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Maxwell-8

Overspeeding an 4/8-speed

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Maxwell-8

A topic about 2stroke swap a WH, got me wondering, My WH has a 1 to 1 polie ratio. perfect speed in all gears, and i would image making the low range gears more usefull.

I don't see much of a problem speeding up an 8 speed as everything is on bearings. What could be a problem when overspeeding a tranny. And how far can you go with polie swapping an 8 speed. 

3 gear Hi, you should start in a low rpm to keep belt slip en the front end down, but what else, should you look out for?

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ebinmaine

First. Let me just point out I am not a transmission tech or engineer in any way. 

 

My thoughts..... HEAT has a great potential to be your biggest issue. 

These transmissions are/were designed to work in a given RPM range. 

In that range they're pretty close to bulletproof given proper care and consideration. 

 

Spinning a bearing or gears faster is going to make more friction...and more heat. 

 

Where's the upper limit?

 

That I don't even dare to guess. 

 

There's a bunch of folks all over the interwebs and tubes running consistently at twice the OE speed or so. 

Much faster than that.....?

 

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Maxwell-8
3 minutes ago, ebinmaine said:

HEAT has a great potential to be your biggest issue

Do these trannys get hot? 

I know the cheap tecumsh alloy trannys, they all wear out at the top input because won't get any grease or oil and is not a roller or ball bearing.

 

Big reason i am doing it, is to be moving at a decent speed without screaming at 3600 rpm. i now mostly run at 2000rpm, sipping fuel. (but for mowing it ain't ideal.)

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ebinmaine
5 minutes ago, Maxwell-8 said:

Do these trannys get hot? 

.

 

Big reason i am doing it, is to be moving at a decent speed without screaming at 3600 rpm. i now mostly run at 2000rpm, sipping fuel. (but for mowing it ain't ideal.)

 

"Known" for overheating?

Not that I've noticed but others could comment. 

 

Most ANY piece of machinery that's run well above it's design limits is going to get heated up. 

 

Note the print in bold above...

It is legitimately possible that at a low RPM and under load you could be damaging the engine. 

 

These are AIR-COOLED. Also OIL SLINGING. No oil pump.  

Minimum rpm should be around 1/2 to 3/4 throttle unless just about to shut down. 

 

 

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squonk

How long a time period do you plan on running? If you're not going to enter it in the Grand Prix of Monaco you should be safe for sort runs. I would run synthetic gear oil.

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Maxwell-8
Posted (edited)
10 minutes ago, ebinmaine said:

 

"Known" for overheating?

Not that I've noticed but others could comment. 

 

Most ANY piece of machinery that's run well above it's design limits is going to get heated up. 

 

Note the print in bold above...

It is legitimately possible that at a low RPM and under load you could be damaging the engine. 

 

These are AIR-COOLED. Also OIL SLINGING. No oil pump.  

Minimum rpm should be around 1/2 to 3/4 throttle unless just about to shut down. 

 

 

INdeed, other manufactures recommend there engines  to run at a minimum of 1500 rpm, i run 2000 rpm little over 1/2 trottle,

and i will not do any mowing with it, mainly forest drives. at longest 1-1.5 hours. 

 

Have never heard of a manual tranny overheating.  but overspeeding could cause higher temps.

Will watching the temp of the fluid be an adequate determination of the heat?

 

Thing is i don't have much choice as the trans pulley is rust welded on.

 

Edited by Maxwell-8

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ebinmaine

IMHO.... If you're running twice the input speed and using synthetic oil as suggested by @squonk I'd really think there would be no issue. 

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Greentored
Posted (edited)

I'm running 1:1 on Hoss, my plow dog/worker's big 8 speed for this exact reason. Top speed maybe 9-10mph but still plenty of oomph to do heavy work.

My off road bomber also runs a big 8 speed at almost 2:1, top speed 18mph. Has been flawless, but broke a reduction gear on Friday, which so far appears to be a fluke or previous owner abuse.

My first trail bomb had a very noisy, worn out, small 4 speed and it ran 28mph. Never hurt it.

Many of the guys out playing with these Horses are running 15-20mph with zero issues, and a few closer to 30+mph with 25+hp v twins. At that speed I dont know what the life expectancy would be but so far appears pretty good- that input shaft is spinning well over 10,000rpms to attain those speeds, and im not doing it haha.

As for heat, I have the habit of feeling the trans case every so often, and amazingly there is little if any heat produced. I run straight 80/90 GL-5 with 1/2qt of lucas oil stabilizer.

Keep it under 15-18mph max and willing to bet it lives a long, happy life. These things are built TOUGH!

Edited by Greentored
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Vurge
Posted (edited)

I have my 656 running a 212cc (6.5hp) Predator and slightly upsized drive pulley.  Top speed is about 8 mph. I just finished several hours of spraying at 5mph (about 1/2 throttle in high gear) while towing a 35 gallon tank.  Used 3 tanks this morning.  Transmission wasn't even warm. The extra speed is nice for traveling back and forth between refills. 

 

 

 

Edited by Vurge
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