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1992 Honda Fourtrax 300
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Discussion Starter · #1 ·
The ATV started very quickly before ( except the last time I started it when it took some cranking). Yesterday would not start with a loud exhaust bang the likes of which I have not had before. Checked spark plug and it sparked fine. Could the cam chain have slipped?
 

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The ATV started very quickly before ( except the last time I started it when it took some cranking). Yesterday would not start with a loud exhaust bang the likes of which I have not had before. Checked spark plug and it sparked fine. Could the cam chain have slipped?
I would check that the valves opening and closing properly first.
Set valves
 

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line up the T in the timing hole on the compression stroke and the piston should top top dead center and the valves loose at .006 if the timing is right ------- I stick a 1/4 wooden dole thru the spark plug hole and watch the piston as it is coming up to it's max peak , when it does , you should see that T should be in the hole
 

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1992 Honda Fourtrax 300
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Discussion Starter · #6 ·
line up the T in the timing hole on the compression stroke and the piston should top top dead center and the valves loose at .006 if the timing is right ------- I stick a 1/4 wooden dole thru the spark plug hole and watch the piston as it is coming up to it's max peak , when it does , you should see that T should be in the hole
Thanks all, the fuel should be ok using same jn my woodsplitter no problem. Will look into Fishfiles suggestion and if all well there check the valve settings
 

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don't over look the fuel , the carb needs to be clean , as well as the tank , water in the fuel can make it huff , puff and spitter ---- if the timing is off , the compression will be effected , did you compression test the engine , that 300 like new will do 205psi , at 100 it dead
 

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when you do a compression test, you gotta have the throttle open. hope i learned that right.. plus ethanol will catch up to you sooner or later, if ya have used that.
 

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Thanks all, the fuel should be ok using same jn my woodsplitter no problem. Will look into Fishfiles suggestion and if all well there check the valve settings
I would be careful putting anything in the spark plug hole; if you get it crooked in there and break it off inside the cylinder with the piston you will be very unhappy.
I did this with a plastic tube on an old Harley i have鈥攕hattered that tube鈥攕pent the rest of the day vacuuming plastic bits out of the cylinder
 

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Goob' , you must have spin that engine over with the key ----- I could see how that could of happen to you , what ever you use to probe the position of the piston needs to be put in the hole with the top of the probe as far to the right side of the bike as possible and the tank needs to be off for sure ------ don't use a screw driver , if your one way bearing is good and you roll the engine to top dead center and bend the screw driver in the cylinder , you can't roll it back , been there before ----a plastic straw might be the thing , but they are getting out lawed fast , I better stock up
 

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1992 Honda Fourtrax 300
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Discussion Starter · #11 ·
I found the T but the cylinder has bottomed (or just about) I assume I need to get the T on the compression stroke. By the way mice had entered the air vent and air filter cabin but had air filter intact. Cleaned the area and filter but no change.
 

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piston should be at very top for tdc, on the compression stroke.
 

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1992 Honda Fourtrax 300
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Discussion Starter · #13 ·
Finally got to it Woodruff key broken. Timing was totally out. Got that replaced with new Honda key (last one I replaced was 2 years ago off shelve from Auto parts dealer).The ATV started ran for 2 seconds quite and would not restart. Cleaned carb but no start, Spark plug sparking, while I had it out poured a little gas into cylinder and it started and ran for 2-3 seconds as one would. Obviously carb problem. With the backfires I had could this have damaged the carb in some way that I cannot detect? Any suggestions?
 

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Finally got to it Woodruff key broken. Timing was totally out. Got that replaced with new Honda key (last one I replaced was 2 years ago off shelve from Auto parts dealer).The ATV started ran for 2 seconds quite and would not restart. Cleaned carb but no start, Spark plug sparking, while I had it out poured a little gas into cylinder and it started and ran for 2-3 seconds as one would. Obviously carb problem. With the backfires I had could this have damaged the carb in some way that I cannot detect? Any suggestions?
if it sat for months end ?, yu'll need to clean the carb.
 

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Hey did you do what Fishfiles recommended with your valves? Is the exhaust valve closing all the way?

鈥渓ine up the T in the timing hole on the compression stroke and the piston should top top dead center and the valves loose at .006 if the timing is right ------- I stick a 1/4 wooden dole thru the spark plug hole and watch the piston as it is coming up to it's max peak , when it does , you should see that T should be in the hole鈥
 

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1992 Honda Fourtrax 300
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Discussion Starter · #16 ·
Hey did you do what Fishfiles recommended with your valves? Is the exhaust valve closing all the way?

鈥渓ine up the T in the timing hole on the compression stroke and the piston should top top dead center and the valves loose at .006 if the timing is right ------- I stick a 1/4 wooden dole thru the spark plug hole and watch the piston as it is coming up to it's max peak , when it does , you should see that T should be in the hole鈥
I was probably lite on the length of time the ATV ran after I first started it. It was probably 10 seconds rather than 2 seconds. Idled well during that time so I would think valves and timing be ok.
 

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Okay so you鈥檙e saying you didn鈥檛 set the valves?
i see it鈥檚 running but cutting out when you hit the throttle?
Possibly A large backfire might rupture the vacuum piston seal. Has the carburetor ever been rebuilt? if not then if you鈥檙e going to take the carb apart to inspect everything, just rebuild it then.
 

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I seen some things happen , that might fit what is happening to you --- 1) if the diaphragm leaks on top the carb it will make it run like it is out of time when you reach 1/2 to full throttle and it will backfire and spit , but run great at idle to 1/2 throttle ---- 2) the connecting rod can get bent , it do't take much , the piston will never fully achieve top dead center when rod is bent , makes it run like it is out of time ----- 3) the valve stem will get bent from hitting the top of the piston maybe from a stretched timing chain , or from metal gauging from lack of lubrication or such , with a bent stem it will stick and the valve not fully close or not open ----- 4) the timing chain will get stretched , you adjust the valves , spin t one time and the adjustment is off 5) you might have a combination of problems ----just throw some stuff off and see what sticks
 
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