The GS850 and the Hacksaw

If you've been following our Project Bike build (and if not, why not?), you may remember that we stripped my mate Gez's GS850 down to use as a donor bike. Then we found that we'd been let down with some of the other bits, and couldn't use it after all. It seemed a shame to just bolt it all back together as it was, particularly as it was a bit of a shed anyway, so we decided to heed the call of the Hacksaw Of Destiny and sculpt it into something a little more aesthetic.

Now there are some folks out there who still consider chopping a bike as some kind of grim sacrilege which will hopelessly impair the handling and performance of a perfectly designed factory bike. Then there's us. And we understand, don't we, that chucking half a ton of metal and plastic in the scrap bin and lowering the centre of gravity by a foot can only improve on the stock product.

Back in the early eighties when everyone was much skinter than today there was a fashion for lowering the seat rails on a Jap four and fitting a custom tank to give it a bit more cred without losing functionality. It's been a year or two since I've been down that route myself, but it does present a really cheap and easy way of putting a presentable and useable bike on the street without breaking the bank. And it ain't rocket science either. So for those of you with big lumpy Jap fours in the shed and an itchy hacksaw hand, here's Dr.Rod's guide to a good old fashioned single top and seat rail conversion, without benefit of a frame jig or safety net.

	Suzuki's GS850 always was a brilliant all rounder even if the stock version displayed all the style and grace of a house brick. The classic brigade have started moth-balling some of these bikes, but you can still pick up tatty but useable examples for well under a grand.
	To make omelettes you first have to break some eggs. Egged on by Dr.Rod and George the Goat, Gez mercilessly tears the hapless GS down to it's component parts. The bike was running fine, so it won't be necessary to rebuild the engine.

Back at Dr.Rod's Shed Of Destiny, the project starts by offering up the new rear mudguard. To make sure the tyre clears the mudguard on full suspension bounce it's essential to work with the swingarm in place and wheel fitted. I've also removed one of the shocker springs to check the clearance with the damper fully compressed.

The GS frame, conveniently, is the right width to mate up to most custom mudguards. However the rear frame members were far too long, so I've lopped nine inches out of each side before slugging and welding them back on to the frame. I've also tacked a bracket across the downtubes to locate the mudguard at the correct angle. If you're working on a chain drive bike don't forget to check tyre to mudguard clearance with the wheel adjusted all the way forwards.

	With the mudguard securely located I can now drop the wheel and suspension out of the frame and turn my attention to the top rails. Like most steel-framed Jap fours the GS has three tank rails, which means you can cut the centre rail free and remove it without the headstock moving out of position.
	While we're at it this is as good a time as any to chop the old seat rails out and chuck them in the scrap bin Now we have a big hole in the middle of the frame and a clear run from the headstock back to the mudguard.

'We've opted to use a King Sportster custom tank which is designed to sit around 1 1/2" O/D tubing. I'm using 3mm wall CDS tube, which is heavier and stronger than the original thin wall stuff and is well up to the job of replacing the three stock tank rails. To start with I'm tacking the new section in at the headstock and mudguard mount before finish welding at the headstock gussets. To make sure the new rail clears the motor correctly it is essential to do this with the engine and carbs mounted in the frame. Don't be tempted to guess it, or you'll never get the engine back in later....

With the new top tube welded in the two remaining stock tank rails can now be chopped out and chucked. Working this way means the headstock is fully supported at every step, and never has opportunity to lose it's alignment.

On to Page Two....