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| Voxonda |
 Posted: Sat Nov 18, 2006 8:19 pm |
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Member
Joined: 01 Nov 2006
Posts: 42
Location: The Netherlands
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Hey to you all,
Like I mentioned in the topic about the camtowers, I'm building an engine for my replica racer. I found out that both my pistons and the cilinderblock are in good shape and are inside the tolerances. Pistons ø60.98 to ø60.985 and the cilinder ø61.01, which I believe is good. Now I am wondering if I should go all the way with 'bigboring' or just keep it 736cc and go with a camshaft, porting, somewhat higher compression and 28m/m F2 carbs. Or is the advantage of a 836 kit that much bigger????
Best regards, Rob |
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| Satanic Mechanic |
| Posted: Wed Nov 22, 2006 3:31 pm |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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Hi Rob,
well it always depends on what you are looking for, and what your budget is. In terms of performance gain, a good cam offers the best 'bang for the buck'. OTOH, a 'hot' cam will move your torque curve upwards, and you will loose bottom end and probably also midrange power. More displacement will add bottom and midrange to offset that and to add to a broad power band.
Speaking of HP for money, porting the head will have the worst ratio (unless you do it yourself  ).
As for the carbs, I prefer the earlier (i.e. K2-K6) carbs to the F2 with accelerator pump - they are easier to adjust (the F2 have a pressed in pilot jet). |
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| Voxonda |
| Posted: Wed Nov 22, 2006 5:55 pm |
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Member
Joined: 01 Nov 2006
Posts: 42
Location: The Netherlands
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Thanks Axl,
Thanks for your reply.
I have 2 other cilinderblocks that I can have 'big-bored', money permitted of course, so i think I leave the original one 736 and go with that for now.
You're correct in your statement about the camshafts, but I am trying to find a 'mild' one and not one suited for dragracing. For the carbs, I think because of the accelerator pump and the somewhat bigger diametre, they may be suited for my purpose. Maybe its possible to remove the pilots and replace them with whatever jets are needed?
Best regards, Rob |
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| Satanic Mechanic |
| Posted: Wed Nov 22, 2006 8:26 pm |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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Hi Rob,
if you are serious about making a Japauto replica, you will have to max out the displacement, just like Japauto did 
As for the carbs, the F2 have 28mm, just like the older non-accerelator pump ones. There are rumors the K6 had 26mm carbs unlike the earlier models which had 28mm as well, but I was never able to verify that.
On the F2 carbs, you could pry out the pilot jets if necessary and press in new ones if you need to change the pilots, but I never tried that. |
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| Satanic Mechanic |
| Posted: Wed Nov 22, 2006 8:47 pm |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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| Oh, and unless you go for a radical cam (and real stiff springs), you won't need to have that additional support through the valve cover. |
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| Voxonda |
| Posted: Wed Nov 22, 2006 9:39 pm |
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Member
Joined: 01 Nov 2006
Posts: 42
Location: The Netherlands
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I would like to go 'all the way' but not at that expense of Euro 1000 for a set of pistons!! That of course without the work on the cases and so on. My 'problem' is that my family would like to have something to eat everyday.
No Axl, it is not the intension to build a true copy of the Japauto's of the '70 but a bike build in the 'spirit of that time'. I would like to show some images but I am not that Whizz kid on the computer, but I have a weblog on which I have started to tell about the build.
http://hondareplica.web-log.nl/
I think you, once again, right about the studs on the camtowers although I think it can do no harm to put them there afterall.
Best regards, Rob |
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| Satanic Mechanic |
| Posted: Thu Nov 23, 2006 6:30 am |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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Sorry Rob, I probably should have put some more simileys after my remark about Japauto and big bore. Of course we all are only have a limited budget for our hobby, and we all have to live with that. No offense meant.
As for the cam support, it certainly doesn't hurt to have them, and if you like them, go for it!.
Nice weblog, by the way, and nice work you have done! |
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