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Big Bores for 70 degrees

Agreed. Its already turbulent as hell exiting the port so theres nothing to disturb really. Important parts will be seat, throat and short radius diameter/shape, rest is pretty much just transport imho.
Cam is too short duration to have any reverse pulsing worth mentioning.
 
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Tom, I won’t be changing the port shape at all. Interesting reading up on port shape, bowl, short turn radius etc but at this stage on this head all I want to achieve is do more than what the Thumperracing porter was doing to more emulate the Berglund head.

What I have noticed particularly with the 70* head is they don’t have a bowl as such and no biased expanded side. The short turn radius looks as though it could do with a raise and the long turn radius could do with a raise. Of course I could be way off but going by what I have read, this looks to be the case.
 
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The lightened CP piston fitted. I had to shorten the Wossner pin a tad as I couldn’t get the circlip in.

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Very cool :)

I understand you arent going overboard right now.
Ill put the pics up I have just incase some nut likes a peak.
The last pic is a bit funny as it says 'low performance' as the F is cropped off :)

Courtesy FP-Engineering doing my head.

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Tom, seriously brilliant. Most would enjoy those pics. Only last night I was wondering how they held the valve open.

That’s some serious flow improvement.
 
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The 610 is back together and running. It’s going nice. But geez, it still vibrates exactly the same as prior regardless of removing 53g from the piston assy. From 70g down to within 16g of the OEM piston assy weight. It can stay like this.
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That's very interesting.

I wonder what it would take to put it back into balance.

I wonder if weight could be added to the counterbalancer, or added/removed from the crank. As in I'd really like to understand how it all works.

I should go read Tuning for Speed!
 
tourist said:
That's very interesting.

I wonder what it would take to put it back into balance.

I wonder if weight could be added to the counterbalancer, or added/removed from the crank. As in I'd really like to understand how it all works.

I should go read Tuning for Speed!
Click to expand...

At this stage it’s indicating to me the issue is elsewhere. You would think if the inbalance was due to excess weight at the piston assy and reducing this, you’d be in the ballpark. I’m wondering whether the inbalance is elsewhere.

I do have a ThumperRacing balanced to the CP piston here. That was for another project.
 
What I was thinking is getting a 78mm crank off ThumperRacing. It would then complete a 660 with all the parts I have, oh I’d need another piston kit as those cranks run a 19mm pin from memory. My 610 kits I have here are 20mm pins. I have a 570 motor here with a blown crank. I could do the 660conversion to it. Also I bought a KTM conrod repair kit for this blown crank. It would give me two 610’s and a 660.
 
I found the vibration. It’s the handlebars. When you place a finger on the triples, virtually no vibration. Same anywhere over the bike.
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Out for the run in today. Well that lasted all for 1/2 an hour, then into it. Beaut day for it. Getting a sniff of Spring. The 610 with the current mods is one nice motor. My problem has always been ‘I want more’. Today proved that the 610 can be too much. Not that I’m having troubles handling it. I would like more. Just that there isn’t a lot of traction the bigger you go. I’ve never been about going fast, even though I don’t have troubles doing so, just that I’m all about having fun. This is where this bike excels. This bike will lift like no other. Awesome fun.
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tourist said:
Yesssss!!!

re. bar vibes: Mine had these on it when I bought it: https://www.ktm-parts.com/SXS14125200.html

They seem very nice. No vagueness. Haven’t tried without.
Click to expand...

Sorry mate, it still vibrates way too much. The ride today confirmed it. It’s going to have to stay like this for quite some time. Got other projects to do.

Be buggered if I know what could be causing it though. :furious:
 

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