Mag flange

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double h
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Fri Jan 18, 2019 11:21 am

Never thought about different cut outs for the transfer port when I bought the flange. It's an early Spanish li 150 s2 with an sil Gp 150 top end. It wouldn't pull in top gear with a 45 max speed. Could this be my problem?Image

holty
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Fri Jan 18, 2019 2:45 pm

in a word no, it would improve performance if it matched, but I think you have a problem elsewhere, did you do a leakdown test before stripping it, and a check of the timing, plus plug chop ?

johnny650
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Fri Jan 18, 2019 2:48 pm

very unlikely i would say but we really need a lot more information about your setup ........carb, atomiser jets, inlet manifold, exhaust , , stator points gap / elctronic stator ignition advance , gearbox etc etc .

I just spent months sorting out my scoot which involved removing and replacing my top end 3x times replacing the crank and drive side oil seal changing the cylinder from 150cc to 200cc back to 185cc changing from points to electronic and half a dozen carb and jet changes. I tried various timings and in the end one day last week it all came together and the scoot really flies now.

poor performance its frequently down to incorrect ignition timing and or incorrect fuel air mixture or poor supply but poor compression , crankcase leaks and inappropriate gear ratios and other things can also be an issue . A compression test and leakdown tests would be a good place to start

If you were able to upload a video or better still helmet cam of your scoot we could better advise .

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double h
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Fri Jan 18, 2019 3:07 pm

holty wrote:in a word no, it would improve performance if it matched, but I think you have a problem elsewhere, did you do a leakdown test before stripping it, and a check of the timing, plus plug chop ?
Done a leak down with a very slight loss from the exhaust manifold. timing was strobed and spot on. There were no symptoms of an air leak . Done a compression test and it's down at 75 psi cold so will set the squish ,put the og mag housing in and take it from there. The plug colour was good. Cheers.

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garry inglis
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Fri Jan 18, 2019 4:17 pm

refit the barrel and piston and look at were the piston is to the bottom of transfer ports if its sitting below or sitting above the bottom of transfer port this is were you could be losing power you want the crown of piston level with the transfer port and about 1mm over exhaust port to set it up

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double h
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Fri Jan 18, 2019 4:18 pm

Ok cheers.

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garry inglis
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Fri Jan 18, 2019 4:23 pm

by the way that looks like a 200 mag housing as they have a bigger transfer cut

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double h
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Fri Jan 18, 2019 5:19 pm

garry inglis wrote:by the way that looks like a 200 mag housing as they have a bigger transfer cut
Yes it is, it stated all models when I bought it and didn't pay much attention to it on the rushed rebuild. I was hoping this was causing poor fuel delivery but alas no.

johnny650
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Fri Jan 18, 2019 11:38 pm

what ignition advance did you set ? depending on the current advance, you might pick up some high rpm power by retarding the ignition slightly although that would probably reduce low down power a bit but that doesn't sound like it would be an issue lol Let us know how it goes good luck

johnny650
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Sat Jan 19, 2019 5:48 pm

ok .................sorry my suggestions were of no interest to you . Good luck anyway

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