RDDR- big?

[SRXer]

Dont suppose anyone would have measurements of a Suzuki DR engine or somthing simular so that I could see if i can fit a large single inside my RD250 frame?

http://www.photobox.co.uk/album/26444811

or any advise with this sort of thing.

[Happy Daze]

You can fit just about anything you like and fairly easily when you have a steel cradle frame. What you need is the bottom loop of the donor engine, cut out the existing loop, lift up the engine/loop (bolted together) on a jack, center it up, check the chain and get welding.

[SRXer]

Wont that seem untidy as its all probably different widths etc
and it may still not fit as I dont think you could make this bike lower without causing other problems.
I was thinking it would just be a case of making new brackets to match the new engine.

[Happy Daze]

It is as tidy as you make it,I've done it several times myself. Things to watch are small like sprockets(width and pitch), carb clearance and stand heights. You're spot on about ground clearance though, especially with rear suspension. Carbs and sprockets will still be an issue if you keep the standard frame. If you clean the paint of your frame and examine the standard of the factory weld, you may not be as apprehensive about cutting it up.

[guest27]

looks a tidy bike as it is - why the want for a thumper in there?

Dont forget most thumper engines are about twice as tall as that RD lump, there may not be enough height in the frame.  Have a stalled pjx putting a Rotax in a TZR frame - have had to cut a monster hole in the bottom of the tank to get the head and carb in place whilst still keeping good chain line etc.
Found this pic on another thread - shows the height of an XT lump, the stroker frame has not been designed to take the gubbins on the head.

Cracking looking bike mind....


Avoid the Rotax made lumps unless you want to faff about with the rear end too - they have the chain drive on the right and a co-ax kickstart on the left

Mind - I think the 440 Maico lum I have inthe shed would fit well - but do you really want a piston ported MX lump  lol!!

R

[Dave#22]

Hi, if it's the DR BIG motor(750 & 800), then the rough dimensions are height of engine-500mm, length of crankcase lug to lug-350mm and sprocket height from frame lower rail-150mm, it is a rather BIG engine due to the wet sump.....if you need any more info, just ask.
      Dave

[guest27]

Mmm dry sump maybe easier to fit, mind you then need an oil tank and the stroker oil tank will not really be big enough.

R