t25 1.9 dg 1986 fueling

[trex100]

hi guys , I have a t25 1.9 dg and have some slow running issues , ie when cruising below 30, up to speed bumps and in 2nd gear on low over run the bus appears to develop an almost bunny hop effect but will easily pull out of it so I was wondering what could cause this , almost feels as if the slow running carb is gummed up but I am not familiar with how the carbs work on t25's

does the carb have a low rev side and a high rev side

if so do they develop this type of issue?

before I bought it it may have been stood for a while with petrol in the carbs I have been out on a couple of 20 mile runs with it once its warm its fine it pulls well so that is what make me think I have a fuel at low revs delivery issue , can carb cleaner be used with out any issues , I know the carb was rebuilt quite recently but this was before the bus had been stood for nearly a year as failed the MOT on emissions a couple of tests ago but emissions are now fine

thanks in advance