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'75 low lead gas user
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nokitov
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Joined: May 05, 2008
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Location: Pittsburgh, PA

PostPosted: December 24, 2008, 11:07 pm    Post subject: '75 low lead gas user

Merry Christmas guys and thanks to Romer on the Shine Your Side Covers Ideas. Got the Right cover looking good and I'm on 320 grit right now. Anyway, I just remembered that my '75 was a low lead user and with low lead gas out of the picture for a long long time I was wondering is there something I need to do to the valves to make it more compatable to todays 87 octane no lead gas? Seems to me that I read somewhere that I need to change them out but I'm starting to forget more than I remember anymore. Was that the only question I had? Can't remember.
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gordo
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PostPosted: December 25, 2008, 12:43 am    Post subject: Re: '75 low lead gas user

93 octane,I've seen valve seats cut right into a cast iron head,no seat's.And no problem's with the valve's.You should be ok with the stock set up,just keep it tuned & valve's adjusted properly.
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Retiredgentleman
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Location: Calgary, Alberta 1978 XS650 SE

PostPosted: December 25, 2008, 1:57 pm    Post subject: Re: '75 low lead gas user

I have found that regular low test gas works fine in my 78SE. My engine is apart right now, and valves/valve seats were in good condition...................just needed lapping.
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nokitov
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PostPosted: December 25, 2008, 4:47 pm    Post subject: Re: '75 low lead gas user

yeah but werent 78's designed for no lead?
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xsjohn
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PostPosted: December 25, 2008, 4:52 pm    Post subject: Re: '75 low lead gas user

Dang.....tune it for premimum (92-93).........it's still junk compared to the 94 octane regular of the 60's.......

xsjohn
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BigGeorge
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PostPosted: December 25, 2008, 6:16 pm    Post subject: Re: '75 low lead gas user

nokitov... What I think you are asking is do you need hardened seats installed to compensate for the lead being removed from the fuel. For many years lead was used in fuel to cushion the valve against the seat and when they went to no lead, some older vehicles had problems with the valves pounding the non hardened seats right out of the head. Manufacturers then started installing hardened seats right at the factory. I do not know what year Yamaha started doing this. Maybe someone else can chime in here and enlighten us both..............BG
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nokitov
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PostPosted: December 25, 2008, 7:05 pm    Post subject: Re: '75 low lead gas user

Big/George, that sounds like the concerns I've read about in the past. I guess I have to weigh possibly using an additive for the lead no longer in the fuel, replacing the head with one with hardened seats, hardening my seats, or nothing.
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jayel
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PostPosted: December 25, 2008, 7:56 pm    Post subject: Re: '75 low lead gas user

notikov your motor is new enough it doesn't need the lead the manufactures were swithing over in the 60's to the harder seats valves and guides
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nokitov
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PostPosted: December 26, 2008, 1:07 am    Post subject: Re: '75 low lead gas user

So it's further resolved, if it ain't broke, don't fix it and use 93 octane for cheap insurance. Thank you.
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Last edited by nokitov on December 26, 2008, 8:02 pm; edited 1 time in total
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Tomterrific
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PostPosted: December 26, 2008, 3:28 pm    Post subject: Re: '75 low lead gas user

High test, high octane premium gas is still no lead. The stock seats are fine with no lead. You should use high test, high octane fuel because of the very real risk of detonation. If you are worried about 20 cents, just think how much a holed piston from detonation will cost. And as far as not needing premium fuel, 95% of the time s*** gas is fine, it's the 5% when conditions are ripe for detonation that your engine needs premium.

Not everyone holes a piston every year but several people do. Everyone of these folks whether they ride an old Brit bike or a Yam650 had cheap 87 octane in the tank. This is one place "penny wise and pound foolish" is a great saying.

Tom Graham
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