carby problem?

Hi, I have an old gpz250 that spent most of its life in a shed. It had a lot of work done before I got it so I'm basically running it in. Done about 500k on it and the engine is settling down. The problem is it now idles at around 1200-1300 for a while then after it warms up jumps up to 2200 or so. I'll stop at the lights, it drops to 1300 then slowly increases. As it gets warmer after about 20k it doesn't drop below 2200. I run it on BP premium unleaded (95).
Whats the best way to deal with this. Its a cheap bike I got to learn on for a year so I don't want to spend a lot on it. I suspect the carbys are cleaning themselves out but not sure. I am also mechanically inept.

Don't use PULP

make sure your throttle cable is lubed.

ta, the throttle cable seems OK. I'll try a tank of ordinary unleaded and see what happens.

if you're overly worried about your carbies
put some carby cleaner through the tank
not a whole bottle though, say a third of one of those bottles to a full tank

Check ya spark plugs (may need new ones)

Failing that, it's not that big of an issue, just turn the idle down a little bit so normally it's at about 1100, then see how high it idles otherwise

does it jump all over the place, or does it slowly creep up from time to time?
if its the latter, may i suggest you check the carb boots (between the engine and carbs) for air leakages? sounds like what i had happen to my old cb250 before i killed the farker (melted a hole in a piston the size of a 5 cent peice)

hi, it creeps up but when I come back from a run and turn it off then restart it after about 15 min it jumps straight up so I'll start with the fuel and look for leaks in the boot. the joys of old bikes.

its ntoa fuel leak, its an air leak.

best trick to try and check is to spray aerostart around the carb boot while the engines settled down. if it changes revs at all, voila, carb boot leak.

Also whie your doing this make sure you dont get any going into the airbox as that'll screw with the test and give a false positive

I sort of meant that. I'll change to ULP rather than PULP and see what happens, then look for the air leaks.

just doublechecking to make sure

not a problem. I wouldn't want to hurt the poor old thing.

I sort of meant that. I'll change to ULP rather than PULP and see what happens, then look for the air leaks.

you have more probs than fuel

start looking for the airleaks

you could also have posible crap in the carbs

your not wrong. petrol coming out of the carby tonight. oh joy

the needle/seat combos are probably gunged up after a couple of years in the shed, and your fuel lines might need replacement as well ( its pretty cheap).

keep the updates coming.

sent him off to the mechanic this morning.
the f^&%$*% petcock didn't stop the petrol completely so the shed needs airing.
probably take a week for him to be attended.
have to ride my wife's scooter