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Post by speedracer741 on Oct 17, 2007 0:05:04 GMT -5
Hello all, my first post. I manufacture valve train components in small runs and have been asked about oversize valves for the SR500 numerous times so I have decided to do a batch. My question is: did Yamaha use the same valve size in all of the SR/XT/TT engines over the years or will I need to make more than one model? Thank you  |
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lurch
Full Member
Posts: 217
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Post by lurch on Oct 17, 2007 1:44:59 GMT -5
Hi
I'm sure that the early XT/TT used smaller inlet valves , one of the SR Guru's will be along shortly that will know the sizes for certain .
Are you making them out of stainless ? I could/would be in the market for a set for sure
Welcome to the forum
LURCH
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Post by wotavidone on Oct 17, 2007 1:54:27 GMT -5
The information I have been given is that up to 1980 in Australia, XT and TT had smaller inlet valves than the SR. At the XT/TT Muster in Tanunda the other day, the "experts", of which there seemed to be an inexhaustible supply, reckoned that my '81 XT would have the bigger inlet valve, part number prefix being 2J2 Of course we all know the definition of an expert. As a mate used to say, mixing algebra and plumbing, "X is the unknown quantity, and a spurt is a drip under pressure." Mick |
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Post by frankyb on Oct 17, 2007 7:59:04 GMT -5
Hi guys, this is what ive found over the years. Late model xt and tt motors have the same size valves as the sr. I dont know what year the change was made, but ive done enough xt motors to know that the late model ones are identical to 2j2 sr heads. Heres one for speedracer, i have some xs650 inlet valves that are one mil bigger than an sr exhaust valve. Can these valves be used [after seat cut oversize and stem shortened] as exhaust valves in an sr, or is the metalurgy different between inlet and exhaust valves? Cheers Franky b.
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Post by miker on Oct 17, 2007 12:10:34 GMT -5
According to an article in _Cycle_ on the '78 SR500E, the intake valve is 47mm on the SR500 and 45mm on the XT500.
miker
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Post by speedracer741 on Oct 17, 2007 19:38:55 GMT -5
Thanks guys! This info is very helpful. I have been making and selling 2mm oversize valves for the XS650 on ebay since 2004 which is how I have gotten requests for the SR valves. The SR having larger valves makes sense since I have heard of XT/TT engines having SR heads on them. The only problem I am having at the moment is the availability of blanks with large enough head diameters. The stock Yamaha valves have a stem of around .313" and the only blanks available big enough have a .311" stem. This would only be a problem if one tried to use the stock guides but since anyone doing this much work would be using aftermarket bronze guides that require honing anyway this may be a non issue and work out just fine. Also if SR valves are an oversize in the early XT/TT heads perhaps I should only make an oversize for the SR? I will be looking on ebay for some used heads so I can get some sample valves and seat diameters to determine the best options. I would like to be able to provide years and applications to buyers so they are getting the right parts and I am no expert on the design changes of this engine. I have done mostly vintage 4 cylinder stuff. I greatly appreciate all of your help on this and if all goes well I will have a completed set within the month!
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Post by speedracer741 on Oct 18, 2007 1:34:10 GMT -5
Ok, found some more info. According to a parts supplier, the 47mm intake fits the '79 and later XT/TT and all SR heads. The pre '79 XT/TT are indeed 45mm. And all years and models use the same 39mm exhaust valve. The blanks I have found have have a head diameter of 48.7mm intake and 41.2mm exhaust. These can then be turned to the finished diameter. I will most likely leave the intakes where they are and go 41mm on the exhaust unless there is a benefit from that last 0.2mm without compromising seat integrity. Rather than go with a conventional stainless valve I will be using the more expensive iconel alloy which is a high nickel/cobalt steel. This is most often used in turbocharged applications and has a higher surface hardness and temperature threshold than stainless, a good choice in air cooled engines. It's the same as I have used in the XS650 and performed flawlessly in competition. Will keep everyone posted!
