Jump to content
Sign in to follow this  

83 XL600R; to stroke or not to stroke?

Recommended Posts

Finally tore my big red pig down to replace second gear, found out after getting the motor apart that one of the three dogs had sheared clean off. I've got a few general questions and a few specific ones as well, many one which im sure have been answered somewhere sometime on the forums, but through my brief research I guess I decided I'd rather just start a thread for my specific build and my wants from the bike. So, I appolagize in advance i any of this has been gone over in another thread.

So the first bit of info you need to know is that the motor being built is an 83 XL600R. I have a parts motor with beautiful tranny from an 85 XR600R. The transmissions are identical as far as I can tell aside from the countershaft(if I remember correctly) being the same length and diameter as the XL's, but the splined portion that the gears ride on is a bit longer. In turn, the gear that rides on the end of that shaft is my gear in question, 2nd. On the XR, the splined portion is slightly longer and the teeth on that second gear are a bit wider. My question is, would I be able to use the slightly wider 2nd gear on my XL shaft? Or could I simply swap over the whole XR tranny if need be since it's in beautiful shape and appears to be basically the same trannny?

Next up is the crank/rod/piston. I've got the longer stroke crank out of the XR that needs a new rod, but is a good crank. Would the longer stroke still do ok cruising at 65mph or so and not overheat? Id read that part, or all for all i know, of the reason for the shorter stroke on the XL was to keep piston speed down and mid-high rpm cruising. Would that extra 5mm stroke make that big a difference. Also how much of an advantage would it make? I'd rather have all the torque concentrated into a small RPM range, which from what I gather is what a longer stroke tends to do, but I don't want it overheat or be limited to my wide open throttle use because of it. I'm thinking I might just keep the XL stroke but replace the standard bowl shaped low comp. piston with an 11.0 Wiseco or whatever theyre rated at. I just don't know well enough what all of these changes will do as far as performance and feel and just need an idea of what might be a good combination of crank, piston, and flywheel as well; I'd noticed that the flywheel on the XL was just a tiny bit bigger in diameter and a little bit beefier/heavier. To my understanding the heavier flywheel will do somewhat along the same lines as the longer stroke in the sense that it focuses more of the power into the lower rpms and increases torque.

 

If someone with build experience with these RFVCs could chime in with some personal knowhow, or better yet some links to different threads and web pages that I probably should have come across first! lol

 

Also I've  got a camshaft too, I'm thinking it's either out of an 85 or 88 XR600R. It's got a little bit taller cam lobes and looks like it would swap right over. Would that make much of a difference or was there some reason for the shorter lobes on the XL?

 

Thanks guys!!

Dylan

Share this post


Link to post
Share on other sites

I lost a crank in my XL so I converted it to the longer stroke XR with a 102mm JE 11:1 piston.  I used an XR flywheel too for lighter weight.  I also added an NX 5th gear for overdrive.

 

Transmissions are interchangeable through 87, they changed the gears a little 88 0n but they are interchangeable to the early shaft if matched with the appropriate gears.  I had to use XRL gears in my trans to make the nx second and fifth work.

 

XR and XL cams are identical.

Share this post


Link to post
Share on other sites

Good questions YX600, I'd like to know also, because I'm getting ready to tear into my 2 parts motors.

Share this post


Link to post
Share on other sites

alright, it's getting close to parts orderin time...

I read another thread about a guy swapping parts from an 83 XR onto his 86 XL or something like that, and it seems like you're the guy to talk to on this matter davek! lol. I can't decide whether it would be worth it to get the XR crank rebuilt and use it in my XL, or if I should just keep the XL stroke and get a high comp piston...the XL crank doesn't NEED rebuilding, but it'd probably be just plain stupid not to since I'm already replacing half of the bearings and all the oil seals/o-rings etc. I'd also love to do the NX 5th gear mod, especially since i've already got both shafts rebuilt and out sitting on my bench waiting to go back in the motor, but my google searches haven't turned up any solid sources from which to get the elusive 5th gear...

