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  #21  
Old 04-18-2019, 11:59 PM
Denny Denny is offline
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Looks like you have a few different problems there with the set up.
1. Exhaust too close to the drive belt, move the driven tward the front. Belts don't like heat. It will also give you a better wrap on the drive sprocket (the small one).

2. I don't know what your gear ratios are but they look lousy. Go to 10 tooth drive sprocket and a 60 tooth driven sprocket in #40 chain size.

3 By going to a #40 chain it should buy you a little clearance between the driven clutch and the back plate.

If you do as I have outlined you will be pooping in tall cotton.

Denny
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  #22  
Old 04-19-2019, 10:09 AM
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yeah few different problems indeed;

that gear ratio wouldn't work very well (if at all it'd be a terrible belt shredder)
that combined with the powerloss due to the TC is a sure way of failing in very short order.

Do not forget that the original engine (a gy6) was INTERNALLY geared at around 4:1 maybe lower
(and that Without the CVT)
thus it's nowhere NEAR an industrial engines complete lack of internal gearing.

Soo yeah, scrap that 520 sprocket and find one with at the very least 55T in #40
and use a 10T TC sprocket
So you end up with a 5.5:1 chain ratio
if you have larger than 20" wheels and or a total weight of more than 550 lbs (all passengers seated)
you even need ten more teeth on the axle in order to get this thing moving.

No wonder the engine plate flexed btw.. putting the sprocket on the far end of an unsupported shaft is a terrible idea!

You'd need a torque bar in order to do such thing.. and frankly it makes more sense to just move the axle sprocket over instead.

'sid

PS really.. everything on that kart apart from the colour is
a less than optimal idea I'm afraid..
the engine is a lousy replacement for the original gy6,
the Series40 is a terrible idea with the backplate like that,
the gear ratio is surely the worst and MUST be changed in order to have any fighting chance at all
And the last two combined..
with putting the TC sprocket on the far end of the shaft is only
making things worse.
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  #23  
Old 04-19-2019, 10:53 AM
67StingrayJ 67StingrayJ is offline
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Quote:
Originally Posted by Denny View Post
Looks like you have a few different problems there with the set up.
1. Exhaust too close to the drive belt, move the driven tward the front. Belts don't like heat. It will also give you a better wrap on the drive sprocket (the small one).

2. I don't know what your gear ratios are but they look lousy. Go to 10 tooth drive sprocket and a 60 tooth driven sprocket in #40 chain size.

3 By going to a #40 chain it should buy you a little clearance between the driven clutch and the back plate.

If you do as I have outlined you will be pooping in tall cotton.

Denny
Is there any way I can have the driven "float" and still utilize the back plate? I'm thinking a longer jack shaft with the sprokets like shown. Ibviously I'd have to cut up that mounting plate a bit but that's easily said and done.
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  #24  
Old 04-19-2019, 10:58 AM
67StingrayJ 67StingrayJ is offline
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Quote:
Originally Posted by itsid View Post
yeah few different problems indeed;

that gear ratio wouldn't work very well (if at all it'd be a terrible belt shredder)
that combined with the powerloss due to the TC is a sure way of failing in very short order.

Do not forget that the original engine (a gy6) was INTERNALLY geared at around 4:1 maybe lower
(and that Without the CVT)
thus it's nowhere NEAR an industrial engines complete lack of internal gearing.

Soo yeah, scrap that 520 sprocket and find one with at the very least 55T in #40
and use a 10T TC sprocket
So you end up with a 5.5:1 chain ratio
if you have larger than 20" wheels and or a total weight of more than 550 lbs (all passengers seated)
you even need ten more teeth on the axle in order to get this thing moving.

No wonder the engine plate flexed btw.. putting the sprocket on the far end of an unsupported shaft is a terrible idea!

You'd need a torque bar in order to do such thing.. and frankly it makes more sense to just move the axle sprocket over instead.

'sid

PS really.. everything on that kart apart from the colour is
a less than optimal idea I'm afraid..
the engine is a lousy replacement for the original gy6,
the Series40 is a terrible idea with the backplate like that,
the gear ratio is surely the worst and MUST be changed in order to have any fighting chance at all
And the last two combined..
with putting the TC sprocket on the far end of the shaft is only
making things worse.

Ouch, you really know how to kick a man when he's down. It's ok. I want honest answers, even if I don't like them.

I agree with you about the thing flexing with that gear way out there like that. I don't know what I was thinking. That's why I wanted to move it next to the back plate. But the problem I ran into then was the bolts hitting the driven and the back plate. So last night I ordered some 10mm flat head screws. I plan on tapping the hub and countersinking the head in the sprocket. Thoughts? I feel like it's worth a try...

