January 20, 2021 at 1:59 pm #35775EddiebKeymaster
Rank: Round the World Adventure Globetrotter
- Town/City: Tauranga
- Bike: Suzuki DR650 ADV, BMW R100GS
I wonder if it’s possible to mix and match DR650 and LS650 Savage/S40 Boulevard engine parts to make a factory long stroke DR650 motor?
I know in the GSX/GSXR line it’s possible to mix different generations of motor parts to get unique new engine sizes, for example mixing 750cc short stroke and long stroke motor parts can result in a 814cc engine.
Looking at the specs the DR650 has a bore and stroke of 100mm x 84mm while the 650 Savage/Boulevard has a bore and stroke of 94mm x 94mm. So if you could match the 94mm stroke of the Savage/Intruder with the 100mm bore of the DR650 you’d get 730cc.
The DR650 valves are very small so you’d probably want to go bigger there also to allow that extra air to flow, the Suzuki Freewind used the DR650 motor but with bigger valves so that would bolt on, but it also had a 2 intake/twin carb head which would be awkward getting to fit in the DR frame. You’d need to make a custom Y intake to use with a single carb for it.
But where do you stop?
Procycle in the US developed a 725cc big bore kit, which was later replaced by a 780cc big bore kit and the differences where significant, but a long stroke motor would act differently.
Procycle went on to create a 1 off DR900 using their 780cc big bore kit and a custom manufactured 10mm longer stroke crankshaft with a 5mm shorted conrod to make the rod and piston fit within the DR cylinder wihtout requiring a spacer, I think the inside of the DR engine case had to be shaved as little to fit the extra throw of the crank.
Attachments:January 23, 2021 at 6:33 pm #35788BrainflexParticipant
Rank: 1200cc Rider
- Bike: CT110, Husky TE 250, DRZ250, CB500X
Start by looking at part numbers and see if there is any similarities. Look at bearing sizes to see if there are common parts.
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