7 inch comet driven unit help

[Whitetrashrocker]

There is talk about 3 hole positions in the driven units to adjust tention. Mine has no such holes.

Could someone please post a picture and perhaps some measurements as to hole spacing?

Not hard to drill a new hole but I have no idea as to where.

Thanks!

 

[itsid]

frankly you should not drill holes in your cam if you do not have them already.

But if you insist.. IIRC on a series 40 like you have (I think that's the TC we talk about, correct?)
the holes are about 90° offset, the single one you have is the SECOND hole on a three hole cam.
So one to the left, and one to the right to make it a three hole cam.

Oh and a series 40 is 7.5" according to the documentation, the 7" pulley is a "big" series 30 pulley.
So that's a bit confusing...

'sid

PS You'll end up using the second hole (the one you already have now) eventually anyways... so why bother?

 

[Whitetrashrocker]

Why? Because I can't leave things well enough alone. If some one says it can't be done I call bs and do it anyway.

I'm not sure which model for sure but the driver looks like a 40 series and the driven probably is a 7.5 inch. It only has one hole for the torsion spring to go.
I understand that more or less tension affects how soon the unit changes gear. I want that option.

Like I mentioned I got 2 Dingos with different tire size. I want to make them as competitively close as I can.
Also one of the engines blew the balancing shaft out the case and I'm replacing it with a predator 301.

I play with blown alcohol dragsters and extreme rock crawlers.
Just picked up a few karts to play in the yard and have no idea on this stuff. I mean I get the basics but the details are new.
You guys seem to know your stuff.

 

[itsid]

if unsure.. POST PICS!

Always post pics, they are handy and just because you are not yet able to identify a part, that doesn't mean neither one of us could

Aanyways.. I'm nearly certain it's exactly 90° offset;
but let's just see if someone chimes in that actually has one to measure it.

'sid

 

[Whitetrashrocker]

Here's the inside of the driver and a bad pic for the driven but I'll try to get a better pic tomorrow. And I'll show off my gas tank while I'm at it.

 

[itsid]

yes.. although there is a very slim chance it's not a series 40 driven, it is more than just likely it IS
The driver for sure is a series 40 and the driven back face looks like a series 40 too, so I'm rather positive

'sid

PS wait.. do both of your karts have only a single hole in the driven unit?
IIRC you said you had two dingos with series 40 TCs, correct?

 

[Whitetrashrocker]

I did a screen shot of something with the 3 holes but the format isn't compatible to upload.
There is another thread also showing the same 3 holes. But the pic is taken at an angle and hard to determine location.

Is there a nice pic of the inside taken straight on?

---------- Post added at 10:06 PM ---------- Previous post was at 10:02 PM ----------

Correct both carts have the same tc set up.
Neither have adjustable driven units. One hole only.

---------- Post added at 10:10 PM ---------- Previous post was at 10:06 PM ----------

And both had the medium Flyweights instead of the heavy as noted by the chart posted in my other thread.

Karts came from different sources about 6 months apart and when looking at the engine vin they were made one day apart from each other. Odd.

 

[Joe-405]

You don't need the extra holes to change spring tension. Just turn it tighter or loser past the nubs and retighten it.

 

[Whitetrashrocker]

Here's some better pics.

 

[itsid]

You don't need the extra holes to change spring tension. Just turn it tighter or loser past the nubs and retighten it.

Uhm NO!

do not do that

first: the valleys are offset by 120° not 90... and you only preload the spring by ONE valley at all...
so "one looser" will not be preloaded at all! (baaad.. it'll just sling open, no torque at all)
one tighter will basically lock the driven in torque mode and you will barely see any speed.

'sid

PS yep 90°.. the other two are sitting right in the cast circles..
that's a nice reference point no?

 

[Joe-405]

Uhm NO!

do not do that

first: the valleys are offset by 120° not 90... and you only preload the spring by ONE valley at all...
so "one looser" will not be preloaded at all! (baaad.. it'll just sling open, no torque at all)
one tighter will basically lock the driven in torque mode and you will barely see any speed.

'sid

PS yep 90°.. the other two are sitting right in the cast circles..
that's a nice reference point no?

Well crap I wonder if I did it on the minibike. But that wont limit rpm just speed tho correct ?

And do you have a video of winding it. I should still check it.

