Introducing "Merc", the Murray racin' rally!

Here's "Merc" -

Your basic everyday Murray widebody LT on the outside, with a couple zombie related decals of course. On the inside however...:

Modified briggs 28ci flathead w/ late model 'large magnet' steel flywheel (john deere briggs avs spec) and 9A charging system (regulated) with matching coil, steel ring gear, complete governor removal (keeping oil slinger installed), 25ci head with 'fire slot', atv carb upgrade with custom manifold, high flow 'cherry bomb' style muffler to be installed with custom manifold...  and a .67:1 overdriven pulley ratio from engine to lightly modified peerless 820 5 speed. The 820 is going in today, as is belt and new 1/4" fuel line from tank to carb

Sounds like a pretty fun machine! I didn’t know there were any performance gains from replacing the flywheel...how big are they? Enough to feel? I have a few flatheads and that seems like an easy way to get a little boost

CraftsmanQuad19 wrote:

Sounds like a pretty fun machine! I didn’t know there were any performance gains from replacing the flywheel...how big are they? Enough to feel? I have a few flatheads and that seems like an easy way to get a little boost

I don't know that it's a performance boost per-say, but what it does offer being steel over cast iron is likely like a lightened flywheel on a vehicle - faster throttle response. I figured it had to be cast iron too, but I guess there were a few AVS briggs out there that JD specified they wanted a steel flywheel. So, I used it. I THINK it'll be just a hair quicker off idle, than it would be with a stock type flywheel. it's just a tiny tad smaller, maybe 1-2MM under stock. So it also necessitated the use of the big magnet charging system as it too is just a hair smaller. At least in theory. Should be able to find out today

You know, I'm man enough to admit a mistake. It's still cast iron I think, but a much lighter casting. The information about a JD spec briggs with a steel flywheel is true, however I cannot find a 'real' one. Sorry!

Bit of an update to Merc - trans serviced, oiled and mounted. I created a check valve type vent after threading the fill hole and adding some appropriate fittings. The check valve is much like an air blow off valve, but very lightly sprung, I can give a good but gentle breath down the tube and it pops open. Figured that'd be a good setup for filling with more oil and speeding it up. Won't let anything in, but lets it vent. Also, decided on a set of ratios, not sure which I'll run now that I think of it - I have the option of an 8 inch front, which barely clears anything but will fit, or a 5 inch, or the stock 3 inch. I have a 3, 5, 6 and 8 inch for the rear. I'm considering making it about twice as fast as the last murray I had which topped out at 18 at stock rpm (governed). With no governor whatsoever, and the 8 inch front, I'm thinking the 5 inch rear would be perfect.

I put some 18x8-8 knobbies on it to get it back on wheels, but really don't like the feel - they're really really stiff for a 2 ply. I'm probably going to a set of 4 ply kenda speed racer @ 20x8-8 that has about 2 hours run time on the pair. Technically they're front tires, but have plenty of tread and beat turfs any day

I had hoped to get it done today to show off to the original owner tomorrow, but it just doesn't look like it's going to happen. Anyway, here are some pics of the work in progress: