Spluttering

[popkat]

I feel I ought to know this and have an idea but i'll ask anyway. Small throttle openings between 2.5 and 3.5k rev the bikes farting, spluttering and lurching. It started a while back and has got worse the last couple of rides, it's a bit better when it's fully warmed after a few miles, but when the choke is first taken off it's bad (doesn't really do it when on choke)..F2 model, end cans fitted, pair system blocked off with the reeds flipped over (but was doing it a bit before this was done, just got worse recently).
Cheers.

[lloydie]

Sounds like its running lean down low .
When was the air filter changed ?
When was the carbs last cleaned ?
When was the plugs last changed ?

[Redthunder]

If the F2 has a vacuum pipe to the petcock, check this hasn't split, come off or even has a pin hole!

[VTRDark]

As lloyd said check the air filter and a carb sync is probably a good idea but I think I would be looking at tweaking the fuel screws a 1/8 to 1/4 turn out if things improve with the choke out.

(:-})

[edds11]

mine carb farts between 2500 3000 all the time, I can improve it but never get rid of it.

[8541Hawk]

The problem you are having is right at the top of the pilot circuit range as the needles start to lift around 3-3.5K RPMs

So either one of your jets picked up a bit of crud and is clogged or the adjustment screws need be be turned out slightly.

If it was running fine and just started acting up I would say pull the pilots and clean them.

[popkat]

Thanks guys. I had a quick look this morning and noticed the large rubber cover/flap that sits over the rear cam cover had slipped on to the rear exhaust header, melting the end of it nicely, i was sure it went back on right but must have slipped off the tab when i put the tank on then it's slowly slid backwards since, anyway put it back in place and the burnt bit doesn't show, had a look at the vacuum pipe and it's properly connected both ends, not able to check for pinholes as i only lifted the tank, (tank off is 2 person job really on an F2), I've only got a few tools at home so will do it when in the workshop next week, i'll turn the pilot screws out a bit and check the plugs, and if time i'll balance the carbs..
When i first blocked off the "pair" it was only giving the occassional pop on the overrun, but since the spluttering got worse it's popping back more, something has changed in the last 6 weeks and 300 or so miles, I blocked the pair pipes and airbox with short hoses with a bolt in the end, they are all still good. Other things i did when i blocked the pair was stopper mod and set the TPS as low as i could get it, think it was about 540. when the bike was all std it coughed occassionally and lurched a little at 3k constant throttle at low speeds ie in slow moving traffic, it wasn't a problem just seemed normal for a vtr for me, the problem now is the same but worse so it's exagerated whats already there, if i can get it back to how it was before i'll be happy that all is good. cheers.