Stewie Posted September 30, 2016 Share Posted September 30, 2016 Hi Have you got 1/2 hour to read this. Need some help please for my 1971 AT1 DT125. Only covered 3000 miles This has been a full nut and bolt restoration but starting at the beginning. Purchase the bike from USA as a non runner, The bike would not start, and had no compression so took the head off and found that the rings had picked up onto the piston etc. So the story starts Rebore,new piston and rings, checked timing new points,started on the button and ran well for five mins then stopped . Hmmm back firing could not start it,so stripped the carb again .bingo it started and ran for Five mins ,then stopped again. This time thought it must be condesor,so changed this and it ran for around you guess it 5 mins. Check the coil and was in spec but as it was 40 years old I purchased a new one. 2 week wait for it to come. Trailer the bike for a MOT and said yes I can know take it out on the road! Five mins of riding it it stopped and I could not start it (by the way every time it stops I have fuel, good spark, good compressions) So as it had a little end play in the main bearing on the generator side I thought .Hmm it must be the crank seals. So strip it down new main bearings, new double lip seals, new small ends, new gaskets, re time, etc. So two days ago after putting in the engine I could not wait to start it and ride the bloody thing. Had lots of trouble starting it ,but when it did run , guess what ran for 5mins then stopped and just back fires. So some checks, carb strip down again, points checked,Wiring checked, timing checked, exhaust not blocked, has fuel getting to the plug, has a good spark, has compression. Has me stumped! Maybe I cannot see the wood for the trees but if any one lives near Reading Berkshire. Please come and bend my ear.and I will buy you a drink! Thanks for taking the time of reading this long winded story. But running out of ideas and pacience ! Regards Stew Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 30, 2016 Moderator Share Posted September 30, 2016 Hey Stew always 5 minutes, seems a little too long for the time to empty a carb float bowl but here's what i'd do...take off the fuel pipe and see if there's a good strong flow of fuel through it? There may be filter gauzes in the fuel tap and maybe even inside the fuel tank, or even blockages in the float needle valve or carb fuel spigot This problem stinks of fuel to me! 2 Link to comment Share on other sites More sharing options...
slice Posted October 1, 2016 Share Posted October 1, 2016 Yeah as Airhead say's sounds like fuel blockage. Link to comment Share on other sites More sharing options...
KevtheRev Posted October 1, 2016 Share Posted October 1, 2016 Dont forget to check the vent in the fuel filler cap isn't blocked with crap and causing a vacuum to form in your fuel tank . 2 Link to comment Share on other sites More sharing options...
JimR Posted October 1, 2016 Share Posted October 1, 2016 It's odd it backfires if it is fuel starvation .. with no fuel one would expect no back fires (nothing to combust) can I ask how you set the timing ? Link to comment Share on other sites More sharing options...
Stewie Posted October 1, 2016 Author Share Posted October 1, 2016 Hi Guys Well charge the battery again and tried to kick start it to get max volts etc. Wanted full power to go to coil and not the starter. No joy. Clean / checked the carb again all good, fuel runs from tank with no problems. Re checked the timing eg DTI in top of plug, points open at 1.8 mm BTC with weights held open. Took off exhaust and tried to start it still no joy! Warmed the new plug to see if that will help?.Tried the Old plug? Must be missing something but what it is ????Hmmmm. Thanks you for your inputs so far. Regards Stewart Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 1, 2016 Moderator Share Posted October 1, 2016 32 minutes ago, Stewie said: Hi Guys Well charge the battery again and tried to kick start it to get max volts etc. Wanted full power to go to coil and not the starter. No joy. Clean / checked the carb again all good, fuel runs from tank with no problems. Re checked the timing eg DTI in top of plug, points open at 1.8 mm BTC with weights held open. Took off exhaust and tried to start it still no joy! Warmed the new plug to see if that will help?.Tried the Old plug? Must be missing something but what it is ????Hmmmm. Thanks you for your inputs so far. Regards Stewart Hang on, I thought this was a runner, well for 5 mins anyway! Now it wont even start? Link to comment Share on other sites More sharing options...
Sacha Posted October 1, 2016 Share Posted October 1, 2016 When mine was running and then suddenly quit starting it was because I'd sheered the woodruff key. Any chance that's why it's not starting now? 2 Link to comment Share on other sites More sharing options...
JimR Posted October 2, 2016 Share Posted October 2, 2016 23 hours ago, Stewie said: Hi Guys Well charge the battery again and tried to kick start it to get max volts etc. Wanted full power to go to coil and not the starter. No joy. Clean / checked the carb again all good, fuel runs from tank with no problems. Re checked the timing eg DTI in top of plug, points open at 1.8 mm BTC with weights held open. Took off exhaust and tried to start it still no joy! Warmed the new plug to see if that will help?.Tried the Old plug? Must be missing something but what it is ????Hmmmm. Thanks you for your inputs so far. Regards Stewart aha its a 12 volt one with leccy start !!! check the battery is charging when you get it going again .... (you will need over 12V in order for the bike to start) you should get 14.5~14.8 volts at around 3k rpm .. the die after 5 mins could be due to the battery voltage droping to low .... are the brushes long enuff ... if you can not see the red ware mark replace them as a matter of course, if this is good you need to look at the VR unit .... if you undo the 2 screws on the VR lid you may see a rather burned set of points, which you dress down and perhaps alter the red painted screw (this alters when the charging kicks in) screw this in Correct ign timing method :- set the engine to tdc and gap the points to 12 thou ... open the bob weights on the advance unit .. I used to use a cycle spoke bent in half to ensure we were at full advance then wind back 1.8mm and get the points to break also check when you refitted the advance unit that it lined up correctly with the groove in the rotor 1 Link to comment Share on other sites More sharing options...
