Dolmar 420 problem

[Jensent]

Saw fires first pull. Starts on 2nd or third pull. Engine idles smoothly. When speed increased engine speed becomes irregular with or without bar and chain. Looses power to the point it will not pull the chain in the cut. Replaced plug , washed air filter, cylinder and piston look like new. Cat,muffler and spark arrester clean free from soot. Fuel from same can as three other saws. Carb adjustment restricted by orange sleeve on high speed screw. I'm thinking compression and ignition ok. Problem seems to be fuel system. How do I service the tank vent? I think it is a small fiber plug on the lower left rear handle. I'm wide open to suggestions. Need a source for parts as well. I would rather keep the saw stock than attempting to modify it as I have no experience.

 

[Andyshine77]

Make sure the ignition wire isn't shorting somewhere, and that it fits on the plug securely. Make sure the fuel lines are in good shape. Seeing that it's a 420 and a bit older I'd go through the carb just because. If none of that helps you probably have a bad coil.

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[Chainsaw Jim]

Sounds like either it needs a new carb kit, bearings, or bearing seals.

 

[7sleeper]

For me it sounds more like proper carb adjustments need to be done. Remove the limiter caps and adjust the carb properly.

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[Jensent]

Took saw to dealer. Rev limiter is cutting in at 11500 rpm. Is this normal? Would like a bit more speed if it can be had with-out major mods. Saw is stock with kat and carb adjust limiters in place. Dealer indicated carb limiters in stock condition will prevent saw from running both rich or lean. If this is true I would like to leave it stock.
Thanks
Tom

 

[merc_man]

Took saw to dealer. Rev limiter is cutting in at 11500 rpm. Is this normal? Would like a bit more speed if it can be had with-out major mods. Saw is stock with kat and carb adjust limiters in place. Dealer indicated carb limiters in stock condition will prevent saw from running both rich or lean. If this is true I would like to leave it stock.
Thanks
Tom

Like mentioned above. Probly the coil. It will have a rev limiter built in thats failing.

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[merc_man]

I got a 420 as well. I think its supposed to rev about 13000 rpm.

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[7sleeper]

Sorry fella's but you are both wrong! Reg. RPM is 13500. So either you definately need to remove the limiters and set the carb correctly (which I personaly see as the problem), or have the coil replaced.

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