Running rough, running out of ideas.

Hi all,

Sorry it's so long but I'm having problem with the sv running rough, to be more prescise it has very little power across the rev range, idle is fine.

The problem first started with a lack of power which was caused by a loose breather hose, fixed.

About three weeks later the problem came back but intermittently, it'd backfire a few times then be ok or problematic. I changed the spark plugs and ht leads and that seemed to sort the issue, for a week.

Then came the backfires again and poor power but this time it stayed.

So I then replaced the carbs (as the new plugs were very black within a week), choke cable, checked the fuel pump, fuel tap/filter they were all fine, I also drained the fuel and found nothing untoward in the tank.

This made a slight improvement in power delivery but no way near what it should be..

On the way back tonight she coughed, spluttered and died. I can now start her but as soon as I open up the throttle the smallest amount the bike cuts out....

I've also checked all the ignition resistance readings and they check out ok, the only thing I've yet to do is swap the ecu out.


Does anyone have any other ideas?

Cheers,
Sarj

[yorkie_chris]

Water in the juice?

Hole in the carb diaphragm?

Sounds like the carbs or the choke but you've checked / changed those. Air filter OK?
I wouldn't have thought a dodgy ECU would cause sooty plugs but if you get a cheap one it might be worth trying that. Or wait for a suggestion from someone with more know how than me.

Hi,

Thanks for the replies, I've replaced the carbs, choke cable and done a fuel system drain, check with no problems.
The Air filter is also clean, and all air pipes are good with no leaks.

Cheers,
S

Originally Posted by Sarj

Hi,

Thanks for the replies, I've replaced the carbs, choke cable and done a fuel system drain, check with no problems.
The Air filter is also clean, and all air pipes are good with no leaks.

Cheers,
S

The Ignition control unit on the curvy does just that. Nothing to do with carburation so I understand.

Also, the choke only affects idle and small throttle openings so should have been OK elsewhere in the range.

If your ignitiion was at fault you would be getting unburnt gas. Have you checked that you are getting a good spark?

If not that then the only other thing I can think of is a sticking inlet valve. But then I would have expected it to run on one cylinder.. ??

Have you done a compression test?

I've checked the sparks and they're fine.

I've yet to do a compression test but I was thinking along the same lines.

Cheers,
S

Originally Posted by ejohnh

The Ignition control unit on the curvy does just that. Nothing to do with carburation so I understand.

Also, the choke only affects idle and small throttle openings so should have been OK elsewhere in the range.

If your ignitiion was at fault you would be getting unburnt gas. Have you checked that you are getting a good spark?

If not that then the only other thing I can think of is a sticking inlet valve. But then I would have expected it to run on one cylinder.. ??

Have you done a compression test?

[jambo]

Given it's dying as soon as you rev I'd be thinking leccy. Simple point is there are 2 carbs, and however bad one is you should be able to rev the bike on one cylinder, for it to cut that suddenly I'd be looking at electical stuff.

You've checked the spark at idle, but if it's idling fine, and then dying this won't rule it out. Just my first thoughts.

Sounds like it's flooding when you gas it. You say plugs were black or gassy? I suspect that it's electrical too, somehow, not enough good spark hitting it under load. maybe ignitors ? patience and you'll sort it. he he, i'd have pulled my last few hairs out by now.

I guess it could be electrical, the new plugs were very black after a week.

If the all the ignition system resistence readings were fine, could it be something breaking down gradually or under load?

I've replaced the ht/coil leads, I guess the only other thing left to check is the ecu...?

Cheers,
S

Get a colourtune on it to see what's happening in the cylinder. Just don't electrocute yourself repeatedly with it.... which I'm sure no one has done....ever