Hi everyone. I have a trials tiger cub running a 14 tooth front sprocket and a 64 tooth rear sprocket and a 428 chain. The gearing is perfect for trials but I had a plan do some occasional green laning so my thoughts was to replace the rear sprocket with a 52 tooth for green lanes and revert it back to the 64 tooth for trials. On fitting the 52 tooth rear sprocket the chain was touching the top of the swing arm pivot point. Even with me sitting on the bike and compressing the suspension the chain was still slightly touching. With the 64 tooth sprocket fitted there is a 7mm gap. I guess that the other option is to replace the front sprocket for a larger one (such as a 17 tooth) and then fit the 52 tooth on the rear and see if it clears ok  but it's not a 5 minute job to revert it back to the 14 tooth  and I cannot find a 428 17 tooth front sprocket anywhere. So does anyone have any ideas please. Thank for reading my waffling on and any suggestions would be greatly appreciated. 

 

I know you will probably ignore this, but the chain will wear a couple of grooves, then will be fine. Keep it lubricated.

Many thanks for the reply. I'll keep that in mind but I don't think my conscience will let me allow the chain to drag on the swinging arm pivot point!! I have a road cub and there's a good gap with the 17 tooth front sprocket so maybe this will be the only way out?? Does anyone else use their bikes for dual use and if so what set up have you got? 

1 hour ago, MrMud said:

Many thanks for the reply. I'll keep that in mind but I don't think my conscience will let me allow the chain to drag on the swinging arm pivot point!! I have a road cub and there's a good gap with the 17 tooth front sprocket so maybe this will be the only way out?? Does anyone else use their bikes for dual use and if so what set up have you got? 

😆 didn't think you would go for it, but remember the original primary chain tensioner was steel and I never had to replace it in over 30 years.

Actually you've just jogged my memory and I think that the Francis Barnett chain ran over a (very grooved) steel tube! Maybe I could source or make a rubber swingarm protector that the well lubed chain would run on or a top chain roller. Back to the drawing board!! 

Pit Bike Black Extra Long Chain Slider. Swing Arm Protector Symoto Chain Guard | eBay

 

Thanks stpauls. I've just ordered one and I'll see how it fits and works. Have you or anyone else tried one of these??

Hi MrMud, I have just brought a Triumph Cub Trials, what carb are you running on? mine has an old 376/272 Monoblock which was for the scrambler I believe, It cuts out when I blip the throttle and someone suggested I should put a Amal 600 concentric 24mm on it to get a smooth tick-over and a good pickup.

I'm running an Amal 622 R300 which is a 22mm bore Mk1 concentric. This came on the bike when I bought it and it has been faultless. It picks up straight away and ticks over and runs really smooth. It also starts first kick. I also have the electrex world electronic ignition which makes a big difference over the standard ignition set up. 

Thanks for coming back, I have a 622 R300 22mm. I'll give it a go to see how it is on mine.