 

and after reading that guys thread, I'm rethinking my decision on keeping my XL forks, but not sure which triple tree to get as far as model and year that still has the ignition switch mounts and steering stoppers but the correct diameters for the spare 86 XR forks that I've got sitting in my shed...I think the XR forks might almost be sprung a little stiff for me, and the XL's were just about perfect, but I really don't feel like bending a tube one day when I hit the hidden tree limb/stump that's bound to pop up here and there LOL

 

I'm definitely undecided on what to do with the engine though...to stroke or not to stroke, that is the question

Share this post


Link to post
Share on other sites

the flywheel was another of my concerns; I figured that the XR crank would make better low end torque, and that the XR flywheel would allow it to rev more freely to compensate for the longer stroke? As far as power of the magnets and the ability to power the XL lighting system, I wouldn't think that the flywheel itself would have anything to do with that but correct me if I'm wrong... so to my understanding, if I do decide to stroke it, the XL flywheel on the XR crank would probably be overkill and would make high RPMs somewhat difficult to get to

Share this post


Link to post
Share on other sites

im also thinking now maybe on selling both sets of forks that I have and getting the newer cartridge style/triple tree setup. which years/models would fit my 83 XL frame?

Share this post


Link to post
Share on other sites

83 through 87 XL/XR stuff can be swapped at will pretty much if you use the corresponding parts, like XR piston with XR crank, and so on.  The trannys interchange too.  If you want to do the NX fifth gear you will also need the gear that it engages since they changed designs of the dogs 88 on, so you need to scare up some later gears to go with it.  Later XR or XRL will work.  The best source for The NX fifth is a Japanese source Motobike.jp.

 

There are XR cranks that are fully usable on eBay, I have been watching one for $69. and free shipping, I doubt you could get yours rebuilt so cheaply.  You would probably want the XR flywheel too, I did that on mine, also found on eBay.  No worries about the charging system with the XR flywheel.

 

You can get an XRL triple tree upper to retain the ignition switch and steering lock and use the larger XR forks, though it does not bolt up to the original gauges without fabrication.  I did use a CR upper on mine when I did the CR forks and figured out a way to adapt the stock XL gauges.  I did a post on ADV describing how if you want to go that route, XR upper is similar.  I think XR 600 lower has the same stops.  I have the upper, maybe even the lower.  The front wheel will fit if the axle size is the same, if not you can swap bearings and speedo drive to the later 17mm size too.

 

Dave

Share this post


Link to post
Share on other sites

I lost a crank in my XL so I converted it to the longer stroke XR with a 102mm JE 11:1 piston.  I used an XR flywheel too for lighter weight.  I also added an NX 5th gear for overdrive.

 

Transmissions are interchangeable through 87, they changed the gears a little 88 0n but they are interchangeable to the early shaft if matched with the appropriate gears.  I had to use XRL gears in my trans to make the nx second and fifth work.

 

XR and XL cams are identical.

Hmmm. That adds up to 654cc by my math. Quite the sleeper in an old XL. I have a 641 in my 500. Rumor has that the XL cam has the same lift but 10 degrees more duration than an XR. I've never degreed the 2 out to verify /disclaim that. It's not enough difference to decide which to use on that count only. I'd go with the one in the best condition. I suspect the XL cam may be worn if the lobes are smaller than an XR.

Edited by valvesrule

Share this post


Link to post
Share on other sites

looks like I need to get a set of 91 XR600R forks; apparently that's the year that Honda switched that model to cartridge style, but hadn't increased the diameter of the front axle yet, which would allow me to use either the XR or XL front wheels that I have. Then I would need the XR650L triple tree assembly and would fabricate the bracket...SO anyone wanna buy a set of 86 XR600 forks to partially fund this? lol. I'm thinking I'll just put the XL front end back on and ride it until I bend it or until I have the cash to pick up a whole front end assembly off a newer model..

 

So is there a big difference between the NX 5th and XL? worth tracking it and whichever other gears I would need down?

 

thanks guys!

 

Dylan

Share this post


Link to post
Share on other sites

The NX gear is higher yet.  Quoting from memory but close enough for comparison, the XL fifth gear is 1:1 or nearly so, and the NX gear is .8:1.  In my calculations back in the day, I found that it equated roughly to one tooth higher on the countershaft.   The numbers showed that the stock XL fifth with a 16T sprocket was very close numerically with the NX fifth and a 15T sprocket.

 

On the other end of the spectrum, if you go all the way and put in an NX/XRL low gear you equate to one sprocket tooth lower there too.  So in effect you have a low gear on c./s tooth lower and a high gear one c/s tooth higher without changing sprockets.   In my opinion it is the transmission they should have put in all 600's and 650's.

 

There is another option on gearing as long as you got me wound up, and that is to replace the clutch basket and crank gear on the XL/XR with one from an XRL.  The XRL primary gearing is higher again by the equivalent of roughly one c/s sprocket too.  It affects overall gearing obviously since it is before the transmission.  Honda changed the ratio to reduce load on the transmission gears according my reading on the subject.

