Hello to all,

I am new to the site and it seems that there is a lot of really good info here. I tried searching throught he threads to see if anyone has had this problem before and could not locate any info.

I have a 1991 moto4 250. It has been a great bike until about a month ago. It has started to pulsate when ideling. Up and down. Then it will stay up then try to die out. It is running rich right now. I rebuilt the carb to the factory settings and reset the new float. I replaced the throttle cable. I changed the plug. And as far as I can tell it is all to the factory settings of the Yamaha book. I also did a compression check and it was reading at 107 which the book said was in the normal area. Any help would be great. This bike is used for hunting in Florida, so I made a snorkel kit for it out of 2 inch pvc. I also made sure all the connections are sealed with silicone. Another thing I noticed is that I can unscrew the air needle almost all the way out and there is no change. I hope I have put enough info in here for the pro's that really know how to set these things up.

Thanks in advance.

 

Your problem might be that you have a crack or small pin holes in your intake hoses, this would cause the engine to continually suck air and also suck fuel, so check the rubber hoses that connect your carbs to your head.

If it's not that check your valve clearence, I could see the reving up down happening because you intake valves are not shuttin all the way. Most people don't ever adjust their valves, the wait for the them to start ticking, but in your case they wouldn't tick if the rocker is pressing down on them and not letting them close all the way.