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chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

Murry riding lawn tractor re-engine

Due to a tale of woe that I'm not gonna get into, our 1995 Murry 42" lawn tractor ended up with a worn out (now seized engine) Poking around the web, I found that the exact B&S 14.5 HP replacement engine had a price of just over $1K. You can buy a low end lawn tractor for that!
After digging around some more, I found a new 18hp B&S engine for just under $400, delivered. (with a shipping weight of about 80lbs that's quite good!)
The engine is a common engine for many of the current lawn tractors, as well as sort of a universal replacement for many older tractors.
What are the differences? (Other than HP?)
Old engine had the classic metal shroud, new one has a plastic one.
Different air filter and housing.
same shaft size and length.
Different wire colors and termination plug.
No muffler and no exhaust extension pipe.

I thought this cannot be too big a problem, considering that I was used to dealing with equipment that had hundreds of wires going and coming- after all, there are only a few wires involved.
Starter Positive lead - rather obvious due to size terminal, and red color.
DC output from on engine alternator obvious, due to inline diode.
Fuel cut solenoid grey, also easily traced by gently pulling the wire.
Now comes the more interesting wires
Magneto shutdown lead usually black
AC lead from alternator also usually black

Mower side two two pin connectors matching two connectors on old engine.
Wire colors change at the connectors.
The factory wiring diagram is of poor quality, and almost useless, due to lack of detail at the ignition switch.

New engine came without information concerning the single 6 pin connector as to what was what.

Three of the leads are obvious
Starter positive lead
Fuel Solenoid lead
DC alternator output

Not so obvious, and can cause possible damage if not connected properly
Magneto shutdown/ground lead
A/C alternator lead.

To add insult, the new six pin connector is a molex style connector with larger pins than the old connectors.

At this point, I've identified the tractor side leads, and the new engine leads.

Next effort (when it stops raining, likely tomorrow)
Mount new engine (Spent today getting the old engine off and cleaning up the mower with a pressure sprayer. The old engine had a lot of time, was using oil, and had a leaking lower seal to boot!

I was going to use a new muffler. Unfortunately, the correct exhaust extension for it has not come in, so I'll reuse the old one.



Msradell
P.E.
Premium
join:2008-12-25
Louisville, KY

Have you looked here: »www.gobookee.net/briggs-and-stra···-wiring/ for the wiring diagram for the motor you have? I have them available for most motors.


chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

1 edit

Click for full size
Actually, the tractor was the bigger hassle. Right now, I'm trying to find a source for the mating 6 pin male pin connector, so that I don't need to mess with the engine connector.

The way I went about things involved pulling the metal shroud from the old engine, tracing the wires back to the wires from the tractor, and marking them. I did finally find the engine diagram for the new engine on the web, and checked it against the engine.


DataDoc
My avatar looks like me, if I was 2D.
Premium
join:2000-05-14
Martinsburg, WV
Reviews:
·Comcast
·Suddenlink

Try this place for the Molex connector: »www.parts-express.com/pe/showdet···aign=pla
--
Whatever doesn't kill you makes a great story.


chuckkk

join:2001-11-10
Warner Robins, GA

The parts express Molex connectors are similar, but not a match! This connector
has 3 "D" shaped contact wells, and the Molex has all circular wells.


HarryH3
Premium
join:2005-02-21
kudos:3
Reviews:
·Suddenlink

You'll find that connector on many Craftsman (Made by AYP?) tractors. I've looked at a couple of parts sites, but it seems they only sell the complete harness. Maybe find a repair shop that has a parts graveyard that you can scavenge from?



DataDoc
My avatar looks like me, if I was 2D.
Premium
join:2000-05-14
Martinsburg, WV
reply to chuckkk

Maybe you could just replace it with the Molex, if you know how to solder.
--
Whatever doesn't kill you makes a great story.


