New project...

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Greg · #16 Post by **Greg** » Sat Mar 25, 2017 11:31 pm

Mango ..

Mine's had a rebuild using an RD400 crank and DT175 pistons which, if my research is correct, gives longer conrods and shorter pistons but a different angular rotation (I should have paid more attention at Uni!) which improves it's midrange...

I've had the carbs apart three or four times now and everything that I can clean is "cleaner than a man called David..." but there's a possibility that there's a blockage in the air correction circuit which needs the little brass sealing balls popping out to get into. That's a job for next week!

#17 Post by **mangocrazy** » Sun Mar 26, 2017 9:39 pm

Greg wrote:Mango ..

Mine's had a rebuild using an RD400 crank and DT175 pistons which, if my research is correct, gives longer conrods and shorter pistons but a different angular rotation (I should have paid more attention at Uni!) which improves it's midrange...

I've had the carbs apart three or four times now and everything that I can clean is "cleaner than a man called David..." but there's a possibility that there's a blockage in the air correction circuit which needs the little brass sealing balls popping out to get into. That's a job for next week!

So basically it's a long-stroke version of an RD350LC with a bigger capacity. That would certainly have more midrange!

Have you had the carbs ultrasonically cleaned? Gerry Pell (a doyen among tuners) recommended me to use first gen YPVS carbs, as they carburated perfectly on an LC.

Greg · #18 Post by **Greg** » Mon Mar 27, 2017 8:52 pm

Interesting thing with the carbs - I'll look into that one if I can't get mine to behave - I've done everything I can so far - short of U/S cleaning - to divest them of whatever's causing the problem - soaking in carb cleaner followed by a very diligent blasting with 90psi air ... TBH it's the low to mid rpm range that's suffering so it's the pilot jetting probably, but these carbs are so simple that there's nothing much that can go wrong.

Regarding the crank, there's no sign of a spacer under barrel, so now you've said that I'll have to check the stroke to see if it's 62mm (RD400) or 54mm (RD350). If it's 54 then it's just the 400 rods that have been fitted.

This AircooledRDclub posting explains the physics behind the long rod mod..

G

#19 Post by **mangocrazy** » Tue Mar 28, 2017 12:24 pm

You're a bad man, Greg showing me a link like that. That could lead to all sorts of expenditure if I'm not careful...

Greg · #20 Post by **Greg** » Tue Mar 28, 2017 1:01 pm

Yeah I know, it's ridiculous how quickly the urge to spend takes hold...

I'm probably close to £500 so far, with new tyres, the missing grab-rail, finding a replacement oil pump, intact side panels, ... and a set of YPVS expansion chambers ...

Ahhh... it's just as well that my adding up skills are shite because it's probably more than that...

BikerGran · #21 Post by **BikerGran** » Tue Mar 28, 2017 3:14 pm

It's better not to think about it!