1300 SP on a 1600 gearbox

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1300 SP on a 1600 gearbox

Post  George&Charlie on Sat Aug 18, 2012 2:18 am

I know someone on here will be able to give me the answer to this straight away, so here goes...

I have a borrowed 1300sp engine that I'm going to chuck in the orange beetle temporarily while I finish rebuilding the 1600. Will I come across any issues with the smaller engine on the larger gearbox? I know there are lots of problems with clutches slipping when putting larger engines on smaller gearboxes, but didn't know what problems are likely to occur the other way around?

Cheers
George
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Re: 1300 SP on a 1600 gearbox

Post  Rob on Sat Aug 18, 2012 6:03 am

If its just a temporary measure it should be ok.

The 1300 might struggle a bit but you'll just find you need to hold the lower gears for longer.

You might find the clutch is different which could be an issue. 1300sp would have originally have had an early clutch but your GT box will need a late clutch.

if it had been a 1600 you could have swapped but 1300 will be 180mm and the 1600 200mm so unfortunately not an option.
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Re: 1300 SP on a 1600 gearbox

Post  George&Charlie on Sat Aug 18, 2012 7:37 am

Rob wrote:If its just a temporary measure it should be ok.

The 1300 might struggle a bit but you'll just find you need to hold the lower gears for longer.

You might find the clutch is different which could be an issue. 1300sp would have originally have had an early clutch but your GT box will need a late clutch.

if it had been a 1600 you could have swapped but 1300 will be 180mm and the 1600 200mm so unfortunately not an option.
Cheers Rob, you're exactly right, the 1300 engine had a 180mm flywheel and a smaller clutch. I've swapped the flywheel and the clutch over, after a lot of straining and swearing Mad . It's in now though, I'll get it all wired up and running tomorrow Smile

Cheers mate
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Re: 1300 SP on a 1600 gearbox

Post  Rob on Sat Aug 18, 2012 8:22 am

The only issue that is now going to give you is your going to need the flywheel for the engine rebuild which is why i didn't suggest it.

Best to find another flywheel to use on the new engine.

At the very least you'll need to the flywheel to set the endfloat which you could do with another flywheel. It should be near enough to make it possible to swap them over at the end and then check and reset if necessary.

Ideally it would be best to have the whole bottom end balanced, for that you'll need everything from pulley through to clutch.
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Re: 1300 SP on a 1600 gearbox

Post  George&Charlie on Sat Aug 18, 2012 8:41 am

Rob wrote:The only issue that is now going to give you is your going to need the flywheel for the engine rebuild which is why i didn't suggest it.

Best to find another flywheel to use on the new engine.

At the very least you'll need to the flywheel to set the endfloat which you could do with another flywheel. It should be near enough to make it possible to swap them over at the end and then check and reset if necessary.

Ideally it would be best to have the whole bottom end balanced, for that you'll need everything from pulley through to clutch.
You're quite right, I contemplated whether or not to put the flywheel on the 1300 but after inspecting it, it's probably best I replace it with a new one anyway as it looks like it's seen better days. I'll definitely be getting the whole bottom end balanced though.

Talking of flywheels. would there be any benefit of getting a lightened flywheel on a stock 1600 or is that a performance engine thing?
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Re: 1300 SP on a 1600 gearbox

Post  Rob on Sat Aug 18, 2012 10:05 am

It really depends what your after.

It will make a big difference to the way the engine revs but the trade off is loss of momentum, ie you need to keep on the throttle as the engine won't run on after you come off the gas.

If you building it as stock then I would keep it standard weight. If you going for a larger cam and bigger carbs then it's worth considering.
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