Surging Problem

Reply

  #1  
Old 05-16-03, 05:50 AM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
Need Help with my Mystery Machine!

I was given a small riding mower and it stopped working properly this week. Here's the info: Its a Murray RER circa 1970. According to the service shop it's supposed to have a B&S engine - for whatever reason, I think it has a Tecumseh on it now. The only engine markings that I could find were a string of numbers stamped into the engine shroud, they are as follows.......
170702 0689-01 7001071 That's exactly as they appear. Could someone help me ID this engine?

Here's the problem....surging. Sometimes it'll be ok right when it starts up, and sometimes it won't be. Sometimes it'll be ok under load, and sometimes it won't be???

First I tried to adjust the carb because it seemed like there was too much or too little gas getting to the engine, but the adjustments had no visible effect so I took apart the carb and cleaned it and noticed that the needles were badly worn. They have grooves around their tips. (this carb has two adjustments on it, High speed and idle) The only thing the carb cleaning accomplished was to completely screw up the valve that is operated by the float. Apparently, some of the crud in there was helping it to operate properly cause now it never shuts down the fuel flow from the tank. (I did check the float for leaks and there aren't any) In fact, soon after I put it together, I let the mower sit for a while and when I came back to try to start it I found that is was hydro locked. I got that controlled by limiting the gas flow with the shutoff valve at the tank, but it definitely needs a rebuild kit. How can I get the right kit for the carb since it too may not match the rest of the tractor or the engine either for that matter? Do carbs have an identifying mark on them or a serial number somewhere that will help me get the right parts for it?

Adjustment of the carb still has no effect on its operation.

Finally, I had another tractor that had a similar surging problem that was corrected by replacing the condenser. So I want to replace that too. Yet another reason that I need to know what make of engine I have in this thing.

I hope that some of this information is useful in helping you diagnose my problems. If there is more that I should be giving you guys, please let me know. At the very least I need to know which engine company's markings these are!

Thanks in advance.
 
Sponsored Links
  #2  
Old 05-16-03, 09:30 AM
Joe_F
Visiting Guest
Posts: n/a
It sounds like a B&S engines. Tecumseh engines have letters in the model # (HS50-67169B, H60 two of mine), etc.

Call up B&S (www.briggsandstratton.com) and ask for a parts list and owner's manual for your engine, giving all #s you find. They will get you the proper documents. You will then know what parts are needed.

Definitely sounds like a flooding/carburetor issue.
 
  #3  
Old 05-16-03, 09:42 AM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
Thanks for the tip Joe. I'll stop by the local B&S shop and see what they know.

Thanks again.
 
  #4  
Old 05-16-03, 10:49 PM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,821
Hello hb2u!

You definitely have a Briggs and Stratton engine. I believe it is a 7HP (17 cu. in.) with a vertical flo-jet carburetor, plain bearings, and a rewind starter. The carb is probably right for it, since you cannot really interchange them much (may have a newer or slightly different one from another similar engine of the same make and close size). Just ask your small engine shop for a carb kit for the model# you gave us, and it should fit, even if the carb WAS robbed off another similar engine.
 
  #5  
Old 05-18-03, 07:09 AM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,723
hb2u:

I had the same problem with extreme flooding after cleaning the carb and replacing the float on my 8 hp Tecumseh.
Just by accident I noticed the rubber seat for the float needle sitting on the floor!
 
  #6  
Old 05-19-03, 05:08 AM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
NEED MORE HELP!!

Thanks for the info guys... BUT Cheese, you were mistaken. The fellow that had this before me put a COMPLETELY DIFFERENT carb on the machine. I took the engine number to the local B&S Dealer and he gave me the carb kit and the only thing in it that fit was the needle valve. NOTHING ELSE WAS EVEN CLOSE! Not even the gaskets were close?!

The carb that's on it now is wierd. Its set up like this....


port to engine....Carb with bowl on bottom....top air intake..rear intake (Plugged)



It has not only the 1 inch diameter hole out the top end for the air filter intake. it also has a 1 inch diameter hole out the rear of the carb (RIGHT NEXT TO THE AIR INTAKE) but this hole is plugged with what looks like chewing gum.