 

I did a spreadsheet with several examples of transmission, primary and final drives represented for comparison and posted it sometime back on this site.  I concluded at that time that my ideal gearing would be full NX ratios in the trans and XRL primaries and 14/43 finals.

 

In the end on my bike I have NX second and fifth, my XRL first gear turned out to be not usable on assembly and I din't want to wait for another so I assembled it with the XL gear.  I wish now that I had waited just to have the "full meal deal".  As it is I have XRL primaries and 14/45 final gearing.   I pretty much take off in second at all times on the slab since first gear is just an exercise in lofting the wheel, actually second can be too.  On the highway top gear is nearly ideal for the power to weight ratio I have.  If I had the lower first gear, I could have the gear I only use on the trail be even more useable on the trail.  If I am ever forced to go back inside the cases I will put in the lower first, but I have no plans to do it otherwise, effort exceeds value.

 

Dave

Share this post


Link to post
Share on other sites

I rather like the first and second gear, got a buddy with an 85 XR600R that says 1st is too low for trails and 2nd is too high, but I find them just fine for my style of riding. Not worth swapping out several gears to first lower the 1st gear, then to also lower 2nd just to close the gap. Doesn't seem practical for my specific wants and desires. I do definitely want the NX 5th though, and possibly the clutch basket swap but probably not seeing as how my clutch basket is in BEAUTIFUL shape lol. Just out of curiosity though, although you probably already answered this and I just breezed right by it, but you said the XRL basket is geared about a tooth higher...this would in turn LOWER the entire tranny ratio, or do I have it backwards and it would actually raise the ratios? If it lowers the gearing, I suppose it could definitely be something worth doing in the future since it could probably be done with the engine in frame. Would this require the main shaft off of the XRL as well or do they all share the same tranny shaft diameters? Same for the NX 5th gear, this gear will fit on my XL shaft, correct? Or does this mod require I use both shafts from an XRL? or XLR whatever TF it is lol. I'll have to do a search for that thread you mentioned, rather than making you explain all of this LOL

 

Thanks much!

 

Dylan

Share this post


Link to post
Share on other sites

huh interesting i just came across a thread that states the following

 

XL600R

Primary Reduction 2.188 (70/32)

1st Gear '83-84 is 13/32 (2.46)

1st gear '85-87 is 13/31 (2.38)

'85-'87 XR600R & XL600R

31/13 2.38
28/17 1.65
25/20 1.25
23/23 1.00
21/25 0.84

 

so according to this, my XL, being an 83, has a slightly higher first gear than post 84 XL's and XR's. This would explain why my buddy's XR's first seemed too high for the trails while mine feels just right. hooray :) . finally a bike that I'm happy with the gearing in, as long as I can get one of those NX of FMX 5th's to fit on my XL, er actually the XR tranny is the one that's goin back into the XL....hmmm which just got me thinking, I've got both the 31 and 32 tooth main shaft first gears to choose from...I could almost like the lower XR 1st, albeit a very slight difference. decisions, decisions.  :banghead:  lol

Edited by YX600

Share this post


Link to post
Share on other sites

The XRL primary ratio is higher geared.  I said it equates in the end to the equivalent of one tooth higher c/s sprocket when calculated numerically.  The actual tooth count on the basket is less, and correspondingly more on the crank gear.  If you want lower primary gearing you can hunt down a clutch basket and crank drive gear off the XR500. All drive gears and baskets interchange as the shaft sizes are the same.

 

The NX gears fit right on the XL shaft.  The dogs did change on fifth gear in 88 so you need the companion gear next to it.  If you were to decide to do the NX low gear that would require a mainshaft change, but the countershaft could remain the same,  you would have to change the c/s low gear to match.  The NX second and fifth gears will slip right in and do not require a matching gear on the opposite shaft somehow magically.

Share this post


Link to post
Share on other sites

right on, I'm startin to get it now. You don't by chance know the exact ratios for the XR500 basket/crank gear? I'm seeing quite a few on ebay for around $50. If they raised the primary ratio to reduce wear and load on the tranny though, it might be a step backwards to rebuild my whole engine just to thrash it with a harsher primary drive. Might just leave well enough alone I suppose and just try to hunt down the FMX/ euro NX 5th gear and accompanying 2nd gear(I think?) that 5th engages into. 