MrFixit1

join:1999-11-26
Madison, WI
reply to chuckkk

Take a very close look at the back ( wire ) side of the connector .
If you are lucky , you will see a part number for the connector housing .
Buying " Molex " connectors is like buying paint , there is an almost infinite number of choices
If the pins look the same , and only the housings are different . you will find that the pins are removable from the housings allowing you to reuse the old housings .
Only try this if the pins are identical !
The best online source for parts like this is »www.digikey.com/?curr=USD , but using their online catalog can be a pain .


iknow_t

join:2012-05-03
reply to chuckkk

all the info you should need , with the part no's for the connectors is here. »www.briggsandstratton.com/us/en/···ment.pdf

Expand your moderator at work


LazMan
Premium
join:2003-03-26
canada
reply to chuckkk

Re: Murry riding lawn tractor re-engine

I put a new engine in my old Craftsman tractor last year...

After several days of trying to find a connector to mate with the harness from the engine, I ended up chopping it off; and just used individual butt-connectors to splice the wires one-by-one; then wrapped the entire bundle in tape, and some split-tube to make it pretty...



shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA

1 recommendation

^^^ this

I have swapped a dozen engines. I try an keep extra connectors from the old mowers but on the 6-pin, I often just splice it in.


chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

1 edit

The connector pins are the same as the molex style pins used
on P/C old style HDs! That's fortunate, since Radio Shack carries the pins (and several molex shells, just not the series with the three "D" shaped holes. What I'll likely do is not use the connector shell, and individually sleeve the mated connector pins with shrink tubing. The molex pins suffer from all the classic problems associated with the "ear" retaining scheme. We easily removed three of the four pins from the six pin shell. One pin had a folded ear making removal difficult. I have access to the correct crimping tool, but will wait until tomorrow, when the shop is open.

The only confusing factor in the engine wiring can easily be solved by removing the plastic shroud, and confirming which black wire goes to the magneto.

What got to me was that the wire colors are sort of standardized, except when they are not. (Both engines and tractors!) On the older engines, using two two pin connectors, which of the magneto and AC alternator wires appeared on which connector varied.

On the tractor side - -
Using an ohm meter, the light circuit can easily be traced from the light wiring to the alternator A/C lead if the light circuit does not run through the ignition/start key switch. Some tractors have a light on position on the key switch. By disconnecting the battery, it is relatively easy to safely trace all the needed wires- if you select the appropriate key switch positions for the trace.

The seat interlock switch is a player for the magneto grounding lead.
IE Key switch in the run position, seat occupied, Mag ground line not grounded. Seat unoccupied, Mag ground line grounded.
Key switch in the off position, Mag ground line grounded regardless of seat switch.
Alternator DC wire usually hard wired to battery plus through a fuse and possibly an Amp meter.

Fuel solenoid wire connects to battery plus when key switch is in start and run positions, open in off position. A few tractors had an upset switch that can open the fuel solenoid line.

The biggest problem so far was getting the spring loaded drive belt tension pulley in the proper position to put the drive belt back on the motor drive pulley. It takes two people, or some fancy type of clamp or block. We used a piece of rope and a 2x4 as a lever.

Monday, weather permitting, the rest of the underside belt guides, mower deck, etc. will get put back together.

One other little detail. Seems that the typical lawn tractor battery can be "fast charged" at up to about 6A for a short period. Then 2A or less until it's fully charged. I have a "fancy" computerized multi chemistry charger intended for use with various batteries from LIPOs to PB. You can charge (to a usable level) a tractor battery in a few hours, but to fully charge properly, it may take about 12 hours or so. The allowable charge rate tapers to a low level as the battery gets closer to the correct voltage. The fully charged voltage range varies a bit -
13.8 to about 14.6, depending on the exact PB battery chemistry. Slow charging is better, since it helps to properly reform the plate surfaces.


HarryH3
Premium
join:2005-02-21
kudos:3
Reviews:
·Suddenlink

said by chuckkk:

The biggest problem so far was getting the spring loaded drive belt tension pulley in the proper position to put the drive belt back on the motor drive pulley. It takes two people, or some fancy type of clamp or block. We used a piece of rope and a 2x4 as a lever.

Sounds like you're having a fun time.

