Alright guys, my friend rescued his dad's Canadian-spec (everything's written in French and English) 1981 Craftsman mower. It has a single cylinder 4 stroke 11hp Briggs and Stratton engine. So far it's got a fresh battery and tires, new sparkplug, new fuel lines, and we took the flywheel off and wired in a new coil.



We can't get it to start though. We know how carbs work basically, but don't have a high level of troubleshooting ability. It has compression. It has spark. How do we know if the carb is bad? We put the lever thing in the "choke" position and it cranks and cranks but won't fire. We tried a bunch of starter fluid, and we we even tried pouring a little gas in the carb. Can the magneto somehow be messed up and the timing off? Or if it gets spark at all, can I assume the plug is being fired at the correct time?



Part of the problem is that I don't know what each adjuster screw does and which ones are truly important. Could somebody tell me what these screws do and if they're important? How do we check if the timing is correct?

6/9/2009 9:57:03 AM

I think my dad bought that same mower brand new from Sears. Biggest P.O.S. ever. Kept it for two years and sold it to buy a John Deere.

6/9/2009 10:04:31 AM

after you spin it for a while, is the plug wet w/ gasoline?

6/9/2009 10:29:38 AM

is the plug even getting fire at all?

you can check it with a light to see if it is getting fire then check the plug by removing it and holding it against the block to see if it is firing real quick

If it isnt then check the gap on the coil, and if it is firing...for timing if the flywheel key isnt sheered then it should be ok.

6/9/2009 10:48:35 AM

those carbs are bulletproof, take the nut/jet screw off the bottom, take the bowl off, clean everything well, and spray some carb cleaner through the jets to make sure everything is clear, it will run

set the idle and main 1.5 turns from seated and start tuning from there

6/9/2009 10:50:13 AM

^yes.


I have a briggs book if you want more info on that engine




ALSO:


if you are in the business of hotrodding... I did a homegrown port&polish on mine (exact mower)! worked well.


--I've also run a 6", 3.5", 1.75" and 1.5" pulley on the transmission.... stock is ~10". My favorite setup is the 3.5". Tops out ~12mph with a little governor massaging.

6/9/2009 10:55:48 AM

Dude, I can do those carbs in my sleep, with both hands tied behind my back, blindfolded, with just my tongue.

Got my 25 year old Murray running like a champ. What 69 said...clean that carb out. The needle in the middle of the bottom of the float bowl is high speed mixture. The one on the top of the carb is the idle.

Turned up the governor on mine...she'll tote the front wheels GOOD now in 5th. I must have pulled them about 2' at least...and maybe 3. HIGH, that is.

Jeepman has seen this feat.

[Edited on June 9, 2009 at 11:01 AM. Reason : LOL...wheeliez on the Murray POS.]

6/9/2009 11:00:49 AM

The motor does have spark. I grounded the plug myself and saw it. I don't think it gets wet with gas. It may in fact be a carb/fuel issue which is why I am seeking TWW knowledge. First thing I will do is clean everything out.

Now in the pic I posted which has certain components numbered, help me label this so there is no misunderstanding:



1. main mixture screw
2. high speed mixture
3. unimportant?
4. I see this linkage moving when the adjuster lever (choke, drive, etc) is in certain positions
5. idle

6/9/2009 11:53:38 AM

1. idle screw
2. main jet (not an adjustment, you unscrew it to take the jet out)
3. air filter housing screw
4. throttle linkage
5. air filter housing screw
6. mian adjustment is in the center of the float bowl nut

linkage for throttle plate thing - choke linkage

[Edited on June 9, 2009 at 12:00 PM. Reason : just take it apart, it hase 6 friggin pieces man, it's not a 4 barrel rochester]

6/9/2009 11:58:47 AM

Quote :

"Canadian-spec"

i see your problem.

i'll bet a dollar the needle/float is hung shut or hung open. make sure it doesn't have any pinholes in it either when you pull it. they develop with age/neglect and then you have a gas logged float that won't seal the needle to the seat.

6/10/2009 10:54:24 PM

wait. you are building a rotory motor, which clearly takes rocket surgery to get to work, but you can get a riding lawn mower started.

j/k man. im going to have to agree with the above

6/10/2009 11:07:22 PM

I do feel like a little bitch right now. This mower is kicking my ass. I was on the phone with zxappeal for a while and we couldn't figure it out, although he may be able to quickly get it figured out if he comes by. We pulled the carb off and cleaned it thoroughly with carb cleaner. We sprayed the motor intake and exhaust ports pretty good with carb cleaner and flushed it all out with turning the motor over. We set the idle screw and the main screw (bottom of float bowl right?) to 1.5 turns open.

