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yz426onNOS

%$#^%$^

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Well the stupid bike is now broken again. It wont start kicks over like a 2 smoke. Only 20 gallons of gas since the last rebuild. Had some piston slap befor. Now it wont run. The decompression lever dose not even open the valve. It's like there is no valve there. When it started (before it broke) It would only run at full throttle and die. Now it wont run.

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What was rebuilt on it?

I suggest - piston / rings/ Cam chain/ valves

Who did it....I would see if they will fix it for free or very discounted - if properly done they will last...and last

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I'm bored to 450 with 13.5.1 and reliability has never been beter. There perfectly fine if you do it right and take care of it.

Now weren't you just saying something about reliablitily in another post??? :thumbsup: Obviously something was not done right as you said. :devil:

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I'm bored to 450 with 13.5.1 and reliability has never been beter. There perfectly fine if you do it right and take care of it.

Now weren't you just saying something about reliablitily in another post??? :thumbsup: Obviously something was not done right as you said. :lol:

You got me. It was running great. I think it might be the wrist pin. Possiably the piston slap. It sounds as if it was rattling. Kinda like a loud rattle/knock/tap. I kept on trying to start it. I wore a hole through my new work boots. :devil: It would start but not idle then die. It would only run high RPM's. I checked the valves and clearences before I tryed to fire it. Then put it back together and it would not run. :awww: Then I pulled the decompression lever after awhile and it stopped working. I checked were it went into the head. Appeared to be working on the outside. But it feels like there is no valve to open.

You can kick it over like a 2-smoke. But when you do that and give it gas it locks up like normal. Like it has compression. It seems to get close to starting but dose not even make it. I dont know what the hell happened. I wana tear it down but cant afford to fix it yet.

Maybe I snapped the timeing chain. Or the wristpin seized. What do you guy's think?

Durring the last rebuild it recieved:

-port and polishing

-13.5.1

-450 bore

-new one piece valves

-new valve seats and guides

-the gouges in the head were welded up and machined smooth (from when the intake valve blew off)

BTW: It's not on NOS (yet).

What do you guy's think?

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What do you guy's think?

I think you need to tear it down and go from there...no real way of assessing damage until its torn apart.

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If you have compression with the throttle open but nothing with the throttle closed, then I would start by checking your idle adjustment. If the idle is set very low and the slide goes all the way down in the carb, then it will not idle and not enough air will get sucked into the cylinder with the throttle closed to give any real compression.

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If you have compression with the throttle open but nothing with the throttle closed, then I would start by checking your idle adjustment. If the idle is set very low and the slide goes all the way down in the carb, then it will not idle and not enough air will get sucked into the cylinder with the throttle closed to give any real compression.

Thats right. I belive it's fine. But i'll check it again. But what do you think happened to the exhause valve. The lever has no strain on it. Like there is no valve.

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That's tough to say, might want to remove the valve cover and have a careful look. Do you have access to a leak down tester? If so, hook it up and put your ear to the exhaust pipe. Hear air rushing? If yes, then you're exhaust valves are leaking for some reason (clearance too tight, valves or seats burnt, valve hung open, etc...).

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