Planet Minis - View Single Post - Z50R engine trouble, need some help, video inside

mexicanyella · 06-25-2009, 07:29 AM

Early softtail. Hardtail carb was more square-looking in the bowl; had different "guillotine"-style choke instead of butterfly.

I'd say if the bike runs well with the second carb, your work there is done. Take the shiny carb apart at your leisure and figure out where the blockage is. I don't have a Z50R carb here to look at, but from the vid and posts it sure sounds to me like there's a blockage in there somewhere and the bike's running lean enough to have poor throttle response and make little popping backfires occasionally.

As mentioned above, dirty, pitted or incorrectly gapped points can sometimes do this too, although when they do you'll usually get a dry, sooty black spark plug from the weak spark/incomplete combustion. These symptoms, when they come from lean mixture, instead should give you a real clean whitish plug from overheating the plug.

In any case it sounds like your problem isn't points this time. But don't be afraid of the points. Get yourself a flywheel puller and swing by a NAPA store and get yourself a points file, and a good feeler gauge. And a can of electronics cleaner. File 'em flat if needed, clean them with the spray cleaner, set gap to .012"-.016". (You have to set the gap with the flywheel installed, because the points cam is part of the flywheel, but it's easier to file them with the flywheel off).

More than 90% of the time that's all you need to know about older Z50 ignition systems. It's an easy process and diagnosis gets easy once you've done it a few times.

Cool bike; high-five yourself a little bit.

06-25-2009, 07:29 AM	#16 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 984	Re: Z50R engine trouble, need some help, video inside Early softtail. Hardtail carb was more square-looking in the bowl; had different "guillotine"-style choke instead of butterfly. I'd say if the bike runs well with the second carb, your work there is done. Take the shiny carb apart at your leisure and figure out where the blockage is. I don't have a Z50R carb here to look at, but from the vid and posts it sure sounds to me like there's a blockage in there somewhere and the bike's running lean enough to have poor throttle response and make little popping backfires occasionally. As mentioned above, dirty, pitted or incorrectly gapped points can sometimes do this too, although when they do you'll usually get a dry, sooty black spark plug from the weak spark/incomplete combustion. These symptoms, when they come from lean mixture, instead should give you a real clean whitish plug from overheating the plug. In any case it sounds like your problem isn't points this time. But don't be afraid of the points. Get yourself a flywheel puller and swing by a NAPA store and get yourself a points file, and a good feeler gauge. And a can of electronics cleaner. File 'em flat if needed, clean them with the spray cleaner, set gap to .012"-.016". (You have to set the gap with the flywheel installed, because the points cam is part of the flywheel, but it's easier to file them with the flywheel off). More than 90% of the time that's all you need to know about older Z50 ignition systems. It's an easy process and diagnosis gets easy once you've done it a few times. Cool bike; high-five yourself a little bit.