Changing speed with sprockets?? Possible??

[newargoowner]

Can I increase the speed (+5 mph or so) of my Argo by changing the size of the idler sprockets on my transmission? (Would I need to change the chain links? add some? or not? This is a 1987 IC 8X8 with high and low range transmission.

[jerseybigfoot]

Yes there is probably room to do that, you would need a shorter chain. There are some calculations on line to determine the pitch and distance for the sprocket pitches. you don't want to chose a sprocket with a tooth count that requires a half link to work. you can also change gears in the trans. Check with ODG on which series trans you have. It should be stamped on the top of the trans. Check that the engine revs to the proper RPM and your clutch is working properly. the engine may also bog when you turn at the higher speed with a different gear ratio. More power is also good.

Nice hardtop

[Jeff t-boss]

Also remember that as you change your sprockets to increase speed, you will also DECREASE torque.

[Stonewall]

Can this be done on a t-20 machine too? I would like to give my Hustler a speed boost, and have been wondering what the best way to do it would be.

[newargoowner]

Thanks for the info. I picked it up last November. I have been working on it (when i can) since... It may need a new belt. The hardtop is a bonus.

[Robinhood02]

Can this be done on a t-20 machine too? I would like to give my Hustler a speed boost, and have been wondering what the best way to do it would be.

stonewall, yes you could weld bigger sprokets on the T20 (drive side) but it is easier to put a smaller sprokets on the driven side, go 2 teeth smaller increments at a time so you don't have to fiddle with half links ( i have done it to my Max IV)

[Stonewall]

it is easier to put a smaller sprokets on the driven side, go 2 teeth smaller increments at a time so you don't have to fiddle with half links

My driven sprockets are welded onto a sleeve that bolts on the axle, so they would be expensive to experiment with. I would like to get around 25-30 mph. I have a 25hp Kohler, and I plan on putting the 24" Argo tires on it. But I don't want to over do it and not have enough torque. What ratio do you have on your Max, and how fast does it go?

[Robinhood02]

yup that is exactly what i'm talkin about ,you take those sleeves and have the driven sprokets machined off and then weld the new sproket on in its place,(it is MUCH easier to do that then it is to remove the trani ,then rip the trani apart to get at the sproket shafts so that you can machine them off and weld new ones on , a far more expensive experiment) the new sprokets to fit your sleeve is about $6 each at your local brg store, to have the old ones cut off and the new ones welded on probly another $30
PS how many teeth on the sproket on the sleeve ? What size tires do you have on it right now ? and what is your top speed right now ?
i can do some calculations to achieve your desired speed
I removed 2 teeth and gained about 4 mph for a total speed of 25 mph with 21" tires and still retain enough bottom end power

[jerseybigfoot]

The best bang for the buck is to modify the engine to rev higher You will see a significant ground speed difference by getting the engine to rev to 5000 rpm. V twin Briggs and Kohlers can safely rev to 5000 rpm with removed governors, modified valve springs and cut keys on the flywheel to advance the timing. The stock carbs and exhaust wont let them rev much higher under load. This also gives you instant throttle response and better mid-range torque.

[Robinhood02]

The best bang for the buck is to modify the engine to rev higher You will see a significant ground speed difference by getting the engine to rev to 5000 rpm. V twin Briggs and Kohlers can safely rev to 5000 rpm with removed governors, modified valve springs and cut keys on the flywheel to advance the timing. The stock carbs and exhaust wont let them rev much higher under load. This also gives you instant throttle response and better mid-range torque.

but dont you sacrafice alot of reliability and longevity by doing those mods ?? those motors normaly rev about 2800 to 3200 rpm , boosting that to 5000 cant possibly be good for it in the long term , is it ?? and removing the governor doesn't that mean it could be over reved ? it's not like we have another gear to grab in these things to prevent that ?

[Stonewall]

PS how many teeth on the sproket on the sleeve ? What size tires do you have on it right now ? and what is your top speed right now ?
i can do some calculations to achieve your desired speed
I removed 2 teeth and gained about 4 mph for a total speed of 25 mph with 21" tires and still retain enough bottom end power

I currently have the origional 21" Rawhides on it, and with the K341 that (supposedly) runs 4000 RPM I get around 20-22 mph. I don't know the tooth count on the driven sprockets off the top of my head, but I will look and post that tomorrow. I am going to put on 24" Argo tires, and would like to get at least 25 mph, but would prefer more like 30-35 mph. When I put in the CH25, I am not going to use a stock exhaust, I am going for dual straight pipes out the side.

[jerseybigfoot]

but dont you sacrafice alot of reliability and longevity by doing those mods ?? those motors normaly rev about 2800 to 3200 rpm , boosting that to 5000 cant possibly be good for it in the long term , is it ?? and removing the governor doesn't that mean it could be over reved ? it's not like we have another gear to grab in these things to prevent that ?

90% of the time you are driving at the lower speeds. I have performed these simple mods on a number of engines without any issues. The problem with the stock engines in amphibians is they were made for fixed speed applications with fixed timing and fixed mixture carburation and not for motor vehicles. My intent is to not build a racing engine and race it. Although if you build a race engine with mild compression and a mild cam it will probably last as long as a stock engine if not longer. B&S Race engines like Bandolero's or Hodge's will have solenoid shift starters and will have more reliable starting. We recently put a small block Briggs Hodges engine in a Max 2 and not only does it have more usable power but its smoother and easier to control. We were also able to up the alternator size to 20 amp in the same package.
Yes you can over rev the engine the same as you can over rev your automobile.

[Robinhood02]

the difference in top speed in going from 21" to 24" tires is about 11.5% so it should increase your top speed from 22mph to 24.5 mph just by changing the tires ,presuming your rpm remains the same

[Stonewall]

I think that the CH25 runs about 3600-4000 rpm, but I don't know for sure. But it sounds like 35 mph is within reason, maybe 4-6 fewer teeth?

[Robinhood02]

I think that the CH25 runs about 3600-4000 rpm, but I don't know for sure. But it sounds like 35 mph is within reason, maybe 4-6 fewer teeth?

yes it doesn't sound like it can't be done and the 4000 rpm would sugest that it'll have the power to at least come close to maintaining that rpm, 6 teeth may be getting close to the 20% to 25% margin ,i suspect that will be too great of a change for that little motor. but it will really depend on what the count is on that driven sproket.
Dont forget , the SMALLER the tire the less stress on the chains, the smaller the sproket the greater the stress on the chains