Tight CVT belts

[kosmos]

ok, since I'm not having any current apparent problem with the new belt, what would cause this sudden jump in temperatures? anybody got an idea they've came across with this before? is my belt the cause? it seems like it has to be its the only change. with the old belt + the lightened drive ramp piece, the temps stay under 350. went back out and went on a long ride seeing my top temps. they barely climbed up to 352, the same gravel hills I ride on didn't have any high temps when I rode on them. Know I didnt pay much attention to the temperatures tho when I put on a new belt until I was this far away from the house. That CHT gauge though does keep track of the recent highest temp and I was at it when I was on the gravel hills.

[kosmos]

ordered a new honda bando belt from the oem. will be in. I'm going to assume my hotter temps were from the tight belt. I've never had an oem belt ever fit as tight as at the least how the bando made in japan belt I just bought did. and ive never had a problem so far with an oem belt.
I dont know if i'll get to test temps with the new honda bando belt tho. im so tempted to bolt on my 72cc malossi kit, just got a file and chamfered the ports today so its ready to bolt together. Dont know if I'll make it. But I am assuming the tight belt - more friction gave me higher temperatures. Ive just never saw the belts that come from OEM ever fit on as tight as this bando made in japan aftermarket belt did.

[kosmos]

I got the new belt but, I swapped out CVT transmnission with the ZX before it came in. Not going to do this check right now. The new Honda Bando belt is 1/16 of an inch smaller than the stock used belt, and 1/16th of an inch longer than the Bando Made in Japan belt I bought. All I can assume is that because of, how tight the belt fit fitting it on the bike that this is what caused the heat issue I got, plus the little nicks dug in the plastic slide guides being caused by it.. I did readjust the jets and it ran worse. Before when my main jet was smaller and it was getting hot on me, i upped the main jet and the bike didnt get as hot, like under 350 after upping the MJ, and the bike ran better. WIth the old stock belt on it didn't over heat with the main jet i had in it before too.  I never had these tight like this belt issues with a stock Honda belt ever before and never taken a belt off a scooter that came with it that was this tight from my experience.  and none of these other problems or issues

If i have any similiar results tuning this ZX transmission I'll report it. And when or if ever I put the stock transmission parts back on, I'll report on the tightness as putting the belt on and if I have any overheating issues. But the last time I tried the stock CVT and the Made in japan bando belt, ran great but was overheating, and putting a larger main jet caused it to run worse. DOesn't seem like adding more RPMS to the motor would cause a well tuned motor to start overheating.

Too many problems I seen to trust belts that don't go on that fits "like a glove". my ZX belt im using is a 669-18-30 and fits fine and any other stuff about it i'll report in another thread maybe a build thread

[oldgeek]

There are so many things to take into consideration, belt length and belt width need to be measured and considered. Very small and seemingly insignificant differences can have a huge impact on CVT operation. Very small changes to the length of the drive boss can make a significant difference on launch and top speed. Changing the fixed half of the variator will have a considerable affect due to profile differences and boss length changes it usually causes. I am not a huge fan of the aluminum variator fixed front halves. Yes I use them but find the stock steel Kymco ZX fixed halves work better in many cases.

I dont understand the "tightness" you mention. I can easily fit belts of different lengths and widths, as long as they are not grossly short. Installing a belt the way you do, and the way most people do is incorrect IMHO, and can lead to not getting the variator tightened correctly.

I put the belt on the front pulley drive boss first, then I install the drive face and tighten it using an impact with a torque stick. You have to put your fingers on the moveable variator half and keep it pushed back so the weights do not get out of place. Doing it this way insures that you are getting the variator tightened correctly. Then you pull the belt down into the front pulley and it will keep the variator pushed back fully so the weights do not get out of place. Now you have the opportunity to check how the belt fits on the drive boss. Is it getting all the way to the boss? No, then shim your boss until the belt does. Does the belt seem to have too much room on the boss between the front pulley halves? Yes, use a shorter boss or different fixed half and check again. Testing and eventually experience will help you get that part right. If the belt slips on launch a bit, the boss is likely just a tad too long.

