Series 30 torque converter on a 11 HP engine?


New Member
Hi all,

First post here so let me introduce myself real quick, I'm Nico from Sweden. Recently got inspired to build a mini bike after seeing a bunch of videos on Youtube that looked like it would be way too much fun.

So I went and got me a little 70s kids dirtbike for parts (wheels, fork) and a mid 80s 11 HP B&S engine.
I live out in the woods so I will be doing mostly offroad riding with it, and not necessarily very fast. That lead me to my first problem, I see that centrifugal clutches don't like slow speeds because of the slippage at low speeds. So I figure I'd probably be better off getting a torque converter. I like acceleration more than I do top speed too ;)

Over here the same kits with primary, secondary, belt, plate, cover that are all over ebay are sold for about $230, but the store specs it at 7-13 HP, while everyone else writes 8 HP.
So that makes me wonder.. Are they just making those numbers up? Is this a different kit? Are all other sellers wrong?
Here's 2 pictures of the kit that they have on the site, to my untrained eye it looks like the exact same parts as the ebay kits.

So I'm looking for a bit of advice here.. Will this kit, or any of the series 30 clone kits work for 11 HP (and later on some tuning)?
If I get one of those kits and it turns out it doesn't work or wears out quickly, will a series 40 or 44 work with the same C-C distance between clutches?
If I can avoid it I don't want to spend $400 on clutches right now, but as I'm going to be building a custom frame, what kind of torque converts I'm getting is a pretty crucial decision. If possible I would like to build the frame right the first time :)

Any info is welcome!
Many thanks in advance :)
With fabrication skills to create a frame, I'd suspect you could easily adapt older snowmobile parts?
A Comet 94C Duster or the better 102C with a tapered shaft adapter makes drive easy. Golf carts have used a version of the 102C with engagement as soon as engine fires, and tuning bits from engaging there to crazy high revs are available. 94C pucks/springs can work from 1500 engagement-up. Same with driven and jackshaft parts.


Active Member
The 30 series will work on 10hp engines but the bike needs to be geared so that the clutch will not be slipping real bad when loaded down, whereas the 40 series would be able to grunt more before slipping. The Super Broncs are a prime example with a 30 series on a bike that big with 8 & 10hp engines but they can slip a bit when loaded down and overall work pretty good. If you can spend the money, the 40 series would be a heavy duty clutch setup that should last a long time but they are harder to install then the 30 series in your pics.

Just completed the one not in the snow which is a 10hp with a 30 series clutch and it works good, and the one in the snow has the 40 series with a 8hp.


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"so I will be doing mostly off road riding with it"

If you are doing it right the first time go with 40 series.
Make a Jackshaft to mount the driven to.
Drive the rear wheel off the opposite end of the jack shaft (#40 chain and sprockets highly recommended).
And if you don't have brakes on your wheels you can add that to the jackshaft in the form of a band brake and puck.

Tho you can get away with cheaper Chinese Drivers and Drivens (Comet is best) ALWAYS buy genuine Comet belts.
I bought the kit you show. They claim it will work up to 13 hp, when I got the kit I found it to be a series 30 with a 1" driven pulley is all. Rather than use the aluminum backing plate I am using the pulleys with a jackshaft and using a common spacing for both series 30 and 40, so if the 30 doesn't cut it, I can easily change to the 40. Remember the 40 driven pulley in an inch bigger around and needs more room, so set up jack shaft to fit the bigger pulley. I also question if the small 5/8 shaft on the 30 will hold up to the larger hp. If my budget will allow I will put a 40 on my bike, but if things are tight that month it gets the 30 I already paid for.