We tried putting gas directly into the engine. We tried adding it directly into the carb. We tried starter fluid. We compression tested it and it was at 80psi cold. We tried different positions on the selector lever, mostly "choke" or "fast." The plug is still getting spark when we ground it out and based on my untrained eye it is at least a somewhat regular spark. My friend did some kind of adjustment to the points as well. The fuel line is clean. Yet no matter what we do there isn't so much as a sputter from the thing.

Quote :

"i'll bet a dollar the needle/float is hung shut or hung open."

Which screw is that? Which number from the pic I posted? I pulled the jet out of the carb and inspected it, it looked good. With the jet out I put a bunch of carb cleaner in the float bowl and then drained it all out.

6/11/2009 1:39:23 AM

the float is the little doughnut looking thing made of brass inside the bowl on the bottom of the carb. the needle is attached to it. in combination, they regulate the fuel flow/level in the bowl. setting the proper float level is important as well for fine tuning. one of if not the most common problems with that style carb if they sit is them sticking closed or open. hordes of bikes/atv's use that style too. if you know one is going to be sitting long, you should always shut off the fuel and pull the screw on the bottom and drain the bowl. some even have a little drain plug beside the adjustment screw.

as for baseline settings, i've always used 2-2.5 turns for the one on the bottom of the bowl, especially on a cold motor. it shouldn't make much difference though, as long as the float is working and the needle is sealing they'll at least hit or run poorly on damn near any setting.

all that aside, since you didn't get any results from putting something flammable directing into the intake i would turn my attention to spark/timing. it's definitely possible you're getting some spark but not enough to ignite anything. things to check:

-is the plug gapped somewhat close?
-is the magneto gapped correctly to the flywheel?
-are the points gapped correctly to the condensor?
-are there any holes burned through or other deformities on the points?
-is the condenser grounded well?
-cracks/dry rot along the plug wire?
-is the flywheel/crankshaft key in good shape (i.e. not sheered or missing)?

personally, i hate points and eliminating them from the equation would be my first move. a fresh plug wouldn't hurt either. solid state ignitions are fairly cheap, perform better, and require 0 maintenance. a kit to replace/rebuild the points is probably a lot cheaper though. do one of the two either way.

i've got a briggs & stratton service manual around somewhere if you want to borrow it. it's just a matter of finding it...

6/11/2009 2:37:30 AM

Quote :

"one of if not the most common problems with that style carb if they sit is them sticking closed or open. hordes of bikes/atv's use that style too. if you know one is going to be sitting long, you should always shut off the fuel and pull the screw on the bottom and drain the bowl"

yep, i have to drain the bowl on my boat motor after every fishing trip. that gas/oil mix will gum the needle up quick.

6/11/2009 7:07:09 AM

you should be able to run the mofo off of starting fluid, get rid of the damn points setup and put a newer coil on, or you can get a kit for your coil, both less than $30

6/11/2009 10:58:37 AM

you should be able to run the mofo off of starting fluid, get rid of the damn points setup and put a newer coil on, or you can get a kit for your coil, both less than $30

6/11/2009 10:58:58 AM

Bringing back this thread with new info. The mower is mine, and here are the model numbers etc:

11 HP Briggs and Stratton 4 Cycle

Model 252707
Type 0132-01
Code 82032411

New parts:
-Coil
-Spark Plug
-Starter Solenoid
-Battery

I tried to clean the points and it didnt make a damn bit of difference. The spark just seems too weak to ignite the flame. I dont know what its going to take to get this damn thing to run.

6/25/2009 3:12:43 PM

is the air gap set correctly between the coil and flywheel?

6/25/2009 3:32:01 PM

^good idea. when i raced karts we ran 5 hp briggs and set that gap w/ a piece of doubled up oil filter cardboard that miced to be pretty close to what we wanted

6/25/2009 5:31:03 PM

^^, ^ pretty sure i mentioned all that like two weeks and several posts ago.

^^^cleaning the points is only part of the equation. if you insist on keeping them and not converting to solid state, you need to invest in a rebuild kit. they're cheap as hell. if you've cleaned the points contacts, they're gapped correctly, not pitted, the flywheel/magneto is gapped correctly, then it's got to be the condensor. get on it! this thread should not still be going on.

6/26/2009 2:30:07 AM

^^wasnt so much of an original idea as a double check

6/26/2009 8:01:27 AM

word up magazine

6/26/2009 9:55:33 AM

have you checked the resistance across the points?

stick the condensor to your tongue, is it any good?

