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Tuning of The RD350LC

Tuning data RD350LC.

NOTE: As always, the author of this story can not take any responsibility for damages arising from the use of this information. Tuning is ALWAYS at your own risk.

So much for the bad things, now let the fun begin!

The following story with tuning data is posted in the forum by “picobello”.

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I started with a standard RD350LC 1980 which was previously owned by Andy Bloemhart, one of our neighbors with an RD to RD-cup had participated therein. Broken crankshaft and cylinder and piston, so the block had to open …

I had raced a couple of years with two strokes at the SOBW I wanted because I still had open optimize this immediately block.

New pistons, cylinders and cut another crankshaft and we were back on track. Then I came across an article by Howard Read who had raced in England with this type RD. Some other items read, the data from all these tunings proposals “analyzed” and my own interpretation left to loose. From this the following tuning steps are incurred are:

Squish measured: 2.4mm 1.5mm about what is too much. The squish should be 0.9mm.

1.2mm thick gasket which moves to the Waste container.

Squish in the cylinder head is different from the piston crown, and is therefore adapted to the angle of the piston.

Cylinder flattened in order to obtain the desired 0.9mm squish and hereinafter referred to as a groove for a VITON “O” -ring (better able to withstand higher temperatures and coolant) is inserted. Combustion chamber made beautiful spherical (half Bol form). Cup finishes below.

Hereafter, the cylinders come to the turn. The outlet port 1.5mm up file out / milling without however widen the gate. Sides finish so that the piston ring will not happen in the gate. The gate opens now as it is well 27.5mm from the upper dead center (top does not need to be cylindrical, good measure). Cylinders at the top “cleaned” so that they are flat. Cylinders are now ready.

Boyesen mounted double diaphragm valves and stoppers opened further to about 11mm (more went I do not because of the limited space in the cylinder). The membrane blocks I have nothing changed but this seems a bit extra to get its power.

Luchfilterhuis modified by the intake trunk (let’s call him here) shortened to 10mm. Here are still to gain some additional programs by making the inside side of the housing to smooth and remove the filter.

The parts that I had were 28mm carburetors an air-cooled RD which fit perfectly on the manifolds obtained by the RD. They just did not have oil injection injectors. Carburettors fitted with these injectors to still continue using the oil pump.

All assembled again and mounted the cylinder with liquid gasket and O-ring. B10EV spark plugs installed and put the ignition of 2.0mm to 1.9mm for top dead center to top dead center.

assembled standard exhausts. (A well-calculated expansion pipe can work with a good setup here also give some extra horses)

Because of poor chain and sprockets it immediately but replaced with new ones. For a tooth behind a tooth bigger and smaller (case had no original rear sprocket, front sprocket was deliberately chosen because larger the expected higher power).

After driving into the cylinders / pistons could start the big party. Of course, I had already taken off during running and again met the new power curve RD.

In it’s like most RDs from 6000 rpm starts the party: wheelyyyyyyyyyyy …

Two is different than most standard RDs. From 6000 rpm the weather feast: Woohhwww again using a wheely purely on the gas without the clutch (or a power drift in the curve, or both …..)

Engine does not rev as standard RD but has a greater capacity at constant toptoerental.

Power, according to Howard Read 52bhp which is about 10 more horsepower as the standard RD but without the Boyesen membranes without the airbox modifications and without the 28mm carb programs. With these extras you will have some extra horsepower at your disposal

The RD is not like before cranking by hand, the compression is so high that sometimes you can even step on the kickstarter without him going through his compression!

However, fuel octane gasoline because of this high compression.

I hope you got excited with this “publication” to have to try it for yourself. It’s really worth it.

There were several people riding on my RD those fast engines were used to, but all of them were very surprised by the brutal (wheely) power of my RD …



*Article of its own auther

Have any Question or Comment?

3 comments on “Tuning of The RD350LC


Bad English……hard to understand .

William Clarke

Would be a good article if the grammar was better. I take it he is a foreign guy which can be excused, but someone should have re written it.


Yes as original article is in Dutch and translated by google. If you can translate this article i’ll update the/edit the post for other readers.


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