A Sears Craftsman 3 in 1 Convertible, B&S 18HP Twin, L-Head, 42” cut, Lawn Tractor.
Tractor Model 917.254860 Engine Model 422707 Type 152201 Code 92092112 See Pix

That I have a question 'bout the:

Clutch Drive.

I have a lot of trees, and shrubs to mow around so I do a lot of backing up. That part is okay, what gets me is the “jackrabbit” starts when going forward.
I know I'll get used to it after a while, but has anyone ever tried to modify the way it engages?

If I increased/decreased the spring rate of Part # 55 (middle-right of page 34) in the 3rd pix, Part # and description 105709X Spring Return Clutch 6 75 Would it make a difference?

Would a new spring make a difference? Using the engine code, the engine was made in 1992-93 ergo, the Tractor, and the spring would be approximately 17 to 16years old, and may have lost its resiliency.

Thoughts?

Regards

k

Hi,
Apologies for passing this over; the fact that the spring is older will only serve to reduce the aggresiveness. I will say that Murray had the only good solution I have seen. Normally belts grip by the angled sides. Their solution was to grip by the sides at the engine drive sheave and to grip on the inside flat on the transaxle input sheave. This allowed enough slippage to take out the aggressive engagement by a small amount of slip at the start of engagement. I know they share vendors for transaxles which means that the sheaves will directly interchange) but without looking up the gear ratios involved; I could not tell if an interchange is viable.
Peace,
Clarke

Not a problem crigby,

Your explanation gives me food for thought though.

::thinking out-loud:: Hmmm... I wonder if I could build-in some slippage by changing the belt dimensions... maybe the way the belt keepers are adjusted.

Thanks crigby I'll post back if I come up with an idea.

K

Hi,
Please feel free to try out some of my current references:
Lawn Mower Parts and Lawn Tractor Parts Snapper Cub Cadet MTD and More (http://www.outdoordistributors.com/)
Snowmobile Parts, ATV Parts, Go Kart Parts, Mini Bike Part, Lawn Mower Parts, Chainsaw Part and Small Engine Parts (http://www.mfgsupply.com/m/c/index.html)
For belt dimensions. I would actually think that a sheave swap would be more dependable. Murray actually had good success, though bad business practices elsewise.
Peace,
Clarke

Hi,
please feel free to try out some of my current references:
Lawn Mower Parts and Lawn Tractor Parts Snapper Cub Cadet MTD and More (http://www.outdoordistributors.com/)
Snowmobile Parts, ATV Parts, Go Kart Parts, Mini Bike Part, Lawn Mower Parts, Chainsaw Part and Small Engine Parts (http://www.mfgsupply.com/m/c/index.html)
for belt dimensions. I would actually think that a sheave swap would be more dependable. Murray actually had good success, though bad business practices elsewise.
Peace,
ClarkeThank you for the links.

The sheave swap would be "more dependable".

Last night, on the first site I found the Sheave part # AYP123667X was a good # for the DANA Transaxle that's in there. (Model # 4360-56).

Would finding the gear ratios, be just a matter of measuring the inner circumference of the engine and transaxle sheaves and division or would knowing the O.D. of the transaxle sheave be sufficient?

Regards
k

Hi,
Actual reduction is a matter of the ratio of the sheave diameters and the tooth count on the respective gears, mostly the gears though one is necessarily dependent on the other. I think a close diameter match of the transaxle input sheave will probably be sufficient. 1st gear is rarely needed and high gear gets you to and from the garage.
I add a Spicer breakdown which tells where I got it as well (one of my "prime" resources when answering here.) It tells the tooth count for each gear.
To explain the mechanics to it; power enters by #16 and is transferred to #42 which is locked to the splines of shaft #44 along with gears #46-49. All gears (# 29-33) on the adjacent shaft spin at their respective rates (determined by the tooth ratio) but do nothing unless the keys #22 happen to by locked into the recesses in the inner circumference of that gear. If locked into a gear, that gear and shaft #24 spin at a rate determined by the tooth count ratio which spins gear #20 that is locked by splines to the shaft. It meshes with the large part of #38 which has its smaller part meshed with the geared part of the differential #57. From there it is axles, wheels and tires and the movement from engine to transaxle to earth is complete.
That is except for reverse; those 2 sprockets and chain accomplish that. Gears meshed turn in opposite directions, and sprockets connected by a chain turn in the same direction which translate to directions at the axle. Of course, that could mean one forward and multiple reverses given the right circumstances (it actually occurs on a few models made - an old Simplicity Broadmoor can have 3 reverses and 1 forward if the twist in the belt is reversed.)
Peace,
Clarke

Thanks Clarke...

My Quest for a Murry transaxle input sheave begins...

Regards
Steve

There has been a recent spate of valve adjustment questions for the OHV engines, but as noted in my OP I have a 17 year old L-Head twin that to my understanding is much harder to adjust.

I would have to dis-assemble the engine down to the valves, replace with new valves, reassemble. Take a gap reading, and then grind the valve stem(s) to obtain the proper play.

I can vision this taking at least two, maybe three tries before I would get it with-in specs.

Can readings be taken before dis-assembly, and then go, and purchase the longer stemmed valves or could it be as simple as putting the (new) stock valves in, and be with-in specs?

Of course, New seats, seals, retainers, keepers, tappets, bushings, springs, lube, gaskets, torquing, would also be in the equation for the job.

One other thought,
Should there be any consideration to re-building the bottom end, since the top end will become stronger after the valve job.

k

Hi,
Current OHV engines generally require a once-in-a-lifespan valve adjustment in the first 120 hrs. That is the rocker arms, etc. seating in.
The older L-head engines have the clearance reduce from wear and tear and so tolerances get tighter. Since the disappearance of leaded fuels, almost no burnt valves or corroded mufflers. The valves can be removed, the stems ground to clearance and the valves lapped to re-seat.
Peace,
Clarke