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Bike Review - Posted 17th June 2013
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Suzuki GS1000 Winter Project - Part 3

Duncan Cooper returns his GS to the road after it spent seven years in storage. This time, he can't avoid cleaning the carbs...

Last time I finished painting the fuel tank and, not content with watching paint dry, decided to rig-up a temporary fuel supply (a plastic funnel from the kitchen. Possibly not ideal) to see if I could fire up the Suzuki after its long slumber. However, the GS just pulled the duvet back over its head and snored loudly.

Every bike needs a funnel... While waiting for the fuel tank paint to cure, Duncan decided to see if the bike would run. It wouldn't, and the fuel pooling on the floor led him to believe the carburettors needed attention

It made a loud cranking - not firing - noise. This and the pool of fuel that gathered beneath the bike led me to believe that I'd need to give the carburettors some attention before it would 'rise and shine'. I'd built up my hopes that an MoT was just around the corner so this discovery was a bit of a low point, but onwards and upwards… Luckily my friend Andy had just bought an ultrasonic cleaner, and they seem to be all the rage for cleaning carburettors these days.

I borrowed the ultrasonic cleaner and then procrastinated wildly to avoid the dimly remembered horrors involved in removing the bank of four carbs. A heck of a lot of washing-up and vacuuming got done that day. You see, the carbs are stuck tight between the cylinder head and airbox, with hose-clipped, stiff stubby rubber collars on both sides. It's only possible to remove the airbox once the carbs have themselves been removed, and apparently it's possible to remove the carbs once the airbox has been removed… To put it another way, it's like trying to get a toasted sandwich out of a sandwich maker without being able to open it. I wonder how they got them into place at the factory - did Suzuki develop teleportation technology back in the 1970s but kept it secret to avoid compromising their conventional vehicles business? Possibly not.

Every bike needs a hair-dryer... Don't you just love banks of carburettors? They sit tight between the cylinder head and the air box. Skilful use of a hairdryer to soften the inlet rubbers and airbox plastic helped to wrestle them free

So to get the damn things out I undid the airbox bolts which allowed it to be moved about, oh, 2mm backwards; completely removed the hose clips and played a hairdryer onto the carb-to-cylinder head rubber collars and into the air box to soften its collars and the plastic of the airbox itself. This allowed the wall of the airbox to be flexed back a few more millimetres and the bank of carbs to be heaved backwards (urrgh!), half out of the cylinder head inlet collars and then yanked upwards (rurgh!), deforming the rubber collars until they finally let go and the carbs could then be pulled forward out of the airbox collars and then wriggled sideways (sigh) out of the bike.

Every bike needs a sleeping dog... Buster managed to sleep through the carb wrangling. Or maybe he's unconscious due to WD-40 fumes

It's not a pretty operation. Maybe Suzuki have got teleport. Actually, it wasn't as bad as I remembered and Buster-The-Dog slept through the whole process so possibly I didn't strain and curse all that much after all. The secret might be a warm day and a hair dryer set to maximum stun. Did Suzuki invent the hair dryer?

I left Buster sleeping in the sun and carried the carburettors off to the kitchen table where I could examine them properly and have a nice sit-down. They didn't look too bad from the outside (a light coating of oily dirt surely being a good thing) but removing the float bowls revealed old fuel the colour of tea. Yuk. I hate tea. And so, apparently, does the Suzuki. Unscrewing the needle valves exposed gritty particles that had clearly been the reason for the valves not closing, resulting in the pool of petrol on the floor. I also found fine grit in the emulsion tubes, under the main jets.

Every bike needs some dirt in the carbs... The outsides of the carbs didn't look too bad but inside the old fuel had turned to colour of tea and the needle valves were fouled by gritty particles. There was also grit it the emulsion tubes, so probably the jets as well, hence it was clear why the bike wouldn't start

All of which I was delighted to find as it was a clear and visible reason for the bike failing to start, all easily dealt with by a good clean. I suppose a quick squirt about with some carb cleaner may have been all that was required but as I'd got an ultrasonic cleaner (and wasn't afraid to use it) I decided to strip the carbs right down and zap them with some ultrasonics.

