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Post by mikeley on Aug 27, 2013 14:05:33 GMT 1
Having run the bike in and not gone above 6000 rpm or into the power band for a couple of hundred miles, I've now discovered I have a detonation problem. If I run the bike around my local 30/40 mph roads it seems fine but when I take it onto the dual carriage way as soon as I get up to 6500/7000 rpm in 6th gear at about 55mph it sounds awfull and loses power. At this time the temperature has also risen to three quarters or just over on the gauge. When riding around the streets it seems to stay around the half way mark. The first time this happened I also had what I think was coolant leak onto my boots so today I took the head off to replace the cheap gasket with a Yamaha genuine one. I found that the top of the piston had some light marks in the centre where it had over heated and started to melt. I am also going through spark plugs like no tomorrow. The bike won't start on the kick start unless you use a new one? It will bump start though. I do currently have a chrome radiator grill. Could this cause the over heating resulting in detonation? The carb has a 210 main jet, standard filter and all speed exhaust. Please help.
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Post by mikeley on Aug 27, 2013 20:07:51 GMT 1
Having done some research it seems maybe I have a squish problem. What is the ideal measurement for squish clearance on a mk1 rd125lc? Could this be causing the detonation?
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Post by steven on Aug 28, 2013 0:40:32 GMT 1
Hi, From G.Bells book "2 stroke performance tuning" it says that 100cc-125cc the squish clearance should be 0.6 - 0.8 mm steven.
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Post by mikeley on Aug 28, 2013 20:16:21 GMT 1
Thanks Steven, my squish is about 1.5mm. Has anyone else experienced really bad detonation? Could it be the fact I have a mk1 engine in a mk3 bike with mk3 cdi? Could the timing be out?
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Post by eddie1969 on Oct 3, 2013 17:14:16 GMT 1
Hello, I have the same problem ,after a lot of searching i think that the hi speed exciter coil on the stator is causing the troubles My bike runs fine until 7000rpm and then sounds as if it is misfiring,i changed cdi but nothing happened If you find out anything new ,i will be happy to hear about it Gr Edwin
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Post by mellow on Oct 3, 2013 19:30:26 GMT 1
If I run the bike around my local 30/40 mph roads it seems fine but when I take it onto the dual carriage way as soon as I get up to 6500/7000 rpm in 6th gear at about 55mph it sounds awfull and loses power. At this time the temperature has also risen to three quarters or just over on the gauge. When riding around the streets it seems to stay around the half way mark. That sounds really familiar Attachments:
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Post by chippy348 on Oct 3, 2013 23:42:29 GMT 1
What heat range plug are you using ?
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Post by eddie1969 on Oct 24, 2013 20:09:27 GMT 1
Finally solved my problem,turned out to be the carb,changed to another one and it ran ok Have to do final settings I discovered the holes of the stator are made slotted so you can adjust the advance I read also that the play in the feedwheel and stator screws can make up to 4 degrees in timing Gr Eddie
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Post by simon998 on Aug 15, 2020 8:55:39 GMT 1
Ever get to the bottom of this?
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