I don't know if this is a throttle body of some sort off a go cart or what? I don't really know why a carb would have two large input orifices.

It does have a separate vent hose that goes back to the crankcase breather, so that's not what it's for. It's got me stumped. Any new ideas?

What do I do now besides go to the shop with the carburetor in hand and start ripping through kits til I find one that fits?

Are there any ways to identify this mystery carburetor?

Thanks fellas.
 
  #7  
Old 05-19-03, 09:46 AM
Joe_F
Visiting Guest
Posts: n/a
Yes, bring the carburetor (and preferably the machine) back with you to the small engine shop and have the guy go through it.

I know Tecumseh carburetors have the model # stamped on the carburetor, I think Briggs does as well. In that case, you'll get the right kit and parts.
 
  #8  
Old 05-19-03, 10:17 AM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,821
The hole in the rear of the carb is supposed to be plugged, but with a large welch plug, not chewing gum, lol. The carb identified by the model# is a vertical flo-jet. I guess I assumed too much thinking you would be able to get a kit by the model#. If it has a carb for a horizontal shaft engine, the needles for those two carbs are interchangeable, but pretty much nothing else is. There is almost no way, other than some good engineering, that this carb could work on a horizontal shaft engine, because the governor would not work. If that is what is on there, it shouldn't be unless someone has put the wrong engine shroud on the engine with the wrong model#s on it.

Many if not all of the older flo-jet carbs don't have any #s.

There are only 2 basic flo-jet designs for that size and age engine. One is horizontal, the other is vertical. (carb, not the engine). There is a chance that the engine shroud with the model#s is not original to the engine, so to get a better idea....is this engine vertical shaft (coming out the bottom), or horizontal shaft (out the side)? Does the carb intake tube drop down, then make a 90degree turn and go sideways, or does the whole carb go sideways? I will help you figure out what you have and need.
 

Last edited by cheese; 05-19-03 at 12:36 PM.
  #9  
Old 05-19-03, 12:05 PM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
Here's some more info...

Hi cheese. The engine is a vertical shaft engine. the piston moves horizontally, parallel to the ground and the rotating shaft of the engine protrudes down through the frame of the tractor to the drive pulley that works the tranny and mower deck.

As you look at the tractor from behind, the gas tank is mounted to the left of the (pull) starter assembly and the air filter housing is on the top right side of the engine directly opposit the gas tank and directly above the carburetor assembly. (The spark plug is directly in the center of the rear of the tractor and is mounted parallel to the ground.)

As you stand on the right side of the tractor and move your eye from the rear towards the front, you move from the port where the aspirated fuel enters the engine head to the bowl and jet assembly - at the top rear of the bowl and jet assembly is where there's a set screw(NOT A NEEDLE) that you can adjust to increase the RPM of the engine, this is where the governor attaches to the carb - then as you move your eyes forward again you move past the Air intake and finally come to the chewing gum plug. A little bit further ahead after this point is where the governor linkages are tied into the governor. The FAST / SLOW throttle adjustment cable is in this area too and there's a wire set in here that looks like it'll ground out the ignition system to turn off the tractor if you push the throttle past the fast setting.

Aspirated fuel enters the engine via a 90 degree turn but remains in horizontal motion. the turn does not lift it up or down.

One of the screws that holds the airbox in place is about 6 inches long and screws into the bottom of the carb throat just a 1/4 of an inch behind the chewing gum plug(inside the carb)

The bowl is round and the float is a donut shape. There are only two adjustable jets on this carb, one through the bottom center of the bowl and the other through the top, slightly to the side of the carb that empties into the engine.

Hope this info helps you help me. Thanks a lot.
 
  #10  
Old 05-19-03, 12:48 PM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,821
OK, as your model# indicates and your description indicates, you have a flo-jet carb....for a vertical shaft engine. This should be easy for the parts house to give you a kit for. Try asking for a kit for a 190702 (very common engine that should have the exact same carb..8hp briggs like used on snappers). I bet, since the model #170702 is so old, maybe the dealer you went to has no parts lookup for it. (I don't either). Is there a possibility that the first 7 in your model# is actually a 9? If so, it IS the common 8hp briggs, used by snapper and probably every manufacturer at one time or another.
 
