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Changing my CAG from 25H to T8F

27K views 31 replies 6 participants last post by  MrKitty  
#1 ·
I want to change the gear ratio. Looking at Ebay they have both the 25h size and the T8F size. What came with it is the 25H (I think). One my other bikes has a fatter more substantial chain and gears. Only way I know of describing it is that it's just a little wider than a standard bicycle chain. So, I would like to change over to the T8F. So, do I have the terms correct ? What I'm calling the 25H is a lot narrower than a bicycle chain. Any recommendations ?
 
#2 ·
The spaghetti thin #25 is indeed the skinniest of chains and the non dogbone oval shaped links is the TF-8mm....

Cags came with both styles so does pocketdirtbikes and pocketquads

Recommendations depend on the type of ratio youre looking for meaning whats on it now and how do you want to make power improvements..
 
#3 ·
Best way to find out is to measure the center to center distance between the pins, that's the pitch. The #25 is 1/4" or 6.35mm between pins. The T8F has an 8mm pitch.

There is the common #25 size and the superior 25H. The 25H has wider link and joiner plates (1mm instead of 0.7mm) and if it's a good brand can handle quite a lot of tension. I personally don't see a reason to go away from a 25H chain but there could well be something I am missing here.
 
#4 ·
Best way to find out is to measure the center to center distance between the pins, that's the pitch. The #25 is 1/4" or 6.35mm between pins. The T8F has an 8mm pitch.
There is the common #25 size and the superior 25H. The 25H has wider link and joiner plates (1mm instead of 0.7mm) and if it's a good brand can handle quite a lot of tension. I personally don't see a reason to go away from a 25H chain but there could well be something I am missing here.
Yes you have researched and have concluded well....

Only one question to ask yourself.....

What size chain do you see on those expensive euro made racers pushing 16hp to the rear wheel????

It takes a bit more power to turn the 8mm chain which is almost the same size as the #35 chain but doesn't work well without dremeling the sprocket teeth
 
#6 ·
HI, I have a similar question. I am trying to figure out what size motor and clutch to replace for my middle son's Apc mini chopper rebuild. I measured the center from pin to pin on the chain and it is more like 1/2 in or 13.5 mm? I thought it was a 25H it a T8f but now I'm really not sure? Any help would be great! THANKS
 

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#9 · (Edited)
That looks like bicycle chain, Not #25 or T8F, but maybe its just the photo. Are the chain side plates stamped with anything?? I have never seen a 43 or 49cc piston port engine that did not have T8F chains to the rear wheel, and I have many bikes. See photo.
My first 2 Cags came with 25H chain, my last had T8F chain
Better to buy a $15, T8F 6 tooth 3rd bearing clutch housing, Enough 8mm chain and a Cag 54tooth T8F rear gear. Better count your chain links.
 

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#10 ·
This is the motor I am considering. It looks similar and has same looking teeth but it says for T8F chain? Below is the motor that was on it ? Looks like the same clutch but it only had 2 bolts for the clutch that would line up with the motor mounts. My older son's chopper has a motor like pictured on top from eBay.
 

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#15 · (Edited)
Those 7:1 , 5:1 and 3:1 reduction transmissions have sprockets for 25/25H Tf8mm and #415.....

What you dont know is one time on one of my X1's I actually ran a #41 chain on those same sprockets bike type chain sprickets too....it was just a huge wide monstrosity.....lol

There's like 3 different clutches available for it...

Good luck
 
#14 ·
That new engine is the engine the bike came with, you can change the sprocket teeth size, even use 25h or T8F sprockets and chain. He had to run the Cag engine backwards cause the drive chain is on the right, and Cag on the left. But, when you mount either engine like that it turns backwards, and that little 3 to 1 or 5 to 1 trans reverses the engine direction so the rear wheel turns forward, the CVT belt trans reverses direction also.
 
#16 ·
Thanks for all the suggestions. I am going to stick with the 25H. I am changing the front sprocket to an 8 tooth from the 6 it came with. I want a higher top end. I do need a new chain because the one I have has stuck links that bend but not easily. Soaked it in gas for days and oiled it up and it still makes popping noises when it rolls over the front sprocket. After all the measuring and "putting a wrench on it" I figured it was a 25H. But then I saw some little markings on a few links. pics attached.
 

