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Discussion Starter #1
Sorry guys haven't posted in a very long time been too busy at school, but I need some help I am rebuilding this foreman 500 I rebuilt the topend with new timing chain piston and rings, it never ran good before i rebuilt it it would bog down cough splutter and never ran properly so a rebuilt the carb and put it on and started it today and it ran really hot and popped through the exhaust and airbox, I put the old jets back in making no difference it pops out the exhaust on deceleration and I can feel the heat from the exhaust, it has no air leaks from what I can tell and the carby has no adjustment the pilot screw tis like a half moon shape so I can't turn it and the needle has no grooves to move the clip.

anyone got an idea what I should do motor is stock no mods

here is a vid of what it sounds like (the motor is quiet its just the echo of the popping in the shed)

https://youtu.be/xjv-ZPN2e6E
 

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You could have an exhaust leak at the pipe to head union. What does a new spark plug look like after running for a few minutes? If it is bone white, your engine is running very lean.

It could also be a timing problem, especially if it is popping back through the airbox. With this situation, I would not run it hard because you are probably close to seizing a piston.

Rick
 

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didn't sound terrible. Timing off or valve need finer adjust? did you rebuild the top end too?
 

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Discussion Starter #5
You could have an exhaust leak at the pipe to head union. What does a new spark plug look like after running for a few minutes? If it is bone white, your engine is running very lean.

It could also be a timing problem, especially if it is popping back through the airbox. With this situation, I would not run it hard because you are probably close to seizing a piston.

Rick
Ill check the exhaust and check, there is a pic of the plug its white not bone white but whiter than I would like, ok I,ll check the timing out I thought I had it right but ill double check it
 

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Discussion Starter #6
didn't sound terrible. Timing off or valve need finer adjust? did you rebuild the top end too?
I made exhaust and intake the same normally i wouldn't but the manual said the valve clearance was the same is that right? yes rebuilt the top end
 

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Discussion Starter #7
Jake, Good to hear from you again. I was wondering what happened. Good luck on the rebuild.
Yeah im still around schools too hard too much homework, but im stillin doin bikes, ill try to hop on more often
 

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Discussion Starter #9

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Discussion Starter #10
ok correct me if i'm wrong but for me to check the timing im going to have to pull the motor right?
sorry first time doing one of these 300's are so much easier!! im gonna check the valves but im leaning towards one tooth out on the timing
 

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Jake, I was in AU a few weeks ago. Did a short walkabout around Sydney. Before that, I was in Indonesia, up around the Bali, Jakarta, Makassar, and Sorong areas.
Except for the high cost of things in AU, I always enjoy my visits there!
 

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Discussion Starter #13
Nope. You set the engine to TDC and make sure you do it on the compression stroke (lesson I just learned the hard way).

Engine to TDC, then flip the bike up on the rear rack and pull the front cover. You should see two index marks, one on the cam, one on the cam gear, and they should both line up with the index mark on the case.

http://www.hondaatvforums.net/forums/repair-maintenance/48817-06-foreman-top-end-noise-2.html#post431939
Ok happy I dont have to take the engine back out I will check the timing on the weekend and see so if it was out it would only be out 1 tooth right?
 

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Nope. You set the engine to TDC and make sure you do it on the compression stroke (lesson I just learned the hard way).

Engine to TDC, then flip the bike up on the rear rack and pull the front cover. You should see two index marks, one on the cam, one on the cam gear, and they should both line up with the index mark on the case.

http://www.hondaatvforums.net/forums/repair-maintenance/48817-06-foreman-top-end-noise-2.html#post431939
Ok happy I dont have to take the engine back out I will check the timing on the weekend and see so if it was out it would only be out 1 tooth right?
Probably. Mine was out 180 degrees. Still fired right up, but sounded like little men with sledge hammers were trying to get out of the top of the engine.

Got it lined up properly, and it's as quiet as a new wheeler now.
 

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Discussion Starter #15
Ok i checked the timing and it is fine valves are fine, but I noticed a clicking sound in the push rod so I have pulled the head off and when I hold the exhaust push rod turning it over I can feel it click back down like its sticking for a little before coming back down, and its just not smooth like the intake side, could this be the problem? I have pulled the followers out swapped them cleaned them and its still sticking.
 

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Discussion Starter #16
I tried different cam followers and it still sticks could it be a worn cam making it click??
 

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Discussion Starter #17
Ok I think i have figured it out the depression mechanism on the cam is not working properly allowing the exhaust valve to stay open much longer than it should so I messaged partzilla to see if they have one in stock
 

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Discussion Starter #18
Ok I got my new cam in and out it all together it is now quiet and doesn't sound like a bunch of miners trying to escape but it's still running lean not as bad it pops on
de acceleration and sounds like it misses sometimes but when I put the choke on its fine and runs great I have adjusted the pilot screw gone through the carb 3 times and stuck a kit in it I shimmed the needle with thin washers since it has no adjustment and it's slightly better but still pops and farts and doesn't run well with no choke any ideas at all??
 

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Is the carb, especially the main jet and emulsion tube scrupulously clean? You might try a fatter main jet. If you need choke, you are definitely lean and hot, possibly close to seizing a piston.

Rick
 

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Discussion Starter #20
Is the carb, especially the main jet and emulsion tube scrupulously clean? You might try a fatter main jet. If you need choke, you are definitely lean and hot, possibly close to seizing a piston.

Rick
Main jet is brand new I have tried the old one back in and it ran the same, what is the emulsion tube?
 
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