I have an old kaw kv75 / mt1 trail bike and cannot get it to start ! Compression – good, spark – good, fuel and air – good. This is an odd set up with no valves and wondering if anyone has any insight on how the fuel air mixture gets up to the cylinder head for ignition.
Kawasaki KV75 No Start
- Thread starter ohiocycle
- Start date
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motodevo
Miniriders OG Master Spanner Spinner
Its a piston port 2 stroke, so effectively the mixture is drawn in beneath the piston , as the piston goes down and seals off the intake port, the only place left for the mixture to go is through the transfer ports that transfer it to the top side of the piston, ie combustion chamber where it is compressed and then ignited and the whole process repeats. So to put it simply, there are ports in the barrel that start at the bottom of the barrel and come out just above midway in the stroke of the barrel that transfer the mixture to the combustion chamber
headsmess
Miniriders OG
good old two strokes.
simplest engines to fault find in.
first, try a new plug. if that doesnt do much, next step.
rip off the carb. rip off the exhaust. pour some fuel down the intake port. it should start. then rev its tits off for a second or two, then die. if it does...check that the exhaust isnt clogged up...old oil and mud wasps are the biggest issues. if you cant blow through it easily, its clogged, needs burning out. you heat it up with a blowtorch tril its smoking, and point an air gun inside it. it makes a LOT of smoke! and sparks! its sort of fun to do
so, it started, and the exhaust isnt blocked? tear the carb apart, make sure the jets are clean, and give it a soak in something like acetone for a day or two, blow every single hole out well! after removing jets, air screw, etc. often bikes are left sitting with a bowl full of fuel which turns to hard yukky stuff and blocks them up. theres a lot of tiny little holes that need clearing out, occasionally with the help of a guitar string (.010 or so). be careful not to damage anything when poking wire through.
if it DIDNT start...then theres still a few things to check.
crank seals. if the crankcase doesnt seal, the air/fuel cant get up to the cylinder properly. two strokes should have TWO compressions, one as the piston goes up, and a weak one as the piston goes down. the downstroke one should be there whether the plug is in or not. oil streaks behind the magneto are a sure sign, its a bit harder to tell if its the one behind the clutch, other than a lot of oil getting into the crankcase...
magneto...not sure what year the bike is, but if its an old girl with points, you have to refer to a manual and set the points. that can be a right pain in the rear to do. give them a file, clean them up, set the dwell, gap, and opening point...fun
also, theres always the possibilty that someone has pulled the flywheel off before, failed to get the key in place, and while its making spark...it isnt doing it at the right time. pop the nut off the flywheel and make sure the key is in the slot.
and then, with getting a new plug...if the old one is black and oil soaked, try using one thats a few numbers down in the heat range(assuming you get NGK which is the ONLY plug to use, ha ha). plugs clean themselves from the heat of combustion... if they idle, they dont get hot and tend to foul up, so get a hotter plug. if you ride full throttle, they get HOT, so get a colder plug.
make sure the coil is well grounded, so pull it off, give the mounts a sand, bolt it back on. you dont want any rust or paint between the coil and the frame.
just because it has spark when you test it with the plug out, doesnt mean it has spark under compression. the beauty of CDI ignition... powerful sparks
simplest engines to fault find in.
first, try a new plug. if that doesnt do much, next step.
rip off the carb. rip off the exhaust. pour some fuel down the intake port. it should start. then rev its tits off for a second or two, then die. if it does...check that the exhaust isnt clogged up...old oil and mud wasps are the biggest issues. if you cant blow through it easily, its clogged, needs burning out. you heat it up with a blowtorch tril its smoking, and point an air gun inside it. it makes a LOT of smoke! and sparks! its sort of fun to do
so, it started, and the exhaust isnt blocked? tear the carb apart, make sure the jets are clean, and give it a soak in something like acetone for a day or two, blow every single hole out well! after removing jets, air screw, etc. often bikes are left sitting with a bowl full of fuel which turns to hard yukky stuff and blocks them up. theres a lot of tiny little holes that need clearing out, occasionally with the help of a guitar string (.010 or so). be careful not to damage anything when poking wire through.
