725 performance problem

[Guest]

Just got a 725 running that sat in the shed for somewhere around 25 years. The problem I am having is it doesn't want to "rev up". Over 1/2 to 3/4 throttle it dies like it's starved of fuel. Choking will get it to pop a few more times, but it still dies. Is this a carb problem that I should look at rebuilding the carb, or just an adjustment? Runs good up to 1/2 throttle. Any help would be appreciated.

[SmilinSam 3,190]

Sitting that long it wouldn't hurt to give the carb a good clean out. Could be a little out of time too, but i'd clean the carb first and put a new plug in it. Sam

[thedaddycat 152]

I'd also check the gas tank, fuel filter, and lines. See the recent post about cleaning the gas tank. Filters and lines are cheap so just replace them if questionable. If you do replace the lines, check your clamps while you're at it. I have three 725's, two of which I have yet to even try to start. The third one I got on e-Bay, but it has an engine knock when cold so I hardly ever run it. When I do run that 725, I have to let it warm up slowly or it will die if I try to get it to rev too high. It takes about five min. or so to warm up. Have you tried letting it warm up for an extended period before going full throttle?

[Roy 0]

No need for warm up if everything is OK. As advised above, I suspect troubles in the fuel system and/or govenor. I just picked up a 725 and it starts and runs fine without sustained warm up as does my B-1. Roy

[johnmonkey 4]

I was thinking it may be in the governor linkage. Does the linkage move freely? Is the linkage in the correct holes? Just a thought John H

[D-17_Dave 11]

Sounds more like your carb is not getting enough gas flow. clean out the tank, replace the shutoff valve, filter, and line. You should have a steady stream of gas the size of the fuel line not conected to the carb.

[ka9bxg 3]

That is a model 19 d engine.I bet that it runs good when cold but once it warms up (5 to 10 minutes) it starts to miss and back fire.If this what you are getting then it is the coil.I know that it sounds like the carb but from doing 6 of these engines in the last couple of years I know that it is the coil.Not even a spark tester will tell you this.I know that it is a lot of work to replace it but it is the only way to get it fixed.Bob

[roma3112 0]

I would tend to lean towards the coil as well, reading through all the comments seems to have eliminated a fuel side causation. I agree yess it is a pain to replace the coil (lord knows i have had to do it twice on my 3112 NOTTT FUN) I think that if you get yourself a new coil you will be pretty happy.

[SmilinSam 3,190]

If you had a 12V coil from a Kohler or a car you could hook it up to the points and battery with a shut off switch in line and try and run the engine battery ignition like the kohlers . I have done this with some of my Briggs and they run great, and keep running great. Saves time of taking the engine down to fix the problem. Don't use a graphite lead wire, use a copper wire lead.

[HubbardRA 17]

I just replaced the external coil on a Kohler. Could not get the carb to adjust to smooth out the engine. Changed the coil, carb adjusts fine. Rule of thumb: If you think it is carb, then fix ignition, and vice versa. Rod H.