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Posted By: Tigernuts Tight small end T140 - 05/02/21 1:08 pm
I've finally got round to starting to build my T140 engine, with the TSS crank and specially made rods from Steve Campbell (Thunder Engineering). The virus got me, hence the delay. Anyway, the gudgeon pins seem far too tight in the small ends, especially the timing side one. The drive side pin pushed through fairly well and the piston can be rocked by hand without much effort, But the timing side piston requires considerable effort to rock it. When looking at the g.pin while rocking the piston, it is the piston moving around the pin, not the pin in the rod.

I tried applying heat and it all felt fine (not a great deal of heat - not too hot to get hold of the piston). I have never had gudgeon pins this tight before in a Triumph engine - usually, the pistons will wobble back & forth freely under their own weight, with all the movement being between the pin and the rod. So my question is, how tight is too tight? I will give Steve a ring on Tuesday but if anyone can give any advice / info in the meantime, I'd appreciate it. Thanks
Posted By: Hillbilly bike Re: Tight small end T140 - 05/02/21 2:14 pm
Just the fact that one is different than the other says it's wrong. If the pins are the same size then the rod small end sized incorrectly...Sent the rods back.
I'm no expert but have fitted full floating pins in a variety of bikes and auto engines.In all cases the pin slid into the rod easily at room temperature but was a tight clearance.
Posted By: Tigernuts Re: Tight small end T140 - 05/02/21 6:06 pm
Yep, that's what I was expecting these to be like.
Posted By: quinten Re: Tight small end T140 - 05/02/21 6:20 pm
did you try both pins in the tigher hole
to confirm that its the little end hole and not one of the pins ?
Posted By: Tigernuts Re: Tight small end T140 - 05/02/21 8:29 pm
Yes!
Posted By: TinkererToo Re: Tight small end T140 - 05/03/21 9:16 am
I'm sure Steve Cambel will put this to rights. I have a pair of Thunder rods to go in my special stroker engine, and recently did a T110 iron race engine with Thunder rods, and they were fine
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