Max IV Speed Mods

[fulleraviation]

After researching this fourm, I discovered that NONE of us can leave our machines alone!

As most of you have probably read in past threads, I have modified my 18HP Vanguard some, and installed the red clutch spring. Most of my riding includes 50 to 75 mile rides, and I am finding myself wanting more speed for the level fast trails.

I found that increases with RPM after the clutch runs out only gained 2.5 mph. At 4000rpm w/ the 26's at 3psi I am doing about 19.8/20mph. At 4500rpm I might hit 22 or so.

I pumped the tires up to 8psi which increased ride height 1/4". Not much difference in the speed.

Some of the older posts talked about a 25hp Kohloer with a high speed clutch, which is a canceled model. Could a high speed clutch be the answer w/o trying to change sprokets on the T-20?

I am already planning more mods to the vanguard that should really add performance.

I want to be able to run about 30mph.

So, to increase speed you could:

1. go with larger diameter tires

2. increase engine RPM

3. High speed clutch ??? not sure, hope someone can answer this

4. change gearing on T-20

5. ALL of the Above

What do ya think? Please, help me spend my money

[Roger S]

I'm surprised at your top speed, I thought a max was geared higher than that.. I'd think gearing (lower primary sprocket?, I have no experience with max). You'll need the extra ooph of engine mods if you gear it up.

[jerrynuss]

I think you are on the right track because I have an attex that has a huge primary clutch at least two inches in diameter over a stock max clutch.

[mightymaxIV]

After researching this fourm, I discovered that NONE of us can leave our machines alone!

As most of you have probably read in past threads, I have modified my 18HP Vanguard some, and installed the red clutch spring. Most of my riding includes 50 to 75 mile rides, and I am finding myself wanting more speed for the level fast trails.

I found that increases with RPM after the clutch runs out only gained 2.5 mph. At 4000rpm w/ the 26's at 3psi I am doing about 19.8/20mph. At 4500rpm I might hit 22 or so.

I pumped the tires up to 8psi which increased ride height 1/4". Not much difference in the speed.

Some of the older posts talked about a 25hp Kohloer with a high speed clutch, which is a canceled model. Could a high speed clutch be the answer w/o trying to change sprokets on the T-20?

I am already planning more mods to the vanguard that should really add performance.

I want to be able to run about 30mph.

So, to increase speed you could:

1. go with larger diameter tires

2. increase engine RPM

3. High speed clutch ??? not sure, hope someone can answer this

4. change gearing on T-20

5. ALL of the Above

What do ya think? Please, help me spend my money

Fuller I would be very carefull about gearing the T-20 up. You will gain some top end but lose some of that every important gearing you need for mud. I don't quite understand why you Max has a 20 MPH top end, mine is much faster but I guess I have a different driven clutch. But I think I have a solution for you. Bring that Max over to Savannah and run it awhile with Heath and I through the swamps. You won't have to worry about trails because there are none. You won't have to worry about top speed because you won't be able to go over 15 MPH anyway.(JUST A JOKE-BUT IT IS AN IDEA) Really- I never have to consider top end around here.

[liflod]

My 1999 Max IV with the 18 HP has hit 24MPH with 5 people in it. That was clocked by GPS. My friend rode behind me and clocked me at 24-26 MPH according to his speedo.

[liflod]

Are you sure your belt is tight enough? A loose belt will not allow full speed. Tight to me is about 1/8" play at the engine clutch while squeezing the belt and looking at the air gap on the crankshaft.

[fulleraviation]

I check the tension a little different, but do not have more than 1/8 of an inch air gap. It is also a new belt, just installed when I went to the red spring. Since day one it was only a 20mph machine at the most.

Got a call into RI to see what they say. Their literature says 20mph also. If it were faster you would think that they would boast.

Thanks,
Rut

[fulleraviation]

Well, I heard back from RI and they really do not know what to recommend. They suggested I check my RPM's against another tach. I will do, but I know that I am well over 4000rpm for sure and still getting less than 25mph at my reading of 4700 to 4800 rpm.

[mightymaxIV]

Are you sure your belt is tight enough? A loose belt will not allow full speed. Tight to me is about 1/8" play at the engine clutch while squeezing the belt and looking at the air gap on the crankshaft.

Fuller, I agree with lance your belt is not tight enough, if you put spacers under the engine the clutch will engage faster and you'll have better top end. Lance recommended this to me and it works. It also takes out that awful belt sqeak that I just hate! You might want to talk with Route 6x6 about a high speed clutch for your engine. Also your red spring might not be broke in yet. As it gets some hours on it it will losen up and hopefully increase your top end. For right now I woundn't do anything other than tighten the belt a little and give it some time.

[fulleraviation]

Been trying to get Richard on the phone, it's busy. I was going to check on a high speed clutch.

My belt is tight. At idle the belt is turning the T-20 just a little.

[fulleraviation]

That was a $300 phone call! I have a high speed clutch on it's way from Richard's Relics.

Look's like I will be moding the engine again soon!

BTW: I also spoke with Brandon Price the Missouri Max Dealer today. He seems like a great guy and spent some time on the phone with me. His advice was free and friendly. Anyone looking for a new or used ride should give him a call. He even has a toll free number 888-826-1704.

I will post again when the new unit gets installed!

Rutledge

[Roger S]

So how does this work, it's larger in diameter? Does the driven clutch have unused travel to open up wider/higher geared?

[fulleraviation]

Good questions. I do know that it is an 8 inch diameter and would assume that the driven clutch would open further, but do not know.

This is a $300 test. Dan Edwards "mightymaxiv" is the test bed for tires, I figured I could test the clutch. Keep your fingers crossed.

Richard said, it will NOT effect the low end.

I know, sounds to good to be true huh!

I will keep you posted.

Rut

[mightymaxIV]

clutch

So how does this work, it's larger in diameter? Does the driven clutch have unused travel to open up wider/higher geared?

Roger, the clutch is larger and expands the belt on top further out there fore increasing the ratio or making the ratio higher as you get into higher speeds. I am not sure but I think the Kawasaki engine already has a clutch very close to this.

[Roger S]

I understand the idea of a larger diameter on the engine's clutch, if indeed this is what it is. My question is what's happening on the t20's clutch. Does it have unused travel right now, 'cause it's gonna need it.