6/28/2009 8:41:32 PM

7/21/2009 1:06:59 AM

[Edited on July 21, 2009 at 9:36 AM. Reason : psi]

7/21/2009 9:08:48 AM

i had a dream that i was a pro lawnmower racer last night. this is wierd

7/21/2009 11:13:11 AM

haha THE TRIMINATOR




arghx needs that dremel p&p and a 1 of 1 long tube header made specifically for this mower

7/21/2009 11:16:51 AM

I did that with a Briggs 8hp motor. Also trimmed down the valve stem just a tiny hair...enough to totally negate the "Easy-Spin" starting, which is essentially just a tiny little bump on the exhaust cam lobe to provide a lil bit of compression relief. In order to crank, you'd have to rotate back off of compression enough to build some momentum or you'd tear your arm out of the socket and/or shear the flywheel key. Oh, and electronic ignition module. all of 10 bucks.

She'd run like hell. On a Clark Bobcat dunebuggy style frame with a CVT. It was much heavier built than those Manco pieces of shit.

7/21/2009 11:21:10 AM

yeah im sporting the 400cc briggs 11HP.

GOT THAT 190% GOV-NAH override as well. we turn whaever my foot demands.

7/21/2009 11:24:35 AM

that video could only be better if you were wearing a cape

7/21/2009 11:29:47 AM

we built a yard kart once w/ a leftover 5 hp briggs from a kart racing outfit we bought. steel sleeve motor that had a 14" straight pipe, carb had been setup on a flow bench, billet lifters, hardened keepers, we cut valve pockets, Dyno slapper cam that was floating the valves, cut the head on a belt sander, "unbreakable" rod with some kind of lightened racing piston we found in one of the boxes of junk. we ordered some kind of CVT/torque converter thing because we had some pretty big knobby tires on the back. strapped it all on an old murray frame that had been replaced on warranty when the steering wheel fell off the steering shaft. we welded that back on, bought some spindles and tires, fabbed up some pedals and linkage. very last thing we put on was brakes. it took about 30 yards to stop that thing from wide open.

[Edited on July 21, 2009 at 11:52 AM. Reason : d]

7/21/2009 11:52:37 AM

I am humbled.

7/21/2009 12:06:04 PM

this may end up being a mini buildup thread

first of all, we converted to solid-state ignition after finally getting the part. My question is, the coil assembly looked so much simpler than the old points setup--what is so high tech about it that it wasn't used in the first place on mowers?

second, the jumping is pretty solid on this thing since all the mowing stuff has been removed for weight reduction. the storage place we keep it at actually has a few steep inclines in the concrete. one of my friends was getting 2 feet of air and doing some BMX shit with the front wheels. But this thing needs more top speed. Where can I get some pulleys and how much do they cost? It's probably maxing out at 10mph right now. I know you can get a lot of mowers up to 25-30 without much modification.

third, is there some kind of governor we can adjust or any other kind of free mods possible here that don't require much work?

And we've been thinking about doing a custom smoke stack or something on there. but we went to see if we can retain the muffler because it really is pretty loud since we always run it at full throttle in 5th. We pulled the muffler off initially but it was just too loud to carry a conversation.

7/21/2009 12:21:10 PM

when i say "murray frame" i meant one of those murray go-karts like they have at walmart, not a lawnmower.

^definitely make sure it doesn't have any type of governor in it. most of my small engine experience is on the 5 hp briggs motors that we raced with. for yard kart stuff, all you had to do to disable the centrifugal governor on a stock 5 hp briggs (they put these motors on a lot of tillers) was to remove the linkage from the little pin thing that flew out to the carburetor. i don't have a clue about that motor.

we also rebuilt a 1 cylinder kohler motor for a 70s something john deere, but it was built for reliability and not fun

7/21/2009 12:48:34 PM

Quote :

"But this thing needs more top speed. Where can I get some pulleys and how much do they cost? It's probably maxing out at 10mph right now. I know you can get a lot of mowers up to 25-30 without much modification. third, is there some kind of governor we can adjust or any other kind of free mods possible here that don't require much work? And we've been thinking about doing a custom smoke stack or something on there. but we went to see if we can retain the muffler because it really is pretty loud since we always run it at full throttle in 5th. We pulled the muffler off initially but it was just too loud to carry a conversation."

I'm going to go ahead and say [NO] to the estimated 10mph top speed. more like 5 (if that.)


from my post way above:

Quote :

"if you are in the business of hotrodding... I did a homegrown port&polish on mine (exact mower)! worked well. --I've also run a 6", 3.5", 1.75" and 1.5" pulley on the transmission.... stock is ~10". My favorite setup is the 3.5". Tops out ~12mph with a little governor massaging. "

the limiting factor on the gearing is the input shaft speed on the trans.... if you ever get up to 4-5k rpms on that engine, wth a 1.75" pulley... the input is turning something close to 10k. that thing whines.

things to consider:

- get the tallest tire you can. this obviously increases gearing with no change in transmisssion revs.

