Curvy running poorly.

[live steam]

HELLLPP!!!

Hello guys.

Im almost giving up with my SV, shes a pain in the ****!! Owned her for a year so far and when she runs properly shes beautiful!

The Story so far....

Bought her a year ago, on the ride back from suffolk to southampton she would only get up to 90. Stripped down the carbs to find restricted throttle slides. Bought a new set of unrestricted ones and fitted them. Ever since then she has alternating periods of I'd say three weeks or so of being a good girl and a bitch. When shes a bitch she won't get over 60, and then one day i'll hoon it up and suddenly shes got full power back untill 3 weeks or so later when she will suddenly just drop back down to sod all power. I've tried cleaning out the carbs and jets and shes had new plugs. Now about two weeks ago was a good week , I was on my way home from work late that evening (I wasn't hanging around). Next thing the powers dropped off and I see an orange glow behind me, Sparks galore from the exhaust!! That was it, got her recovered and stripped the engine down over the next few days, apart from the exhuast valves needing a bit of lapping in I found nothing amiss so shes been back together for about a week (plus a carb strip and clean) and shes not a happy bunny at all. Idle is either all or nothing, odometer has suddenly stoped working today after stripping the carbs (this is probably me forgetting to re attach something) and she has very little power, almost less than before. Anyone with any suggestions? Im going to re check the timing and valve clearances on saturday and I did reassemble her at 4 in the morning to get to work. But theres been no adverse noises from the engine. One thing I will say is the reg/rec's faulty but I don't think that would affect anything.

Any Ideas.....

[m1tch_1987]

Did you change the fuel filter when you cleaned the carbs out etc? The carbs might be clean but there might not be any fuel getting to them!

[ghigo]

has it got the right jets in as when they restrict them dont they change the jets? id prob book it in to a tuner a get the carb properly set up,
hope this helps

[mikerj]

Is it dropping onto one cylinder when it's misbehaving? If so have you checked/replaced the spark plugs recently, and cleaned up the HT leads and caps?

[yorkie_chris]

Odometer not working, you mean tacho? If so then that is likely you knocked wire off the front coil when putting airbox back on.

Sparks out of the exhaust are usually the packing, or carbonous sh*te, getting blown out.

[Sir Trev]

Have you checked the operation of your choke plungers and the state of the cable (as you mention carbs I'm assuming this is a curvy). I had eratic idle and running due to problems in this department and is an easy check.

[BoostFairy]

As ghigo said, why don't you take it to a dyno and get the carbs jetted properly?

[yorkie_chris]

They don't change jets for restriction.
A jetting problem would be continuous not intermittent.
Might be worth making sure the jets are standard, there is a good stock air filter in etc.

Waste of money to dyno if it's got another problem.


What colour did the plugs come out?
Check/remove the foam under tank, it can get sucked down and block filter.

[BoostFairy]

Ahh cool i didn't realise the jets weren't changed for a restricted bike,

However fuelling requirements change a lot with engine temp, ambient temp and altitude. So an engine that runs well on a hot day with a slightly lean mixture may well not run very well on a cold day, which would could account for the intermittent running.

May also be worth while checking timing, if this is changing due to worn parts etc it could also account for a bike which runs well sometimes and badly other times, very retarded timing also increases exhaust temp (a lot) which again may explain the op's sparks from the exhaust.

[BoostFairy]

Had a quick think,

if the bike was lean it would be spluttering all over the place, I think ignition timing would be a good place to start looking.

[m1tch_1987]

Check the plugs first and report back on the colour of them

[SpikeTM]

Sounds very much like a coil breakin up under load

[BoostFairy]

Yes but the OP doesn't say anything about misfiring, i think a coil breaking down would cause a misfire.