Author Topic: Hmmm looking for more top-end. Piston Port 250.  (Read 1199 times)

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Offline John Orchard

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Re: Hmmm looking for more top-end. Piston Port 250.
« Reply #15 on: April 12, 2019, 06:26:13 PM »
Took the bike for a blast up the street today, much better, before shortening the header the top-end power was about 60% of the midrange, now the top-end is about 90% of the midrange.

Next mod is to dig through all the old pipes l have laying around and find a cone, with a less acute angle & shorter, than the current 'baffle' cone (the reducing one), this will make the powerband narrower but boost top-end.
Johnny O - Tahition_Red factory rider.

Offline John Orchard

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Re: Hmmm looking for more top-end. Piston Port 250.
« Reply #16 on: May 03, 2019, 01:56:38 PM »
Well l went-the-hack in the ports this week; up the street, top-end off, grind ...... repeat, garage littered with slices of piston skirt :-)

Found the top-end ;-) got so much now the clutch needed some work to stop it slipping. Yeh she needs a stab at the clutch lever to get her moving out of tight corners, in my front yard lol (if l let the rpm drop) but it gets back in the power quick & easy.

The first time l took it to the track a couple of weeks ago, l rode for much of the day, it didn't use any fuel ! even with a radically ported DT1MX barrel, she's bound to use more now :-)

 Racing Classic Scramble Club's event at Eurack (near Colac, Vic) this Sunday, l'm looking forward to see how it goes, l'll enter Pre 70, Pre 75 & Pre 78, stay tuned ;-)
« Last Edit: May 03, 2019, 04:39:22 PM by John Orchard »
Johnny O - Tahition_Red factory rider.

Offline topari

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Re: Hmmm looking for more top-end. Piston Port 250.
« Reply #17 on: May 03, 2019, 02:42:29 PM »
John, are you able to post a picture of your bike?
topari

1979 IT400F, 1984 kdx200

Offline sleepy

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Re: Hmmm looking for more top-end. Piston Port 250.
« Reply #18 on: May 03, 2019, 04:11:51 PM »
You could have an issue in Pre78. The rules states that it is for 1975 to 1977 machines only. Seems odd as it is the only class that doesn't permit earlier machines.
Be ok in Evo though.
Good to hear it is going better. Clutch will need Barnett springs or if they are the original glazed plate you may get by by bead blasting them.

Offline John Orchard

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Re: Hmmm looking for more top-end. Piston Port 250.
« Reply #19 on: May 03, 2019, 04:37:33 PM »
I think I'll have to pay Photobucket, I have so many pics saved with them, will get some pics up soon.

This is only a club-day, they might need my entries to get full fields anyway?  CSC only run up to Pre 78, pity they'd get a couple more riders if they included Evo (plus I could run my KX400A5 ;-) ); an extra 3 riders with an extra 2" travel isn't going to do jack-shit to the track ;-)

I increased the preload on the clutch-springs a touch and deglazed the metals on the concrete garage floor, plus a little more push-rod freeplay  :-)
« Last Edit: May 03, 2019, 04:44:21 PM by John Orchard »
Johnny O - Tahition_Red factory rider.