I don't understand the problem with the drive belt. On my Craftsman, all it requires is to press the clutch/brake pedal, and lift the brake-lock lever while releasing the pedal. Tension is released and the belt can be easily changed.

chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

The old Murrays with the hydrostatic tranny are not that easy.
If you don't get the drive belt and tension-er just right, there is a strong chance of damaging the plastic tranny cooling fan blades.
Actually, the rope and 2x4 trick worked well. The initial difficulty was getting the rope around the idler pulley arm. (Work by feel)

I ran into another little "gotcha". Seems that the new engine throttle adapter bracket with the slider and throttle cable clamp looks identical, but is not. The cam that pushed the choke via a sliding wire loop is about 1/2 inch short of contacting the sliding wire loop.
The new engine did not have anything connecting to the carb choke arm. in addition, a screw was installed in the #3 position.

Perhaps the engine variant was originally intended for a constant speed application, such as a pressure sprayer or vertical generator?
In any case, a hydrostatic drive mower, using the current models as a guide, can use either a constant speed or a more normal version.

I'll do a first time fire up tomorrow, and see if I need to reuse the throttle bracket from the old engine.

There still is a muffler to plastic shroud clearance issue to be solved. The frustrating part is that engine mufflers seem to be another thing that is not very well documented or even organized.

If my neighbor had re-licensed his utility trailer, I'd use it to haul the mower to the briggs service dealer on the other side of town, and see what they have that fits. It's a big hassle to load the mower onto my pickup. The wheel wells get in the way, and getting the mower over them is the hard part. (At least without scratching things up.)

If all else fails, the short cylinder head to muffler pipe could be cut and extended. (Involves a trip to the welding shop, etc.)


iknow_t

join:2012-05-03

1 edit
reply to chuckkk

all the pulleys should have steel rods that prevent the belt from coming off the pulley too far. and you'll want to get that choke working. you should just have to adjust the cable so when in choke mode, the cable extends far enough to activate the choke. by pushing the outer part of the cable further in the clamp. I assume you have a one control for idle/fast/choke? the newer engines may need a separate cable for the choke and throttle, depending on the way the engine is set up, but can be changed. and if you look up that engine on the briggs site, they have a lot of info on various mufflers that can be used on it.


chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

With the available mufflers, I can reuse the Murray original muffler if I use a second extension pipe to move the muffler away from the plastic engine shroud. Or, with a new extension pipe, I can use a newer style rectangular muffler. I looked into several solutions and parts. On that interested me, if nothing else works, was a long bent exhaust pipe, and use an automotive small engine muffler. Naturally mounting can be a problem. Murray used a plastic nose on the hood, and plastic skirts as well, so the muffler and pipe need to stay away from those as well as the engine shroud.

A fly in the ointment for Tuesday was that the the starting solenoid coil is not getting 12v wwhen the ignition switch is in the start position. The fuel solenoid does get power, so 12v is making it to the ignition switch. It's likely that a start interlock switch is involved,
and it's probably gonna be on the underside of the chassis and hard to see. It might have gotten disconnected during pressure washing or during belt/pulley work. Going direct from the battery to the solenoid coil allows the starter to operate, so the solenoid is OK.

Spent half the morning looking for the Molex pin crimper so that I could return it to the computer shop. Didn't find it. After work my son told me that he had stopped by on his way to work, picked up the crimper, and taken it to the shop for me. Guess he though he might need to use it.


chuckkk

join:2001-11-10
Warner Robins, GA

Next chapter in the saga!
Found the start circuit problem. A connector on the underside was disconnected. (Neutral Switch) Engine runs, but needs governor adjustment.



shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA

Why do you say it needs a governor adjustment? RPM too low?

If it is "hunting" in RPM that would be a mixture issue.


iknow_t

join:2012-05-03
reply to chuckkk

said by chuckkk:

Next chapter in the saga!
Found the start circuit problem. A connector on the underside was disconnected. (Neutral Switch) Engine runs, but needs governor adjustment.

it's probably just a throttle cable adjustment that's needed. don't try to adjust the governor without an accurate and properly set up tachometer. if that flywheel explodes from excessive speed, it can kill you..

chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI
reply to shdesigns

The Mixture adjustment screws are a thing of the past on the new engine! As supplied, the choke butterfly has a spring load in the carb. No wire connecting link between the throttle bracket cam and the choke. Screws in "R" and "#3" on the bracket.

