Cleaning up behind the port window - cylinder liner issues

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NewbieDAN
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Suzuki 2-Strokes: 1972 GT380

Cleaning up behind the port window - cylinder liner issues

Post by NewbieDAN »

Hello all, I'm chasing some advice. I've got a GT380 I'm preparing to do some very mild clean up work around the ports, remove imperfections, slightly reprofile without getting too carried away.
My issue is this...there's a few casting imperfections around the transfer ports where the cylinder liner joins the cast walls for the cylinder jug. Basically material needs to be added or filled in these locations behinds the port window to form a nice roof to the ports, to have good air flow.
Is it possible to add material so it can be smoothed out?
What should I use?
I'll try to add a photo
Craig380
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Re: Cleaning up behind the port window - cylinder liner issu

Post by Craig380 »

Hi and welcome. Sometimes the casting of the cylinder is pretty crude and the port tunnels don't match the windows in the liners. However on a mildly-tuned street motor like the 380, I don't think it makes any noticeable difference - especially given the hassle of building up the alloy so it can be flowed.

I think the only reliable way to build up the alloy would be puddling in new metal with weld, which would be a hassle.

My 10 pence worth is, leave those bits and clean up the exhaust port: smooth the angle on the floor of the port and make sure that's all nice and smooth. A set of expansion chambers transforms the 380, so those are worth playing with, too.
1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed
NewbieDAN
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Suzuki 2-Strokes: 1972 GT380

Re: Cleaning up behind the port window - cylinder liner issu

Post by NewbieDAN »

What about JB-weld or some epoxy filler?
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Alan H
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Re: Cleaning up behind the port window - cylinder liner issu

Post by Alan H »

If it came loose, it would be catastrophic.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
Vintageman
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Re: Cleaning up behind the port window - cylinder liner issu

Post by Vintageman »

If all transfer heights are the same with respect to the liner I would not think the fact the cast aluminum was higher would be a noticeable flow match problem.

I have seen high temp epoxy used on intake port, but think temps may be too high for transfer port roof.
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tz375
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Re: Cleaning up behind the port window - cylinder liner issu

Post by tz375 »

I have a set of barrels with Devcon F in the transfers, so it can be done but it will not stay there forever and needs a good key to promote adhesion.

The other answer is to raise all the transfers enough to clean up that mess and raise the exhaust ports by an appropriate amount to make more HP to go with 550 carbs and chambers..
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