I'd had the bottoms off these carbs in the past (to change leaky needle valves) but the top halves were new territory for me. I've only ever completely stripped down CV carbs before and this Suzuki has slide carbs where the pistons and needles are positively raised by the twist grip (rather than by a pressure differential caused by opening a butterfly valve). A throttle link rod skewers all four and allows a single cable to lift the slide / needle in all the carbs via bell cranks bolted onto the link rod.

The chokes are worked in a similar way, except they aren't chokes. They add extra petrol rather than reducing air. This integral method of linking the carburettors means that once you start to take one apart then you have pretty much taken them all apart, so care must be taken not to mix up the bits as this is very poor form and would cause confusion later - because all four carbs are not quite identical.

Every bike needs some carbs in dirty water... Duncan borrowed an ultrasonic cleaner, disassembled the carburettors and put batches of parts in. The cleaning fluid got murky really quickly. What was going on below the shimmering surface?

Everything seemed in order, the needles and slides looking completely unworn, so I heated up the ultrasonic cleaner and spent the afternoon loading and unloading small batches of parts. The clear blue cleaning solution soon went murky and made it difficult to tell if the parts were being cleaned or completely dissolved! I did things in small batches for two reasons:

1) To avoid mixing up the parts from each unit.
2) Because the cleaner tank was too small to put anything other than a small batch in it.

Actually, to give it its due, the 2500ml tank was just about right for cleaning carburettors and I was pleased with the results. It's not magic though. To make the outside of an oily and weather-beaten casting look really good you need to help out by scrubbing the nooks and crannies with a toothbrush and finally polishing with a bit of Autosol to bring out the shine. But on balance I found the cleaner very effective and I'd get one myself if I hadn't already got Andy's.

I reassembled the carburettors. The only new parts needed were a couple of needle valves which I hadn't done previously and nice shiny stainless screws (well-greased) for the top covers and bottom float bowls. The thread of the original screws were fine but the once posi-drive heads had nearly all been re-cut to slots.

Every bike needs clean carbs... The cleaner actually worked and, with a bit of scrubbing and a final dab of Autosol, they came up well

As an aside, I'll say a few words here about corrosion, stainless steel and grease. My many bitter years' experience of pulling grubby old bike to bits has led me to suspect that when people replace old bolts with nice stainless steel bolts they don't see the need to thoroughly grease them. 'Ooh, I don't want to dirty-up these lovely shiny bolts with foul grease! And being stainless they won't rust and seize anyway!' they seem to think.

Damn them all.

While it's true that the stainless bolt won't rust, the material it's going through - particularly aluminium alloy - will corrode like mad due to the electro-chemical reaction set-up by having two dissimilar metals together in a damp environment. The corrosion will swell (and aluminium oxide swells up more than most) and thoroughly seize the stainless bolt in place such that its head rounds off when you try to undo it.

How can we prevent this terrible state of affairs? Well, if we thoroughly grease the bolts then water won't be able to propagate along the thread to create the damp conditions that start the reaction between the dissimilar metals, and then we'll all have bolts that screw out as well as going in. Wouldn't that be ace? Sorry to go on, but I've just had a bad-bad-bad experience with stainless bolts in alloy fork legs…

GS Suzukis on

OK, back to the plot. By skilful use of a hairdryer and a touch of red-rubber-grease, I managed to get the bank of carburettors slotted back into place, even though it was like getting a sandwich into a toasted sandwich maker without being able to open it. I can see why so many of these bikes have lost their airboxes and just use individual filters or trumpet inlets.

I rigged up the temporary fuel tank and pushed the starter button. After some cranking as I fiddled with the choke-pull, the bike fired up and ran happily with not even the slightest trace of petrol on the floor. Hurrah! I warmed up the bike, blipped the throttle a few times…and then had to put it away again as I now needed to finish off the proper fuel tank and go and buy the bike its own battery.

Next time: is it done yet?


When he's not rebuilding his Suzuki, Duncan runs Bikeheart European Motorcycle Tours. His aim is to guide you on your own trusted motorcycle on a motoring adventure of a lifetime. Bikeheart carefully select their routes to reward those looking for a riding and cultural experience, in regions where the weather should be better than at home. See

Every bike needs four clean carbs... Clean carburettors reassembled and ready to be forced back into place on the bike

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