What I'll end up doing - -
Remove R & #3 screws. Adding wire connecting like from old engine.
Using my automotive timing light with built in tach to see what the max engine RPM as shipped is, and the governor arm position.
Move the Governor arm slightly on the governor shaft.
See if the engine RPM went up or down.
Readjust as necessary in the proper direction.

Gave the old engine less some parts to the local parts dealer.
(Gets it out of my drive and garage.)
Known good parts left were magneto, carb, starter, fuel solenoid,
alternator, and flywheel. Since the engine was in use from 1996,
and burned oil at an ever increasing rate, it would have required at least an overhaul. Parts and so forth might have exceeded the $399 cost of the new engine, even before my stupidity with the oil.
Two summers ago, it was obvious that the 42" Murray was quite long in the tooth, to say the least. Sears had a sale going, and with various discounts, I ended up with a y4000 24HP twin cylinder
manual tranny mower for right at $1500 when all was said and done. It seems to do well on my large hill. The Murray has the advantage of automatic convenience, but the price paid is poor uphill drive.
Either will tow the D/R leaf vacuum I have. (Trees, leaves, etc.)

I don't mind doing such things once in a long while, and it's been decades since I had anything to do with small engine replacement and overhaul. Naturally, that increased the time needed, if for no other reason than having to find various tools as I needed them.
At my age, it takes a lot longer to do things than it did a couple of decades ago.

I used to buy 21-23" push rotary mowers for less than $100, and scrapped them when the engine was shot. Like everything else, the old $99 mower is about double in price, and those with a powered drive just that much more.

At 68, I'm really not into pushing a lawnmower around in the GA sun.
(About an acre of grass to cut!)



Cho Baka
Premium,MVM
join:2000-11-23
there
kudos:2
Reviews:
·TekSavvy DSL

said by chuckkk:

At 68, I'm really not into pushing a lawnmower around in the GA sun.
(About an acre of grass to cut!)

Get a goat!
--
The talented hawk speaks French.

chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

Property is not zoned for agriculture! (No goats in other words!)
Anyway - -
Had a chance to work on the throttle operation a bit today.
Idle is now correct, was too high.
Adjustment to the throttle cam on the side bracket brought the idle down to normal, and, using the choke wire link from the old engine, adjusted the side plate choke cam.
It looks like I'll end up using the frequency measurement capability of one of my DVMs likely by connecting it to the magneto kill wire.

One cylinder engines with a flywheel driven magneto fire once per revolution, and have an inherent "waste spark" feature on a four cycle engine.
So - 3600 RPM/60 =60RPS, or a sort of 60hz signal on the magneto line.

An associated task has to do with the drive belt idler/tensioner.
It looks like there is enough wear to cause something to scrape.
(Pulley bearings or bushings are suspect.)

The replacement engine as out of box, was setup for separate throttle and choke cables. The original engine setup was for a combined throttle/choke cable.
(Details, details.)

The governor lower spring called for by the "books" is a green spring.
The one on the new engine looks like it is not color marked.


chuckkk

join:2001-11-10
Warner Robins, GA
Reviews:
·Cox HSI

After a break in and misc minor fixes, etc. the mower is back in service. Engine runs well after a short warmup.
I about had a heart attack the other day. One of the first mowing runs for any length of time, and with all the up and downs on the hills resulted in some oil on the top rear of the block and the seal where the upper and lower block are joined. Checked the oil level, was OK, but slightly above the top dipstick hole. Drained a small amount of oil, until the level matched the dipstick hole. Cleaned off block to see if the oil leak continued, and ran the next day without a problem. More extensive use planned when the weather permits. Leaves this time instead of just grass cutting. Still need to tweak the deck height and levelling just a bit.