Lack of power on Curvy

On saturday, I adjusted the clutch at both ends, oiled and removed some freeplay in the choke cable and took up freeplay in the throttle cables.

On starting her up she wasn't running smoothly, so fiddled with the idle mix till she seemed right.

Set off today, NO POWER!

Stalled a couple of times and will not run well under load.

Any ideas?

I'm thinking as there was freeplay in the choke cable, that it may be something to do with that? Maybe the plungers have moved further than they have in recent years and then stuck?

OK. I've had the carbs off, and basically, they're not in the best of shape. Previous owner, or at least, someone who has previously worked on the carbs, has left chewed screws in them. Great!

Have tried to extract the screws holding the plungers on, but they will not budge, and can't get mole grips on to them. Had a good inspection of them, and see that one of the mixture screws underneath looks buggered.

Does anyone out there have any ideas on why my bike is dying under load?

[Taipan]

If it wasn't like it before you adjusted the choke and throttle cables it must be them. I'm assuming you've somehow slackened off the throttle cables so you're not actually getting any throttle action? Can you see if its actually opening the throttles when you turn the twist grip?

Yes. I've been back over everything and really can't see why it's behaving like this.

The choke makes considerable difference between on and off. With the bike warm, the choke on full will take it up past 4k, off it idles nicely at 1.4k.

The throttle picks up the revs in an instant, but under load it dips sharply and requires much more to prevent a stall. Revving on the side-stand, the revs are slow to drop off, and on the road when moving, it's like the throttles not closing and fuel keeps running through. I have checked the cables at the bottom end, and they seem to move fine, without being slack or too tight.

Incidentally, while I have balanced the carbs, I'd say the rear cylinder exhaust is not as hot as the front, but she's had new plugs two weeks ago.

I'm almost ready to concede defeat and take it somewhere, but a, I'm not sure of anyone local that I can trust, and b, I'm very skint.

I really need to be back on the road by wednesday for work.

[Taipan]

I cant think what you could have done with just cable adjustment that would have done this? Did you have the airbox off and adjust at the carbs end or just at the twist grip? I checked your location and sorry mate but I'm hundreds of miles away. Anyone local to you? Two heads are always better than one when you have a puzzler? If it wa sfine before it must only be something simple.

Stupidly (see my sig), I decided after tea, to go out and see what the difference was in the heat between the two exhausts. So, I check the rear and that was stone cold, then check the front, and burnt my finger.

First thing tomorrow, I'm going to disconnect the rear lead and pop a spare plug in it to see if there's a spark. I may have dopily not realised that she might only be firing on one, and adjusted everything to get her running at stand-still, well enough for that, but I'm not sure what I could have done to stop the rear cylinder from firing.

If she's not firing on the rear, the carb would still pull air and fuel through, right? Giving the impression at that part of the machine that she was going, when actually not?

Makes me sad seeing the castrator washers in the cylinder head ducts. 11 months to go.

[5hort5]

ouch - tried that test on the weekend myself but used damp kitchen role to get for a sizzle instead of skin

[Taipan]

Originally Posted by boot

Stupidly (see my sig), I decided after tea, to go out and see what the difference was in the heat between the two exhausts. So, I check the rear and that was stone cold, then check the front, and burnt my finger.

First thing tomorrow, I'm going to disconnect the rear lead and pop a spare plug in it to see if there's a spark. I may have dopily not realised that she might only be firing on one, and adjusted everything to get her running at stand-still, well enough for that, but I'm not sure what I could have done to stop the rear cylinder from firing.

If she's not firing on the rear, the carb would still pull air and fuel through, right? Giving the impression at that part of the machine that she was going, when actually not?

Makes me sad seeing the castrator washers in the cylinder head ducts. 11 months to go.

Aye, a cylinder or engine is just an air pump that we introduce a flammable mixture to. So yes it will drag through a mixture.

I've been reading your thread about your revving issue, the drop off you're having is similar to what I was experiencing on cold days, before I started buggering about.

At least you have spare carbs.

If it wasn't for the fuel I've been inhaling all day (spaced out dude! ), I'm sure the snow would have seen me off.

[Taipan]

Originally Posted by boot

I've been reading your thread about your revving issue, the drop off you're having is similar to what I was experiencing on cold days, before I started buggering about.

At least you have spare carbs.

If it wasn't for the fuel I've been inhaling all day (spaced out dude! ), I'm sure the snow would have seen me off.

You haven't got contaminated fuel have you? When my SV sat outside for a while I had water slowly leaking into the tank. Each time I started it, it ran worse. I'd start on one cylinder and eventually break into two. But after a while I only had one cylinder running. As I tried to pull away it would fart, pop and die on me etc.

If this sounds familar you could stick a glug of meths in the tank and top top with fresh fuel. Then drain the fuel bowls (you can just get in there with a long ball ended allen key). Now spin it over untill it drags the fresh fuel/meths/contaminated fuel mix through and you should be okay to go.