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@  Tinderbox : (23 November 2018 - 12:31 PM) Afternoon all. Happy to be here with my '03 1300!
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@  oldanddribbly : (08 May 2018 - 10:27 AM) just took my bike out of winter storage and no current to the ignition. Nowt! battery been on optimiser and has full charge. Any ideas anyone?
@  lawtom : (04 May 2018 - 06:13 PM) Thanks boot. Got it sorted.

Photo

Head Skimming


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9 replies to this topic

#1 bettyswollokss

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Posted 30 July 2018 - 11:51 AM

Any One got any info or knowledge on head skimming for more grunt, I mean as in the best amount to remove, know anyone who's Done it?
I'm Only 4fut3 But I Look A Lot Bigger From A Distance?

#2 racerrad8

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Posted 20 August 2018 - 08:35 PM

Any One got any info or knowledge on head skimming for more grunt, I mean as in the best amount to remove, know anyone who's Done it?

You can remove material from the head gasket surface to raise the compression. But that lowers the head and essentially makes the timing chain longer. So, you will need to use adjustable camshaft gears to ensure you can adjust the cam timing after cutting the head surface.

 

http://www.rpmracingca.com/proddetail.asp?prod=Head%3ASCG


Randy - RPM


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#3 bettyswollokss

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Posted 20 August 2018 - 09:55 PM

Thanx for that. I was aware of the need to degree in the cams, thanx for the link. Any idea how much is safe? I know I'm going to have to get the plasticine out at some point, but if someone else has done it it would be good to compare results.
I'm Only 4fut3 But I Look A Lot Bigger From A Distance?

#4 racerrad8

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Posted 21 August 2018 - 05:09 PM

Thanx for that. Any idea how much is safe?

 

Since we use are engines in the race car, we see a lot of head warpage. We cut them multiple times and finally discard when we get into the intake valve seats.

 

Sorry, I cannot offer a number that is what is best as we don't machine for performance, but for head gasket sealing.

 

You do not have to worry about any type of piston to head contact, no matter how much you cut.

 

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#5 bettyswollokss

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Posted 21 August 2018 - 09:26 PM

That's good to hear,nice one. How much do you take off at a time then, 1mm? 2mm?
I'm gunna dyno the bike before, then do the head work and dyno again. It's my winter project.
How much power are you getting out of the engine, ever dyno one?
I'm Only 4fut3 But I Look A Lot Bigger From A Distance?

#6 Boot

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Posted 22 August 2018 - 01:24 PM

Would it be better to fit higher comp pistons?


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#7 bettyswollokss

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Posted 23 August 2018 - 06:01 AM

From where? If you can show me where I can get my hands on higher compression pistons that only require a rebore I'll consider them. A head skim is a lot cheaper, the most expensive part is the head gasket! That's why I always start there, I'm taking the head off to get the studs done so Im buying a new gasket anyway.....
I'm Only 4fut3 But I Look A Lot Bigger From A Distance?

#8 racerrad8

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Posted 24 August 2018 - 03:49 PM

That's good to hear,nice one. How much do you take off at a time then, 1mm? 2mm?
I'm gunna dyno the bike before, then do the head work and dyno again. It's my winter project.
How much power are you getting out of the engine, ever dyno one?

We usually only cut to get the head flat again, so I really don't know what we cut off. We have dynoed many, but since they are in a race car, the HP numbers are skewed by the additional drag other drive train.

 

There are several different overbore options available. Since your "1300" is actually 1250 cc, you are gaining at least 100 more cc with either of these kits.

 

Hank Scott has a 1350 slipper skirt kit: http://shop.rrcperformanceengines.com/product-p/wiseco-82mm.htm

 

or

 

Curt Andrews has a 1380 full skirt kit: http://andrewsmotorsports.mybigcommerce.com/ross-piston-kit-yamaha-fj-1380cc-83mm-99791-83mm-pk/

 

I have used both kits with success on customer builds.

 

Randy - RPM


Edited by racerrad8, 24 August 2018 - 03:51 PM.

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#9 Boot

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Posted 29 August 2018 - 11:37 AM

Like Randy said. :D

Andrews Motorsport has a shop on Ebay.


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#10 bettyswollokss

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Posted 09 October 2018 - 10:27 AM

Well the plan is taking shape, I'm not going to big bore it, financially it's not really an option, and it's my everyday bus so...
Just done a dyno run and it's putting out 86ftlb, which is plenty, gunna fit a dyno jet kit and sort the top end out as it was only pushing 99.2bhp it was running stay rich. So fit the the dyno jet, dyno, skim head and dyno again, that way I can see what it's given torque wise.
I'm Only 4fut3 But I Look A Lot Bigger From A Distance?




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