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bogging at high speeds


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Has anyone had bogging problems at high speeds?  I know a guy who said his truck runs okay at low speed, but as soon as he jumps on the highway and hits high speeds....his truck starts to bog out and evenetually stall out. His truck does not have a Catalytic converter on it, so I told him that the muffler is probably clogged up and choking the motor....is this correct info? or can it be a carb issue? spark plug issue....what do you guys think?

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Fuel filter needs changing. A dirty filter will pass enough gas for around town but at highway speeds the demand is more than can get through ad the carb runs dry. They are cheap and easy to change and if it turns out this isn't it, no harm done.


Have your 'friend' look at the sight glass on the front of the carb with the engine running. The fuel level should be at or close to the dot on the glass. If the fuel level is too low the float level is set too low and again the engine will use fuel faster than it can get into the carb and run dry.

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I just had this issue start last week but it wasn't from a dirty filter I recently checked mine and it was clean and all my fuel lines are fairly new. What ended up being the issue for me was the fuel pump I believe, it pumped and flowed fine but once I got up to 90+ it would bog a bit and I'd have to drop down to the 80's. Pump took a crap on me yesterday I replaced it and I'm not having any issues now

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Okay so it sounds like both you guys are leaning towards a fuel issue, Does that mean that the exhaust issue I was talking about would happen at both low and high speeds if indeed that was the issue? or is there a chance it still could be an exhaust issue from the "Cat" being cut off?

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I had a 720 that bogged too. It was fuel starvation. But it was from the floats on the carb, not the filter.  Floats closed to early, so under high rpms/speeds it would starve itself.


Clogged filter could cause it too. I'd read what mike said and give dat a try first.  Not having a cat shouldn't hurt anything other than emissions. Really a cat from what I understand just gets hot enough inside to burn off any remaining gas fumes etc

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New filter, new fuel pump, re-built carb.....  Got it! :thumbup:


No. Do the easy cheap things first. A new pump is not going to fix a badly adjusted float.


For carb icing you need near or below freezing combined with high humidity. California????? Your 720 should have a stove pipe from the hot exhaust to provide warmed air to the carb. It's job is to prevent carb icing

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