Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: spooky on September 27, 2021, 01:11:25 PM

Title: thirsty 250rs
Post by: spooky on September 27, 2021, 01:11:25 PM
My condor/250 honda occasionally runs badly, i found the air filter intake hose was split, replacing will be interesting as i am not sure what it is off, i suspect its non desmo Ducati ?  anyway, i bodged a repair and after a few miles it started misbehaving, i found that if i leaned it over to tap side it would run again for a short while. No reserve on it so i drained out what was in, less than 3 litres.. tank is supposed to hold 14lt and from full to when it starts to run badly i can only do about 100 (fastish) miles.... question is what mpg should a cb250rs get ?   45-50 seems a bit rubbish      also was unable to fill it up to check tank volume because petrol station queue was overflowing onto the road and was about 20 cars long, i decided to leave the fuel for all those `deserving` people in the queue....
Title: Re: thirsty 250rs
Post by: themoudie on September 27, 2021, 01:37:28 PM
Aye Rufus,

I get about 60mpg out of the 450 Duke at the moment on too low gearing and a 32mm carb, whilst a friend has a CB250RS that achieves 80mpg regular. So, besides emptying out the tank, I would check out for filters in the fuel tank side of the fuel taps and flush the whole system out and give it a blast with an airline, if you have one. Also check the carb filters for blockages and sediment in the float bowl.

Once you have been through that little lot, put a good quality lawnmower filter between the tank feeds and the carb for extra insurance. Use Castrol Valvemaster for every fill up, 1ml to 1l of E5 or E10.

Carb air filter hoses can cause all sorts of problems on Ducati singles, maybe better with a K&N pod filter straight over the carb intake. I know it's a CB250RS, but, you never know.

Finally, sentence taken from a short online review
Fuel consuption was about 5 litres/100 km ridden hard or as little as 3 litres/100km riden gently.
That works out at between 56 and 95 mpg and I suspect on those Dumfries roads your giving it a bit of welly! ;) ;) ;) ;) ;D So, I wouldn't think much wrong with the carb, just E10!  :(

Link to quoted review:CB250RS_review (

As for the lemmings .....!  :( >:( :-X  As posted in rants!

Good health, Bill
Title: Re: thirsty 250rs
Post by: kevberlin on September 27, 2021, 06:35:02 PM
I recently collected a Cb250rs from the south coast and rode it 162 miles iback home,
Looks like about 80mpg as far as I can see., albeit at a steady 50-55mph
All the best
Title: Re: thirsty 250rs
Post by: spooky on September 28, 2021, 10:44:02 AM
I think i need to check the sprockets, it may be running the standard Condor with rs front , it does rev quite high , it probably won`t make much difference to economy but you never know.  Checked the tank while it was drained and it`s very good, there is only one tap and there is a very small balance pipe to get the last of the fuel across, i am hoping that the (badly) repaired air hose will make a bit of difference, then i will try a pod filter as Bill suggested. No crud came out when i drained tank or carb..