DIR Return Create A Forum - Home
---------------------------------------------------------
CycleKarts GB
HTML https://cyclekartsgb.createaforum.com
---------------------------------------------------------
*****************************************************
DIR Return to: Tech Forum
*****************************************************
#Post#: 14123--------------------------------------------------
Jackshaft sprocket mounting
By: StefanN Date: December 6, 2025, 2:53 am
---------------------------------------------------------
There’s quite a lot of talk about jack shafts on the forum at
the moment.
I would be interested to read/see people’s experience of fitting
small sprockets on jack shafts:
What size jack shaft have you used?
What’s the smallest sprocket you’ve used on the jack shaft?
How have you attached the sprocket to the jack shaft (photos)?
#Post#: 14124--------------------------------------------------
Re: Jackshaft sprocket mounting
By: Jimr1999 Date: December 6, 2025, 3:08 am
---------------------------------------------------------
Good question Stefan, I forgot to mention what I was talking to
Steve about in the post.
The jackshaft from Gemini that replaces the TAV2 one but with an
extended inner is pictured below. It takes the standard TAV2
sprockets and was the one I was talking to Steve about, From
memory, I was talking to Pred about a similar set up for his Rat
by using the shaft as a jack shaft. It is fat in the middle to
suit the TAV2 bearings and keywayed both ends for the sprockets
with a thread both ends for the nuts. It is about 250mm long.
The closest you could mount the sprockets to each other woud be
about 90mm centre to centre.
JimR
#Post#: 14125--------------------------------------------------
Re: Jackshaft sprocket mounting
By: NewbieNick Date: December 6, 2025, 4:28 am
---------------------------------------------------------
Hi Stefan , my Marmon wasp uses 219 sprockets throughout.
Smallest size available is 60 tooth from Talon,63 tooth from
everyone else. However if you’re struggling for room there are a
lot of smaller split sprockets with key ways for 30 mm axle/lay
shaft, these are 428 pitch. Loads of different tooth counts
search on eBay.
Regards Nick
#Post#: 14126--------------------------------------------------
Re: Jackshaft sprocket mounting
By: NewbieNick Date: December 6, 2025, 4:38 am
---------------------------------------------------------
Hi again Stefan, Oke kart parts sell 428 sprockets.
#Post#: 14128--------------------------------------------------
Re: Jackshaft sprocket mounting
By: Granville Date: December 6, 2025, 9:56 am
---------------------------------------------------------
For The Wrecker I have used a 3/4” jackshaft from Amazon. In the
jackshaft kit it came with a 10T sprocket, keyway bar and grub
screws so I used that on the Jackshaft. The jackshaft is
mounted between two steel plates that form the engine and
reverse gearbox mounting using 3/4” bearings as shown in the
image and u shaped adjusters for tensioning the chain that are
locked down with bolts above and below the bearing.
From the reverse gearbox there is a 10T sprocket that goes to a
T30 sprocket on the end of the jackshaft. Then from the 10T
sprocket on the jackshaft up to the Diff sprocket (think its a
T39 from memory)
#Post#: 14131--------------------------------------------------
Re: Jackshaft sprocket mounting
By: Ian F Date: December 7, 2025, 3:57 am
---------------------------------------------------------
Hi Stefan,
GNasher uses a hollow 25mm kart axle, with kart sprocket
carriers and 219 sprockets throughout. See Nick's comments
about available sprocket sizes. Parts were bought at Kartmania
kart-jumble at £20 for the axle, £5 for one sprocket carrier and
£7.50 for the other. Sprockets were only £1 each.
Desperate Dan, that I built for Ian Smythe, uses the 30mm axle
that came with the doner kart (new full-length key bought for
the CK), then some sort of sprocket carrier that also came with
the doner (never been able to source another one). For the other
end of the axle Jim T made an adaptor shaft to go in the hollow
axle shaft to take a small 420TAV sprocket. On the axle used an
OKE short wheel hub carrier for the axle sprocket, but had to
weld up the sprocket's mounting holes and re-drill the PCD to
suit the wheel hub. Further details in the build diary.
#Post#: 14133--------------------------------------------------
Re: Jackshaft sprocket mounting
By: Ade Colmar Date: December 7, 2025, 5:55 am
---------------------------------------------------------
In an attempt to keep things simple with bearings and sprockets
I used 30mm layshaft and hollow axle. The layshaft is a short
length of 30mm bright bar with a keyway cut in. The big
sprockets are 420 and range between 37 to 43 to change the
gearing. The small jackshaft sprocket is a split 428 item with
21 teeth (the smallest in 30mm) from OKE Karts. Although 420
and 428 chain are the same pitch, the roller width and diameter
are slightly larger for the 428. So that I can run with 420
chain throughout, I reduced the width of the 428 21 tooth
sprocket by about 1mm.
It all works fine, but I would like to find a better solution
using a matched sprocket smaller than the current 21 tooth item.
*****************************************************