Bigger 350 cc Cylinder - BMW G310 R/GS Forum
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post #1 of 8 (permalink) Old 08-28-2019, 11:41 PM Thread Starter
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Bigger 350 cc Cylinder

I was going through possibility of making the 313 cc cylinder to bigger one and BMW's 350 cc scooter the C400X felt like direct fit but I am not sure on it's construction to accommodate the water jacket, plumbing, crank rod length etc.
The bore is same in both engines at 80 mm only stroke is longer on 350 cc engine at 69.6 mm against 313 cc engines 62.1 mm, so this 7.5 mm adds extra 37 cc, the power figure is same but it comes as early as 7500 RPM against g310's 9500 rpm.
Worth considering if it needs only the cylinder kit replacement with timing chain, longer crank and few small bits here n there.
Members having access to c400x engine physically or over the net do share more info on the same. I am sure this mod is going to sort out those issues of bike lagging the power and shutting down at low speeds.

Triumph Tiger 800 XCX 2016
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post #2 of 8 (permalink) Old 08-29-2019, 06:48 PM
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nope, don't think it will fit. Also, bear in mind that the engine in the G310 is turned 180 degrees compared to the scooter and the C400X.

What are these 'issues' of the bike lagging the power and shutting down at low speeds? I haven't heard of these.

P.S. it would be nice to get a bit more power out of the bike, but where do you stop? Any more power and the bike would no longer be suitable for beginners.

Last edited by porth; 08-29-2019 at 07:06 PM.
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post #3 of 8 (permalink) Old 08-30-2019, 03:01 AM
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same diameter, longer travel distance, same amount of fuel = not the performance increase you are looking for
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post #4 of 8 (permalink) Old 08-30-2019, 11:51 AM
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Longer stroke would increase torque which is what the bike needs but it would be a ridiculous amount of work and expense. Just get a more suitable bike and be done with it.
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post #5 of 8 (permalink) Old 08-30-2019, 12:01 PM
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I agree with oldtimer - it really isn't worth it for 37cc. I'd be surprised if you got much more than 1 or 2 hp at best out of that...

More to the point, even if the crank rod and piston would physically fit in the 310 engine, you can bet the profile of the piston and cylinder head would be different so you'd not get the correct combustion chamber profile without further machining - it would be a complete waste of time.

Ride the 310 for what it is, and if you genuinely need more 'performance' get a different bike...

... or go mental and try swapping another engine into the frame perhaps ;o)

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post #6 of 8 (permalink) Old 09-03-2019, 04:26 AM
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I think that an easier and significant improvement will be made when someone manages to enable re-mapping.
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post #7 of 8 (permalink) Old 09-03-2019, 10:23 AM
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I plan to put the REMUS exhaust onto my 310 GS. This is mainly for the better routing of the exhaust for off-roading, but it's specs say it will increase torque & HP. That is about the best increase for the lil' GS you'll find currently. I'll let you know if I can feel the difference once I get it & have some miles on it to know for sure.
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post #8 of 8 (permalink) Old Today, 04:51 AM
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Get GS F850 new bike or get GS650 Engine and figure out frame mods to mount it would cheaper project compared to 37cc project.
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