Now its time to install the clutch/rear pulley assembly. Hold the rear pulley assembly with both hands and loop the belt around the rear pulley and pull the entire assembly to the rear of the scoot and down while using your fingers to compress the rear pulley half towards the clutch. The belt will help you spread the pulley and hold it open while you slip the rear pulley assembly onto the primary shaft. A word of CAUTION make sure you have the belt way down in the rear pulley, you need to have plenty of slack so you can install the rear pulley straight onto the primary shaft. You do not want to do this at an angle because you may damage the needle bearing in the rear pulley if you try to do it at an angle. One issue with this method is if you run a very strong contra spring it may be harder to get the rear pulley to separate, but it can be done and it gets easier as you learn the technique. I run fairly soft contra springs due to the few hills around here. I recommend running the softest spring you can get away with.

So the last step is to pull the belt that is near the bottom of the case to the rear a few times until the rear pulley closes all the way removing the slack from the belt. This allows you check where the belt rides in the rear pulley and how tight the belt is on the drive boss.

Don't forget sharpie marks on the variator and the rear pulley will help you to find out how the belt is traveling in your CVT.

[kosmos]

Jun 11, 2023 13:49:42 GMT -5 oldgeek said:

There are so many things to take into consideration, belt length and belt width need to be measured and considered. Very small and seemingly insignificant differences can have a huge impact on CVT operation. Very small changes to the length of the drive boss can make a significant difference on launch and top speed. Changing the fixed half of the variator will have a considerable affect due to profile differences and boss length changes it usually causes. I am not a huge fan of the aluminum variator fixed front halves. Yes I use them but find the stock steel Kymco ZX fixed halves work better in many cases.

I dont understand the "tightness" you mention. I can easily fit belts of different lengths and widths, as long as they are not grossly short. Installing a belt the way you do, and the way most people do is incorrect IMHO, and can lead to not getting the variator tightened correctly.

I put the belt on the front pulley drive boss first, then I install the drive face and tighten it using an impact with a torque stick. You have to put your fingers on the moveable variator half and keep it pushed back so the weights do not get out of place. Doing it this way insures that you are getting the variator tightened correctly. Then you pull the belt down into the front pulley and it will keep the variator pushed back fully so the weights do not get out of place. Now you have the opportunity to check how the belt fits on the drive boss. Is it getting all the way to the boss? No, then shim your boss until the belt does. Does the belt seem to have too much room on the boss between the front pulley halves? Yes, use a shorter boss or different fixed half and check again. Testing and eventually experience will help you get that part right. If the belt slips on launch a bit, the boss is likely just a tad too long.

Now its time to install the clutch/rear pulley assembly. Hold the rear pulley assembly with both hands and loop the belt around the rear pulley and pull the entire assembly to the rear of the scoot and down while using your fingers to compress the rear pulley half towards the clutch. The belt will help you spread the pulley and hold it open while you slip the rear pulley assembly onto the primary shaft. A word of CAUTION make sure you have the belt way down in the rear pulley, you need to have plenty of slack so you can install the rear pulley straight onto the primary shaft. You do not want to do this at an angle because you may damage the needle bearing in the rear pulley if you try to do it at an angle. One issue with this method is if you run a very strong contra spring it may be harder to get the rear pulley to separate, but it can be done and it gets easier as you learn the technique. I run fairly soft contra springs due to the few hills around here. I recommend running the softest spring you can get away with.

So the last step is to pull the belt that is near the bottom of the case to the rear a few times until the rear pulley closes all the way removing the slack from the belt. This allows you check where the belt rides in the rear pulley and how tight the belt is on the drive boss.

