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Post by jdl357 on Oct 25, 2017 12:26:59 GMT -5
I've got a real annoying problem with my CVT belt. It seems to be vibrating and slapping against the cvt cover and actually leaving marks! It's kind of annoying. I just got a new rear pulley and clutch so I know it isn't that, so I'm going to look at the variator to see if anything is out of place. Has anyone ran into this problem before?
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Post by pinkscoot on Oct 25, 2017 12:37:36 GMT -5
It sounds like the belt isn't the right size. When its on does it sit down on the drive boss and at the top of the clutch pulley?
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Post by jdl357 on Oct 25, 2017 13:48:37 GMT -5
Belt is correct 788-17-28 Bando brand. Almost brand new. Everything seems to be sitting right. Going to take variator apart when I get off work.
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Post by geoffh on Oct 25, 2017 15:16:21 GMT -5
plus 1 with pinkscoot which engine is it,not wishing to upset anyone but I think there,s a typo in the parts catalouges (spell check)which is trickling back down to cause confusion.Bog standard long case minarelli = 738 16.5 I use a Naraku belt.
geoff
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Post by ThaiGyro on Oct 26, 2017 5:39:13 GMT -5
I'm with PinkScoot...check the belt width and length...sounds way too long. Your new one should be shorter than the old one by a few millimeters/centimeters.
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Post by 90GTVert on Oct 27, 2017 10:21:36 GMT -5
To me, this is normal. I also used 788-17-28 belts when I was using standard or non-OR aftermarket parts. Now I use an 816 with the OR. Happens with all of them. If a 738 fit on the stock pulleys on any of my Chinarelli engines, it would be junk because the belt would be way into one of the pulleys at rest. It would be a dog off the line and have low top speed. I have used long belts with standard pulleys too, and also found that that makes them sluggish on takeoff until some of the slack is taken up. In my eyes, a proper belt can reach the center of the variator and the outer edge of the rear pulley simultaneously, without much slack to speak of. If the belt can't do that, you can't get the full range of ratios that the CVT system is capable of. Too long and you get slack that can also cause poor performance or could possibly allow the belt to travel off of a pulley.
It's normal for a belt to vibrate, obviously at some points. If it's excessive, then you may need a stiffer contra spring (or replacement of a worn spring) or perhaps there's some sort of alignment issue with the pulleys or some other mechanical problem. Could be a bad belt. Having slack in the belt at times is normal though.
I have tried to grind down areas in the CVT cover, but it didn't really matter. I can't get the clearance without totally cutting the cover in large areas and didn't want to create edges for the belt to hit. Mine will wear the lettering off of belts a bit over time, but seems to do no real damage. I see much more wear on the sides of the belt than the outer face, so belts end up being replaced well before the outer face would ever be an issue.
For full disclosure, I do tend to run contra springs that are softer than many. I'm not a fan of big stiff springs. They need to be stiff enough to keep enough tension on the belt to avoid slip and excessive slack, but too stiff and they're tough to work on, can prevent the CVT from reaching it's max speed ratio, and stress the belt or waste power by stretching the belt really tight.
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