I'm worried about going to a #40 chain. Aren't they smaller therefore weaker?

I appreciate the feed back. Seriously...
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  #25  
Old 04-19-2019, 11:06 AM
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Quote:
Originally Posted by 67StingrayJ View Post
Is there any way I can have the driven "float" and still utilize the back plate?
Nope!

imagine the driven would need an inch of room traveling inboard;
there is no way to cut enough off the backplate and still call it that
(remember you'd need the full 7.5" diameter circle cut out)

Actually it'd be easier to cut a much smaller circle and flip the driven inboard (swapping your reverse wound against the std wound spring of course)
but that'd need a heavy steel can
to attach the jackshaft tube to the backplate of course
and likely some additional bracing as well..
maybe so much bracing in fact that it'd interfere with the engine crank case.

Forget about the backplate!

get a seperate jackshaft and do it right.

'sid
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  #26  
Old 04-19-2019, 11:15 AM
67StingrayJ 67StingrayJ is offline
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Quote:
Originally Posted by itsid View Post
Nope!

imagine the driven would need an inch of room traveling inboard;
there is no way to cut enough off the backplate and still call it that
(remember you'd need the full 7.5" diameter circle cut out)

Actually it'd be easier to cut a much smaller circle and flip the driven inboard (swapping your reverse wound against the std wound spring of course)
but that'd need a heavy steel can
to attach the jackshaft tube to the backplate of course
and likely some additional bracing as well..
maybe so much bracing in fact that it'd interfere with the engine crank case.

Forget about the backplate!

get a seperate jackshaft and do it right.

'sid
yeah, I agree. I already contacted GPS and asked for a return. I'm worried aobut that they will say. The plate have been put on and taken off several times already, and has lots of chips in the paint as a result. I'm sure they can repaint it.

Would it be possible to sketch something up or show me specifically how you mean you would do it proper? I'm trying to figure out how I would really mount the drive and driven in a way that I can still adjust for chain tensioning.
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Old 04-19-2019, 11:44 AM
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Quote:
Originally Posted by 67StingrayJ View Post
Ouch, you really know how to kick a man when he's down. It's ok. I want honest answers, even if I don't like them.

I agree with you about the thing flexing with that gear way out there like that. I don't know what I was thinking. That's why I wanted to move it next to the back plate. But the problem I ran into then was the bolts hitting the driven and the back plate. So last night I ordered some 10mm flat head screws. I plan on tapping the hub and countersinking the head in the sprocket. Thoughts? I feel like it's worth a try...

I'm worried about going to a #40 chain. Aren't they smaller therefore weaker?

I appreciate the feed back. Seriously...
Trust me: I'm sorry about that..
we've seen several tries so far on replacing gy6-es with industrial engines,
and frankly it never was as expected AFAIR.

Not too many happy faces with anything gy6 involved so far at all.. too many hiccups, too many differences in what people suspect to be 'identical' engines (different internal gearing for scooters and karts just naming one most overlooked issue).

So the only thing we can really do is to point you towards all hiccups and mistakes,
it's a bit late along your rebuilt I'm afraid,
but it still is important to get all of them fixed;
especially since the error margin of such conversion from gy6 to industrial is very narrow and even a minor mistake can make for an unhappy rider in the end.

I -usually- do sound harsh anyways...
due to a lack of lingual finesse on my behalf.
And me trying to leave no room for misinterpreting kindness as "it's all good" doesn't help in that regard either.

Sorry, I never meant to bring you down!
I want you to move quickly towards a good functioning setup to be a happy rider in as little time possible
(or say with as little money and time wasted)

Quote:
Originally Posted by 67StingrayJ View Post
yeah, I agree. I already contacted GPS and asked for a return. I'm worried aobut that they will say. The plate have been put on and taken off several times already, and has lots of chips in the paint as a result. I'm sure they can repaint it.

Would it be possible to sketch something up or show me specifically how you mean you would do it proper? I'm trying to figure out how I would really mount the drive and driven in a way that I can still adjust for chain tensioning.
GPS is a good company; You do not hear many complaints
(I cannot think of a single one atm)
So I have high hopes that they'll agree to take it back, even if you added minor scratches to the backplate.
I'll cross my fingers for you!

The setup is quite easy actually
here's a jackshaft base plate on a yerf dog for example
(I bet GPS has something very much alike .. maybe they're willing to exchange)

(as you can see the series 40 driver is even installed on the engine already)
All needed is such thing and the std wound spring together with a good enough sprocket ratio to get back on track.