Stewie Posted October 5, 2016 Author Share Posted October 5, 2016 Hi Jim Thanks for all the advice The timing I have set up as per your details etc the same way I have been doing it. The battery is fully charged and have tried kick starting it from freshly charge battery but still no joy. I thought today I had done it! as I stripped down the carb for the 100 time and found that the brass floats made a rattle. Hmm check in boiling water and found a leak. Drained and re solder the small hole. But my heart sank again as still no joy in starting it up. Just purchased on line some easy start. will keep you all posted. thanks again for all your help chaps Regards Stewart Link to comment Share on other sites More sharing options...
nayruf Posted October 6, 2016 Share Posted October 6, 2016 Hi Having read and re-read the posts Carb = check, Tank = check, Ignition/timing = check, Condenser/points = check, Battery = check charged, Compression = check, Coil = check, Kill switch short = maybe? Apprehensive about suggesting this as it may be a bit silly, so going on the assumption of there are no silly questions only silly answers, Would it be possible for the exhaust or intake side of things to have some kind of restriction maybe an old rag or some internal packing slowly creating a restriction? 1 Link to comment Share on other sites More sharing options...
anyoldiron Posted October 6, 2016 Share Posted October 6, 2016 Stewie. lm not familiar with your model, but the problem sounds like something that i had on a bike that gave the same symptions as you describe. Does your bike have a stator (they look something like the picture)? The problem with these buggers are that over time and heat cycles the insulation on the windings breaks down. They will test fine when cold, the bike will start and run fine, but as soon as it gets hot and the windings expand they short out and the bikes dies. http://i875.photobucket.com/albums/ab316/Canadiancountrycabins/Marks/s-l500 1_zpsnp6dnigo.jpg 1 Link to comment Share on other sites More sharing options...
Stewie Posted October 6, 2016 Author Share Posted October 6, 2016 Hi Nayruf and Anyoldiron Took the head off today to check yet again, put the air line down in the ports etc. blown into the exhaust as well.This has turned up nothing!. Put the DTI on top of the Piston and checked once again on the timing.all ok Put the head back on, put Easy start into the cylinder . Turned it over on a fully charge battery. Just a few back fires. That was It. Anyoldiron this has an electro generator so different set up to the coils. Thanks anyway. Will strip down and take the Generator off this weekend to see if the key has gone( but checking the timing, and being spot on it cannot have gone but I have only taken it off once and it must be feeling left out as every thing else has been taken off at lease 5 to 10 times). But it failed to start before the strip down and when I did take the gen off it was the first time in 40 years and the key was fine. But why not check again as I cannot find anything else to recheck. Thanks again. Regards Stewart Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 7, 2016 Moderator Share Posted October 7, 2016 I worked on a DTMX once, I replaced the source coil Timing was set spot on just like yours, nice spark at the right time and all that just like yours...it wouldn't spark and just spluttered and backfired just like yours...what cured it? I reversed the ground and feed connections to the source coil...bingo spot on after that Link to comment Share on other sites More sharing options...
Stewie Posted October 8, 2016 Author Share Posted October 8, 2016 Thanks Airhead. When it's stopped raining here will try that. Oh when the problems first started before the rebuild I purchased a new coil and fitted but it still stopped after 5 mins. But will try this and will let you know! Thanks Stew Link to comment Share on other sites More sharing options...
Stewie Posted October 9, 2016 Author Share Posted October 9, 2016 Dear Airhead and all I changed the two wires around on the coil as per Airheads instruction. Checked the spark at the plug and just the same spark as when the connection were round the other way. Put the plug in kicked it over and .............. It started !!!!!!!!!!!!!!! Ran sweet as a nut! ( very thing new,timing spot on etc) Put The rest of the bike back together as most things have been taken of for checking And have just gone for a 10 mile ride,the first time I have ridden it since owning it and rebuilding for a year. Airhead I would have never thought of changing over the coil wires and I'm endebted to you.. I have got the biggest smile on my face and cannot think why it ran before. Maybe it was the coil heating up then going short circuit? Thank you all again. Regards Stewie 4 Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 9, 2016 Moderator Share Posted October 9, 2016 Fantastic news I.m kinda glad it happened to me once and was able to pass it on all I can think is that the coils we both fitted were perhaps wound in the opposite direction to the originals and somehow that mattered? 2 Link to comment Share on other sites More sharing options...
slice Posted October 9, 2016 Share Posted October 9, 2016 Nice one Airhead always good when your solution helps someone else. It's the smallest things that make the most problems. 2 Link to comment Share on other sites More sharing options...
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