Alan.Tdm Posted November 29, 2017 Share Posted November 29, 2017 My newly restored Dt 125 LC 1 is down on power ie not pulling fully in top gear. I’m going through the list of possible causes. One could be a weakened spark. I’ve been told that the igntion coil (flywheel) can degrade with age ? I know the compression/ fuelling/ sprocket ratios are okay. I will clean the front exhaust expansion chamber but it does not seem blocked Link to comment Share on other sites More sharing options...
Moderator Cynic Posted November 30, 2017 Moderator Share Posted November 30, 2017 Down on power is a very open statement. Can you explain it in a more detailed way with some kind of reference. "Top speed on a flat is 45mph and chokes on WOT." For example. For all i know you could weigh 22stone. On some 125 bikes a flappy jacket or a mild headwind will render top all but useless. Link to comment Share on other sites More sharing options...
Alan.Tdm Posted November 30, 2017 Author Share Posted November 30, 2017 The bike is a DT125 LC 1. At the moment top speed is about 50/55 mph and ‘bogs down’ in top gear on the road. I only rev it to 6 k as still running in. The engine has been fully rebuilt so compression is okay plus seals. I’ve rebuilt the carb and cleaned the fuel supply. Also fitted new reed valves. New sprockets are the correct ratios. The front expansion chamber may be partially carboned up which I can check. The bike was running fine when it was last on the road 20 yrs ago. I read that the igntion coil can degrade with time although the resistance values are in range ? Link to comment Share on other sites More sharing options...
finnerz89 Posted November 30, 2017 Share Posted November 30, 2017 50/55mph at 6k is pretty good I reckon. Don't be afraid of taking it above that rpm while running in, just don't hold it there for long. The top end on my DT is at like 11500rpm, and I wouldn't put it in top gear until about 9000 minimum. 1 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 1, 2017 Moderator Share Posted December 1, 2017 Know how far i rode my tdr running it in at under 6k....? NOWHERE. All that running in rubbish is cobblers. I did a steady trip to my mums ( under 10 miles) to be sure nothing fell off, leaked. Then rode normally. Avoid really hanging on the throttle or brutal down changes for a bit. Otherwise just use it. That bore will do 15k tops before being done. How much longer will you get chugging around at 6k. I bet less. You could even glaze the bore with modern oil and lose performance. Its a smoker mate. Av it. 1 Link to comment Share on other sites More sharing options...
Alan.Tdm Posted December 1, 2017 Author Share Posted December 1, 2017 Recommendation from the engine rebuilder who said take it easy for first 100 miles. Top gear is waste of time at the moment as engine has not got enough power to drive top gear. However there is a local company that can test the whole igntion system components so I’ll check this route out Link to comment Share on other sites More sharing options...
finnerz89 Posted December 1, 2017 Share Posted December 1, 2017 Before going down that route stop being a big Jesse and open it up! Going in to top is pointless unless you're doing high rpm. So grab a handful and give it some Link to comment Share on other sites More sharing options...
Alan.Tdm Posted January 19, 2018 Author Share Posted January 19, 2018 Sorted ! Weak spark due to faulty HT coil. Replaced with new one. Also igntion source coil rewound to. Running fine now 1 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 19, 2018 Moderator Share Posted January 19, 2018 Nice one, glad its fixed. People hardly ever come back and say what the problem actually was thanks. Have you nailed it yet, eh?? Link to comment Share on other sites More sharing options...
blackhat250 Posted January 20, 2018 Share Posted January 20, 2018 Well done, i was thinkn the same,,,[ as cynic& finners] coz i rode aprilla125 , last year,, and it was ahoot above 7k, , and flat below that ,, it was faster than my DT400, [ NOT BOTTOM END ]. . Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 21, 2018 Moderator Share Posted January 21, 2018 yep, A freind had an Apprilia 125, she came round to my house saying it didn't sound right, no power. I tried it with choke and it ran worse. so I blipped the throttle to wide open and managed to red line it and all the crap came out. She the bike below 6k and basically the poor bike was 4 stroking. as it could'nt burn the fuel. Now she guns it everywhere 1 Link to comment Share on other sites More sharing options...
Recommended Posts