thebrick5150
XS650 New Member
New here and getting ready to build a chopper and wanted to know has anyone tried or has done a reverse head? Like some have done on the old triumphs.
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reverse head
- Thread starter thebrick5150
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Welcome to the forum thebrick5150. There's a couple threads here on that, try this one:
http://www.xs650.com/forum/showthread.php?t=2469
http://www.xs650.com/forum/showthread.php?t=2469
Yeah, that's a great idea--put the hot side of the head in back and get it out of the air stream to keep things nice and toasty.
thebrick5150
XS650 New Member
I see what your saying but would it get to hot to run properly or do long trips on? it would still get some air flow.
jd750ace
Front Toward Enemy
Some of them do get too hot, even with the exhaust in the front. Relatively high oil temp is not uncommon, even in moderate temps for some.
$0.02
$0.02
650performance
XS650 Addict
Oh, come on Griz ...
You're completely ignoring the extra power boost afforded by the ram air effect of having those carbs facing the incoming air flow. And, I'll reveal a little known tuning secret that with the head reversed you can go to 40MM carbs on both sides, which takes advantage of more incoming air. Of course, to balance the system the pro tuners then fit 2 inch straight through exhaust pipes. (unless it's a 750, then then you go to 2 and a quarter inch i.d., especially if you have a hot cam)
Also, everyone knows that keeping the carburetor side of the spark plugs cooler (which is impossible on the stock setup!) adds serious horsepower.
Further, you have to take into consideration that the higher temperatures - even if it nudges toward the detonation zone - will provide more complete burning of the fuel - air mixture for even MORE power!
You know all this stuff. It's selfish of you to keep it from those wishing to extract full performance from their machines.
I trust you'll be more forthcoming in the future.
You're completely ignoring the extra power boost afforded by the ram air effect of having those carbs facing the incoming air flow. And, I'll reveal a little known tuning secret that with the head reversed you can go to 40MM carbs on both sides, which takes advantage of more incoming air. Of course, to balance the system the pro tuners then fit 2 inch straight through exhaust pipes. (unless it's a 750, then then you go to 2 and a quarter inch i.d., especially if you have a hot cam)
Also, everyone knows that keeping the carburetor side of the spark plugs cooler (which is impossible on the stock setup!) adds serious horsepower.
Further, you have to take into consideration that the higher temperatures - even if it nudges toward the detonation zone - will provide more complete burning of the fuel - air mixture for even MORE power!
You know all this stuff. It's selfish of you to keep it from those wishing to extract full performance from their machines.
I trust you'll be more forthcoming in the future.
650performance
XS650 Addict
Oh, come on Griz ...
You're completely ignoring the extra power boost afforded by the ram air effect of having those carbs facing the incoming air flow. And, I'll reveal a little known tuning secret that with the head reversed you can go to 40MM carbs on both sides, which takes advantage of more incoming air. Of course, to balance the system the pro tuners then fit 2 inch straight through exhaust pipes. (unless it's a 750, then then you go to 2 and a quarter inch i.d., especially if you have a hot cam)
Also, everyone knows that keeping the carburetor side of the spark plugs cooler (which is impossible on the stock setup!) adds serious horsepower.
Further, you have to take into consideration that the higher temperatures - even if it nudges toward the detonation zone - will provide more complete burning of the fuel - air mixture for even MORE power!
You know all this stuff. It's selfish of you to keep it from those wishing to extract full performance from their machines.
I trust you'll be more forthcoming in the future.
You're completely ignoring the extra power boost afforded by the ram air effect of having those carbs facing the incoming air flow. And, I'll reveal a little known tuning secret that with the head reversed you can go to 40MM carbs on both sides, which takes advantage of more incoming air. Of course, to balance the system the pro tuners then fit 2 inch straight through exhaust pipes. (unless it's a 750, then then you go to 2 and a quarter inch i.d., especially if you have a hot cam)
Also, everyone knows that keeping the carburetor side of the spark plugs cooler (which is impossible on the stock setup!) adds serious horsepower.
Further, you have to take into consideration that the higher temperatures - even if it nudges toward the detonation zone - will provide more complete burning of the fuel - air mixture for even MORE power!
You know all this stuff. It's selfish of you to keep it from those wishing to extract full performance from their machines.
I trust you'll be more forthcoming in the future.
No, my friend, it was just memory lapse. I'd completely forgotten Bart Markel's many victories after he left Harley Davidson to race the Grand Prix circuit for Yamaha on a 750 twin with a reversed head. My bad.
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Aw, we're just tossing around a little ancient history. You should see some of those old pics of Markel throwing sparks off his mile shoe at the Isle of Man--a Google search would probably turn 'em up for you.
hoffman900
XS650 Addict
Oh, come on Griz ...
You're completely ignoring the extra power boost afforded by the ram air effect of having those carbs facing the incoming air flow. And, I'll reveal a little known tuning secret that with the head reversed you can go to 40MM carbs on both sides, which takes advantage of more incoming air. Of course, to balance the system the pro tuners then fit 2 inch straight through exhaust pipes. (unless it's a 750, then then you go to 2 and a quarter inch i.d., especially if you have a hot cam)
Also, everyone knows that keeping the carburetor side of the spark plugs cooler (which is impossible on the stock setup!) adds serious horsepower.
Further, you have to take into consideration that the higher temperatures - even if it nudges toward the detonation zone - will provide more complete burning of the fuel - air mixture for even MORE power!
You know all this stuff. It's selfish of you to keep it from those wishing to extract full performance from their machines.
