btomo Posted December 14, 2012 Report Share Posted December 14, 2012 Hi I have a 2007 sherco 290 which was running fine, it started from cold in around 5 kicks and 1st kick every time when warm. It had a bit of a rattle from the engine so i decided to pull it apart and replace the piston and rings and little end bearing. I did this and went up from a 'B' piston to a 'C' Everything came apart ok and went back together ok too. Finally got it running after a lot of kicking over but i guess that must be normal after a strip down. After it had been running for a bit and got to operating temperature I turned it off and tried to start again but it needed a good 15 mins of kicking over it would finally start but would take a lot of work. Every time it is stopped after running it takes a lot of work to get going again. I took the tank off to check everything and all is bolted up as it should be, compression on the kickstart feels the same as before and plenty of fuel coming though. I pulled the plug out and checked the spark and it seemed ok, tried a new plug but the symptoms are the same. Is this normal behaviour when changing a piston or can anyone offer any tips? Thanks Quote Link to comment Share on other sites More sharing options...
tltel Posted December 14, 2012 Report Share Posted December 14, 2012 hi btomo No not normal behaviour. Does it run ok when it does start? Is piston in back to front? TLTEL Quote Link to comment Share on other sites More sharing options...
copemech Posted December 15, 2012 Report Share Posted December 15, 2012 Couple of thoughts. Did you have the carb off? Might give it a good cleaning after it has set a bit, or been upset. What plug and what gap is it set to. Standard plug, BP5ES needs a .05-0.6mm setting. Check for consistant spark, although it is difficult to see in the daylight. Quote Link to comment Share on other sites More sharing options...
btomo Posted December 15, 2012 Author Report Share Posted December 15, 2012 Thank you for the replies. Piston is the right way, arrow to the front, ring gaps at the back. Yeah runs lovely once it is going. No haven't touched the carb, might take it off and clean out just to be sure but it runs ok once has started. Didn't actually check the plug gap but tried a brand new plug, turned the light off and it sparked every time, it might seem a bit weak but not sure how strong & bright the spark should look. Just can't understand it cos everything seems to be as it should be, it just won't go. Quote Link to comment Share on other sites More sharing options...
paul w Posted December 15, 2012 Report Share Posted December 15, 2012 start again, take the barrel off, make sure the ring gaps are on the pins and rebuild again, use a new head gasket or O rings (cant remember which your bike has) and a new base gasket (correct thickness). If you hav'nt changed anything else in the re-build the issue has to be in what you've done first time around. let us know what happens Quote Link to comment Share on other sites More sharing options...
ham2 Posted December 15, 2012 Report Share Posted December 15, 2012 Detox that carb' first...then; Consider: Temperature induced resistance in the stator coil, when it cools after 15mins it'll fire up as if nothing was wrong?It happened to me ,I hope it's not happening to you; it was very difficult to diagnose the problem, I had to switch components with a mates bike to pin-point it (after I had checked all the simple things first !). Quote Link to comment Share on other sites More sharing options...
dombush Posted December 15, 2012 Report Share Posted December 15, 2012 +1 on Paul W's advice just start again and check the basics while its apart. I could be something deeply complex, but most problems are issues with the basics. This way, you can move onto the next level of complexity knowing you double checked the fundementals. Dom Quote Link to comment Share on other sites More sharing options...
tltel Posted December 15, 2012 Report Share Posted December 15, 2012 did you check the squish clearance when you put it back together? If you fitted new gaskets did you check piston / head clearance? Not sure it would give your symtems but it is quite importantant. Probably should be between 1.5 and 2.0 mm. If not enough it will probably knock. TLTEL Quote Link to comment Share on other sites More sharing options...
copemech Posted December 16, 2012 Report Share Posted December 16, 2012 These bikes did come from factory with more than one gasket for squish setting, however I doubt that would be a starting issue. Not all bikes had them, as they are a select fit thing and the second gasket comes in different thicknesses. Giving the carb a good clean is essential, however I am a bit concerned about the plug(verify type) and gap issue as this can be critical. There is good reason for this, too much to get into here, yet just another fundamental that needs to be established. I cannot recall how they come set, but i do think it was too wide. As Dom says, basics first! However, if you are sure about the rest, you would not need to tear it back down. Quote Link to comment Share on other sites More sharing options...
btomo Posted December 17, 2012 Author Report Share Posted December 17, 2012 Pulled apart again yesterday and found the rings upside down! Didn't even know they were directional, they only had an 'R' on them which I searched to find what it meant and had no results so just put them in! All sorted now and it went 1st kick when all back together! Thanks to everyone for your advice. Quote Link to comment Share on other sites More sharing options...
paul w Posted December 17, 2012 Report Share Posted December 17, 2012 He shoots, and he Scores, !!!! 2.0mm squish clearence? you could get in that and measure it with a ruler. ! Quote Link to comment Share on other sites More sharing options...
copemech Posted December 19, 2012 Report Share Posted December 19, 2012 He shoots, and he Scores, !!!! 2.0mm squish clearence? you could get in that and measure it with a ruler. ! Paul wins the self induced class! Quote Link to comment Share on other sites More sharing options...
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