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Flgwheel 600r compared to 650l

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You're not going to even get close to the XR600R flywheel weight because of the starter gear and clutch on the XR650L flywheel. You can only remove what you can and that is it.

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You're not going to even get close to the XR600R flywheel weight because of the starter gear and clutch on the XR650L flywheel. You can only remove what you can and that is it.

The starter gear doesn't spin with the engine, so it's not rotational mass and therefore not really part of the equation. I weighed them all at one point, but dont have the energy to search down the posts where I posted the weights. You can get the XRL flywheel withing a couple of pounds of an XR600R unit, but getting it down to the same would be tough as the XRL unit weighs almost twice what the XRR flywheel does (without the ring gear).

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The starter gear doesn't spin with the engine...

Great point.

A couple pounds is a huge difference though. I have rode both and I have to say that the extra 35-40 pounds of the XR650L total weight really could use the extra flywheel weight to make the bike less prone to stall on tight trails. I put the XR600R engine in my XR650L frame and dropped all the extra weight of the e-start parts plus I used a much lighter battery because it does'nt need to start the engine. The higher primary ratio on the XR650L also could use the heavier flywheel, not to mention the final drive ratios, of which the XR650L is higher. Once I get my bike back on the road with the XR600R primary (and engine) and with the XR650L first gear, NX650 second gear, FMX650 fifth gear and XR650L final drive of 15/45, I should'nt need a lot of flywheel.

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OK... here's what I know from "been there done that"

 

Here is what got me started down this path. XR600R and XRL flyweels. Big difference! The XRL flywheel weighs about nine and a half punds with the ring gear. The ring weighs about a pound and a half, so that leaves you with about eight pounds of spinning weight on the XRL. The XR600R flywheel weighs five pounds! So... you have three pounds of "extra" weight on the XRL.

Flywheels.jpg

 

Here's a unmolested XRL flywheel next to the one that is in my bike. You can see that we carved off the silver steel ring (nasty stuff... peels off the lathe like steel wool). This process only peeled one pound off of the flywheel so I am still two pounds heavier than the XR600R flywheel.

IMG_0140_zpsd5a8f12a.jpg

 

Here it is mounted up

IMG_0144_zps9c48cfb2.jpg

 

How's it do on the trail? Meh... not a huge difference. You can feel it, but it is not a huge difference. The engine spins up easier... snappier. It will still tractor with the best of the them though so no real loss on the bottom end.

 

One of the other fears that has been discussed is the need for the extra mass to help the starter spin. My engine has a higher compression overbore piston and had a hotcam (until about a month ago...meltdown). Hotcams do not have a auto decomp like the stock cam. It was a bit of a strain sometimes to get the engine spinning.... before and after the flywheel diet. I don't think the loss of a pound really made a difference there. I have the stock cam back in it now and it spins easilly.

 

Putt, putt, putt

980990_232338710267189_433867835_o_zps6a

 

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How's it differ on the street?

Between the lighter flywheel and the FCR squirt... it gets intersting coming out of a corner when I get frisky with the right grip. You really need to have the front tire on the ground when cornering.

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