VF500 Idle issues

Hi
I have some idle issues.

Bike starts fine with choke on full, after or within 2/3 mins carefully backing off the choke the bike is idling just a little high at around 1500rpm. Temp gauge needle goes into the cold zone. As the engine starts to warm up a little more the idle starts to become a little erratic, a little lumpy. Blip the throttle to around 2500 rpm and the rev counter needle stops at around 2000rpm and then a good few seconds later returns to 1500 but then possibly goes lumpy and stalls.

Start bike..... fine no problem. Engage 1st take the bike for a couple of spins around the car park and the pull up. no problem. As the bike gets warmer (temp gauge needle to middle) and another circuit the engine cuts out whenever I roll back off the throttle. Bike starts but have to keep holding on to the revs.

I was told the bike had not been used very much since 2009 maybe no more than 4000 miles in that time .I was also told that the carbs had been cleaned, and that the idle was set a little high.

Bike runs fine when cold but gets more erratic as it gets to operating temp.

What could be causing this/ solutions

Carbs need a better clean or certain specific things need to be properly looked at and cleaned?
Vacuum hoses checked for leaks/ replaced ?
Valve adjustment? its done 31.5K and is due for valve check and adjustment in 500 miles (or possibly just get it done now)?

Any thoughts/ advice would be welcome, I am trying to stay positive! I read in one posting on here where a guy said something along the lines of " Well its worked fine for the best part of 20 + years it can work perfectly well again" so with that in mind I am trying to not feel to down and depressed ! Old bikes are like old classic cars, I love them but they can drive you crazy at times ! (Oh why did n`t I get finance and buy a spanking new CB500?!!!)

Rob

 

Assuming you are OK with actually riding the bike the best thing to try first is a long bike ride being pretty agressive with the throttle. Petrol is a good solvent and if there is crap in the carbs this might shift it. Also fill it with the Shell V Power or the BP equivalent and run a few tanks of that through the carbs.

 

is bp or shell v more solvent than others? and what grade of fuel to put? i am going to try this out on my next tank to see if my bike runs better. having the same issues as whats being described.

 

slo jets in carbs need cleaned

 

The Shell V Power grade in the UK and the BP Ultimate are reported to have a more sophisticated additive package that includes more detergents. If the carbs are really clogged then nothing but a strip down is going to help but a tank of the good stuff is worth trying first, you never know...

 

You can get useful info about carbs by draining the float bowls into a paper towel, inspecting for varnish, rust, water, debris: all indicate separate problems.

Petrol tank must be spotless inside or carbs may soon clog again.


Do checks to find any airleaks around boots or loose clamps. (Can you trust your mechanic ?)

Nexttry turning IN (CW) each idle mixture adjustment screw 1/2 turn to lean the mixture ( best done with cold engine), and ride again. Bikes that run worse at idle when hot suggest a too-rich idle mixture, as an ordinary rule-of- thumb with a scientifik basis. Or maybe on of the choke enrichment plungers is stuck partially open ?

Get it warmed up, and let it idle at about 1200 for 3-4 minutes; then stop, wait for things to cool down, remove and inspect plugs for soft and dusty or wet and black deposits.

Replace the plugs if they're anything much more than Cadbury Dark Milk Chocolate black, and start with a clean slate.