Original Owner 86 LT-F230

Engine starts and idles like it was new, but when you begin riding it will bog out, sputter and often die.

First thought was carb, so pulled it off, cleaned and rebuilt with new kit. Reinstalled, again starts and idles like new -> same problem.

2nd thought back to basics: Fresh gas, new plug, added a little sea foam for the hell of it -> same problem

3rd thought: fuel delivery issue - as in fuel can't keep up? Pulled line off vacuum operated pump - pumps fuel good and increases with throttle so assume good, -> same problem

4th thought: ignition issue? ran machine with inline spark tester, actually drove it with spark tester hooked up so I could watch it, but its hard to tell what cuts out first. I also resistance tested CDI pick-up coil as per manual and it measures in spec. ->

I am running out of ideas. I don't really want to start guessing and throwing parts at it. I am thinking of having another go at the carb?

anybody have any suggestions what to try next?

 

Have you checked the tank vent, if blocked you get a vacuum in the tank once the machine has run a while. If that isn't the fault, it is worth trying a new ignition coil, they can play tricks like this. However, on the ignition side, pick up and exciter coils can also give trouble, and I don't like the substitution way of mending things either. I blow through all jets and passageways in a carb with compressed air, this usually fixes them first time.

 

Thanks merman

I will check the tank vent next.

I pulled and bench tested the coil and it reads at just below the bottom of the range. So definitely going to change that out.

I was always afraid to go into a carb on anything, less some of the magic might come. I've gotten braver with experience, and thought a rebuild kit was standard procedure, but I see what you're saying, machine is 34 yrs old and the parts are removed looked fine

 

I've never been able to work out why people think they should always use a rebuild kit on carbs. With car engines, they often do over 100,000 miles before the carb gets a clean, and jets may well get worn, so new jets could well be a good idea, but quads don't usually get that sort of use, CD carbs always wear the CD piston as much as anything, and you don't get them in a rebuild kit anyway.

 

OK, so new aftermarket coil - no change

fuel vents seemed clear but blew them out regardless - no immediate change.

while on vents, noticed that I couldn't blow any air through carb vent. Put the compressed air to it and something let go and air began to flow. still cut out on throttle on test ride

while scratching my head watching it idle, seemed to me that no air was moving through the air intake even though I had removed the snorkel. I began eliminating more of the air system until I was running machine with carb intake wide open (no air filter or intake components connected) This is the first time the machine ran right. Did a lap around the block with no issue. There did not appear to be anything foreign in the air intake assembly, so I reassembled it carefully, paying particular attention to line everything up right and tighten everything down.

It seems to be running good now, touch wood