Garygazza Posted May 22, 2011 Share Posted May 22, 2011 Hi all,I picked up my 1978 xs250 yesterday and went out to give it a run.I noticed at the bike was surging a bit.I then opened it up to go over a large bridge and got to about 65mph when it started to die like fuel starvation.I came to a stop and it idled but would not respond to the throttle,however after leaving to idle for a few minutes I was able to carry on my merry way.With the bike still surging a bit I decided to chance overtaking a slow car and as I was alongside it died like fuel starvation again and cut out.It would not restart but after a while it did but would not rev up and now it stalls.I suspect carbs or air leak.The bike had a full carb clean ,new filters etc before I picked it up and I put fresh fuel in the tank.I have notices the rubbers between the carbs and head looked perished which I feel would not help.Ive seen some inlet rubbers from Yambits are they of good quality? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 22, 2011 Moderator Share Posted May 22, 2011 fuel tank could be corroded letting rust dust into the carbs and bocking them. The air hole in the fuel cap could be blocked or the float height is incorrect (haynes is wrong, it should be 26mm not 32mm) Link to comment Share on other sites More sharing options...
Garygazza Posted May 22, 2011 Author Share Posted May 22, 2011 I opened the fuel cap but it still made no difference.I have an inline filter which seems ok.Thank you for the infomation on the float level height.I will get in the man cave this week and have the carbs off and reclean. Link to comment Share on other sites More sharing options...
Garygazza Posted May 23, 2011 Author Share Posted May 23, 2011 Just an update,took carbs apart today.Found the right hand slide jamming up and not returning to its rest position.This was due to the spring above the diaphragm not located correctly.I checked the float level and this was set at 30mm .Cleaned out all the jets and cleaned the slides with solvol autosol and set the floats at 26mm.Can you tell me the best position to set the needle valves(both are set 1 position up from the bottom position ).How many turns is a good place to start with mixture screws? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 23, 2011 Moderator Share Posted May 23, 2011 Just an update,took carbs apart today.Found the right hand slide jamming up and not returning to its rest position.This was due to the spring above the diaphragm not located correctly.I checked the float level and this was set at 30mm .Cleaned out all the jets and cleaned the slides with solvol autosol and set the floats at 26mm.Can you tell me the best position to set the needle valves(both are set 1 position up from the bottom position ).How many turns is a good place to start with mixture screws? leave the needle valves for later, its only for the top end. pilot mix screw 3 to 3.5 turns from bottoming out Link to comment Share on other sites More sharing options...
Garygazza Posted May 26, 2011 Author Share Posted May 26, 2011 I have completely cleaned carbs and replaced o rings on the main nozzle.I have new inlet rubbers and gaskets fitted,the pilot mixture screw set at 3 turns from rest(they were set at 1 and a half turns before strip down) and the floats set at 26mm (30mm before strip down) and the air filters are new.The bike starts on choke but there is no fast idle(it did before problems).The bike smells very rich and seems slow on throtle responce when revved up whilst stationary and slow to return to idle ,then unless the idle screw is wound up it stalls.I have screwed 1 pilot screw right in and it does not effect the running.Which way do you turn the pilot screws to weaken mixture? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 26, 2011 Moderator Share Posted May 26, 2011 I have completely cleaned carbs and replaced o rings on the main nozzle.I have new inlet rubbers and gaskets fitted,the pilot mixture screw set at 3 turns from rest(they were set at 1 and a half turns before strip down) and the floats set at 26mm (30mm before strip down) and the air filters are new.The bike starts on choke but there is no fast idle(it did before problems).The bike smells very rich and seems slow on throtle responce when revved up whilst stationary and slow to return to idle ,then unless the idle screw is wound up it stalls.I have screwed 1 pilot screw right in and it does not effect the running.Which way do you turn the pilot screws to weaken mixture? in weakens the mix! the slow to return to idle usually means its weak. If when it is warm, what is the response like then? Link to comment Share on other sites More sharing options...
Garygazza Posted May 26, 2011 Author Share Posted May 26, 2011 Hi Drewpy thank you for your help,when it is warm it still tends to be slow returning to idle.I have sprayed wd 40 over the carbs and pipes but does not effect the running.I have read other posts and it does seem a weak mixture is the most likely problem of this issue,but it smells very rich?Im assuming if the floats were set wrong it clold flood but no fuel is leaking from the carbs.I am running the bike without the fuel tank via a petrol reservoir.Think Im going to have to strip down again.The one thing I did notice when I replaced the o rings on the main jet nozzle was that the groove where the o ring sits were different to each other. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 27, 2011 Moderator Share Posted May 27, 2011 have you put the O rings back the correct way? mikexs describes the way they go in in the advert for bs34 carbs Link to comment Share on other sites More sharing options...
Garygazza Posted May 27, 2011 Author Share Posted May 27, 2011 have you put the O rings back the correct way? mikexs describes the way they go in in the advert for bs34 carbs Have stripped down and rechecked and adjusted the float level again.Bike starts up and idles ok.The revs also drop ok and does not smell as rich.I think I had 2 issues because the right hand exhaust smelt of fuel?also the right hand downpipe was cold so obviously not firing.I removed the points cover to check for a gap (gap present),I started the bike and armed with a piece of cardboard and slotted between one set of points,when removed the revs went up and the bike ran better.A dirty set of points now cleaned and will give it run tomorrow.Thank you Drewpy for your help,your a diamond geezer. Link to comment Share on other sites More sharing options...
SPUDGUN Posted November 14, 2012 Share Posted November 14, 2012 I have had all the same issues and done everything you did bar the points. I also put in a replacement petcock kit but when ON it still allows a trickle through so not sure about that. STILL dies after 5 mins though so obviuosly haven't got to the bottom of it yet at least I have eliminated, float levels, dirty carbs, fouled plugs, plug leads, leaking petcock... so now clean air filter, check points, could it be valve clearance??? ignition coil??? sorry flying blind here. Any other suggestions. She's a nice looker at least Link to comment Share on other sites More sharing options...
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