Belt change for upper end response

[tripplec]

My sled is sluggish at the upper end. The RPM do get up to about 8k but top speed is below the sleds ability. I had feedback the the secondary clutch sheave spacing could be an insue (Large sheave contect to the chain case). The belt is slightly worn in my estimation. 3-4mm below the top of the sheave. I have a spare and it is the same width as what is on it. I got the sled this way and have not replace the belt. I haven't put many km on it myself about 1000km in two years. Bottom seem fine and reverse is too torquey (digs a hole and I get stuck) even with easy throttling. This had a fuel/temp management system for the carbs with Normal/Oxigen settings on a switch. Our gas has ethenol added and may be considered as oxigenated but . I can't say it makes it difference in my drive. I does seen to drink oil but I was told that won't slow it down.

I can see that the belt change appears complex and maybe a special tool is required and I hope to pickup and try a new belt this season.

Any help with the belt change process and/or what might be slowing it down would be helpful. I noticed some info that mutiply head gaskets were used. I can see only one(or it certain appears as one) below the cylinder top about 1/16th thick.

Thx

 

[grapeape]

3 small bolts on the back of the secondary (8mm head) have washers under them. Take out the washers. To remove belt set your parking brake, and twist the helix on the secondary and push. This will loosen up the belt. Pull up on the belt to wedge it in the seconadry. Remove belt from seconadry and then primary clutch. If you really need a special tool, go to your tool box, grab a 12mm wrench, put it on one of the 3 nuts that holt the helix on the secondary clutch and try to tighten it. This will twist the sheaves open making it really easy to push and pull the belt up.

 

[tripplec]

I have been looking at several belts online. It seems various source carry only one brand. Two local sources carry either Gates and the other Dayco belts. Some have said that Carlisle are very good but I have not located a source here and comparing prices as well. My sled is not used for extreme response etc (long track) but I notice two different belt suggested by Gates website. 138-4432 (same for Dayco) and 138-4420 marked preferred. It seem slightly sorter. Hmmm

The Yamie belt I have is a 89L-17641-01 and that means nothing to me if it is even correct for the clutching.

 

[bluemonster1]

go only with an OEM Yamaha Belt.It is your best choice with less chance of a breakdown or explosion of belt fragments everywhere. As soon as you start changing to another brand,you'll have to re-calibrate your clutch again.RPMs will change from aftermarket belt and a OEM belt.
I had a Ultimax belt.It seemed really fine.Sled really pulled good,softer compound and better bite.BUT it only lasted 150 miles and then she grenaded on me(close to home).Thought I blew my motor.It put a pretty nasty dent in my footwell,and grabbed the speed0 line and mangled it good.Nearly pulled the speedo off from the dash.That was a really expensive day for me.
The cost of the belt plus a new speedo cable.

 

[bluemonster1]

I forgot to mention.You can pick up a belt change tool that mounts on secondary shaft and with the L-wrench you insert in the plate and crank it clockwise to open the sheave so you you can pull belt off easily.I hate doing it by hand myself....rich at richmotorsports carries them changers.

 

[tripplec]

go only with an OEM Yamaha Belt.It is your best choice with less chance of a breakdown or explosion of belt fragments everywhere. As soon as you start changing to another brand,you'll have to re-calibrate your clutch again.RPMs will change from aftermarket belt and a OEM belt.
I had a Ultimax belt.It seemed really fine.Sled really pulled good,softer compound and better bite.BUT it only lasted 150 miles and then she grenaded on me(close to home).Thought I blew my motor.It put a pretty nasty dent in my footwell,and grabbed the speed0 line and mangled it good.Nearly pulled the speedo off from the dash.That was a really expensive day for me.
The cost of the belt plus a new speedo cable.

Well thats an eye opener. My belt is less than an 1/8" worn (thats the spare I have) the other is the same if I recall. Although it rides low in the secondary clutch I may just adjust the spacing and see how it works out. I read about the tool and will look into it.

Thx....

 

[tripplec]

Well the 12mm wrench is clearly the ticket for getting the secondary sheeve shifted to spread for the belt removal. I nearly took it out and then put it back since it clearly would work. I need to clean and polish the clutch faces a bit but other than fine emery paper I am not sure what is best to use. The belt is down a bit in the 2nd dary clutch maybe 2-3mm but I am not certain if I can raise it any higher. I verified that the yamaha belt installed it the correct one. The drive may not be my problem. I did oil the rollers on the main clutch and face. It seem to snap in quick when it hit the correct RPM.