Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors

Sign in to follow this  
TomF

Surging in a Briggs 18 hp

Recommended Posts

TomF
Am tuning up a tractor for a friend. It has a 1997 B&S 18 hp twin. It tends to surge or "search", even at high throttle. A little richening with the choke tends to solve it. Can anyone give me a rundown on things to try to fix this? Where should I logically start? Carb adjustment? Fuel line blockage? Please help me with some age-old wisdom. Thanks! Tom

Share this post


Link to post
Share on other sites
arjr111
Tom, I would start with the obvious, remove fuel line, replace inline filter (if it has one), remove carb. bowl, check for sediment. Spray some carb. cleaner on the parts. Adjust carb. needles setting, as per manual, and see how it runs. A carb. rebuild or thorough cleaning may be necessary. Surging can also be caused by the govenor springs being set wrong. See link......Good luck Art http://www.perr.com/tip5.html

Share this post


Link to post
Share on other sites
HubbardRA
First of all, does this carb have an adjustable main jet or is it one of the newer fixed jet carbs. If it is adjustable, all you need to do is richen the jet a little. If it is a fixed jet carb, you will need to remove and clean the jet. Use a single strand of wire and make sure there is no varnish build-up in the jet orifice. If this doesn't do it, then you will need to find a very small set of drill bits, and open up the diameter of the hole in the jet about .001 inch. This is an extremely small change so be careful. If you remove too much, you can't put it back. I recently went through this on a B/S Vanguard that I purchased. It purrs like a kitten now. Rod H.

Share this post


Link to post
Share on other sites
Dutch
Be careful enlarging a fuel jet with a drill bit, you can't "go back" to OEM specs that was engineered to be optimum . Not only that, but the spiral cuts often let less fuel pass even though the hole is larger.

Share this post


Link to post
Share on other sites
TomF
Rod, this is one of the newer engines with the fixed main jet. It probably good that we go through all the other obvious options first like the fuel line, filter, etc. I assumed the problem was a gas-starved engine, but was also hoping to not have to get into the carb due to time constraints right now. Thanks, everyone, for your input. I like to hear the order in which the experts attack problems like these. We neophytes can go far down a path in ignorance sometimes. Tom and son Peter Feldpausch

Share this post


Link to post
Share on other sites
HubbardRA
Dutch, you are right, as usual, about the spiral cuts and not being able to go back. I was trying to say this is a last ditch fix if none of the other options work. On the fixed jet carburetors, mixture problems are very common. One small engine mechanic told me that when he had to replace one of thest carbs, he usually had to try at least three different carbs to get one that gave the correct mixture. Also when I sail .001 enlargement, this will usually only break out the varnish that is coating the jet. Most times I use the un-fluted smooth portion of the drill bit for this operation. I have seen a friend use a piece of smooth wire and turn it by hand till it abrades itself through the hole. Anyway it was only a suggestion (not for a novice), since it worked for me. I have worked with carbs on many machines since I was a kid and I am now 50+ and know that carbs are not magic. If you understand them, you can fix them. Rod H.

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

  • Who's Online (See full list)

    • casinojim
    • SmilinSam
    • DaveTenney
    • midnightpumpkin
    • Homelite-t10
    • Alltractoredup
    • Hick
    • DaveBsACs
    • Brighammer
    • Brettw
    • Ronald Hribar
    • phillobbezoo
    • Bear
  • Today's Birthdays

    1. 1978Simplicity7016H
      1978Simplicity7016H
      (20 years old)
    2. Robert McCain
      Robert McCain
      (32 years old)
  • Recent Status Updates

    • gwiseman

      gwiseman

      Club banners are available  for members use during show season https://simpletractors.com/forums/topic/57849-simpletractors-club-banners-available/
       
      · 0 replies
    • gwiseman

      gwiseman

      Today is SimpletrACtors founder Kent Thomas' birthday. RIP my friend.
      · 3 replies
  • Adverts

×