Drive belt width

[Bazooo guy]

I want to replace my drive belt with one that is 1 1/4 " wide.
The belt that came with it was 1 3/16" and is running deeper into the secondary as it wears on the edges and the secondary cant close any further.

Question is will a wider belt work with my primary or will it engage too soon.
The primary clutch on the rotax lists a 1 3/16" belt should be used but im thinking if I install a wider belt that is a bit longer it might be ok.

[teeko]

If it is dragging on your clutch can't you just slide your motor back a bit to reduce tension?

[Bazooo guy]

The problem is the secondary cant close any further to push the belt to the outside so im thinking the belt is not wide enough.

[thebuggyman1]

Look at your primary and the belt you have now (motor NOT running). Push the belt to one side. How much clearance is there?
If you have 1/8" or more you will be fine. Going to a 1 1/4" wide belt is only 1/16" wider....barely enough to see.
I've done the same thing a couple of times and it works well. It makes the belt ride higher in the secondary and gives more low end because of it.

[Bazooo guy]

If it has the 1/8" clearance on the primary im wondering
if the belt is longer will it ride higher on the primary at idle and not grab
Or is that part of the tension and belt deflection adjustment?

[thebuggyman1]

I'm not following......
The belt deflexion has to be right for the clutches to cycle equally. The start of the climb in the primary= secondary starting to spread/belt sink.
A longer belt, without adjusting for tension, will mean higher rpms to engage, and higher gear ratio when it does.....and loss of efficiency/performance.

[Bazooo guy]

But with a wider belt wont the primary engage sooner?

[thebuggyman1]

Not really. To test this, watch your primary as you give the motor throttle. As it comes off Idle it will move that 1/8" clearance very quickly. At this point the primary has enough centrifical force to overcome it's internal spring(s), but no other forces to hold it back. The sheave will move quickly until it hits the belt. The resistance in the secondary will hold it from moving up the primary too quickly......unless the belt is loose, then it can move freely till it tightens.

[Bazooo guy]

Its a two stroke so the clutch starts to close around 4000 rpm.
Is that too high?
Its working like a stall converter right now so I guess im trying to
lower the engagement rpm without changing the internals of the clutch.
Can it be done by using a wider belt?

I realize the deflection needs to be adjusted and the belt needs to be longer than the one
I have now to make up for the diameter difference of the secondary.

[thebuggyman1]

4000 rpm sounds like it's set up for racing to me. What type of clutch is it, and how many R's can your motor turn?
In any case changing your belt will not fix this.

"I realize the deflection needs to be adjusted and the belt needs to be longer than the one
I have now to make up for the diameter difference of the secondary."
Too short of a belt will be tight on your primary's center at idle and the machine will still try to move before the clutch has engaged.
Looking at your original post/picture, I'd say that your belt is just plain worn out......maybe more pictures of the set up would help???

[Bazooo guy]

4000 rpm sounds like it's set up for racing to me. What type of clutch is it, and how many R's can your motor turn?

how else would you want it set up?
The clutch is off a 399 Rotax that idles at 1800 rpm.
The clutch starts to engage around 3500 and the engine redline is 7000 rpm
I usually drive it between 4000 and 6000.
Thanks Jim...... after reading your post and watching this video it looks like my belt is too short and there isnt much clearance on the primary so a wider belt would need to be longer to ride higher on it.
In the video you will notice:
The secondary will spin at idle if its in neutral.
When i put it in gear the secondary stops but still wants to creep.

http://www.youtube.com/watch?v=RGA4KYaoFzA

http://www.youtube.com/watch?v=5cHoc8NFE8w

The deflection is around 1 1/2"
What i noticed is i can drive on flat ground and the primary closes very little so the revs stay high.Good for climbing but im trying to get it to upshift a little sooner.

[Bazooo guy]

heres a picture of the clutch.



the belt is 1 3/16 wide and showing signs of wear on the edges.

[thebuggyman1]

Call Roy @ Quality Drive Systems he should be able to set you up with the proper belt.