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Yamaha RD LC Tuning

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If you've never ridden a standard LC before there can't be many left the experience may surprise you. The soft lightly dampened forks bottom under braking so much so a heavy come down from a wheelie could cause a thump on the mudguard from the twin banjo under the yoke . The rear shock is'nt much better. The brakes are nothing like you're used to on today's bikes. The engine has little before 6,000rpm then power seems to double by 7,000 giving a great rush of speed and adrenaline.

The original swinging arm bushes are crap, check and replace them .The pads tend to taper from top to bottom they will tip in the caliper Ferodo are the best replacements use sinted pads only . Calipers constantly seize, a good stripping ,cleaning and lubricating is essential if you ride hard . You can try this with your calipers to . Leaving the air box on helps keep a wider power spread. taking the filter out makes it a little sharper during the summer. {all ways do a plug chop after any set up mods}.

Fork Braces reduce fork flex under braking, Sorry they don't because the problem is the forks bending backwards just below the bottom yoke. They also increase unsprung and steered weight, when in fact you want to reduce it. A more efficient brace is a stiffer deeper bottom yoke and a larger diameter wheel spindile. That's why bikes with TZR or YPVS forks, yokes & wheels handle so much better .

LC Tuning

TZ big end cages are stronger and have a better load capacity and will fit. For a tuned motor the press fit crank center shaft should be welded and the crank turned to 0.025mm, not the factory's 0.1 However I use 400E web centers .A cheap way to get more power is to skim the head 0.030in and raise the exhaust port 1.5mm After market pipes will do a lot and keep it more reliable then an outright tune, although some pipes just move the power up the rev range.

RD 250 LC BarrelsTheys 250lc barrels use 2 TZ O-rings and no head gasket, notice the rings cut around the liners .not a common mod .

 

 

 

 

A good tune on a 250 will give 45BHP with all the goodies up to 55BHP a 350 can make 70BHP  with all the goodys .You will get around a 15% power increase with a road tune 25% with a race tune. More with all the goodys. The goodies being custom pipes, after market ignition & big carbs.

The 250LC carbs will give more midrange then 350 or YPVS carbs, worth remembering if your tune is for midrange . The TZ dry clutch and gearbox fits in with little trouble .The standard gearbox is fine with 3 TZ 750 clutch springs that's all I do .I find the gear box fine to . A lightened fly wheel is a cheep way to get 500rpm extra and a sharper pick up .It also gives the crank a longer life, Take of no more then 6mm. This will however shorten the life of your fly wheel, keep an eye on it for cracks.

Suspension

Spacers in the fork leg prevent dive and increase pre load allowing the bike to ride slightly higher then it otherwise would . This also increases cornering clearance, Unless the rear is raised also the steering will get slower and more vague any after market shock will raise the rear, a cheep alternative is to put a RD 125LC rear shock that's what I do . To prevent dive a little more oil reduces air trapped in the leg making it build pressure faster under compression. Stiffer springs are a good things but they are not just stiffer under braking there stiff all the time. Heavier oil can help but the damping will also be heavier all the time , a little bit more oil and a heavier oil mix is best .

Information kindly provided by www.rdlccrazy.co.uk.