Here's some technical tips that you may find of interest. If you have anything you think should be included, drop us a line and I shall add it in.
Don't fit oversize rubber on your bike just because modern bikes have big tyres. They were designed for it. The RD wasn't.
Best sizes to go for are 90/90 on the front and 110/80 on the back. These are the closest low profile match to imperial sizes, and usually the manufacturers recommended sizes. And they handle well too. I have been told a 120 won't fit in the swinging arm, and so not tried it. It wouldn't handle even if it did fit. When you squeeze too large a tyre on to a narrow rim, the profile gets distorted. As the side walls are squashed into the rim the tread forms a more circular profile, resulting in less contact patch and the risk of the tyre popping of the rim. Try it if you must but don't say I didn't warn you. Watch out for Insurance legality. If a manufacturer doesn't recommend a tyre, your insurance might be invalidated, even if they fit and work well. At least, they might wiggle out of a claim on the grounds that your tyres weren't 'fit for purpose' or some such crap.
H or V rated? The choice is yours. H rated is enough, tho' Vs might be more stable/grippy.
Brands: At the moment, the best I've tried and would thoroughly recommend, along with loads of other RD riders, are the Bridgestone BT35 and BT45s. I am running them at the moment and they are by far and away the best tyres I have fitted. Metzeler ME33/ME99 are a good combination to go for. Also the Michelin M38/M39 or M48/M49 combinations work well (did 1000 miles round France on them, two up with camping gear, no problems!). Avoid Pirelli Mandrakes at all costs. They're crap. Also Pirelli Phantoms ain't too hot either, OK dry but in the wet... Avon Road Runners? No thanks. These are my personal preferences and views I have learned from experience. Yours may differ. Some might say "I've used brand X for 20 years and I always scrape the pegs etc etc" but times and technology change. Wake up and smell the rubber! It's MUCH better these days. I would recommed you try some newer tyres. You WILL be amazed. Ultimately though, it's your choice.
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Perhaps the most enquired about subject from overseas members!
Boyer Bransden don't make a specific kit for the RD. They do however make Inductive Discharge units for £22 each. You will need two and they use the points to trigger a low voltage signal to fire the plugs. I have not used them, nor do I know of anyone who uses them so I cannot comment on how good they are. If you do, let me know please! Suffice to say the idea sounds good, point life should be longer, sparks fatter but remember you will still have to adjust the points eventually due to mechanical wear.
Piranha are now made by Newtronics. They consist of a transistorised unit to fire the plugs. The cost is around £60 (exc VAT) +postage. Overseas customers obviously don't need to pay the VAT. The points are replaced by optical triggers, that once set will probably never need resetting (no moving parts to wear out). These trigger the transistor switches in the 'Black Box' to make big fat sparks on the plug. I have one on my RD400C and can vouch for it's worth. Starting is easier, the engine revs out more easily, fuel economy is not changed such that I would notice, and I haven't had to retime the bike for 5 years so far (since I fitted it) other than after a crank rebuild!
Where to get them?
Newtronic
Systems (see entry on the
Services page)
What to ask for: If you have a Mitsibushi alternator (generally US models) - YAM2A
European model alternators (Hitachi) - YAM2
Join the club and I'll tell you!
Standard plugs for RD400s and later 250s are NGK B8ES. Early 250s and 350s use B8HS short reach plugs. My bike had B6ES plugs in it when I bought it, presumably to burn off excess oil. No wonder RDs gained a reputation for holing pistons! With plugs rated too hot, and spotty nerds not keeping timing in trim... I now run B9ES plugs as I have skimmed heads and a mild stage 1 tune so I need to run the cooler plugs. Only go up to B7ES if you have severe oiling problems. You run the risk of holing pistons or detonation by running the hotter plug.
Use an 'R' plug (eg BR8ES) if you don't have resistor plug caps. NGK plug caps (the red plastic ones) are usually resistor type. The resistor is only there for RF suppression, so don't worry too much if you don't have one, although it is advisable to fit them eventually. It works out cheaper to get the resistor plug caps and non-resistor plugs.
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It's impossible to give specs to suit everyone. Some people want rev-o-matic™ top end monsters, other want tree stump pulling torque fiends. If I gave one spec, I'd have to give them all. And I don' know them all, so I can't. Also, no way am I opening myself up to some dumbass US litigation because of hamfisted use of a bastard file! Your best bet is to get one the Gurus to do a tune. Harry Barlow, Farron etc are damned experienced at this and do good jobs. It's their business! If you fit K&Ns or Ramair individual filters, fit extension tubes between then and the carb mouth. This tunes out a horrific midrange flat spot that would otherwise occur due to pulse effects reflecting from the closed end of the filter. Don't forget to up your jet sizes as well, otherwise it's bye bye engine. Expansion pipes look better than standard (IMO) and help the engine breath better, although you will probably lose some of that lovely mid-range torque on the 400s. Again watch out for rejetting.
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On the rear standard shocks are fine as long as they are in good nick. People use them for racing on here so they can't be that bad. Better though are Hagon gas shocks, Koni Dial-a-Rides (expensive but worth it - adjustable preload and damping), or Marzochis (a little firm for some people, but the have the benefit of being rebuildable at home). For a Limo ride, sell the wife/husband, re-mortgage the house and get some Progressive 4180 shocks -adjustable damping and spring preload, super lightweight and look gorgeous!
Fit taper roller head race bearing for surer steering, and perhaps a steering damper to iron out any slight speed wobbles or whatever. Get a stiff one up your rear. Ooh err missus! Aftermarket swingers (arms, not sex crazed hippies!) are available in tasty alloy from CMA and Metmachex in the UK. These look the biz and cost the earth ~£300. Braced ones are even better. Fitting a fork brace (Telefix, Micron or homemade!) will stop forks twisting and walking under braking. This is especially important if you have replaced the stock steel mudguard with a fibreglass one. Other tricks included fitting beefier 20mm axles, but this then takes on more engineering skills, but is worth the effort if you are really determined.
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