Don't forget sharpie marks on the variator and the rear pulley will help you to find out how the belt is traveling in your CVT.

is there anything else to explain the overheat issue I had?  2 things I never see are the slide guides getting marks dug into them and any stock Honda belt or original belt off a scooter, ever fit tighter than basically slips right on.  the slack is taken up by putting the front drive face on.  Even my new 669 belt doesn't have any slack using the ZX transmission mod after I tighten down the variator nut.  I never even thought about the belt pinching when I put on the drive face, never had that problem because when you put the drive face on, as long as you push the belt all the way up on the scooter over the drive boss up against the variator, that shouldn't be a problem, because when you put the drive face on, its angle and the belts angle should push it away.  Doing so that way you explained negates my method of telling if a belt fits too tight.  Ive only notice too tight belts on, aftermarkets for my Honda elite or chinese 'who knows what the original belt part # was' bikes.   Also, thats not the way the CVT was engineered or manufactured, pulling the rear driven pulley open while putting the belt on, so theres many things to how a CVT belt fits, and they have to be made to fit it just right.  the width, length and angle, and there is no way adjust them once they are on, they just have to be made right.  This was the way that I have noticed CVT parts break from, I confirm that once I got a 669 belt and put it on my chinese bike, it was so tight i still have that belt and its the smallest 669 belt Ive ever measured or saw.  It blew out the seal in the driven pulley, within 2000 miles.  I then broke 2 more belts.  and replaced the Variator once or twice.  So I know I ran it at least one other time with all brand new cvt components.  And found one other guy who had the same bike and I asked him to measure his belt and it was like 28" exact and every belt I found getting 669-18-30 belts, was smaller, within almost a 1/16 of an inch at the most, and every one gave me cvt failures and broken belts.  
Ever since Ive used this method and never had a CVT issue but when it doesnt pass this test, I get those dig marks in the plastic variator slide guides, or they may break too if its too tight, or this heating issue I had with this one.  
The Bando made in japan belt I got broke in some I have a video but after the last ride i took it on I took it off, and 1/2 mile from home it was running up to 372 degrees along a straight 1/2 mile stretch back up the road.  So even tho in the video it looks like its fitting nice, it was overheating the motor.  There's no other reason I can think of it for it but for the belt overheating the motor, the cvt area geting hot and heat spreading to it or the belt causing too much stress on the crankshaft, pulling against the bearing.  
I made this topic for anyone to give experience with how theirs fits and if theirs works in this and fits in this manner also if so.  I've never saw any success with them.  I'm afraid to ride with them like this but with the low damage from this last one, I may at some time in the future retry it to reconfirm if it gets hot.  i mean it is a decent belt.  But really im worried it will cause something to fail from my experience.
And the manufacturer would not have engineered this belt to be put on using, 'so much pulling it in the rear pulley'.  all  belts have a torque value.   This method I've made up seems to be the most consistent and takes into account all the variables, and aligns with the every stock belt I've ever bought doesn't give me these problems and works and fits like this scenario.  Nothing else I can think of explains the overheating issue.  Just saying its an issue I seen.
the extra pull/torque that the belt gives when just putting it on doesn't seem like it should be there even if when you put the drive face on and it squeezes it up a little up on to the variator and it puts that torque-pull-tightness on the variator/ramp plate/other cvt components, but is extra that I dont think they would have engineered this to be.  there is no way to adjust scooter belts and any time I ever brought this up to someone who works on cars, they say, cant you adjust it?  that would be the only solution, unless you think its engineered different than a car, and there is no adjustments on scooters.  they just have to be made right.  you have to think how these were engineered to solve this issue.  This is my experience with this.  I tried testing it and overheating was a result.  Or I would have just ran it and checked it every 100 miles or so for a while to see.  But supremely tight belts have totally blown out CVT parts on me before.  even tho they said 669-18-30 on them.
heres 2 video links of how the belts install.  I do have a new Honda belt but until i remove all the cvt parts again im not going to do this again until then but ill try to remember to do this. streamable.com/b7z94z  streamable.com/6bv61d

also besides the other measurements of length, the old belt is .5mm thinner too

[kosmos]

Jun 11, 2023 13:49:42 GMT -5 oldgeek said:

There are so many things to take into consideration, belt length and belt width need to be measured and considered. Very small and seemingly insignificant differences can have a huge impact on CVT operation. Very small changes to the length of the drive boss can make a significant difference on launch and top speed. Changing the fixed half of the variator will have a considerable affect due to profile differences and boss length changes it usually causes. I am not a huge fan of the aluminum variator fixed front halves. Yes I use them but find the stock steel Kymco ZX fixed halves work better in many cases.

I dont understand the "tightness" you mention. I can easily fit belts of different lengths and widths, as long as they are not grossly short. Installing a belt the way you do, and the way most people do is incorrect IMHO, and can lead to not getting the variator tightened correctly.

