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Backwards head?

  • Thread starter Thread starter Racing Geek
  • Start date Start date
R

Racing Geek

Guest
Anyone ever flip around the head of one of the GS750 engines or another GS engine so the carbs are in front and exhaust ports are in the back? Doing this would help me reach the goal for my bike a lot better.

I've seen this done with CB350's and XS650's and a couple other bikes but never to a GS motor. Hell, I've even seen a XS650 with a twin cam head. lol
 
Please explain, what is your goal?
shrug2.gif


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Steve said:
Please explain, what is your goal?
shrug2.gif
Click to expand...


My goal with being here on GSresources.com? My goal with doing the engine swap? My goal with reversing the head?

Because....
-- it's different
-- it makes mounting the carbs easier
-- it creates a lot more room on the bike
-- it allows me to make one of the custom rear suspension setups I've got drawn
-- it would get the bike even more attention
-- it would make it WAY harder for others to copy the bike
-- it would theoretically be more efficient
 
Because the head design is not symmetrical - the camchain tunnel protrudes more one side than the other, you'd have to reverse the cylinder block too....which means feeding the oil to the top end by external lines as the oil galleries would not line up.
Then it's machine a spot for the camchain tensioner to fit....
I'd suspect the top fuellers set up with reversed heads use billet cylinder blocks which can be made to suit.
Too hard IMO unless you luck into a billet block.

The twins now, much easier IMO.
 
Last edited:
GregT said:
Because the head design is not symmetrical - the camchain tunnel protrudes more one side than the other, you'd have to reverse the cylinder block too....which means feeding the oil to the top end by external lines as the oil galleries would not line up.
Then it's machine a spot for the camchain tensioner to fit....

Too hard IMO.

The twins now, much easier IMO.
Click to expand...


Ok, now that's the info I was looking for! ;)

I'll guess I'll stick with my "normal" 2 carb setup then.
 
Being different

Being different

Are you planning to use this bike as your daily ride or will it be solely a conversation piece?

The impractical issues are:

1. After fabricating custom headers, collector and muffler, you will be wondering why your bike is so hot to ride. With the pipes at the rear of the engine, you will be struggling to get enough clean air over them to aid in the engine cooling that occurs naturally under the stock design.

2. Your fuel tank will be subjected to additional heat from the headers, especially when the bike is stationery at intersections/traffic lights or in slow moving traffic. This may cause air locks in your fuel line

3. Your carbs will be subjected to forced induction, making them difficult to tune. You will also need a fuel pump to feed them, as gravity feed will not be an option.

4. Timing the cams will be a challenge, with much experimenting/mix and match grinds to consider.

5. As Greg has said, the galleys on the head and block won't line up.

6. You'd need to increase the rake on the steering to allow for the carbs and pods to clear the front fender. That's after you have fabricated a custom manifold to mount the carbs so they clear the down tubes on the frame.

Why not be truely original. You could invert the engine, have a dry sump fitted and claim to own the only GS capable of aerobatics.:p
 
Just a minor correction...they're all capable of aerobatics - it just depends on the rider. Landing right way up however can be the problem....
 
The heat from the header is one thing I was going to say... You would have to insulate just about everything or risk cooking the starter, fuel tank and your seat. If you ran the exhaust through the middle of the frame you would have to relocate the electrics and battery also.

The carbs in the front would be subject to road debris and risk being struck by objects. It would also be a nightmare if you ever got caught in the rain... Also carbs are typically are mounted to the head with rubber so you would have to fabricate some sort of support.

IMO If you were making a rail buggy I would say it would be a great pursuit but on a bike it would seem impractical...
 
I once saw a Kawasaki 750 triple engine in a drag racing cart trike type thing, motorcycle front end, then the driver in a go cart seat, then the engine behind the driver. Two small diameter fat slicks. The head was on backwards with the carbs in front. Three big expansion chambers straight out the back, the carbs sucking air from behind the driver's head. Went through the gears so fast you couldn't rally hear the individual shifts, it sounded more like four misfires. It was just damned near as fast as the funny cars of the day, much less than a second slower. Faster than all of the other stuff that was racing, bikes, cars, all of them...
 
I think the Brit bikes were the only one able to do that with just a little effort. Talking about ram air...
 
tkent02 said:
I once saw a Kawasaki 750 triple engine in a drag racing cart trike type thing, motorcycle front end, then the driver in a go cart seat, then the engine behind the driver. Two small diameter fat slicks. The head was on backwards with the carbs in front. Three big expansion chambers straight out the back, the carbs sucking air from behind the driver's head. Went through the gears so fast you couldn't rally hear the individual shifts, it sounded more like four misfires. It was just damned near as fast as the funny cars of the day, much less than a second slower. Faster than all of the other stuff that was racing, bikes, cars, all of them...
Click to expand...

Lot easier to set up an air cooled 2 stroke engine in reverse configuration. The heads and barrels could be reversed without too much, if any machining changes. Way easier to do this for drags too as overheating issues are very short lived. That's not to say that uncontrolled detonation won't kill your mill during the 1/4 mile run.
 
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hillsy said:
I've seen a Kawa KZ based drag bike with the head reversed. Ran pretty well 8 seconds at a time :)

This guy's building a reverse port CB550 over here:

http://www.dotheton.com/forum/index.php?topic=19961.0

It's a bit different in that he's swapped the valves around rather than turning the head around. A lot of work in that.

Still, it ain't running yet :rolleyes:
Click to expand...

Interesting link to the CB550 reverse port project.

I found this on the same forum: http://thekneeslider.com/archives/2...ted-3-cylinder-motorcycle-contruction-photos/

Seems my idea of inverting the engine too has already been tried.;)
 
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