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Post by StewRoss on Oct 18, 2007 4:37:46 GMT -5
Interesting, keep us posted. SR |
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Post by speedracer741 on Oct 18, 2007 23:42:30 GMT -5
Got the intake blanks today, the exhausts are on backorder but I will go ahead an make some progress on the intakes. Since I am going to be set up to machine these I am thinking of getting a few titanium blanks as well. Not sure if it would be cost effective to try and market them but I want to make a set or two anyhow just to say they exist. Using them would require different seats such as beryllium-copper and lash caps, it could get expensive really fast but an engine with valves this big would really benefit from the weight savings. Not to get ahead of myself with this project but sometimes I have way too much fun playing with this stuff!
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Post by curly001 on Oct 22, 2007 6:00:44 GMT -5
Speed is that your E-bay site smw70ss?
looking forward to the valves keep us informed.
curly.
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Post by marlon on Oct 22, 2007 14:44:35 GMT -5
Keep us posted mate, sounds interesting!
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Post by speedracer741 on Oct 23, 2007 0:33:39 GMT -5
Yep, I'm smw70ss on ebay. Still waiting for the exhaust balnks  . Quick question, I have a set of XV920 Virago heads and I know that the top ends are loosely based on the SR platform. Are the valves the same? The intake is 47mm and is marked 2J2, the exhaust is 39mm and is marked 5A8. Vesrah has different part number for the SR and VX valves indicating that they are different. If they are indeed the same I can use these valves as the template to make the oversizes however if there is a length difference then I still need to get my hands on some SR valves. I wonder how many people would like oversize titanium racing valves for their Viragos ;D |
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Post by curly001 on Oct 23, 2007 0:59:47 GMT -5
Speed the intake is the same don't know about the exhaust as I need 2 for my spare heads I'm getting done.
I don't know about virago riders wanting a set of titanium valves for their bikes but this XT owner wants a set for his bike and a set of your iconel alloy ones for my TT.
Curly
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Post by speedracer741 on Oct 23, 2007 1:47:55 GMT -5
If the intake is the same then the exhaust should be as well. The SR exhaust is also 39mm. I should get a set of actual SR valves though just to be sure. It would be a shame to junk a bunch of blanks as I don't think there is much of a demand in the Virago world for racing components. It does make me think though: get a couple of race prepped 650cc SR topends and drop them on an XV1100 bottom end, 1300cc drive shaft snapper  . Anyway...back to reality. I will look around for some valves this week so I can at least get the steel intakes finished. Then when the exhausts show up I can get them done and get them all heat treated together. I am still pricing titanium blanks but they seem to cost about the same as a finished valve. And the hunt continues....... |
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Post by caferacercarl on Dec 14, 2007 2:42:34 GMT -5
The Virago valve has its join further up the stem than the XT,TT,SR original item, make up some phosphor bronze guides and make the stems 7mm and watch me order multiple sets,Kibblewite do a titanium 49mm, 39mm exhaust,spring set,bronze guides and lash caps etc ,for these in 7mm but it is nearly 900 aussie dollars, love your choice of inconel, do the 7mm thing and the flow increase will make your set worth buying [ guides and valves and two lash caps and possibly just two retainers/collets to suit] as most people have springs these days in there engines. Carl, caferacer m/c NSW australia. 61 2 63377599
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. Quick question, I have a set of XV920 Virago heads and I know that the top ends are loosely based on the SR platform. Are the valves the same? The intake is 47mm and is marked 2J2, the exhaust is 39mm and is marked 5A8. Vesrah has different part number for the SR and VX valves indicating that they are different. If they are indeed the same I can use these valves as the template to make the oversizes however if there is a length difference then I still need to get my hands on some SR valves. I wonder how many people would like oversize titanium racing valves for their Viragos ;D
. Anyway...back to reality. I will look around for some valves this week so I can at least get the steel intakes finished. Then when the exhausts show up I can get them done and get them all heat treated together. I am still pricing titanium blanks but they seem to cost about the same as a finished valve. And the hunt continues.......