat spots.

[Ivan]

If you decide to stretch them, take some measures to assure that the spring rate is close on all four. Something as simple as a single weight placed on each individual spring, and measure the weighted height to equalize their rate. Doesn't mean spring rate will be right, just more equal.

Back years ago I made parts for a moto-gp racer and he did that on every carb setup. Claimed it smoothed out the acceleration,and took out flat spots.

 

Thanks for the suggestion. Its a great idea. I will probably use a bolt or something.