I trust you'll be more forthcoming in the future.
I hope this was tongue-in-cheek!
2" od exhaust pipes from simply turning the head around?
"Ram" air isn't going to be effective until you're reaching VERY high speeds. Think about it, the air in a port is going over 200mph when the valve cracks open. Unless you can raise atmosphere pressure or ram it in faster than it's going through the port, you're not going to see a benefit other than cooler air, which I don't think is a problem on a non-fared motorcycle. Done right, it can help if your "airbox" is running at a pressure lower than ambient due to restrictions in the system, but that's it. I don't think that's an issue for individual carburetors with pod filters.
See the tables here for illustration: http://www.tahas.com/pdf/Dwyer_Velocity.pdf
To run a 2" id primary and a 40mm carb, isn't going to happen short of super or turbo charging. Simple as that.
Lastly, there is a reason the exhaust valve sits into the wind on an air cooled powerplant.
Really?!
I'm reminded of the rear cylinder on my old panhead, rear exhaust, forward intake, shrouded cooling air that's substantially hotter than ambient. Not ideal, but they've survived.
I designed a stealth cowl air pressurized intake system on my 327 vega. Reportedly yields 6% hp boost at 120 mph, almost 10% at 145, you could feel it...
I designed a stealth cowl air pressurized intake system on my 327 vega. Reportedly yields 6% hp boost at 120 mph, almost 10% at 145, you could feel it...
hoffman900
XS650 Addict
I'm not trying to be facetious, but who reported that? On a 500hp small block, that would be 50hp at 145mph...
Using NASCAR as an example, you could be talking 200hp gain at 200mph from 'ram' air induction using those figures...
Here are some figures Bill Jones (does a lot of land speed stuff) uses:
Sea level air pressure is 14.639psi . Find your max speed, and add (whatever that works out to in psi) to air pressure at your elevation. That's how much gain you're receiving. Keep an eye on the barometer sometime at your house and see how much that varies.
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That was an old tip published 30 years ago, for street setups. It compared cowl induction (base of windshield, higher than flat-plate pressure of .00286 lbs/sqft/mph) against typical under-hood open-round air filter setups, and also accounts for the significant temperature difference of the induction air. Of course, the bowl venting had to be contained in the induction zone.
But pressure is a statisical thing, and I like to quantize the effect. The air molecules bouncing around me, sitting in my lazyboy at 80°, are moving at an average velocity of 1100 ft/min. But, at any given instant, some are moving over 2000 mph, some barely moving at all (think of the bouncing ball 'kinetic' motion screensavers). Moving thru the air gives you a pressure value, but that's just a summation of the molecular impact forces. Suppose you could separate the hi-velocity molecules from the slow ones, and order their velocity vector, as in Maxwell's demons? Without any moving parts? A device to do that was invented in the late 1800's, and gives insight to a different perspective of the gas laws. Enuff, net crashes out here and tapping on this tablet is frustrating...
But pressure is a statisical thing, and I like to quantize the effect. The air molecules bouncing around me, sitting in my lazyboy at 80°, are moving at an average velocity of 1100 ft/min. But, at any given instant, some are moving over 2000 mph, some barely moving at all (think of the bouncing ball 'kinetic' motion screensavers). Moving thru the air gives you a pressure value, but that's just a summation of the molecular impact forces. Suppose you could separate the hi-velocity molecules from the slow ones, and order their velocity vector, as in Maxwell's demons? Without any moving parts? A device to do that was invented in the late 1800's, and gives insight to a different perspective of the gas laws. Enuff, net crashes out here and tapping on this tablet is frustrating...
650performance
XS650 Addict
Yeah, Griz, I remember that IOM Markel bike. That's the only XS650 engine I've ever seen with a 22 tooth primary sprocket. I think they figured that so long as they were doing all the shrouding to control heat on the reverse head that they might as well modify the left side of the cases to fit a larger sprocket and gear it up to take advantage of the higher speeds on the downhill side of the mountain.
And, I'll bet that's the only time either of us saw a steel shoe tear-off! The race is so long when compared to a typical flat track race that Bart knew he'd ground through a single layer steel shoe.
Always fun to remember the good old days.
And, I'll bet that's the only time either of us saw a steel shoe tear-off! The race is so long when compared to a typical flat track race that Bart knew he'd ground through a single layer steel shoe.
Always fun to remember the good old days
.hoffman900
XS650 Addict
I have a passing understanding of Maxwell's demons. If I figure out a way to separate and isolate hi-velocity molecules and find a useful application for them for motorcycles, I'll be sure to let you know after I patent it.
That being said, the best you're going to do with a XS650, with a seal airbox and ram air, is to probably bring the airbox pressure close to that of ambient. Weather fluctuations will cause a greater change in air pressure than any other type of system would.
dwyatt
XS650 Addict
If exhaust was meant to go out the front, then why is our arse in the back?
I have a passing understanding of Maxwell's demons. If I figure out a way to separate and isolate hi-velocity molecules and find a useful application for them for motorcycles, I'll be sure to let you know after I patent it.
That being said, the best you're going to do with a XS650, with a seal airbox and ram air, is to probably bring the airbox pressure close to that of ambient. Weather fluctuations will cause a greater change in air pressure than any other type of system would.
Too bad NJ is so far away, would enjoy a 'vulcan mind meld'. The Maxwell demon device was patented way back then, before motorcycles, but the concept found its way into contemporary contrivances, including stuff you have, but the way we're taught about gas laws makes it difficult to explain and comprehend.