if it DIDNT start...then theres still a few things to check.
crank seals. if the crankcase doesnt seal, the air/fuel cant get up to the cylinder properly. two strokes should have TWO compressions, one as the piston goes up, and a weak one as the piston goes down. the downstroke one should be there whether the plug is in or not. oil streaks behind the magneto are a sure sign, its a bit harder to tell if its the one behind the clutch, other than a lot of oil getting into the crankcase...
magneto...not sure what year the bike is, but if its an old girl with points, you have to refer to a manual and set the points. that can be a right pain in the rear to do. give them a file, clean them up, set the dwell, gap, and opening point...fun
also, theres always the possibilty that someone has pulled the flywheel off before, failed to get the key in place, and while its making spark...it isnt doing it at the right time. pop the nut off the flywheel and make sure the key is in the slot.
and then, with getting a new plug...if the old one is black and oil soaked, try using one thats a few numbers down in the heat range(assuming you get NGK which is the ONLY plug to use, ha ha). plugs clean themselves from the heat of combustion... if they idle, they dont get hot and tend to foul up, so get a hotter plug. if you ride full throttle, they get HOT, so get a colder plug.
make sure the coil is well grounded, so pull it off, give the mounts a sand, bolt it back on. you dont want any rust or paint between the coil and the frame.
just because it has spark when you test it with the plug out, doesnt mean it has spark under compression. the beauty of CDI ignition... powerful sparks
headsmess
Miniriders OG
ha ha, i just googled it...i saw someone riding one the other day, registered! awesome!
built in 1980 or earlier...it will definitely be a magneto and points ignition.
and the last thought is that the coil could be failing, or even the condensor (under the magneto) needs replacing.
coil wise, you can test with any type of CAR coil. not a modern CDI type coil.
for the condensor, a 600V 474 or similar (0.5uF) capacitor from jaycar will do if you cant find a suitable one on ebay (or wrecker, repco, etc... for cars. little metal can with a wire poking out one end, usually in the dizzy. dont waste time or money finding/buying the exact one for the model bike, a condensor is a condensor no matter what it came out of, as long as it fits!)
make a decent tuned pipe for it and the thing will RIP! i love two strokes...with tuned pipes
i also see it has oil injection. make sure the pump works and is adjusted correctly, dont try running anything silly like castor oil, always make sure the bottle says "for injected"... or run premix at 25-30:1.
whats annoying (besides wanting one!) is that it may have been owned by a turkey, and has received nasty "tuning mods" such as trimmed piston skirts, etc... its very easy to make more power from a twostroke, if you know what you are doing. its even easier to completely stuff a twostroke, if you dont!
and of course, welcome to the world of twostrokes.
read this link. several times. it covers virtually EVERYTHING. http://www.amrca.com/tech/tuners.pdf
built in 1980 or earlier...it will definitely be a magneto and points ignition.
and the last thought is that the coil could be failing, or even the condensor (under the magneto) needs replacing.
coil wise, you can test with any type of CAR coil. not a modern CDI type coil.
for the condensor, a 600V 474 or similar (0.5uF) capacitor from jaycar will do if you cant find a suitable one on ebay (or wrecker, repco, etc... for cars. little metal can with a wire poking out one end, usually in the dizzy. dont waste time or money finding/buying the exact one for the model bike, a condensor is a condensor no matter what it came out of, as long as it fits!)
make a decent tuned pipe for it and the thing will RIP! i love two strokes...with tuned pipes
i also see it has oil injection. make sure the pump works and is adjusted correctly, dont try running anything silly like castor oil, always make sure the bottle says "for injected"... or run premix at 25-30:1.
whats annoying (besides wanting one!) is that it may have been owned by a turkey, and has received nasty "tuning mods" such as trimmed piston skirts, etc... its very easy to make more power from a twostroke, if you know what you are doing. its even easier to completely stuff a twostroke, if you dont!
and of course, welcome to the world of twostrokes.
read this link. several times.
it covers virtually EVERYTHING. http://www.amrca.com/tech/tuners.pdf
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