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#19 ·
Hmmmm. sounds interesting. I'll give it a try. Diesel fuel, When I was a kid, we used kerosene. probably can't get that any more. I love the smell of Diesel fuel in the morning. Smells like, like POCKET BIKE RIDING TIME !!
 
#20 · (Edited)
Online I get 158 links of 25H chain for $8, and throw the old chain away. I also buy some gold chain, Cad plating cause it don't rust as bad a reg. chain. Once your chain gets loose spots and you adjust it, it will be to loose in spots and to tight in others.
With an 8 tooth pinion it is going to be hard on your clutch pads, and going to lose take off speed.
 
#23 ·
How many links did you order?? I buy stuff from them all the time, but it will take 2 to 3 weeks before it comes, so I plan ahead.
 
#24 · (Edited)
In my initial order I ordered the maximum of 152 links because I wanted as much as possible as I will use a chain splitter to get the length required and then have some left over for spares. Once I had the first order arrive, I checked it and then I ordered more to have enough for my future projects.

By memory the first order took about 2 weeks to arrive and the second closer to a week. That's to here in the S.E end of Australia.

The quality seems to be good but then I have not stress tested it yet and my knowledge is limited. At a minimum I can confirm it's a proper 25H specification in terms of side plate thickness and overall chain width.

My camera has a reasonable macro mode so I will have a go at taking a close up photo of the links to post on here
 
#26 · (Edited)
The chain looks pretty well constructed...

What I do to my chains is slather them in multimetal polish and polish the rollers aswell as the rest of the chain to add a lil bit of extra protection aswell as help it roll alot more smoother against the crude chinese sprockets...

If you take the chain and wrap it around the sprocket you'll notice lil voids under the rollers showing how they don't fit together...

On one sprocket I took a chainsaw chain file and filed the sprocket so the links bottomed out as they should... I even had to reduce the tips on the pinion gear because they were too long and actually adding alot of stiction to the chain when tensioned correctly..

The customized fitment allowed for a smoother ride with alot lesser chain feedback....
 
#27 ·
The 158 link chain is on the way. I like the polish idea. I know the 8 tooth will make it harder to get going but the new engine\carb is going to make up for that I hope. Doesn't matter, I'm trying to go at least 40mph.
 
#28 · (Edited)
If your engine is modded the right way for torque and the clutch has the right carburetor and clutch grab custom tailored you'll pull an 8th up front...It will have the same take off as a stock cag but have alot higher topend speeds...

I've run cags with 7/47 gearing on my 5 port cag and it went 45 with my brother riding it...


Another thing to touch on is the way the rear steel sprockets are manufactured...They're die stamped...

If you put them in a vice you can see the slope to the stamping which in turn kinda gives the sprocket teeth a slight slope to it too...

I fixed mine by bolting the wheel in the swingarm with the sprocket sloped outwards then I hand filed every tooth on the side to make it truly straight...
 
#29 ·
Up date on the app mini chopper clutch, sprocket, and chain. Mine are actually 12 tooth front and 28 Tooth rear sprocket's for 410 or aka #43 bike chain. Cam2 I believe you were correct that the picture I took above was an upgraded 415H chain. Which I think will work as well? I can't seem to find a motor with transmission for this set up? I only find 25H and T8F set ups.
 

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#31 · (Edited)
My stretched twin engine minichopper had really good handling after extensive mods....Good enough to get it to 52mph on a 14 front and a 25th rear gear.........

The #415 is more than adequate and the 415h is even better....I had twin engines pushing about 4.25hp each for a combined 8.5hp...There's no way a single engine build will ever reach half of what I was putting on it..The chain stayed strong ...
 

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#32 · (Edited)
that thing is awesome Cam2 like your saying the chain is the least of his concern I whould be more woreyd about the tiny short bolts holding the sprocket to the rear hub long befor the chain the other thing that likes to break befor the chain is the splind that the front sporket slides over but once that goes you just weld the sprocket to the shaft and go with it 🙂

If you want a unbreakable chain then go with a Shadow conspiracy interlock half link chain I have one on my BMX park bike and dont be a cry baby about the price in the bmx world you get what you pay for http://www.bikeparts.com/BPC438939/...BRBnEiwAqWt1zWUezmTCk1bpjVEsopiEsSiJbbuZBWwzDhG7RkiSPEaxinneBjEKzhoCwcYQAvD_BwE