I put the belt on the front pulley drive boss first, then I install the drive face and tighten it using an impact with a torque stick. You have to put your fingers on the moveable variator half and keep it pushed back so the weights do not get out of place. Doing it this way insures that you are getting the variator tightened correctly. Then you pull the belt down into the front pulley and it will keep the variator pushed back fully so the weights do not get out of place. Now you have the opportunity to check how the belt fits on the drive boss. Is it getting all the way to the boss? No, then shim your boss until the belt does. Does the belt seem to have too much room on the boss between the front pulley halves? Yes, use a shorter boss or different fixed half and check again. Testing and eventually experience will help you get that part right. If the belt slips on launch a bit, the boss is likely just a tad too long.

Now its time to install the clutch/rear pulley assembly. Hold the rear pulley assembly with both hands and loop the belt around the rear pulley and pull the entire assembly to the rear of the scoot and down while using your fingers to compress the rear pulley half towards the clutch. The belt will help you spread the pulley and hold it open while you slip the rear pulley assembly onto the primary shaft. A word of CAUTION make sure you have the belt way down in the rear pulley, you need to have plenty of slack so you can install the rear pulley straight onto the primary shaft. You do not want to do this at an angle because you may damage the needle bearing in the rear pulley if you try to do it at an angle. One issue with this method is if you run a very strong contra spring it may be harder to get the rear pulley to separate, but it can be done and it gets easier as you learn the technique. I run fairly soft contra springs due to the few hills around here. I recommend running the softest spring you can get away with.

So the last step is to pull the belt that is near the bottom of the case to the rear a few times until the rear pulley closes all the way removing the slack from the belt. This allows you check where the belt rides in the rear pulley and how tight the belt is on the drive boss.

Don't forget sharpie marks on the variator and the rear pulley will help you to find out how the belt is traveling in your CVT.

theres a lot of things i want to respond to about this post.  your saying "Is it getting all the way to the boss?".  the belt has to go over the drive boss.  if it won't go over it, if you say to pull the belt into the back just for some slack, then your introducing a whole bunch of other stuff, because this is how the CVT functions.  
 
You said "I dont understand the "tightness" you mention".  I explained it.  Put the belt over the driven pulley and then put it on the front pulley with teh front pulley half off, only variator and ramp with rollers and drive boss installed.  "Tight" refers to if the belt won't slip up and over the drive boss without a struggle.  to me and in my experience every time including this one, when you had to fight with it, it led to problems.  My idea on it is that belts have a torque value on a car.  If you overtighten them, you can tear up bearings and other things.  What ive seen in my own experience is blown driven pulley seals on the movable face part, and the plastic slide guides on the ramp plate on the variator.  those are the only places that you have play at.  those things then lead to further failure, breaking slide guides breaking variators, breaking movable rear pulley seals, locking it opened or something, its broke needs a new seal but during the ride you break belts in both of those situations.

If you go around this check by putting the belt down into the rear poulley by compressing the spring, you don't get to gauge the length in this way tightness of the belt.  width is also another factor but, how this cvt functions, There is always a torque value for belts and they made this this way.  the only  thing I can think of for how they would of gauged this is the belt fitting first off the right way and this is the most clean and tried and true way that I have seen it done.  Never had an issue if the belt had a bit of slop.

And there is some pull by the time you tighten down the front pulley fixed half after the belts went on, as those 2 faces tighten towards each other, the belt is pulled up. 

As far as any future issues after this, I've never had any belt slip issues from a belt with a little bit of looseness when its put on.

I hear you but ive done this a ton of times and every time its led to some kind of problem if not something breaking.  This time it was heat.  Rejetting it didn't fix the issue and the bike sounded fine to me running.  There wasn't a heat issue before.  

And the idea that this is the wrong way to do it, because ... it will pinch the belt between the fixed front half and the boss, i dont see how that could be an issue.  Like if your belt was super tight it might want to pinch itself but, with the front fixed half angling up and the belt doing the same, as they come close its going to push it away and you can just do some tightening by hand first and spin it if you think that it will be a problem.