Bike losing power / cutting out

Originally Posted by yorkie_chris

Someone call?

Balance carbs for the sake of it, WD40 and grease front plug cap up. If it still does it, it's carb ice. Carb ice seems to affect rapid changes in throttle position... like overtaking.

Is this straight forward enough then, the carb balancing bit I mean.

[yorkie_chris]

yeah, need a gauge though. It's unlikely to be the cause of this particular problem but it's worth doing anyway.

Thank's for all the help everyone hopefully I'll get it sorted, if not watch this space.

It's carb icing. You can ride all day to warm the bike but it will still carb ice when your moving. It can happen when it is cold and "dry" (Misty or foggy) or cold and wet. It's all to do with the dew point.

Pro Fst is the best additive which will help but not necessarily cure it. Depends how severe the conditions are.

Being smooth with the throttle will help with the surges. (When you open the throttle rapidly (screwing the ******** off it!) and it "loses power then lurches and speeds up.)

Pulling clutch in whilst moving and blipping the throttle will help (good if you due to overtake or need to accelerate.)

Final thing that can help with cutting out especially at junctions is to increase the idle speed. Maybe to 2k-2.5k. I tend to just open the throttle a bit so it sits at 2k.

I ride every day about 100miles, 365 days a year in all weathers. Carb icing is a problem but you get used to it if you manage it.

Thanks for that mate, appreciate the help.

Just been reading up on this Carb icing and I understand that all UK SV's should have carb heaters fitted.

Were these only fitted after a certain year?
If there is one on my bike (1999 S), where is it?
Are they difficult to replace if there is a problem?
Am I talking rubbish?

afaik carb heaters were on every uk model from launch.

[dizzyblonde]

yep, and they are all plop!

[embee]

The carb heaters were a very marginal benefit, if any, and certainly don't prevent icing.

One issue with them was that the heater sensor, a flat black disc item tucked into the wiring under the tank on the right hand side IIRC, sits in a reasionably warm place so as often as not it doesn't switch on when needed. Find it and get it out into free air if possible, easier with a faired version.

Carb icing as described by others tends to persist when the conditions are right (or wrong) regardless of the engine temperature, especially on the SV or other bikes where there is no air heating system like most carb car engines had (also usually water heated manifold/carb mount). It is most common when ambient temps are round the 2-4degC mark typically.

Also it manifests itself as an unwillingness to change running condition, so often the engine will run more or less OK at steady speed, but won't respond to changes in throttle, or will even cut out completely. This just helps you recognise it for what it is.

Short of re-engineering the bike or getting a pointy, the best way to deal with it is use the Pro-FST fuel additive (one of the few additives I'd ever recommend), use a "premium" fuel when the conditions are appropriate, Shell V-Power or equivalent, and possibly slightly increase the idle speed purely as an anti-stall measure, and move the carb heater sensor.

Ultimately it's something we have to live with and get around, law of nature I'm afraid.

[yorkie_chris]

Just hang the sensor out of side of frame. I ran mine for a bit with an LED on clocks wired to heaters... any day below about 3 deg theyd be on when riding slowly, below about 5 deg they'd be on if you were doing over 50