Revving it at standstill.
 

Bike is great and bulletproof in the normal way, but

Whenever it has been left for a few weeks and is cold, if you rev it even a bit, from a crawl, it cuts out.

This stops after a nice long burst and also when the bike is warm, but even with fairly regular use, i.e tonight, squeeze the throttle lever to get a nice burbling grunt a few times and once that has been achieved - click/rattle and stall.

Once fully warm it is fine, and whenever this happens it is always mid throttle - i.e you twist your right hand whilst the bike is idle or at a crawl and -blip- its dead.

I know it is a minor thing as the bike is such a superstar in how it always starts and how it rides.

Weather? What causes this?

Re: Revving it at stanstill....
 

not 100% sure but it could have somthing to do with the cold and fuel been more dense so in affect floods the bike

Re: Revving it at stanstill....
 

I presume this is humor, you're not serious are you?

Cheers Mark.

Re: Revving it at stanstill....
 

share the wealth of knowledge then mate:D!

Re: Revving it at stanstill....
 

was been serious, but i could have misread what i was quoting hence the not %100 bit, but i read somthing a long while back (when having problems with my 50) that fuel is denser when its cold and can cause bad running, aparently thats why my 50 would smoke like a chimney in the moaning and night but be fin in the day time

:confused:

Re: Revving it at stanstill....
 

look up basic carb operation (idle circuit v main operation circuit) for the original posted issue, and (to point out the obvious) it's air that gets denser in the cold, making the mixture slightly lean (as opposed to denser fuel, suggesting running rich), so of the two options you could guess at; it's the opposite one.

this is basic stuff guys, if you don't know, don't guess.

Cheers Mark.

Re: Revving it at stanstill....
 

Fuel density does not remain constant across a temperature range. Fuel distributors in this part of the world measure the density of fuel when it is sold to retailers and densities from a given batch can vary by ~5% during the course of a day. A/F mixtures still go slightly lean.


However... I doubt that this is the cause of Dizee's problems. Condensation in the bowls (carbs?) or tank (first bit of "fuel" to hit the carbs will be water) caused by warm(ish) days and cool nights, state of tune, condition of the fuel (that was left sitting), carbs, valves, cylinders etc are more likely causes.

Re: Revving it at stanstill....
 

I fully agree to your first point "over a large enough temp range", however for the purposes of the scenario posed "fuel density" is totally misleading and more of no relevance; air density on the other hand does change fuel mixture by a greater margin but we aren't in the arctic or equator, and I doubt it's the cause of the OP problem, merely pointing out the guess by the follow up post, was just that a guess.

The OP has an issue coming of the idle jet onto the main,as the idle circuit is basically fixed and working fine; for any systematic diagnostician this would suggest first making sure everything was clean and balanced on the main circuit, before looking for kryptonite in the flux capacitor ......:lol:

As said it's REALLY BASIC stuff, come on you keyboard experts have google and everything......

Cheers Mark.

Re: Revving it at stanstill....
 

PS. I was agreeing with you, but being just a shade pedantic. :)

Re: Revving it at stanstill....
 

Sometimes when a bike is left the fuel left in the float bowls can dry out and gum up the jets, although this is far more common with 2 strokes that fours.
I've never had an SV carb apart before (I'm assuming it's a carb model) but on some carbs the pilot jets are really prone to this and it's the pilot jet that has the biggest impact on initial throttle openings. Once you run the bike for a while the jet gets flushed through a bit and it clears. Alternatively as has already been suggested it could just be that the fuel in the carbs goes stale and once replaced it runs better, but I'd have thought the fuel in the tank would be just as bad?

Finally it might even just be operator error. Most carb engines won't take a big throttle opening when cold, why not let it warm up a bit before blipping it?