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xs650 > > High Performance Modifications > > Top End Work > > Thin Gaskets for Higher Compression |
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Thin Gaskets for Higher Compression
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 20, 2009, 11:13 am Post subject: Thin Gaskets for Higher Compression |
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Santa is bringing me a set of JE 77mm pistons and I'd like to use a thinner, copper head gasket to raise the compression ratio from the 10-1/2:1 these pistons give, to about 11:1. Anybody done this and can you recommend a gasket thickness?
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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yamaman Support Staff
Joined: Jan 04, 2007 Posts: 1638 Location: Perth Western Australia
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Posted: December 20, 2009, 8:14 pm Post subject: Re: Thin Gaskets for Higher Compression |
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Just need to enter all the details in here, make up the gasket size till it suits:
www.csgnetwork.com/compcalc.html
_________________ Its not enough to have an aim in life, you have to pull the trigger! |
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 20, 2009, 9:27 pm Post subject: Re: Thin Gaskets for Higher Compression |
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Way cool program, will have to measure some volumes first though, but cool.
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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dpmphoto Full Member
Joined: Apr 18, 2007 Posts: 485 Location: syracuse NY
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Posted: December 20, 2009, 9:53 pm Post subject: Re: Thin Gaskets for Higher Compression |
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I read in that 650 performance manual that too much compression on the xs motor can actually hurt both performance and obviously reliability. I don't know if the performance part is actually true but i just thought u might want to investigate
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 22, 2009, 11:51 am Post subject: Re: Thin Gaskets for Higher Compression |
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Too much and this motor can go ballistic, but I'm not aiming too high. The new pistons I just got claim 10-1/2:1, but the Yamaha factory tuners ran this motor at 11-1/2:1. I just thought I check into getting a bit closer to that, but may just leave well enough alone.
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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Srinath Full Member
Joined: Sep 10, 2009 Posts: 343 Location: Charlotte NC
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Posted: December 22, 2009, 1:33 pm Post subject: Re: Thin Gaskets for Higher Compression |
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Flow is far more vital for power than compression.
The second aspect of a head gasket is somehting that people forget about, partially because they have done so well at it for so many years. A head gasket is supposed to blow in order to save the motor. If you check with old school racers they always analyse their failures and so many cases they find that they had a head gasket failure instead of lunching the whole motor. Like detonation or pre ignition etc.
Your thinner gasket could in fact fail to do that and get your higher compression motor to fail in a more $$$ way.
Cool.
Srinath.
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jayel 650Rider Supporter
Joined: Apr 16, 2006 Posts: 3417 Location: SE Iowa 1974 TX650A
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Posted: December 22, 2009, 4:54 pm Post subject: Re: Thin Gaskets for Higher Compression |
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not much point to hotrodding a XS anyway about 35 years late on that, you want a hotrod go buy a Ninja
_________________ all it takes is time and money -- Where are we going and why are we in this hand basket? |
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 23, 2009, 4:53 am Post subject: Re: Thin Gaskets for Higher Compression |
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Good point I hadn't considered on the head gasket blowing! Just looking to raise the compression slightly over the off the shelf JE pistons to be closer to the CR run on the 70's racers. Probably overthinking this. I may reconsider this part of the plan.
As to the flow, it has a Craig Weeks ported head, racing exhaust and 36mm flat slide Mikunis, now waiting on Megacycle cam, think I have that covered.
Only point of the whole build was the fun of seeing what I could do with it. I knew from the start I could buy a slightly used modern bike for less than I would put into this sucker (nearing $7k). It's been a blast to build!
The fun of hot rodding it will be seeing all the young bucks wondering what the hell that damned yellow POS is.
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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Srinath Full Member
Joined: Sep 10, 2009 Posts: 343 Location: Charlotte NC
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Posted: December 23, 2009, 9:20 am Post subject: Re: Thin Gaskets for Higher Compression |
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You want flow, try the backwards head that that one guy did.
But yea carbs in front and exhaust in the back looks absolutely awful.
I'm also building a yellow bike ... I'd put a similar yamaha race pattern on it but I am thinkign down the middle on top, not the side. Yours looks great, but I am running the stock side covers etc and rear fender, so tank and fender have down the center, side covers have smaller down their sides.
Cool.
Srinath.
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xsjohn Full Member
Joined: Jul 30, 2006 Posts: 5857 Location: North Carolina USSA
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Posted: December 23, 2009, 10:58 am Post subject: Re: Thin Gaskets for Higher Compression |
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The exhaust side ofthe thead is what you want to cool...........in the back it will get real hot.......
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 23, 2009, 11:08 am Post subject: Re: Thin Gaskets for Higher Compression |
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I'm running your top end oil cooler to help out.
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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Srinath Full Member
Joined: Sep 10, 2009 Posts: 343 Location: Charlotte NC
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Posted: December 23, 2009, 11:53 am Post subject: Re: Thin Gaskets for Higher Compression |
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xsjohn wrote: |
The exhaust side ofthe thead is what you want to cool...........in the back it will get real hot....... |
Yes and ... well a very small no ...
The exhaust will flow and get out of there better, so it wont be heating up the head and ports and what not as much.
Of course the thing will get less air, though an xs wiht its side angle exhaust ports will be better off than others like a GS500 with a straight on exhaust, but it still wont be as nice and breezy as out in front. Maybe put some extra air flow directing vanes like they did on old air cooled VW's. Not very great again for looks. BTW there is one xs being built that way. Lets see how it pans out.
Cool.
Srinath.
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 23, 2009, 12:22 pm Post subject: Re: Thin Gaskets for Higher Compression |
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I'd like to see that. I'm too lazy to try it, but would like to see it!
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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yamaman Support Staff
Joined: Jan 04, 2007 Posts: 1638 Location: Perth Western Australia
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Posted: December 23, 2009, 12:29 pm Post subject: Re: Thin Gaskets for Higher Compression |
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It's right here mate:
www.xs650.org.au/offbeat.html
_________________ Its not enough to have an aim in life, you have to pull the trigger! |
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dwyatt Full Member
Joined: Dec 21, 2006 Posts: 186 Location: Houston/Malongo, Angola
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Posted: December 23, 2009, 1:02 pm Post subject: Re: Thin Gaskets for Higher Compression |
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Yup, I was right, I'm too lazy to attempt that!
_________________ Current Rides:
2000 HD Super Glide
1983 Yamaha XS700RR
1978 Maico 440 Magnum
1956 Blonde TX Gal |
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