feetupfun Posted May 20, 2013 Report Share Posted May 20, 2013 This bike motor (TY250D with standard carby) started running a bit unsteadily at very low RPM a while back. I have serviced carby and ignition with no fault found or improvement in the way the motor runs found. Today I took the reed cage out for a look and found the petals were not sitting against the seats. I tried turning them over but it made no difference - there was still a gap. I then held them curved for a while and assembled them with the inside of the curve against the cage, and the gap was reduced, but still there. I'm suspecting there might be a problem with the alignment of the reed mounts relative to the reed seats. These Boyesen reeds have been in the bike since 2007, and previous to that it had the standard Yamaha metal reeds. I'm pretty sure the Boyesen reeds sat against the seats back when they were new. Until today I have not reinspected them. Has anyone else come across this problem? Quote Link to comment Share on other sites More sharing options...
guy53 Posted May 20, 2013 Report Share Posted May 20, 2013 David, I had a '' different similar problem '' I explain. When I took the cylinder of my B model to clean the ports I took the reed bloc off and check the petal ( original one ) they where not sitting thght, I check them, they where straight, so I turn my attention to the block, a thin layer of carbon had form close to where they are screwed to the bloc, a careful cleaning did the job for me. Guy Quote Link to comment Share on other sites More sharing options...
canada280i Posted May 20, 2013 Report Share Posted May 20, 2013 If that does not work then 20 quid for a new set of reeds after 6 years is still a cheap investment, and probably due Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted May 20, 2013 Report Share Posted May 20, 2013 I've had the same problem. The rubber coating on the reed was not straight and flat it had worn after 35 years. A new reed block fixed it. Quote Link to comment Share on other sites More sharing options...
guy53 Posted May 20, 2013 Report Share Posted May 20, 2013 David, did you find any noticiable difference when you installed those Boyesen ? Guy Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 20, 2013 Author Report Share Posted May 20, 2013 David, did you find any noticiable difference when you installed those Boyesen ? Guy Guy it was quite a while ago and I don't remember. I will have a look in my log and see if I wrote about it there. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 20, 2013 Author Report Share Posted May 20, 2013 Thanks for the feedback everyone. I will check the reed seats Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 21, 2013 Author Report Share Posted May 21, 2013 David, did you find any noticiable difference when you installed those Boyesen ? Guy Guy my log revealed that at the same time that I fitted the Boyesen Reeds, I also replaced the LH crank seal, which had been leaking, so while it did run much better after the work on the engine, I can't attribute the improvement solely to the Boyesen reeds. David Quote Link to comment Share on other sites More sharing options...
feetupfun Posted June 1, 2013 Author Report Share Posted June 1, 2013 (edited) Today I finally got the chance to work on the bike and found that there were two causes for the uneven running. The main reason was that the pilot circuit was blocked with oil. When I cleaned out the carby the first time, I was not looking for anything in particular, and didn't notice anything special. This time I was paying close attention and found that oil had entered the pilot air hole in the inlet bell of the carby, from the main air inlet tube. There was still quite a bit of oil in the inlet tube today. I suspect that the buildup was caused by the leaking reeds allowing blowback through the carby. The oil was the same colour as the premix oil I use (red/orange), while the air filter oil I use is blue. The tube has a dip in it halfway along which can act as a reservoir for the oil, and when I refitted the carby the first time without cleaning out the air inlet tube, more oil ran down to the carby inlet. What I found with the reeds was that they were still the same as when I put it back together a week or so ago (not quite sitting on the seats). Once I took the boyesen reeds off the cage, using a straight edge I could see that the rubber coating on the reed cage was sitting proud of the area where the reeds clamp to the cage, which was causing the reeds to curve away from the cage as the clamp screws were tightened. I checked two other TY250 reed cages which had been sitting dry for many years, and their rubber sections were less swollen than the one from the bike, but were still slightly proud of the area where the reed is mounted. I test rode the bike after cleaning out the oil problem, but before doing anything to the reeds, and found that while the motor ran much more evenly overall, at very low RPM and low throttle position, and under a slight load, it would misfire once about every 15 or 20 firing cycles. I then fitted a reed cage with standard Yamaha steel reeds, which sat nicely against the reed cage, and test rode again. I found that the idle air screw and throttle stop needed adjusting, but once set for the steel reeds, it ran without the misfiring at very low RPM and low throttle positions. From this I'm assuming that the boyesen reeds not seating properly was having an effect at extreme low RPM and low throttle opening, and may have also contributed to the oil buildup in the air inlet tube. Edited June 1, 2013 by feetupfun Quote Link to comment Share on other sites More sharing options...
guy53 Posted June 2, 2013 Report Share Posted June 2, 2013 Thank's for the feedback David, we are '' almost '' non-stop now at our events ( there are a few reluctant rider, but.. ) and very low RPM and steady low end power make a lot of difference. I use original steel reeds and I have been thinking about trying Boyesen but I am not yet convince. Guy 1 Quote Link to comment Share on other sites More sharing options...
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