Poor running on front cylinder - Curvy.

My sv650x has never quite run right; when cold it most often starts just on the rear cylinder, with the front randomly kicking in. Once warm it runs better, though still a little rough, and it's been noted the exhaust gas is pretty hot.

With air filter off, covering the rear carb with hand causes the bike to stall, doing the same with the front carb causes it to idle slightly higher.

Spark plugs look like so (front on right):



So far I have:

• Checked choke plungers
• New plugs
• Carbs stripped, cleaned and balanced (Thanks Bibio!)
• Coil resistance checked (5 ohms primary, 27 k ohms secondary - same values on both coils)
• Redex applied
• Compression checked (14.7 bar rear, 14.4 bar front)
• Swapped the current spark plugs over

Nothing has made a difference so far, what's left to try?

[embee]

From what you say, sound like it's running far too lean on the front carb (putting your hand over the carb intake works like a traditional choke and makes it run rich). This suggests a possible air leak or maybe a blocked idle jet.

Check the carb is sitting in its rubber correctly, the clip is tightened properly, the rubber isn't split, and the cap isn't missing off the vacuum tapping used for balancing (front right hand side of inlet stub).

If all these are OK, it may be an idle jet blocked, which really means dismantling the carbs to get to it for blowing through and washing out any crud.

The plug can look like that if it's only firing intermittently, fuel builds up making it wet and cold, then it fires and makes it grubby.

Surely what youve just listed wouldnt be an issue if hes just had the carbs cleaned?

[embee]

OK

[jambo]

Originally Posted by embee

OK

Thankfully I had no tea in my mouth as I read that!

"Cleaned carbs" can mean different things to different people. The compression check suggests everything is ok mechanically, so fuel is the most likely culprit. I'd run with embee on this if I were you, his logic is always very sound, and he knows a thing or two about motors and SVs.

If you're uncertain a simple check can be to substitute in a known good bank of carbs from a clean running bike. If the problem persists (and the other checks mentioned by embee don't turn up anything obvious) report back

Jambo
Sent from my thingie

Wasnt being rude, just checking you hadnt missed that on the op.

I spent a long time working on airplanes, and the most logical thing to do to diagnose a problem was to check to see what had been worked on lately. This was often where the problem was.
Everybody hopes to fix things when we work on them, but most everybody sometime or another, makes things worse.

I'll try and get the carbs off tonight and check the seats. If they all look OK and I end up stripping the carbs is it just the idle jet worth looking at?

Originally Posted by Terah

I'll try and get the carbs off tonight and check the seats. If they all look OK and I end up stripping the carbs is it just the idle jet worth looking at?

Did you do what embee suggested and make sure you had no vacuum leaks into the front cylinder?
Any time the carbs are removed, there's a chance they won't properly seal into the intake boots on re-installation.
It's worth looking at the idle jet, but only after you are positive you have no vacuum leaks.

Originally Posted by wideguy

I spent a long time working on airplanes, and the most logical thing to do to diagnose a problem was to check to see what had been worked on lately. This was often where the problem was.
Everybody hopes to fix things when we work on them, but most everybody sometime or another, makes things worse.

Remind me not to get on a plane you've worked on then