SUZUKI RG500

Our Jeff again, talks rotary valve replacement.

G’day! Well I trust you’ve had a good month or so. I’ve been flat stick on the RG500 as the local postman greeted the kids at our mailbox with some RG goodies a few times. Incidentally, our postman is a cool guy, he rides a mint RG400 and drives an AC Cobra and is from your land! We talk bikes a lot if I see him out the front delivering the post. Bikes are a great leveller eh? So, my rotary discs arrived along with associated O-rings and gaskets and some other bits and I got to work. Before fitting the new rotary valves I removed and cleaned the exhaust powervalves. Now, this was a simple task on cylinders one, three and four but cylinder two (front right-hand) proved to be a bit a bugger. In fact, thanks to just 3mm lack of clearance between the valve housing and the frame engine cradle, I had to drop the engine from its mounts and rotate it back 5mm! What a pain in the ass! Of course, I had already painted and re-fitted the front exhaust pipes as luck would have it… Anyway, it’s done for another 3000-miles. The valves were badly coked up so I’m glad I cleaned them up, I also did the exhaust ports with a wire wheel and de-coked the pipes with a strong mixture of caustic soda, plugging an end and filling each one for a week to soak, before blasting them out with high pressure water using my pressure washer. I then checked the torque on the cylinder-heads (12Nm

for the bolts and 24Nm for the nuts) while I had good access and fitted new NGK spark plugs. Turning my attention back to the intakes, new inner seat gaskets went in and the inner seats fitted. I applied thread lock to the inner seat screws and gave them all a whack with an impact driver, as these suckers would cause serious damage if they came loose. The new OEM rotary disc valves went on next, making sure the ‘R’ mark on the valve faces outwards and the timing punch marks on the end of the crank and inner surface of the disc align. I coated the discs with two-stroke oil using an oil can for the initial start-up. The outer valve seats are marked Left and Right. I fitted these with new O-rings and again, thread lock on the Phillips head machine screws that secure them in place. I used some rubber grease to help keep the O-rings in place while I fitted each cover. There is an OEM clamp that goes on the top-left screw of number four cylinder cover and two clamps that go on the screws on the bottom outer

of numbers one and three cylinder covers. These secure oil injection hoses and wiring harnesses so make sure you don’t forget them. Once the covers were on I refitted the magneto inner cover with a new oil seal and thread lock on the four screws. The stator then went on, again with thread lock on the screws. Finally the rotor went back on the cleaned crankshaft taper and the nut torqued to spec (140Nm). I have a flywheel/rotor holder but still needed a mate to help with that job. The magneto cover has a reusable rubber gasket, so that went back on. Make sure you include the small rubber washers that go behind each screw head. After turning the engine over (yep, I had to take the new plugs back out to ‘feel’ compression: DOH!) I was satisfied all was cool and I fitted the carburettors. Using new O-rings and rubber grease to help keep them in place, the four carbs went on. The spacers that go between the body and the outer rotor plate only sit one way, with the small notch facing upwards. If you put them upside down you will not have a direct intake path. I torqued the carburettor mounting bolts to the lower torque setting of 7Nm from 7-9Nm, as this is sufficient and reduces the risk of warping or breaking one of these gorgeous but fragile carburettors. From that point it was a matter of cracking a beer, grabbing a workshop stool, pliers, snips, cable ties and a shed-load of different length sizes of hoses and plumbing them up, taking my time to follow the original route by looking at pictures in the manual. I then balanced the carb slides at idle and at open throttle (see images), fitted the outer manifolds, air-filter, fuel tank, fuel and hooked up a battery. Then 700ml of gearbox oil went in, the painted radiator and fresh coolant mixture poured in and I was ready to fire the beast in to life. After an amber refreshment (Iron Maiden Trooper beer) and a good look over the bike, I cleared the bench, turned the fuel on, gave the RG full choke and three kicks and it fired up! Running on two, then three, then finally four-cylinders, I blipped away until the gauge was in the hot zone then hit the kill switch. By now I couldn’t breathe and being a Sunday, decided the neighbours probably didn’t really want Castrol TTS flavoured lunch as they relaxed in their yard, so I left it at that. Anyway, it was bloody awesome! Next up I will paint the wheels (black), finish the rear end, do the final tuning and chassis parts then sort the bodywork.

WORDS AND PHOTOS: JEFF WARE

1/ Coolant was dumped and the radiator flushed and painted. 2&3/ The powervalves were removed, cleaned and polished then refitted. This required moving the engine back 5mm to access the front R/H valve, due to frame clearance.

8/ The inner magneto cover goes on first, using a new oil seal, followed by the stator and then the magneto flywheel or rotor needs to be torqued up to a whopping 140Nm. 9/ The carbs are fragile and expensive so it is important that they are torqued to spec. I chose the lower 7Nm of the 7-9Nm specification.

4/ New air-filter went in. I decided to keep the intake side standard rather than go with pod filters. Further down the line I may get pods and expansion chambers if I have budget. 5, 6&7/ Fitting the new rotary disc valves is an easy job but it takes careful attention to detail. There are three parts, the inner cover, disc valve and outer cover. Mine were worn in the spline area, therefore noisy. I went with OEM as the ones in the bike had lasted so long, I figured the OEM ones can’t be that bad.

13/ First start up, just a few kicks and she fired on two, three then finally came to life on all four glorious pipes. Happy days! 14/ Right-hand side plumbed up and ready to go. There are a lot of fuel, oil and breather hoses to route on these complex RG500S. 15/ I’m stoked but now have a tough decision. Stick to my plan of original patina and risk damaging extremely expensive OEM fairings, or pop a Chinese 700 quid replica kit on and wrap up the originals and put them away for safe keeping… Hmmm….

10&11/ Using number one cylinder carb as a base, I use a drill bit to accurately set slide balance at idle speed, then the alignment dots on the slides for open throttle using the cable adjusters. Balancing the carbs is important to the overall smooth running of the RG500 and an easy job. 12/ The painted and de-coked pipes and flushed and painted radiator.