1997 Suzuki RF600R – Fuel’s Gold

Last month, when I introduced our latest fleet runner the Suzuki RF600R, I mentioned that it wouldn’t run and that this was to be my first task in getting the bike back on the road. And of course, this was the priority – who wouldn’t want to hear a 100bhp, 600cc four-pot with a carbon exhaust end-can running?

My father-in-law, the owner of the bike who has long-term loaned it to me, reported that he usually fired it up every month or so but in the last year or so, it had refused to start and had simply backfired. Being old-school, he suggested the timing may have slipped.

Searching back through the stack of paperwork that came with it, I found an invoice from a garage five years previously with exactly that as the reported symptom for it not starting. The invoice showed an hour of labour and four new plugs, so whatever the issue was back then, it clearly wasn’t a biggie.

This time around, the engine would spin over perfectly and with a gallon of fresh fuel and a little choke, the first couple of gurgles sounded hopeful. However, very quickly, the smell of petrol began to pervade the workshop and then, a huge, single backfire put pay to all of that.

It was clearly getting fuel, judging by the smell and even turning it over with the choke in but the throttle wide open to try to clean it out made no difference, except for another backfire.

So it was off with the fuel tank (which sits directly above the engine) to try to work out what’s going on. First things first – pop the plugs out and have a look. Sure enough, each was saturated with fuel. So spin the engine over with no plugs to try to clear the cylinders. Once the smell had gone (there was no fuel supply at this stage) I earthed the plug bodies and checked for a spark – a little flimsy perhaps but four sparks.

So I whipped the cover off the ignition pick-up to make sure nothing was amiss there – this effectively replicates the points or magnetic pick-up in a distributor but its position can’t change (causing a symptom similar to timing slip) as the trigger is on the end of the crank and the pick-up can only mount in one position. All appeared good here.

So the only thing left to try was to have a look at the carbs. A mate with far more experience of motorcycles than me suggested that the old fuel had probably gummed up the carbs and they just weren’t working properly, so off with the carbs, drain the float chambers and whip them apart.

The first three were a bit gummy but nothing unduly messy. I cleaned them all out and blew through all the jets and housings and put them back together as they came apart. It wasn’t until the last one that the probable issue revealed itself.

I took the float chamber cover off, removed the float itself and the needle valve and lying in the float chamber, loose, was the starter jet. This meant that pure fuel was flowing into the carburettor and on into the combustion chamber and flooding the motor almost instantly. I re-fitted it and cleaned the rest of the carburettor and reassembled them and re-fitted them to the bike.

While the fuel tank was off and I had access to the motor, I felt it was also worth checking the valve clearances, as the service schedule stipulates they should be done every 7500 miles and they had, apparently, never been checked. Checking them is a job I’m more than capable of, so I whipped the cam cover of – carefully, as it’s sealed with a rubber gasket with two semi-circular cut-outs – and if that got broken, I’d be hamstrung for a good few days…

Once off, one thing I knew already was confirmed – the oil was in good shape. I’d already dipped and looked at it and in the bottom of the sump, it was golden, not black and horrid and it was the same at the top end. I also found out the oil pressure warning light went out almost instantly when cranking the engine over, so that was all encouraging.

Valve clearance checks are crucial to ensure that not only does the engine perform properly, it doesn’t suffer damage. The system on the RF unfortunately doesn’t use adjusters and lock-nuts – there are shims on top of the cam bucket and to adjust them, you have to perform the kind of calculation that sent men to the moon, from the known clearance, the thickness of the existing shim, the speed of light, acceleration due to gravity, the Avagadro constant… you get the idea.

So with my trusty feeler gauge, I lined up the timing marks and set about checking the clearance. The manual states between 0.1-0.2mm on the inlet and 0.2-0.3mm o the exhaust, all with the engine cold. I checked and all 16 clearances were within tolerance – the thinner blade went in and the thicker one did not. Huge sigh of relief on my part, as if they were not within tolerance, I didn’t fancy re-shimming them myself and would have had to put the bike back together and transport it to a specialist.

While I was at it, I also decided to replace the aged – probably original – fuel lines with something that would cope better with the Ethanol content in modern fuels. Most new bikes – my Yamaha Tracer 700 daily included – should happily cope with 5% or 10% Ethanol fuel mixes but older bikes can suffer degradation in the fuel lines and systems from 10% Ethanol fuels upwards.

The spec of pipe is SAE J30 R9 which is ethanol resistant. It’s also high-pressure rated for fuel injection and that means it’s thicker walled than the old pipework. This, in turn, makes it stiffer and also, more difficult to get on the twin outlets for the tank (main and reserve) so a little jiggery/pokery was needed but I got there in the end…

So, it was not time to put it all back together and see whether my handiwork had been successful. After a false start putting the main and return throttle cables on the wrong way round, it was time for a fire-up to see. Inevitably, nothing would happen for a few turns, as the entire fuel system was empty. A gallon of fresh fuel in (I’d drained the tank before removing it), spin it over a few times to prime the carbs and then, a smidge of choke and… away she went. No back-fires, no flooding, just a surprisingly even idle for a stone-cold engine that hadn’t run in around a year.

I let it settle for a little and then, gave the twist-grip a couple of tentative pops and the engine picked-up nice and cleanly with just the slightest hint of not-warm-yet hesitation. It sounded fantastic through the carbon end can (manufacturer unknown – the badge has long fallen off) though if it proves too much for my ears, the outside world or the MoT man, my father-in-law still has the standard can in his garage…

The reason I tackled the engine first was for the buzz that hearing it run gives me. The remaining tasks are essential to the safe and enjoyable running of the bike but are likely to be messier and colder over the next couple of months, so the ability to fire the motor up and hear it run helps to build a picture of heading off on a fun ride in the spring, rather than cleaning brake calipers in the depths of winter.

One step closer to that first ride…