Engine issue with Mackissic 12P Chip/Shred

[beltfed]

Please let me know if this isn't the correct forum.

Please watch this video for the issue I've having. I just picked up a used Mackissic 12P chipper shredder.

Mackissic 12P :: 12p.mp4 video by vabeltfed - Photobucket

Problem is the engine runs for several minutes and then throttles down for several seconds and then revs back up to normal. After about 20 more seconds of normal throttle it repeats the throttle down... etc.

I replaced the spark plug and I'm not sure whats wrong. I've moved the screw at the bottom (needle adjusment?) one way and then back the other way but always put it back where it was when I purchased the chipper/shredder.

8hp Briggs and Stratton. Model: 190402 Type: 6120 01 Code: 96041610

If I can't figure this out I guess I'll have to take it to a small engine repair shop and have them look it over.

Thanks for any assistance.

Thoughts?

 

[rberg]

Sounds like a fuel supply to the carburetor can't keep the float bowl full. Check to make sure the supply shut off valve at the bottom of the fuel tank is fully open. If the chipper has sat a while then you may need to clean out or change out the fuel filter, clean the fuel line, make sure the tank and the fuel supply shut off valve don't have sediment in them.

 

[beltfed]

Thanks for the suggestions. The bottom of the carb bowl doesn't have a shut off valve? The air intake looks like it is coming in from there. I think it also has a governor.

I'll check the fuel line this weekend, doesn't appear to have a fuel filter in the fuel line.

I'm wondering if its the idle / needle valve combo and I have to keep adjusting until its correct?

If all else fails I'll take apart the carb and rebuild it or take it to the local repair shop.

Appreciate the help.