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skillet

XL600 vs. XR650L Cylinder

16 posts in this topic

Trying to decide if the XL600 and XR650L cylinders are interchangeable. I'm going to be boring for oversize piston. The sleeve lengths are the same, as well as the length from the bottom of the sleeve to the bottom of the cylinder. The only difference I can see is the smog ports and the XL600 cylinder is 1 lb lighter on my high tech trusty bathroom scale. Any thoughts?

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Welcome to TT. You did not specify which bike you are trying this swap on I will assume you are on a xr600, cant imagine anyone trying to shrink their 650. I would "think" that they are interchangable. :applause: I do "Know" that there are differences in the piston dimensions, of course the bore is different, but what I am referring to is the distance from the piston pin to the top of the piston. I would "think" that if you used the L model piston with the L model cylinder you would be alright. But please do not do this until you can confirm my "thinking" on this. I would reccomend speaking with Kamell or Freddie at www.xrsonly.com to confirm.

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Thanks, I'll be more clear. The motor is a XR650L. I'm not trying to shrink the displacement at all. Both the XL600 and the XR650L are 100mm bores stock. The XL has a shorter stroke at 75mm vs. the XRL of 82mm. I am aware of the inability to swap pistons between the XL, XR, and XRL, but interestingly, I can find no measurable difference in the sleeves of the XRL and XL. The only reason I'm considering using the XL cylinder instead of the XRL one is that ithe XL is in better shape - no chipped or bent fins. Plus the fact that it is a full pound lighter is always nice when you're building a custom bike. I'll check with the guys at XRsonly to be sure. Thanks, and I'll post the result for anyone interested - sometimes XL cylinders are easier and cheaper to find than XRL or NX650 ones.

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Yes - please post pictures.

I have an '84 XL600R that I am rebuilding with the stock cylinder.

I also have a '96 XR650L project that I need to find a cylinder for eventually.

I've been wondering about the interchangability of these cylinders myself.

On a side note - I still have to find a cam and cam sprocket for the XL600R head,

and have not forund out for sure if an XR600R cam will work in that motor.

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Nummie - I let you know how the swap goes. As far as the cams, they are not interchangeable. The XL cam is longer and the journals are spaced differently. They will not come close to fitting. Are use going to use one of those RS600 pistons? For 17.00 it's hard to go wrong.

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Nummie - I let you know how the swap goes. As far as the cams, they are not interchangeable. The XL cam is longer and the journals are spaced differently. They will not come close to fitting. Are use going to use one of those RS600 pistons? For 17.00 it's hard to go wrong.

I have seen posts claiming that hotcams for the XR600R/XR650L will go into the XL600 with some work. Prehaps they are using the valve cover for a XR and not the XL. I am in the process of putting a XL600 head onto a XR650L. I will get the head tonight.

MGS

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Hmmm...I can see putting the XL head on, but not the XR cam in the XL. I only say that because I had a Megacycle XL Race cam that came with an NX650/XR650L engine that was in parts. I could not figure out how that cam was supposed to work with the XR head. Finally I realized that it was an XL cam (stamped 148-x12). The guy had just thrown it in with some of the other stuff because he did not have a use for it. I'm sure it's possible, but it seems like it would be more cost effective to just buy the proper head/cam configuration.

Out of curiosity, why the XL head on the XRL?

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Nummie - I let you know how the swap goes. As far as the cams, they are not interchangeable. The XL cam is longer and the journals are spaced differently. They will not come close to fitting. Are use going to use one of those RS600 pistons? For 17.00 it's hard to go wrong.

Right - I'll have to find the right cam for the XL.

I found two at http://www.webcamshafts.com/ for $168.

Not a bad deal I suppose, but they require a performance valve spring kit at $207

The good news is that they sell valves and valve guides as well as they can hardweld the rocker arms.

All that stuff would add up quick.

Perhaps I'll go down to my Honda store and see if a stock cam is still available. :applause:

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Hmmm...I can see putting the XL head on, but not the XR cam in the XL. I only say that because I had a Megacycle XL Race cam that came with an NX650/XR650L engine that was in parts. I could not figure out how that cam was supposed to work with the XR head. Finally I realized that it was an XL cam (stamped 148-x12). The guy had just thrown it in with some of the other stuff because he did not have a use for it. I'm sure it's possible, but it seems like it would be more cost effective to just buy the proper head/cam configuration.

Out of curiosity, why the XL head on the XRL?

I run a Hotcams in my XL now. It makes good power, but there is much more in there. The Edelbrock is not the carb for max HP, should have bought the FCR.

The dual carb XL head will flow better than the single carb L head. The intakes are much straighter with more potential flow from dual carbs. Supermono racers prefered XL heads for making more HP. There are two great writeups on some AU website.

I have the XL head now, basically same part as the XRL head. Hotcams will drop right in with the XRL valve cover (different rockers). I will need to plug the decomp port. Other than that everything is a go. Twin Mikuni 32mm flat slides should get the job done.

MGS

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UPDATE - Not sure if Honda used different size head bolts on the XL600 or if the previous owner of this XL cylinder heli-coiled it. Long story short. I got the XL cylinder bored for the 102mm JE Piston, slapped on the cylinder and piston. Went to stick my new Eric Gorr head on top and the darn Head bolts will not thread into the cylinder!:bonk: Different size dowell pins and everything! Guess I'll resleeve the original cylinder.

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A little diggin' revealed the head bolt problem. The XL600 used 8mm head bolts and the XR650L and NX650 used 9mm head bolts. It seems the dowell pins are different too - 10mm vs 12mm, which of course makes sense. Guess I'll just tap the cylinder for the 9mm head bolts. Hope this helps anyone trying to use the 100mm XL600 cylinder to Big Bore their XR600 or GB500.

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I run a Hotcams in my XL now. It makes good power, but there is much more in there. The Edelbrock is not the carb for max HP, should have bought the FCR.

The dual carb XL head will flow better than the single carb L head. The intakes are much straighter with more potential flow from dual carbs. Supermono racers prefered XL heads for making more HP. There are two great writeups on some AU website.

I have the XL head now, basically same part as the XRL head. Hotcams will drop right in with the XRL valve cover (different rockers). I will need to plug the decomp port. Other than that everything is a go. Twin Mikuni 32mm flat slides should get the job done.

MGS

That is really good to know about the dual carbs being preferred. Now how would one get the right amount of flow to feed a 650 converted xl600? Twin Mikuni flat slides as you mentioned, right? Do you have a link to someplace selling them? Are they made for the XL600? How about if someone wanted to use the stock Keihins on such a project?

I'm thinking of undertaking a similar project: 650-ing my xl600. I just want to know what I'm about to get myself into here. This thread helps. There is a guy going by Brucifer on ADV who said to check out his thread(s) here about converting dual carbs to single and vice versa. Still waiting on a link from him over there unless you guys know which one it is.

I'm about to obtain an XR650L complete bottom end, I have an xl600 bottom end with no 2nd gear, xl600 cylinder needing a bore (Wiseco time?) with a low-mileage head, and my current xr600r single carb in need of a top-end build soon to sell to fund the bearings, gaskets, and other things i'll need to do the project.

It might just be the xl600 engine, fix 2nd gear, add the crank from the XRL, and some machine work done to accommodate 9mm bolts like the 650 uses, to handle all that extra compression and displacement's explosions.

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