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Old 09-03-2012, 12:36 PM   #11
1moretoy
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Default Re: what happens when?

since the engine is mounted to the frame vs. the swing arm I have to leave a little slack for when the suspension flexes.
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Old 09-04-2012, 08:04 PM   #12
sho305
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Default Re: what happens when?

I would try a nylon tensioner on the other side with a spring on it. You need to figure out which sprocket is jumping and put the tensioner there so when you back up it pushes the chain into the sprocket. You could also use an idler sprocket with a spring but it would have to be sturdy.
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Old 09-04-2012, 08:16 PM   #13
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Default Re: what happens when?

So I need a tensioner on the top and the bottom of the chain that is jumping?
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Old 09-07-2012, 09:12 PM   #14
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Default Re: what happens when?

tried some sprocket swaps this evening and found out the tranny doesn't seem to be bad after all but here is the deal. With the sprockets like I had them to start with (engine 13, J/S input 25, J/S output 15 and axle 15) this gave me a final drive ratio of 1.92. The popping only occured in reverse. Today I swapped the J/S input 25 tooth for a 15 tooth.
This gave me a final drive ratio of 1.15. The change caused the popping to occur in both reverse and forward now. So my problem seems to be a gear ratio thing. I may go the other way and swap in a 35 tooth at the J/S input giving me a final ration of 2.69. Probably gonna suck with top end speed but just want to see if the popping goes away.
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Old 09-08-2012, 11:09 AM   #15
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Default Re: what happens when?

A smaller diameter sprocket will always want to slip/pop sooner as it has less teeth, if you could run both sprockets larger diameter and still the ratio you prefer that should help.

You are only running the chain one direction right? I'm not sure why it would only do it in reverse then, but you would want a tensioner on each sprocket to lead chain into it. Also check the wear on the sprockets, if the teeth are bent over/worn it will do it worse. Usually once they slip they bend the teeth and with a loose chain it will get worse.

Motorcycles put the engine sprocket very close to the swingarm pivot to minimize change in chain tension, but may not be possible to do in your setup.
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Old 09-08-2012, 03:24 PM   #16
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Originally Posted by sho305 View Post
A smaller diameter sprocket will always want to slip/pop sooner as it has less teeth, if you could run both sprockets larger diameter and still the ratio you prefer that should help.

You are only running the chain one direction right? I'm not sure why it would only do it in reverse then, but you would want a tensioner on each sprocket to lead chain into it. Also check the wear on the sprockets, if the teeth are bent over/worn it will do it worse. Usually once they slip they bend the teeth and with a loose chain it will get worse.

Motorcycles put the engine sprocket very close to the swingarm pivot to minimize change in chain tension, but may not be possible to do in your setup.
Good idea...I may have to try the larger sprockets. I did get another spring for the tensioner and it helped some but still pops if you give it the gas very hard in reverse. It will at least ease into reverse now without popping.

Yes the chain only runs one direction. All the sprockets were new so they should be good.

I have the engine slid back so that the sprocket on the backside of the TAV2 is almost directly over the swing arm pivot. So that should be ok too.

I spent most of the afternoon taking the engine apart and removing the governor today. Very disappointed with the results. I thought I would feel some difference in power but it didn't seem to change at all. Gonna GPS it and see if I got any speed gain at all. Guess that's what I should expect with just a 6.5hp. Since it came in it, I wanted to leave it in, but I may be looking to Big Block it later.
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Old 09-09-2012, 11:38 AM   #17
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Default Re: what happens when?

You could unbolt the rear shocks and move it through the range of movement, then get the chain near tight at the tightest place....if you have not already.

Gov just lets it rev more, if your TAV is not letting it rev more it will not until you reach top speed and it is shifted all the way (like a stock cart will with no gov)....and with higher gearing it may not have the power then to go faster. You can mod the 6.5 quite cheap to get more rpm, if you can get the TAV to rev it harder. Would have to lighten the weights in the primary or something. Stock it may not make much power above 4K or so. I know you can get about 8hp out of them without spending much the parts are really cheap (usually a cam/rod/flywheel/valve springs). Take a look http://www.nr-racing.com/hopupkits.htm Note that if you put a mild cam in (get a marine/torque cam) you may not need the big carb as much because with a cvt you need torque more, with a single gear/clutch gokart they need them to rev out higher for speed so they need to breath better. And I'd leave the whole cooling fan on it.

On the other hand the torque of a 390 or 420cc would do you a ton of good, but I don't think the TAV can handle that much power. You would need to go to a cart cvt or the next comet 40 or whatever it is....that is used on some carts.
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Old 09-09-2012, 02:27 PM   #18
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Default Re: what happens when?

Quote:
Originally Posted by sho305 View Post
You could unbolt the rear shocks and move it through the range of movement, then get the chain near tight at the tightest place....if you have not already.

Gov just lets it rev more, if your TAV is not letting it rev more it will not until you reach top speed and it is shifted all the way (like a stock cart will with no gov)....and with higher gearing it may not have the power then to go faster. You can mod the 6.5 quite cheap to get more rpm, if you can get the TAV to rev it harder. Would have to lighten the weights in the primary or something. Stock it may not make much power above 4K or so. I know you can get about 8hp out of them without spending much the parts are really cheap (usually a cam/rod/flywheel/valve springs). Take a look http://www.nr-racing.com/hopupkits.htm Note that if you put a mild cam in (get a marine/torque cam) you may not need the big carb as much because with a cvt you need torque more, with a single gear/clutch gokart they need them to rev out higher for speed so they need to breath better. And I'd leave the whole cooling fan on it.

On the other hand the torque of a 390 or 420cc would do you a ton of good, but I don't think the TAV can handle that much power. You would need to go to a cart cvt or the next comet 40 or whatever it is....that is used on some carts.
I moved the stock spring on the TAV driven clutch from the #2 to the #1 to tighten up the spring. It will hold longer now before shifting and will actually spin the tires (on dirt). What I am giving up is the ability to keep the engine power curve while going up hills in my neighborhood. I can come to a complete stop on the hill and it will take off like nothing is holding it back but just goes slow until I get to the top of the hill and the road levels out. Then it will pick up speed again.

What is the difference between the TAV I have and the cart CVT you're talking about?

When the 6.5hp blows, I will probably go big block for sure.
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Old 09-09-2012, 08:14 PM   #19
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Default Re: what happens when?

Tav is the same thing just a smaller version for gokarts and other small stuff like minibikes/scooters/small off road buggies. The golf cart cvt is larger and holds up longer, pretty much what was used on older snowmobiles so really they are underpowered and why they last forever on 9hp. Most use a 1 3/16" wide belt though CC use a 1".

It is slowing down because the load is more than the engine can pull, its doing what it should do, you just don't have the power. It may not be running at just the right rpm, they are a pretty simple deal. The more complex ones you can tune better for shift rpm and engagement/etc.
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Old 09-10-2012, 05:43 AM   #20
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Default Re: what happens when?

Thanks Sho...you've been a big help.
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