 

I'm also wondering about the piston...seems like quite a few riders are building these engines with the intention of keeping the original compression ratio or even lower it seems in some cases...is there any advantage to NOT raising the compression ratio/any disadvantages for doing so? I've got a concaved dome shaped piston that came out of this XL, just wondering if I would be taking a step backwards with an aftermarket piston/comp ratio...hmm

Share this post


Link to post
Share on other sites

2.46:1 is lower than 2.38 in actual gearing, though numerically higher.  funny how the two terms are backwards from each other but mean the same thing.

Share this post


Link to post
Share on other sites

I personally like the higher geared primary for a couple of reasons.  You can always change the sprockets (final drive) to get where you want to be if it feels too high.

 

You will need the NX fifth, shop Motobike.jp, that is where I got mine.  The language barrier is there but not bad, they treated me well and their prices are good.  The second gear next to it is US so no problem there.

 

As far as the piston goes, in my opinion more is better.  More compression wakes it up quite well, and more displacement speaks for itself, and reliability is not an issue from my experience.  I ran my 102.4 Wisco 11;1 for over 20,000 miles with no problems.  The only reason I changed it is because I changed cranks for more stroke and could not reuse it.  It was (is) in good shape though I would slip in a new set of rings if I were to run it again.

 

The bike is so much more fun enhanced, I am never going back.  No radical camshaft needed, or desired in my opinion.  I tried a mild grind cam and it boosted my midrange a little and took away some bottom end, I decided I was just as happy with the stock one in the end, it got better fuel mileage.  If it were easy to change I might just slip it back in.

  • Like 1

Share this post


Link to post
Share on other sites

As far as the piston goes, in my opinion more is better.  More compression wakes it up quite well, and more displacement speaks for itself, and reliability is not an issue from my experience.  I ran my 102.4 Wisco 11;1 for over 20,000 miles with no problems.  The only reason I changed it is because I changed cranks for more stroke and could not reuse it.  It was (is) in good shape though I would slip in a new set of rings if I were to run it again.

 

The bike is so much more fun enhanced, I am never going back.  No radical camshaft needed, or desired in my opinion.  I tried a mild grind cam and it boosted my midrange a little and took away some bottom end, I decided I was just as happy with the stock one in the end, it got better fuel mileage.  If it were easy to change I might just slip it back in.

Very close to my experience. I have a 620XL engine that went around 20K and needed rings. Piston was perfect still. I have a fresh XR crank with Hotrods rod I thought of installing but don't want the 102.4 to just go to waste and I have 2 other 80mm stroke bottom ends anyway. The 75mm cranks have better HP potential is what the Honda race program decided back in the 80s so for the hell of it I'm putting the HRC primary and a 350 flywheel on the XL leaving the trans alone for a closest possibly ratio trans and lightest possible rotating assembly. Hanson removes the counterbalancer but that's further than I want to go, rebalancing the crank is overkill for my purposes.

Share this post


Link to post
Share on other sites

Hadn't thought of a 350 flywheel.  Just when you think you are done, something else pops up to do.  Does it have enough weight to still have trail manners?

Share this post


Link to post
Share on other sites

alright so I'm thinking heres my setup. I'm going to get my XR crank rebuilt, I've already got the new rod and big end bearing both of unknown brand from the guy I got the XR from, so I'll probably just end up having to buy a hotrod kit just to get the big end pin and thrust washers, plus peace of mind knowing its not some cheapo rod going back in my fresh motor. Then comes the piston. I've got standard bore, so my question is how large can I go with the standard sleeve before the sleeve walls become too thin? 

I'm going to order that FMX 5th gear tonight, and find the accompanying second(?) gear and order it as well. Gonna keep the XL primary drive, but use the XR flywheel and slightly taller, lower numerically(did i do that right? ;) ) first gear. My valves and guides are fine although I need to scrape some serious carbon out of the chamber, and if my Clymer manual is correct, which I would not be surprised in the least bit if it wasn't, then my outer valve springs have more than the specified standard free length, but the inners are quite "squished". Is the kibblewhite kit worth it or will those titanium seats eat into my precious vintage cylinder head? lol

 

in other news, I got the frame blasted today and welded up a couple spots where the seat bolts on and such. I was going to weld some braces on to the head tube after reading horror stories of cracks and raked out front ends, but after taking a look at it, it looks to me like Honda did a perty good job of bracing it up from the factory. Didn't look like there was much support that I could add without it looking like overkill. I do plan on fabbing some support brackets for the lower linkage-to-frame brackets to make it more in line with the XR frame that I've got. 

I've got the swingarm and supertrapp polished up like a mirror as well, can't wait to get this thing back together .

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...