scotty Posted March 11, 2007 Report Share Posted March 11, 2007 having problems with my 1971 bultaco 250 slimline, It starts but only for 2 or 3 seconds then dies! ive stripped the carb loads of times, the floats ok, jets clear etc! i did jiggle a bit with the carb and got the bike running up and down the road but the tickover seemed high even with the idle screw set right out! ( the throttle cables ok) also the bikes a bitch! to start having to flood the carb lots of times to get it going again? so would this point to worn crankseals??? what are the symtons of worn crankseals? the above? the spark plugs new and theres plenty of compression! ign timing dont know? but when going the bike picked up and rev'ed well! thanks for any replys chaps. Quote Link to comment Share on other sites More sharing options...
paulthistle Posted March 11, 2007 Report Share Posted March 11, 2007 (edited) A crankseal leak can have erratic symptoms. If there is oil on the leaking side it would smoke a white puffy smoke. If you removed the carb and exhaust pipe, plugged the holes, then with the piston at the bottom of it's stroke put 4 to 6 psi in the crankcase through the sparkplug hole. Spray soapy water around the seals or listen for air leaking. If the crank bearings are loose you may try moving the crankshaft up and down. If it moves at all, the crank bearings will need to be replaced. I would also verify the ignition timing. Edited March 11, 2007 by paul_thistle Quote Link to comment Share on other sites More sharing options...
max1956bikes Posted March 11, 2007 Report Share Posted March 11, 2007 sounds like crankseals they have probably gone hard through age.they are cheap and easy to replace so do it any way.normally makes engine run very weak needing lots of choke and uncontrolable tickover normal behavier Quote Link to comment Share on other sites More sharing options...
totalshell Posted March 11, 2007 Report Share Posted March 11, 2007 I'll second the uncontrollable tick over, i didnt fit a crank seal properly once and tick over would go up and up until it was revving its nuts off, sounds like air is getting in if you have to richen the mixture right up so check the carb one last time bolt it all up to the engine and then smear engine oil on all the carb /inlet/ barrel/ joints if it runs ok thats where your problem lies (just a simple CHEAP TEST) the fact that it runs ok when warmed up points to this as gaps close when the engine warms up, if not the crank seals might be waiting for you.. Quote Link to comment Share on other sites More sharing options...
rcgods Posted March 14, 2007 Report Share Posted March 14, 2007 having problems with my 1971 bultaco 250 slimline, It starts but only for 2 or 3 seconds then dies! Had the same problem with my Bulto Slimline.. If the triangle rear box is fitted the bike does the above, without it all is well. If you've got it on the bike, take it off and see if it runs better. Quote Link to comment Share on other sites More sharing options...
ktmsprocket Posted March 20, 2007 Report Share Posted March 20, 2007 Possibles that spring to mind:: Spark plug cap failure Lead to cap has failed or has poor connection (pulled away inside cap) Bodgy plug (wrong plug?) Compression Crank Seals Coil/Stator (corrosion, wiring failed etc) Bad fuel - will smell off Slider guide fallen out in carb General gaskets and seals failure....if you can get it going, spray some carb cleaner around the carb and intake seals to see if changes the idle. Dead rat up the pipe... Quote Link to comment Share on other sites More sharing options...
peterb Posted March 22, 2007 Report Share Posted March 22, 2007 Hi Scotty, Sounds to me very much like the magneto side crank case seal is leaking. Take off the magneto, mark the backplate to re-set the ign, remove the backplate and woodruff key and undo the 6 bolts that hold on the seal retaining plate. Also, there is either an O ring seal or a paper gasket on the seal housing, not sure on the 71 model. Renew housing seal, fit new oil seal, seal spring facing in toward the crankcase and re-fit using grease on the seal lip. If the seal was passing, you usually find an oil mist around the seal housing outer area. Good luck, PeterB. Quote Link to comment Share on other sites More sharing options...
scotty Posted March 25, 2007 Author Report Share Posted March 25, 2007 Thanks for the advise, Ive tried tunning the carb airscrew turned right in the bikes runs much better! but its the same when trying to start it ,ie runs for 2-3 seconds then dies!!! then it wont start again unless you leave it for a while. Ill ring dave at bultaco uk and order a mag side crank seal plus mk1 carb gaskets inc manifold! ill let you know of the outcome, Again thanks a lot for all your answers. Quote Link to comment Share on other sites More sharing options...
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