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Re: ty 175 back fire
Posted: Thu Sep 03, 2009 10:24 pm
by David Lahey
uk steve wrote:The story, the bike got stolen 20 years ago buy a youth he ran the oil tank dry.then we got the bike back & it stood 15 years in the shed with only 943 miles from new.the fly wheel as only ever been off once in its life and that was last week.what happen was i honed the barrel to a oversize piston. she started after 5/6 kicks i set up carb as it was cutting out after half revs.then as it got warm the setup improved to a nice low tick over to full out revs.i run it again that day & it was ok.the next day i lost the spark so i clean points as they looked black on the contacts this got the spark back but remember that the points are the factory once and i have never moved or had to set them from new & 943 miles is nothing to a set of points ? cleand the carb 3 times with air & a syringe filled with cleaner.when its runing it responds to a quater turn & less on mixture screw.
i just rememberd i lost the slide needle & stuck one in out of a larger carb but lifted it all the way up & she ran ok on this as i said.would the condecer brake down with been stood 20 years & cause the back fire. im still going a head with the rebore as the honeing is showing uneven after i ran it.thanks steve
Yes to the condenser being the cause of the backfire and probably the cause of the black points too. To confirm it:
Test option A
Run the motor with the flywheel cover off in a dark place and look in at the points. If they are arcing noticably, the condenser has failed.
Test option B
Use a strobe type timing light and see if the spark timing is steady. If it is jumping around, the condenser has failed.
Re: ty 175 back fire
Posted: Fri Sep 04, 2009 7:04 am
by Stork955
Further to Davids' post, if the points have not been lubricated (a smear of grease on the rubbing block) they can close up in less than this time. Worth having a look at the point gap also while you are in the area and grease if necessary.
Cheers,
Stork
Re: ty 175 back fire
Posted: Sat Sep 05, 2009 6:59 am
by uk steve
stork are you saying that the points could be slow closeing. and i must say thanks for the help
Re: ty 175 back fire
Posted: Sat Sep 05, 2009 9:48 am
by Stork955
Gday Steve, no, I mean the point gap could be closing up - if the rubbing block that opens the points wears as they do, the point gap will be too narrow, and that affects ignition timing until it gets to the point that the bike wont run as there is no spark at all.
175 point gap is 0.014 thou, with a slight adjustment from there to get the points to open at 1.8 mm before TDC.
Cheers,
Stork
Re: ty 175 back fire
Posted: Sat Sep 05, 2009 10:15 pm
by uk steve
thanks again i understand what you say so i will check this midweek