'sid
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Old 04-19-2019, 11:58 AM
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I'd be curious to see if your drive pulley would fit properly if you flipped that around, with the moveable sheave inboard.
Some folks are having good results doing that when using a backplate.
That would solve the problems your having with the driven pulley.
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  #29  
Old 04-19-2019, 12:42 PM
67StingrayJ 67StingrayJ is offline
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Quote:
Originally Posted by Snaker View Post
I'd be curious to see if your drive pulley would fit properly if you flipped that around, with the moveable sheave inboard.
Some folks are having good results doing that when using a backplate.
That would solve the problems your having with the driven pulley.
if you could point me to an example that would be helpful. At this point I'll try anything.

---------- Post added at 12:42 PM ---------- Previous post was at 12:35 PM ----------

Quote:
Originally Posted by itsid View Post
The setup is quite easy actually
here's a jackshaft base plate on a yerf dog for example
(I bet GPS has something very much alike .. maybe they're willing to exchange)

(as you can see the series 40 driver is even installed on the engine already)
All needed is such thing and the std wound spring together with a good enough sprocket ratio to get back on track.

'sid
so how do you keep the driven on the shaft in this scenario? and how do you manage the distance between the driven and the drive?

What did you think of the idea i had where I put the sprocket under the engine?
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Old 04-19-2019, 03:24 PM
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The closest example would be a recent thread right here in Engines and clutches, titled New build with Predator 420cc w/40 series.
I saw a Utube video in the past where someone experimented with flipping the drive pulley and they claimed success.
I just don't know if all of these drive pulley's are designed the same so as to fit "backwards".
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  #31  
Old 04-19-2019, 04:19 PM
67StingrayJ 67StingrayJ is offline
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Ok guys, I did a test and I'm sure about the CVT not working with the back plate. I did a mock up and ran the thing. When you increase rpm the drive swings in and the drive swings out. The back of the two pulleys stays in line at all times. You can clearly see the belt twists. Check out the video I just posted. Never mind the chain, it isn't secured just yet. Focus on the CVT pulleys.


https://youtu.be/mGZ5n6mJOCc

Now look at the second video. In this video I have the driven floating as you guys said it needs to be. You can clearly see that the CVT MUST float if you don't want to destroy belts. It really is a shame GoPowerSports sells this thing.

https://youtu.be/jgskD7wbX74
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  #32  
Old 04-19-2019, 06:14 PM
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Quote:
Originally Posted by 67StingrayJ View Post
if you could point me to an example that would be helpful. At this point I'll try anything.

---------- Post added at 12:42 PM ---------- Previous post was at 12:35 PM ----------



so how do you keep the driven on the shaft in this scenario? and how do you manage the distance between the driven and the drive?

What did you think of the idea i had where I put the sprocket under the engine?
Well, that shaft needs to be replaced (and at least one bearing is missing) it's only to show you the kind of jackshaft and it's _rough_ placement.

it's a plate that directly fits the four engine bolts,
and is secured with the very same bolts to the engine mounting plate
And since the js-plate isn't slotted the center to center distance is fixed chain tension will be achieved like with a a cent clutch by moving the engine back and forth along it's slots
(In that case moved in unison with the JS)

The jackshaft itself is then just an ordinary jackshaft
whatever kind you want (threaded or drilled and tapped or even with a slotted end for a snapring if you so desire)
And the driven is afixed by such means (a nut, a bolt or a snapring)
whichever JS you pick.

You can put the Sprocket where ever you need it to be (within reasonable ranges of course),
but if you want it just below the engine, you will need a different jackshaft setup
two pillow blocks left and right and the TC sprocket in between like so:


And for that you need structural support for the pillow blocks,
that's why I suggested the plate that bolts to the underside of the engine first
Also keep in mind that you need the clearance for a large enough sprocket too..
which looks to be unlikely with the current engine mount *shrugs*

Oh and see.. that setup uses locking collars to keep everything in place, another option I forgot to mention above

In that scenario you run into tension looparounds, but it's still a viable option.
first you tension the chain by moving the jackshaft pillowblocks in their slots,
then you tension the belt by moving the engine.
(and if you cannot achieve good tension, you add/remove a link and start over)


Now chain.. yes 530 chain is way stronger than #40..
But 420 chain is way stronger than #40 and of the exact same outer dimensions as #41 (so it fits all #41 sprockets)

you can safely run your kart with #40 chain,
and certainly run it with 420 chain having quite a security margin left.

