ty 175 back fire

[uk steve]

new to this site im on with a mock rebuild of my ty 175 to see how many bits are missing as i took it apart 5 years ago i started it up ran ok then left it a day started it again and it will start then back fire then cut out. i have to clean the plug to restart it then the same again pop pop then dead.

[Stork955]

Gday, what does the plug look like when it comes out?

Cheers,

Stork

[uk steve]

plug is wet on the tip a quick whipe then it fires up rev pop pop rev dead but will only start with the choke on.the day befor i ran it for 15/20 minuts set the carby up nice tickover and reved out like mx but the piston & rings are new.i started it again later that day roard into life thirst kick i left it on tick over 10 minuts i thought grate stuff.but pop pop dead the next day could it be the rh crank seal as the motor was dry stord for the 5 years

[motodevo]

if its backfiring could be a sheared woodruff key for the ignition rotor

[Stork955]

Gday,
Check and clean the carb before you go any further. Its easy and the most likely explanation, especially with a wet plug.

Cheers,

Stork

[uk steve]

thanks will check both carb & key to day.just a thought i cant help but think the fuel may be wrong.i mixed (4 litres of gas 100ml mineral oil) is this mix ok. thanks for the help

[Stork955]

Gday, thats 40:1 which may be a bit lean, I run 20:1 in my TY's but others don't. I don't think it will be causing your issues however so rule that one out. Let us know how you get on.

Cheers,

Stork

[uk steve]

hi,cleand the carby & it fired up. starts first kick then the same again.but this time the topend was noisy so i pulled it off & found more ££££££££££££ to spend on her.(the wife aint happy) the barrel needs to visit the boaring barr.badly worn around the exaust port.so i think its fireing past, & out. could this be the problem.thanks for the help

[Stork955]

Gday, have you checked ignition timing? That would be my next course of action. I dont reckon a worn bore will give these issues, it probably wouldnt start at all.

Cheers,

Stork

[uk steve]

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