 

[Whitetrashrocker]

That's confusing Sid.
That pic you posted shows one at say 0° the next is at 90° and the third is 180°.

Is that how the line up with the cams?

I thought they would be more of 0° 45° and 90° or something like that.

---------- Post added at 12:58 PM ---------- Previous post was at 12:50 PM ----------

After looking at the pictures a minute, I think I get it.
Still looks like a big spread.

None the less i don't think it's that critical then as for as spacing the holes. I'll try maybe a 45° off of what I have and see if it helps.

---------- Post added at 01:02 PM ---------- Previous post was at 12:58 PM ----------

This is more of what I was thinking....
http://www.diygokarts.com/vb/attachment.php?attachmentid=75926&d=1473647669

 

[Joe-405]

So I just noticed mine has the 3 holes. But only the middle is drilled out all the way.............

Might check yours. And here's a good pic.

 

[Joe-405]

So I drilled one hole and its not far enough out to clear the inner spring guide. So I made my own farther out and it worked good.

If you look at the pic you can see what I'm talking about.

 

[Whitetrashrocker]

Joe, I don't know why those holes are there on yours. There's not even a casting mark on mine of the same.
Probably a different manufacturer?
Is yours a 7.5 inch?


Sid, do you see what I'm talking about in the link I posted?

 

[itsid]

Well crap I wonder if I did it on the minibike. But that wont limit rpm just speed tho correct ?

And do you have a video of winding it. I should still check it.

Correct.. overly tightened the spring will prevent the driven from opening up all the way (your current top speed tells me it's not the case though)
but it'll also delay upshifting (internally) sooo you also lose a bit acceleration

Best video I've seen is the maintenance video made by Grant
www.youtube.com/watch?v=a3FCcLlR-sg

the last minute shows the preloading step.. but it's easy basically.. choose your hole, and preload exactly one valley.

That's confusing Sid.
That pic you posted shows one at say 0° the next is at 90° and the third is 180°.

Is that how the line up with the cams?

I thought they would be more of 0° 45° and 90° or something like that.
...
This is more of what I was thinking....
http://www.diygokarts.com/vb/attachment.php?attachmentid=75926&d=1473647669

No in regards of the one hole you have it is
-90° , 0° (the one you have) and +90°
the cam lobes are 120° apart and it's important to keep the reference.

And yes, the holes on a series 30 are much closer together..
but we talk series 40..

So I just noticed mine has the 3 holes. But only the middle is drilled out all the way.............

Might check yours. And here's a good pic.

that's indeed the view I was hoping to find online earlier.. thanks for posting it!

WTR, if you take a close look you can see that those cast flash circles
are a good point of reference as to where you need to drill.
(and you can clearly see your's is between two such flash circles just as the 'std' second hole on the predrilled one)

'sid

 

[Whitetrashrocker]

Ok a 30 series spacing is closer than the 40 series is what I took from that. Correct?

But I disagree about the casting marks your talking about. They are to far inward but they do mark a symmetrical pattern to follow.

Again I'm probably over thinking a simple thing but it nice to see other parts out there. Makes a nice reference.

 

[itsid]

Ok a 30 series spacing is closer than the 40 series is what I took from that. Correct?

correct!

But I disagree about the casting marks your talking about. They are to far inward but they do mark a symmetrical pattern to follow.

HOW DARE YOU :toetap05:
jk..
yes I was talking about their ANGULAR position only.. their lateral position must still be transfered with a compass.
which I think is fairly easy to do
take a compass center it on the jackshaft, draw a circle crossing the centerline of the hole.. that's not rocket science

Again I'm probably over thinking a simple thing but it nice to see other parts out there. Makes a nice reference.

You are.. it's two holes.. 90° offset left and right to the one you have, nothing more to it..
every other thought is wasted mental energy

'sid

 

[Whitetrashrocker]

Why didn't you say that 17 post ago!
Geez.

 

[itsid]

I DID.. (okay I wasn't too sure if it's exactly 90° or just 86° or 93° or something)
but I said 90° offset (angular measurement)
and confirmed that in post #4.

that the holes need to be the same distance from the center was quite obvious (to me)
and that you know that a fixed distance from a center point can be easily marked with a compass... well that I took for granted.. *shrugs*

'sid