I started rebuilding my grandpa's old yamaha moto 4 with the oil cooled 350 motor. I have cleaned out the carb, drained and refilled the gas tank with new gas, new battery, new starter relay, and new air filter. It starts right up and idles good with half choke but will die with choke all the way off and when i run it around the bogs down a little before regaining power and running good. It backfires a little when you first give it some throttle also. My next step is a new spark plug, I just wanted to make sure it ran before putting more money into it because it also needs 4 new tires. Any other ideas what I could do to help with the bogging down and backfire issue? Any help is appreciated

 

Well...it running on 1/2 choke and not running without it tells me your pilot (idle) jet needs attention. It's tiny with tiny holes and is usually the first thing to plug in a carb. Your stumbling also sounds carb related...I think a good cleaning and re-set to baseline is in order...

 

I pulled off the float bowl and cleaned inside there, then I unscrewed what I was assuming was the main jet and cleaned it out, I'm not to familiar with these older models. Is there multiple jets on these carbs?

 

Should be...pilot jet normally next to main...need to look into each hole to find it...you'll need the correct fitting screwdriver...don't strip it!


If not sure post a pic of your carb, upside down, with float bowl off...

 

Well I finally got a chance to get back into the carb, I took the bowl off and there is for sure only 1 jet in there, I cleaned it out again and put everything back together and it runs better but is still backfiring, what I did notice was that all of the gaskets look pretty old, could there be leak and too much air be getting in causing to not run right? I plan to get a rebuild kit that has a new jet and gaskets this week anyways but just wondering if that could be it

 

I just recently rebuilt my banshee from the ground up. And before the rebuild everything worked fine from the engine to the electrical. After putting it all together and mounting my new LED lights when the RPMs increased they blew. Took my multimeter and tested the current coming to the lights and when it's idling I was at 12 volts and when I increased the RPM the multimeter maxed out. After some research I decided to purchase a new voltage regulator/rectifier. I connected the new regulator then went ahead and tested the voltage and I got the same reading. Could I be experiencing a ground problem because I just had the frame powder coated

 

possibly...if you are trying to ground to frame over PC then you may have an issue...especially if it was base then clear coated. PC is a natural insulator. Use a razor blade and get down to bare metal. This would imply that your PC'er coated the threads on the ground bolt...


In any event, just to eliminate that as a potential issue, scrape just enough away to get good metal on metal contact...

 

Hey sorry to jump in on your post but not sure how to start my own... But I have a 1987 Moto 4 350 and a 95 Moto 4 350.. I took the complete wiring harness off of my 95 and put on my 87 including stator pickup coil CDI box rectifier and ignitions coil o and the start unit... I know there is a neutral safety switch on bottom of motor and there is another safety switch on handle bars... My problem is Ivan get fire to coil nor can I turn it over by started button... I had it turning over by the button once now nothing but I get a cick noise from rectifier when turning key on and of but that's it nothing else... And no for when using pull rope.... Any help??

 

I have a 93 350 moto4. it was backfiring real bad due to an exhaust leak. I replaced exhaust gasket and sealed up where the exhaust pipe union is with rv glue and she purs now.