  #11  
Old 05-19-03, 01:31 PM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
Thanks

Thanks Cheese, I'll try that. TYhe dealer actually did call into B&S Support to get the updated part number for the carb kit cause the old number in his system wasn't a valid inventory number.

I think I'll take the carb parts with me and open the new box on the counter to see if they look the same this time.\


Thanks again for all of your help. I'll be sure to let you know how it turns out.
 
  #12  
Old 05-23-03, 07:40 AM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
ANOTHER QUESTION....

I'm going to the shop today to pick up the 190702 carb kit - I'll let you know if that's the right one or not......BUT in the meantime I have another question for you guys. I was reading my small engine repair book last night and it implied (it actually had a diagram of what my carb looks like) that with my FLOW JET type carb, when I do the adjustments, when I have the throttle lever pushed to the FAST setting, adjustment of the idle screw should do NOTHING since all fuel for the engine should be coming through the high speed needle since the throttle plate is allowing a lot of flow through the throat of the carb, thus eliminating the vaccum that would be needed to pull the fuel through the idle ports Is this TRUE IN REAL LIFE, or just TRUE IN THEORY? Cause it seemed to me that the idle screw did impact the way the tractor was running EVEN THOUGH it was operating at the high speed throttle setting....

Also, the book said that for the initial startup, I should screw in the idle screw the "STOP" and then turn it three(3) times!

Does that mean that I screw it in until it stops and then force it in 3 more turns?! Or put it in til it stops and then back it out three turns?

Prior to reading this book, I thought A good starting point was to put the idle screw in until it stopped and then back it out one and a half revolutions. (which coould be taken as three "turns" since you can only really turn a screwdriver 180 degrees easily without letting go of the handle)

Thanks for your continued help.

HB
 
  #13  
Old 05-26-03, 11:25 PM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,821
The high speed screw WILL affect engine operation at idle, and the idle mixture screw WILL affect it at wide open throttle. You have the right idea....first of all, turn the idle mixture in until it lightly bottoms out, then turn it 1 1/2 full revolutions back out. (3 half-turns). Then, crank it up and rev it to full throttle. Screw the high speed mixture screw in until the engine begins to surge, run badly, or die. Then counting the # of turns, back it out again until the engine begins to chug or surge again. Then divide that # by 2 and tighten the screw that many turns. (split the difference). Then go back to idle and adjust the idle speed and make fine tune adjustments of the idel mixture screw until you achieve the best idle and throttle response.
 
  #14  
Old 05-27-03, 04:58 AM
Member
Thread Starter
Join Date: Dec 2000
Location: PA
Posts: 117
Thanks a MILLION!!!

Cheese and Joe F. Thanks a million. Cheese the new engine code that you gave me WORKED. got the right parts without any problem. The carb was back together and I moved 7 yards of topsoil this weekend with that tractor pulling my dump cart. (thank god I didn't have to do it with a wheelbarrow!)

The carb now also has a shiny new welch plug in the space formerly occupied by chewing gum.

Thanks again for all of your help. It's truly appreciated.
 
  #15  
Old 05-27-03, 07:52 PM
mikejmerritt
Visiting Guest
Posts: n/a
Tuning a Carb is an Art....

Just couldn't help but observe that cheese describes something that can't be taught two posts down. You just have to do enough engines that you feel it. Had a guy pull into the shop today and said "Your partner just reached down last spring and twisted a couple of screws and my engine stopped loafing, ran perfect"....his words not mine. I listened to his engine, twisted a couple of screws and what do you know, smooth as silk. All carb problems are not float, needle and flow problems. Tune the low, tune the high, find a nice middle ground and your mower will run well all summer. He said "You charge $5.00 for that !!!", I thought, you pay for what I know in this case not what I do........Mike
 
  #16  
Old 05-27-03, 09:48 PM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,821
Yep...after doing enough of them, you learn or "feel" what needs to be done to get it running right. Following the directions I gave should get the engine running, but the fine tuning is where you can get the engine running like a sewing machine. I know what you mean Mike, some people don't realize that they aren't just paying for labor, they're paying for knowledge. That is why they hire guys like us to work on their equipment, not the guy behind the counter at the convenience store.

Glad you got it running hb2u! You know where to come next time you have trouble!

Take care!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes