jim9755 Posted January 30, 2009 Report Share Posted January 30, 2009 Thanks for all the help with the kickstart trouble i had. The bike is a converted bsa bantam d7 I now have a new problem that has just started this week. After changing the piston rings i have been riding the bike quite a bit and loving it but... the bike now will run/tick over fine and all seems to be good for the first approx half hour of riding then all of a sudden the bike will just die, almost like it has run out of petrol, except that it hasn't. this started a few days ago. normally with the bike warm it will kickstart no problem however once the bike has died like i mentioned above it wont kickstart for a few hours until it has cooled down again. At first i thought it may be the points getting wet as i had been thrashing it through some pretty deep water but i checked them and everything in the cover seemed bone dry? the bike on has basic electrics, just the HT lead from the magneto to the sparkplug. I also thought maybe the spark plug was damaged and when warmed through might have lost its insulation, however i checked an am still getting a spark when warm. Also thought about it been a compression problem but i doubt it as the bike starts fine and will kickstart when warm as long as it hasnt died in the way i mentioned. Also when the bike has died and i try to kick it up it still feels like there is plenty of compression there, like the bike wants to start but just cant. Im now thinking it may be a carb problem but cant understand why this would be a problem once the bike is warmed up, if it was a carb problem the bike wouldn't be running in the first place? Any idea on this new problem would be very welcome. thanks Quote Link to comment Share on other sites More sharing options...
b40rt Posted January 30, 2009 Report Share Posted January 30, 2009 Almost defiantly condensor. Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted January 30, 2009 Report Share Posted January 30, 2009 As previously stated possibly condenser. Also do you have an insulator between the carb and barrel? Wayne.... Quote Link to comment Share on other sites More sharing options...
jim9755 Posted January 30, 2009 Author Report Share Posted January 30, 2009 there is a gasket approx 5 mm thick between the carb and the barrel so i assume this is the insulator you are talking about? i just thought it was a distance piece however it is made of some sort of gasket material as oppose to metal so an insulator makes more sense. i have put gasket glue on this when i was reassembling the barrel as the o ring was a bit flat so i don't think the carb will be sucking air in. will try getting hold of a new condensor and changing that then, thanks for the tips. cheers guys would not have thought of that. Quote Link to comment Share on other sites More sharing options...
jim9755 Posted January 30, 2009 Author Report Share Posted January 30, 2009 if it is the condenser would i still get the spark at the plug when kicking it over? Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted January 30, 2009 Report Share Posted January 30, 2009 Depends on how it's failed. You will get a weak spark or none depending if it's failed open or short circuit. The carb insulator is there to stop too much heat being transfered into the carb and causing problems similar to what you describe, but usually more an issue on 4 strokes in my experience. Wayne.... Quote Link to comment Share on other sites More sharing options...
jim9755 Posted January 30, 2009 Author Report Share Posted January 30, 2009 when it happened the first time i took the spark plug out to check it and there was still a spark there but the bike just wouldn't fire until it had cooled down a couple of hours later. so i guess the insulation in the condenser is breaking down with the heat then? Quote Link to comment Share on other sites More sharing options...
b40rt Posted January 30, 2009 Report Share Posted January 30, 2009 I've had condensors that would work or 20 mins then fail, and work again when cold. Halfords or any motor factor should be able to provide something similar. If it wont fit in its original position, move it. I think there is a post on Montesa re siting. Quote Link to comment Share on other sites More sharing options...
jim9755 Posted January 30, 2009 Author Report Share Posted January 30, 2009 cool cheers, il definatley get one ordered and give it a try, I know a supplier who can get the specific one to fit the D7 so shouldn't have to move it or anything. Thanks for the suggestions Quote Link to comment Share on other sites More sharing options...
jim9755 Posted February 2, 2009 Author Report Share Posted February 2, 2009 (edited) managed to find two new condensors one a new old stock wipac one and the other just a 3rd party spare. tried them both and there is no difference the bike will run for about half an hour then it just dies away still. Any more ideas ppl? im now thinking that maybe it is the carb? Edited February 2, 2009 by jim9755 Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted February 2, 2009 Report Share Posted February 2, 2009 Hi Guy's Hi Jim. Just a thought about your problem, seems to me it could be the crankcase oil seals, or the crankcase drain plug loose., or a crack in the crankcase. Worth looking at. Forest and Trees spring to mind. Regard's Charlie. Quote Link to comment Share on other sites More sharing options...
jim9755 Posted February 2, 2009 Author Report Share Posted February 2, 2009 yeah thanks for the hint was thinking maybe a cracked head or something too. definatley worth checking. i don't think it is the oil seals as i took the dipstick out whilst the bike was ticking over and nothing sprayed out of the gear box and there was no pressure in there when i put my thumb over the hole but you never know. but had the bike out in the snow today got it running but was still conking out every 10 minutes or so now, so i fitted a brand new spark plug, the bike lasted a lot longer with the new plug but still died in the same way after about 25 minutes with the same problem so im wondering if it could be the ignition/ht coil that has died or on its way out? Quote Link to comment Share on other sites More sharing options...
farmer58za Posted February 3, 2009 Report Share Posted February 3, 2009 Jim Replace the coil with another unit. I've had a perfect looking coil malfunction after 5-10 minutes running, then work again after 1/2 hour standing. The only way to fix it was to replace it. Check that your tank breather is working, you could be getting slow fuel starvation from vacuum build-up. Good luck David Quote Link to comment Share on other sites More sharing options...
tsr22b Posted February 3, 2009 Report Share Posted February 3, 2009 A couple of points here, a good condenser is open circuit when measured with an ohm-meter. If they short circuit you will get no spark at all. This problem sounds like a faulty ignition (flywheel magneto) coil. What happens is the coil breaks one of its windings over time, usually through an internal short which has always been there.. At first this is not a problem because the electricity produced can jump the very very small gap. Because there is a gap to jump, heat is produced and burns a small amount of copper, so the gap gets bigger. Eventually the coil fails because the gap cannot be jumped for one of two reasons, either the gap is too big or as normally happens the coil gets hot and loses efficiency and cannot produce enough current to jump the gap. When the coil cools its effficiency is restored. Just check and see if thewre is a dark brown patch on the insulation somewhere, indicating an internal short. In any case, substitution is the easiest way, its only a five minute job on a Bantam. Hope this helps. Quote Link to comment Share on other sites More sharing options...
jim9755 Posted February 4, 2009 Author Report Share Posted February 4, 2009 (edited) cheers once again guys, new HT coil ordered yesterday and in the post, it was only 16 quid so gotta be worth a try, unfortunatly i have to go back to work tomorrow and am going to be out of the country for the next two months so wont have the chance to fit it until april time, but will post when its fitted to tell if it works, fingers crossed it will. Thanks for all the help guys il check the tank breather today too and give it a quick run, see if that makes a difference, i have a feeling it might actually be chocked up with s*it now you mention it, once again would never have thought of checking that so thanks again its gotta be worth a try. Edited February 4, 2009 by jim9755 Quote Link to comment Share on other sites More sharing options...
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