dr-alpina Posted January 7, 2018 Report Share Posted January 7, 2018 Hi there, we have a problem since last week we put a second Sherpa 183 back into life . Engine is totally rebuilt incl. new piston, crank etc. Ignition is the old femsa. new points fitted. new carb. clean filters...When you ride, after one hour, the engine suddenly stops. We have ignition spark, but bike wouldn't start again. If you change ignition plug, it starts again but runs only 30 minutes, then the same procedure, but bike doesn't start with new changed ignition plug, although we have good blue spark...do we have to live with an 1,30 hour riding bike? any ideas? Quote Link to comment Share on other sites More sharing options...
bullylover Posted January 7, 2018 Report Share Posted January 7, 2018 Have you changed the old condenser? If not that sounds like the problem. Even new ones can be dodgy. If it isn`t that just go through the ignition system and check all of the connections including the end of the high tension spark plug lead where it goes into the sparkplug cap. Chop a bit off the end and have a new end to work with. 3 Quote Link to comment Share on other sites More sharing options...
scifi Posted January 7, 2018 Report Share Posted January 7, 2018 Hi Doc, If it is something mechanical, then it could be heat related, such as the capacitor breaking down at high temperatures... Or, it could be the contact breakers closing up... but you do say that there is still a good spark. The simplest explanation is that the tank breather is blocked, and a vacuum is building up in the tank, stopping the flow of fuel. Does it restart better with the Choke / Cold Start device? which could be a fuel supply problem. Best of luck... Quote Link to comment Share on other sites More sharing options...
pschrauber Posted January 7, 2018 Report Share Posted January 7, 2018 How is the color of the plug? Can you post a photo of the plug and what kind of plug you are you using? It might be an airflow or a too rich adjusted carb problem, which I had recently? Quote Link to comment Share on other sites More sharing options...
dr-alpina Posted January 7, 2018 Author Report Share Posted January 7, 2018 1 hour ago, scifi said: Hi Doc, If it is something mechanical, then it could be heat related, such as the capacitor breaking down at high temperatures... Or, it could be the contact breakers closing up... but you do say that there is still a good spark. The simplest explanation is that the tank breather is blocked, and a vacuum is building up in the tank, stopping the flow of fuel. Does it restart better with the Choke / Cold Start device? which could be a fuel supply problem. Best of luck... yes, that is what we thought first...but if you pull off the fuel line there comes a lot of petrol...i will check out that capacitor thing 2 Quote Link to comment Share on other sites More sharing options...
model80 Posted January 7, 2018 Report Share Posted January 7, 2018 Replace the condenser, that will more than likely cure the problem. I would also follow pschrauber's advice and post a picture of your spark plug. 1 Quote Link to comment Share on other sites More sharing options...
lineaway Posted January 8, 2018 Report Share Posted January 8, 2018 (edited) You have a bad ground somewhere, but first do the condenser. I bet it is not the plug, it is removing the cap off the plug. Edited January 8, 2018 by lineaway Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted January 8, 2018 Report Share Posted January 8, 2018 (edited) I had a similar problem and it turned out to be a brand new set of points that had a poor connection where the wires attach as the hole was not fully tapped through. It took me countless hours to find the problem as I thought the wires were tightened up against the screw, but the screw had bottomed out before putting pressure on the wires. But as everyone has said replace the condenser first [I bought one from a mower shop once out of desperation and it worked fine] and check all your wiring joins as well as the kill switch and your earth. Cheers Greg PS a faulty condenser can still give a reasonable spark when you are kicking the engine over! Edited January 8, 2018 by sherpa325 info 2 Quote Link to comment Share on other sites More sharing options...
dr-alpina Posted January 9, 2018 Author Report Share Posted January 9, 2018 (edited) 13 hours ago, sherpa325 said: I had a similar problem and it turned out to be a brand new set of points that had a poor connection where the wires attach as the hole was not fully tapped through. It took me countless hours to find the problem as I thought the wires were tightened up against the screw, but the screw had bottomed out before putting pressure on the wires. But as everyone has said replace the condenser first [I bought one from a mower shop once out of desperation and it worked fine] and check all your wiring joins as well as the kill switch and your earth. Cheers Greg PS a faulty condenser can still give a reasonable spark when you are kicking the engine over! thanks for advice. i will check that at the weekend . here is the plug...ngk 5 Edited January 9, 2018 by dr-alpina Quote Link to comment Share on other sites More sharing options...
bullylover Posted January 9, 2018 Report Share Posted January 9, 2018 One thing I can see with your spark plug is the plug gap looks way too wide. A Bultaco on points need a plug gap of .40mm the same as the points. That would not be causing the problem but it will make it start much easier. Quote Link to comment Share on other sites More sharing options...
dr-alpina Posted January 13, 2018 Author Report Share Posted January 13, 2018 On 9.1.2018 at 11:22 AM, bullylover said: One thing I can see with your spark plug is the plug gap looks way too wide. A Bultaco on points need a plug gap of .40mm the same as the points. That would not be causing the problem but it will make it start much easier. Hi folks : It really was the condenser. Bike runs unlimited now, tested out today... Thanks for your help. 3 Quote Link to comment Share on other sites More sharing options...
dr-alpina Posted January 13, 2018 Author Report Share Posted January 13, 2018 It was the condenser, thanks for your help folks. Bike runs unlimited now... We are looking forward to a nice season with four running Bultos this year 6 Quote Link to comment Share on other sites More sharing options...
dr-alpina Posted January 20, 2018 Author Report Share Posted January 20, 2018 ...after two days riding without problems ignotion broke down again. We checked ht coil and there was no blank steel connection. the frame was painted new and somebody didnt want to destroy the new paint... unfortunately the green wire was also fixed to that point. (no real earth) Now the primary coil was killed...in the end the whole thing was a bad earthing fault. greets dr.alpina 2 Quote Link to comment Share on other sites More sharing options...
Anthony Carter Posted July 15, 2018 Report Share Posted July 15, 2018 Hi everyone I am looking for bultaco sherpa t350 1972 front wheel and hu Quote Link to comment Share on other sites More sharing options...
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