Rotary with belt driven jackshaft.

Cap63

New member
Looking for some advice. I've been running an Aixro XR50 rotary for a few years now with a belt driven jackshaft, no issues. End of last year we replaced the single Bing carb with a twin Tilly setup and but in on Alky, definitely more power and bottom end torque. But now on tracks that actually have some bite, I'm tearing the teeth out or snapping the belt in half. Before this change the last belt I had last over 2 years. I'm curious if I've exceeded what a 8mm belt 20mm wide can handle. I'm researching now but if anyone can point me in a direction it would be appreciated.
Thanks
 

RDub3

Member
Looking for some advice. I've been running an Aixro XR50 rotary for a few years now with a belt driven jackshaft, no issues. End of last year we replaced the single Bing carb with a twin Tilly setup and but in on Alky, definitely more power and bottom end torque. But now on tracks that actually have some bite, I'm tearing the teeth out or snapping the belt in half. Before this change the last belt I had last over 2 years. I'm curious if I've exceeded what a 8mm belt 20mm wide can handle. I'm researching now but if anyone can point me in a direction it would be appreciated.
Thanks
I would recommend one of the Gates 36mm carbon belts, they are spendy but so much stronger than standard belts. They also have a 21mm carbon belt that would probably do the trick. I use the 36mm one on my aixro.
 
A 30mm belt should be fine. I agree a 20mm is a little wimpy. If the carbon belt are the same as the polychains they will snap with any deflection or small amount of debris. I snapped 3 and went to the contitech belts.
 

Phiddy

Member
Yes, I agree with above. 20mm belt works for low HP stuff like a KT100, but you need more for anything over say 25hp. I would go 40mm if belt sprockets are available and affordable. I think 30mm will work though.
 

Revolvor

Member
Hi,

Can you tell me where you bought the Twin Alky carbs please if it was from a dealer ? Would like to buy a set but struggling to find them.

Sid
 

Cap63

New member
Hi,

Can you tell me where you bought the Twin Alky carbs please if it was from a dealer ? Would like to buy a set but struggling to find them.

Sid
I've bought all of my Tillys from EC distributing out of Tennessee. Originally bought these two for an open animal and an F200 in the past, had it redrilled for alky. Do you have a rotary you want to do this to or just looking for Tillys for something else?

Update on the belt, I was incorrect in my original post, I was running the 30mm wide belt. After looking further though inhad a lot of wear on the rear drive gear along with a bad key way. Going to.replace everything and give it another shot.
 

Revolvor

Member
Hi,
Thanks for that info, I’ve a couple of Seatta rotary kart engines, same as Aixro but twin plug / duel ignition, they share same rotors as Norton bikes I have, I’ll not use jack shaft as they are used for twisty short circuits in the UK.

Sid
 
A jackshaft will give you more gear options on short tracks allowing you to use larger diameter gears that will not rob power trying to turn around a smaller gear. What are you using for a clutch?
 

Revolvor

Member
Hi Brian, We run the standard Aixro setup, never seen a Jackshaft on any kart in the UK
 

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I'll try to get you a pick of my set up. I cant get it to copy to the page. Can you send me an email and I will try to send it from my phone.
 
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RDub3

Member
Here is a picture of mine as I was setting it up last winter. Imagine on a Sprint kart you don't need a jackshaft but on a dirt kart it definitely helps.
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Revolvor

Member
Because it’s a short twisty circuit kart we’ve don’t have that much space for a jackshaft by the looks of it as you can see, forgive the Honda Engine 5.5hp engine casings and bolted in pull start, that’s British sense of humour, helps everyone thing they are going to win until we start her up, she isn’t as grotty as she looks, a sleeper 😉

Would love to try one of your twin Methanol Tilly set ups on her.

We have a sister engine that’s in a new TB / CRG chassis but the old 1990s Dino kart is more fun tbh and not that much slower.
 

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Revolvor

Member
Hi,
No one here or in Europe use Jackshafts mate, this karts won loads of open class short circuit races, neither the brake disc or Sprocket have ever made contact with the track ?
 

Phiddy

Member
Jackshafts are for gear ratios over 9:1 found on small dirt tracks here in the states. The asphalt sprint guys dont use jackshafts here either, its a dirt thing. Some guys have to cause they have their clutch mounted on it. But it is a loss of power for sure, Id dump the jackshaft when at all possible.
 
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