Machine ran good then gradually starting running rough, bogging,etc. Always had a pop through exhaust if you held the throttle open for a bit. It seems to be flooding. Gas smell in oil. I pulled the carb and seems to dump fuel into cylinder when cranking over.I'll replace the needle and seat. Anything else to check?

 

take off the carb and give it a good clean if you have not already. Clean all the jets and small passageways.

 

its soaking as we speak. i've ordered a needle and seat. Worked on Mikuni's for 2 strokes, but not 4 stroke. Seems similar. How does the vacuum diaphram work? Seems to me that the diapram moves the slide valve and needle jet similar to the throttle cable on the VM series carbs. Are these fussy carbs to work with?
Thanks

Jeff

 

You pretty well answered your own question about carb differences! Not fussy carbs,cable just opens butterfly and vacuum does the rest. Not as quick as flat slides and such,but responsive enough. Needle and seat wear,float arm wear basically only problem area,BUT same for other carbs also. Good luck

 

Should I replace the diaphram as well? How would I test to see if it leaks?

Jeff

 

i would just change the needle and seat first. chances are it will fix the issue. i dont hear much about diaphams being or going bad.

 

Check the needle jet and jet needle too. I just replaced mine and was having problems you describe and it runs good now.

 

Well... I pulled the carb apart, soaked it in cleaner, replaced the needle and seat. It now overheats. In setting the float level, it says 14.5 - 14.7 mm from from base to float. What part of the float? The metal plate that the needle clips on? If so, where on the plate?
In reading the manual, correct float height helps meter the fuel. Perhaps I have it incorrect and its running lean? I'm going to change the thermostat as well just to be sure. I was going through the wiring and found the wire for the fan was cut so I fixed that. Any other suggestions?
Thanks in advance
Jeff

 

Do a search on bad camshafts, those early Polaris four strokes had a run of cam problems. If the carb thing doesn't help, I bet the exhaust lobe is wore off. Doc

 

Does anybody make an aftermarket cam for the 425? I need to replace mine, and was looking....