The reason I'm for half inch pitched chain (#40 or 420)
instead of 5/8" pitched (530)
is nothing but the thread pitch..
you want a fairly large toothcount on the rear axle, and the bigger the pitch, the larger the diameter of the needed sprocket will be of course (25% bigger to be precise)
And that will cause significantly reduced ground clearance.

OH and sure, you could get a smaller toothcount on the TC sprocket,
but that comes at a price (additional chain and sprocket wear)

Since the power is only transmitted through the engaged teeth on the TC sprocket
and spreading all loads over 5 or 6 teeth is much better
than spreading it over just 3 or 4
(again we talk ~25% quicker sprocket wear)

So IMHO the more teeth the better, even if they're a bit smaller in the end.

'sid
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  #33  
Old 04-22-2019, 06:56 AM
67StingrayJ 67StingrayJ is offline
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OK, tell me why in the following photo is the driven mounted with the movable face towards the engine?






and tell me why in this photo (compliments of GPS website) is the driven mounted with the movable face away from the engine?







I was reading up on symmetrical CVTs over the weekend and apparently the movable face on the drive is to be the opposite of the driven.





SO, now I'm wondering... If I change out the spring on the drive pulley couldn't I flip it around and solve my issue with belt alignment?

Also, I will never stop wondering WHY GPS is selling this thing in this configuration. I think it's a conspiracy to sell more belts...
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Old 04-22-2019, 07:15 AM
J.S.@SMS J.S.@SMS is offline
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No, GPS sells the 40 series with a backplate. Which requires the driven to be run with the movable sheave outboard, like a 30 series. However, when used on a jackshaft not a back plate, the driven can be run with the movable sheave inboard.
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Old 04-22-2019, 07:25 AM
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We've talked about that a series 40 SHOULD be mounted inboard before..
I'm not going to explain that again in all detail again

Just keep in mind that a series 40 is MEANT to be mounted inboard and that's what you should do whenever you can.
if for one reason or another you cannot;
then install a reverse wound spring and mount it outboard, in which case it should be allowed to float (back in) for roughly an inch (7/8" tbp)

the GPS kit with backplate comes with the reverse wound spring pre-installed..
(awkwardly enough not in the pic you posted)
if you flip it back to how it supposed to be, you need a std wound series 40 spring instead!

'sid
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Old 04-22-2019, 09:31 AM
67StingrayJ 67StingrayJ is offline
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Quote:
Originally Posted by itsid View Post
the GPS kit with backplate comes with the reverse wound spring pre-installed..
(awkwardly enough not in the pic you posted)
if you flip it back to how it supposed to be, you need a std wound series 40 spring instead!

'sid
Is it the Driven or the Drive that comes with the reverse wound spring pre-installed?
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Old 04-22-2019, 09:38 AM
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Quote:
Originally Posted by 67StingrayJ View Post
Is it the Driven or the Drive that comes with the reverse wound spring pre-installed?
Driven. As far as I can understand it if your driven comes with a yellow spring it's made to be setup outboard like a TAV30 setup with backplate. (even though most here say it's not optimal because the lack of space to float). If it comes with a red spring you install it inboard as per comet installation instructions.
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Old 04-22-2019, 10:04 AM
67StingrayJ 67StingrayJ is offline
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Driven. As far as I can understand it if your driven comes with a yellow spring it's made to be setup outboard like a TAV30 setup with backplate. (even though most here say it's not optimal because the lack of space to float). If it comes with a red spring you install it inboard as per comet installation instructions.
Thanks! I'll get the regular spring on order ASAP.

I went ahead and got the kart working over the weekend with the 530 chain. I mentioned earlier that I was getting lots of chain slippage due to flexing of the frame/mounting plate and location of the driven. I was able to prove that yes, if I located the sprocket between the back plate and driven pulley it would reduce the amount of flex just enough to prevent chain slippage.

However, I can still detect a fare amount of flex when I drive the kart. Essentially, I don't have enough structural support back there to handle the torque of the engine. Also I don't like the gearing I have (10 tooth on jackshaft and 31 tooth on axle). And like you pointed out, I don't have the room to increase the size of my driven sprocket to get the ~6:1 gear ratio.

So, I spent about $200 over the weekend getting a 420 chain, a 60 and 70 tooth sprockets, and a longer 5/8" jackshaft. I'm going to redo the frame in some way but I'm not sure how just yet. I know I'll need to mount the engine about 2" higher to make room for a larger driven sprocket. Then i'll need to do something to eliminate all the flex I'm experiencing.
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