Similarity between 650L, 600R, and big bore kits.

How much engine architecture is shared between the 650L and 600R? I've been contemplating a big-bore upgrade and was curious if a 650L piston and barrel would fit a 600 case, rod, and head. (I know the 650L has 2mm more stroke, though)

Also, do big bores tend to wear out faster or are they similar to stock regarding time between rebuilds?

The engines share a lot of parts, very similar. I put the top end from a 600R (barrel, piston, head, cam) on a 650L lower end earlier this year and everything is still working. Maybe it shouldn't be? :thumbsup:

I have a 600R lower end and a 650L piston and barrel in the garage, I can mock it up and see how it looks if you're interested.

That would be great if its no trouble.

Do you know if anything on the 650L is beefier than the 600, like rods, cranks, or gearbox parts?

You put the "top end" of a 600 on a 650L...did that include the head?


re: Gearbox parts - the 650L and 600R differ on the primary reduction, and on 1st gear (650L has less primary reduction, but a lower 1st to make up for it)

I don't know if the crankshaft is beefier on the 600R, but it is a bit different than the 650L's. I'll mock up the engine tonight to see if it will work for you. Yeah, I put the whole top end except for the valve cover from the 600R onto a 650L. It was kind of a franken-bike. Had a Wiseco 10-1 compression piston 1.00 mm overbore from the 600, so it was like a 628? Whatever it was, it worked for me.

I bolted up the XR650L cylinder and piston to the 600R bottom end, everything looks the same as the other 650 motor I have. I suppose it could work as a big bore alternative.

Thats cool, thanks.

Now that I think about it a little more, I wonder if the compression heights are different due to the longer(82 vs, 80mm) stroke on the 650.

BTW, a 100mm bore x 80mm stroke give you a 628. I thought it would be cool to get a 660, but I dont know if that gives any room to overbore if the cylinder gets scored. Overall engine longetivity is a concern too.

I just saw a thread about a '94 650L engine on ebay and it got the gears turning. I noticed it has electric start and no kick lever. The electric part just seemed to be a different flywheel side cover(and flywheel too?).

Anyway, I have another question. Are there any reliability issues with the larger big bore kits like 660s? If so, can anything be done about it? And last, can you go any larger than 660 with an XR600?

Here in Italy we usually do this work:

we take the cylinder of the Honda NX650 (dominator) and we bore up to 101mm (in place of the original 100)

We take a JE o Wiseco Piston and we assembly all with the stock XR 600 Engine..

We don't use the motor of the NX because the rod of the NX is longer than the rod of the XR, and the piston of the NX is lower than the XR piston

in fact the displacement of the two bikes with the same bore is different 100mm on the N650 is 644cc on the Xr 600 is 628cc (HRC kit)

I don't know if the NX 650 engine is similar to the us XR650L (here we don't have this bike model available)

(excuse my english, I hope you ave understand)

I don't know if the NX 650 engine is similar to the us XR650L (here we don't have this bike model available)

(excuse my english, I hope you ave understand)

Your English is fine, but I've never heard of an NX650...

This is the Honda NX650 "Dominator"

last version (build in Italy)


this is the first version (built in Japan)


the basic upgrade for an XR600 here is to take a NX650 cylinder (100 mm bore) and a high compression piston for XR, keeping the stock head and XR cams..

I see, its like an XR-L, but with a little fairing.

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