- the factory clutch design will not work with anything smaller than a 6" pulley. that size is no fun anyway... so you are left with adding an idler pulley to move the belt out of the way of the clutch arm. this decreases the amount of wrap on the driven (trans) pulley as well... which sucks because the belt will actually rotate around the pulley whenthe clutch is engaged. I have eaten through a pulley due to that reason. .---the other option is to increase the diameters of both pulleys (to max size allowable for fitment on the drive pulley.), based on your gearing calculations.


- attach a cable to the gov/throttle linkage on the side of the engine... then run it to a pedal.

- I can share my long-tube header design if you want... not too loud

7/21/2009 1:32:15 PM

so what ended up being the thing that fixed it? just switching to solid state ignition?

7/21/2009 2:19:45 PM

solid state ignition fixed it immediately. we had already cleaned out the carb and re-adjusted the screws, so stuff was fine

7/21/2009 3:55:33 PM

let me sell you a header design

7/21/2009 3:59:49 PM

I'd bet that it had a shorted or burned condenser. Kill's em every time.

7/21/2009 5:04:20 PM

6/11/2009

Quote :

"personally, i hate points and eliminating them from the equation would be my first move. a fresh plug wouldn't hurt either. solid state ignitions are fairly cheap, perform better, and require 0 maintenance. a kit to replace/rebuild the points is probably a lot cheaper though. do one of the two either way."

7/21/2009 6:13:59 PM

if you cut a key in half and weld it in right, you can flip the engine pulley and drive the tranny with the big end

[Edited on July 21, 2009 at 7:44 PM. Reason : drill holes from the outside of the pulley shank and plug weld the key in]

7/21/2009 7:43:26 PM

^^ we got sidetracked on other projects (actual cars) and it was a little harder to find the part because the motor is so old

7/21/2009 8:06:49 PM

lol, there are only two for 8hp and up, pre '71 and post '71

you wouldn't believe how much shit is interchangeable

7/21/2009 8:35:43 PM

Quote :

"- get the tallest tire you can. this obviously increases gearing with no change in transmisssion revs."

My friend just bought new tires for the front and doesn't want to spend money on the rear since they're still good, so that will be a long way off.

Quote :

"the other option is to increase the diameters of both pulleys (to max size allowable for fitment on the drive pulley.), based on your gearing calculations."

Say I went with the 1.75" pulley. How would I calculate what size the other pulley should be? Where do I get these pulleys? Are they OEM Briggs and Stratton pulleys off other mowers? A quick google search didn't help much.

Quote :

"attach a cable to the gov/throttle linkage on the side of the engine... then run it to a pedal"

yeah we'll do that eventually. But we pretty much run it at WOT right now (the lever all the way up but not in the choke position) so I'm not sure if that's going to be important.

Quote :

"I can share my long-tube header design if you want... not too loud"

how are you attaching it to the engine? You are removing the factory muffler thing right?

7/27/2009 12:02:22 AM

the exhaust port is 1" pipe thread inside, you can make your own exhaust with a trip to lowes for some black iron pipe

8/4/2009 11:46:13 AM

i did 1" with a plaz'd 2 bolt flange (stripped threads)

stock header from a 95 polaris magnum 425

the tip is a turndown from a stock jetta exhaust (one with the tiny dual turn-downs)



this thing exits in front of left rear wheel

Quote :

"Say I went with the 1.75" pulley. How would I calculate what size the other pulley should be? Where do I get these pulleys? Are they OEM Briggs and Stratton pulleys off other mowers? A quick google search didn't help much."

well technically a 1 3/4" pulley would work decently with the stock engine pulley... they are available at tractor supply - 5/8" shaft diameter. dont get the cast aluminum ones. You will have to reset the clutch position and add an idler. one of these days I'll get mine out and take some pictures

[Edited on August 4, 2009 at 1:22 PM. Reason : -]

8/4/2009 1:05:56 PM

yeah, if you dont support the pipe, the weight/vibration will strip the threads or crack the block

8/4/2009 5:54:36 PM

^^^i'd go galvanized here... get a few different lengths so you can tune it. a two hole floor/wall flange also almost lines up perfectly with the holes you might have on the block. just have to wallow them out a bit in some cases.

8/4/2009 6:39:35 PM

and pork and beans

8/6/2009 9:12:52 AM

man down... blew out one of the oldass rear tires. when we get around to it I think we're going to the pulleys at the same time as new tires

10/3/2009 10:20:05 AM