jim9755 Posted December 28, 2008 Report Share Posted December 28, 2008 im currently having problems with my bsa bantam d3 trails bike and was wondering if any one could offer some hints or help as i have nearly run out of ideas. ok so heres the problem. When ever i try and kick start the bike it wont start cold. The bike will bump start easily enough and once warmed up after 5 or 10 minutes will kickstart first time, every time with little effort. I have changed the spark plug for a brand new ngk plug (correct numbers) I have checked and the plug is definatly sparking. The plug gap is correct 0.018 1inch The contact breaker points gap is correct. i have cleaned the points up i have checked the air filter and it is clean The bike has no lights or any other electrics just the ht lead from the contact breaker to the spark plug I have tried starting the bike with the carb flooded/dry with different amounts of throttle all to no success. The carb is a non standard make (not sure what) and was fitted when i bought the bike I have tried blocking off the air inlet to the carb to try and enrich the fuel mixture to no effect and have tried to start it with out the air filter fitted. I am now running out of ideas short of buying some easy start and spraying it into the carb which i am reluctant to do incase it damages the pistons and also it doesnt really solve the problem. any help, tips or advice will be appreciated thanks Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 28, 2008 Report Share Posted December 28, 2008 Does your bike have a large capacitor/condensor ? I found (before changing to Boyer) that if you took the plug cap off and kicked it over several times, then replaced the cap it would start no problem. This was not a Bantam incidentally. Quote Link to comment Share on other sites More sharing options...
jim9755 Posted December 28, 2008 Author Report Share Posted December 28, 2008 yeah it has a condensor, it is a waco pacy type 55/mark8 contact breaker. il give that a try thanks Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 28, 2008 Report Share Posted December 28, 2008 I should have said that you might be better taking the plug out to stop it fouling. Quote Link to comment Share on other sites More sharing options...
peter9000uk Posted December 29, 2008 Report Share Posted December 29, 2008 You mention you have checked everything except the timing. If I remember correctly Bantams have 3 slotted holes to adjust the timing. ANother thought, what colour is the plug? Quote Link to comment Share on other sites More sharing options...
jim9755 Posted December 30, 2008 Author Report Share Posted December 30, 2008 thanks for the help, had the bike out today and tried the suggestions. none really helped, got the easy start out and got it kick started that way. got it warmed up but noticed it wasnt ticking over too well. thought i might have to strip the carb. then had another thought. the petrol in the tank was quite old so i drained the tank and made up some new 2 stroke got it started and it was running on the new petrol, ticking over great so i think that it was just the 2 stroke oil in the old petrol degrading it. Quote Link to comment Share on other sites More sharing options...
grindrod Posted January 10, 2009 Report Share Posted January 10, 2009 Petrol goes off very quickly in un-sealed systems, glad you got it going!!! To make these run really well you need perfect crank seals and piston rings, they wear out quite quickly with some serious riding!! My D1 benefited from new rings every year!! Quote Link to comment Share on other sites More sharing options...
jim9755 Posted January 11, 2009 Author Report Share Posted January 11, 2009 yeah i think new rings might be another good idea as it is still quite hard to start cold but when warm it kicks over no problem so maybe when everything is cold i lose alot of compression past the rings (until they heat up a bit and expand). havn't got round to taking the head off to check/have a look at the state of things in there though, maybe later this week. thanks for the tip. Quote Link to comment Share on other sites More sharing options...
tsr22b Posted January 12, 2009 Report Share Posted January 12, 2009 Hi, this looks very much like a compression problem. Head and barrel off and check the rings, one may even be stuck in the ring groove. Stuff a rag down the crankcase before lifting the barrel right off in case you have a broken ring. That way the bits wont fall in the crankcase. Incidentally the other cure mentioned about taking the plug out and kicking it over a few times purges the crankcases of unburnt fuel. Nothing to do with the electrics, i would suggest. Just thought also may have a coked up exhaust port. Again this can be scraped out when the barrel is off. hope this helps. Quote Link to comment Share on other sites More sharing options...
tsr22b Posted January 12, 2009 Report Share Posted January 12, 2009 Hi, this looks very much like a compression problem. Head and barrel off and check the rings, one may even be stuck in the ring groove. Stuff a rag down the crankcase before lifting the barrel right off in case you have a broken ring. That way the bits wont fall in the crankcase. Incidentally the other cure mentioned about taking the plug out and kicking it over a few times purges the crankcases of unburnt fuel. Nothing to do with the electrics, i would suggest. Just thought also may have a coked up exhaust port. Again this can be scraped out when the barrel is off. hope this helps. Quote Link to comment Share on other sites More sharing options...
b40rt Posted January 14, 2009 Report Share Posted January 14, 2009 Hi, this looks very much like a compression problem. Head and barrel off and check the rings, one may even be stuck in the ring groove. Stuff a rag down the crankcase before lifting the barrel right off in case you have a broken ring. That way the bits wont fall in the crankcase. Incidentally the other cure mentioned about taking the plug out and kicking it over a few times purges the crankcases of unburnt fuel. Nothing to do with the electrics, i would suggest. Just thought also may have a coked up exhaust port. Again this can be scraped out when the barrel is off. hope this helps. The capacitor gets charged up if you kick it over with the plug out, when you reconnect it you get a better spark. Quote Link to comment Share on other sites More sharing options...
jim9755 Posted January 16, 2009 Author Report Share Posted January 16, 2009 cheers guys, got round to taking the bike apart today, took the head off every thing seemed ok piston is in good condition and the piston rings are all in good order. took the barrel off and seemed ok too, but there were two quite big scratches/grooves on one side near the bottom of the cylinder. Noticed that the gudgeon pin circlip on one side of the piston wasnt actually located properly and has worked its way to the edge of the piston and was probably scraping against the barrel. dont think this would have made a massive difference to the compression but am glad i caught it before any real damage was caused. all the joints seem in good order The exhaust port was slightly choked with carbon, but not to any major extent so i doubt if this is the problem either but will clean it out and box it back up and try it over the weekend. in the mean time any one else with ideas are more than welcome. Also what i thought was a D3 i have now been reliably informed is a D7 so i apologise for my ignorance. Cheers for the help guys. Quote Link to comment Share on other sites More sharing options...
tsr22b Posted January 16, 2009 Report Share Posted January 16, 2009 The capacitor gets charged up if you kick it over with the plug out, when you reconnect it you get a better spark. The capacitor is there to stop the points arcing and wearing or pitting when they open by storing the small amount of stator energy that tries to jump across the points gap when they open. It has nothing to do with the spark at the plug. The stator windings produce electricity which goes (when the points are open) to the primary winding in the ignition coil which then transfers (it is a transformer) to the secondary winding to produce the spark at the plug. The time the points open determines when the spark occurs.(hence the term "timing".) The capacitor is discharged every time the points close. Kicking the bike over cannot increase the charge in the capacitor as it discharges on every rotation. A failed capacitor can stop the spark at the plug if it shorts out the stator to earth, usually because the dielectric material it is made of fails internally. Quote Link to comment Share on other sites More sharing options...
b40rt Posted January 16, 2009 Report Share Posted January 16, 2009 The capacitor is there to stop the points arcing and wearing or pitting when they open by storing the small amount of stator energy that tries to jump across the points gap when they open. It has nothing to do with the spark at the plug. The stator windings produce electricity which goes (when the points are open) to the primary winding in the ignition coil which then transfers (it is a transformer) to the secondary winding to produce the spark at the plug. The time the points open determines when the spark occurs.(hence the term "timing".) The capacitor is discharged every time the points close. Kicking the bike over cannot increase the charge in the capacitor as it discharges on every rotation. A failed capacitor can stop the spark at the plug if it shorts out the stator to earth, usually because the dielectric material it is made of fails internally. I will need to check the description, but the capacitor (big blue lucas) is much larger than a conventional unit. As you say, it discharges when the points close, but if the plug is out it has nowhere to go. Worked for me. Quote Link to comment Share on other sites More sharing options...
tsr22b Posted January 17, 2009 Report Share Posted January 17, 2009 I will need to check the description, but the capacitor (big blue lucas) is much larger than a conventional unit. As you say, it discharges when the points close, but if the plug is out it has nowhere to go. Worked for me. I think we may have been talking cross purposes here! the Lucas capacitor i think you are refering to is the one (from memory )about an inch and three quarters round and about two inches long, type 2MC electrolytic, used in the Lucas energy transfer ignition systems to replace the battery on competition bikes. This is a different system to a flywheel magneto ignition as found on a bantam and a large number of old 2 stroke bikes with points, but works more like a car ignition system where the energy for the ignition coil comes from a battery, or in your case a capacitor. The bike's alternator charges the capacitor in the same way as it would charge a battery. If you have points though you will still have the other capacitor in the primary circuit, or, as it is maybe more commonly known, a condenser. The 2MC will actually discharge when the points OPEN because this is the point where the primary circuit of the ignition coil gets its charge from the capacitor, passes it in to the ignition coil secondary winding where it builds up energy and dissipates across the plug gap. The clever thing about a capacitor is that it has the abilty to charge and discharge very very quickly hence it is just about always storing electricity- like a battery. Hope this clears up the misunderstanding! Quote Link to comment Share on other sites More sharing options...
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