Xl600R/XR650L Hybrid

Hey everyone. I'm going to attempt to install an '84 XL600 top end to a '93 XR650L bottom end. The bike is a 1984 XL600R that I installed the 1993 XR650L engine in.

The parts I'm using are XL600 cylinder, RFVC XR500R head with new Kibblewhite XR600 valves, performance valve job with smoothed up valve seat to port transition, XL600 rocker cover assembly, performance valve springs, hard welded rockers from Megacycle, Megacycle cam #149X9. The specs are: in. lift .400/ex. lift .390- in. duration @ .040 264/ex. duration @.040 260. The piston is a JE 10.5-1 for XR650L 102mm.

This isn't starting out good. I took the cylinder in for boring and the machine shop put a gouge in the very top of the cylinder between the head mating surface and where the top ring stops.:banghead: They said it wouldn't hurt anything because the ring won't go up that high at TDC. I measured the width of the gouge and the distance between the top ring and top of the piston and it's gonna be close. I won't know for sure until I install the piston and cylinder. I hope this isn't a sign of how this project is gonna go.:busted: Bruce

pic?

if they damaged that cylinder bore and it is going to contact the ring, they are liable for that damage. make them get you another one.

rich

whats the advantage of the xr500 head??

I'm thinking that there might be a few issues.

1.) The locating dowels on the cylinder to crankcase and the head to the cylinder. If I remember correctly the earlier engines used smaller diameter cylinder bolts and smaller diameter locating dowels. This should be easily fixed with some simple machining.

2.) Squish band. The XR500 head is made for a 95mm piston and your bore is 102mm. I would think if the head is not machined to match the 102mm bore there may be problems. Perhaps that is why you are using the XL cylinder instead of the XRL one.

3.) Compression. If the 500 was 9:1 the combustion chamber volume is 62.5cc. With the 102mm piston you have 670cc. That works out to 11.7:1. If you machine the head to address #2 above then the number will be a little lower, but still over 11:1. Don't even think of using pump gas until you get some experience with the engine.

4.) The intake. The older dual carb engines had the shock in a slightly different position. Because of this an old dual carb airbox will not easily fit the XRL frame. You might have to go with the pod style filters.

If you can get over the hurdles, the end result should be a screamer with a lot more hp capability than the original XRL engine. Keep us posted with your progress and whatever issues you run into during this project. Many of us here love this kind of thing.

Rich, the machinist that did the cylinder is a friend of mine. I can't be too mad at him. He gives me good deals. This bore job was free! LOL

The XR500 head..... I didn't know it was a 500 head until I REALLY got to examining it.:banghead: I bought it off of ebay understanding it to be a 600 head. My original 600 head was cracked. Since I already spent the dough on it I figured I'd go ahead and use it. Bruce

I'm thinking that there might be a few issues.

1.) The locating dowels on the cylinder to crankcase and the head to the cylinder. If I remember correctly the earlier engines used smaller diameter cylinder bolts and smaller diameter locating dowels. This should be easily fixed with some simple machining.

2.) Squish band. The XR500 head is made for a 95mm piston and your bore is 102mm. I would think if the head is not machined to match the 102mm bore there may be problems. Perhaps that is why you are using the XL cylinder instead of the XRL one.

3.) Compression. If the 500 was 9:1 the combustion chamber volume is 62.5cc. With the 102mm piston you have 670cc. That works out to 11.7:1. If you machine the head to address #2 above then the number will be a little lower, but still over 11:1. Don't even think of using pump gas until you get some experience with the engine.

4.) The intake. The older dual carb engines had the shock in a slightly different position. Because of this an old dual carb airbox will not easily fit the XRL frame. You might have to go with the pod style filters.

If you can get over the hurdles, the end result should be a screamer with a lot more hp capability than the original XRL engine. Keep us posted with your progress and whatever issues you run into during this project. Many of us here love this kind of thing.

Cleonard, all good points you have there. The bike the engine is in is a dual carby so I'm good there. Although I did put the battery in the airbox so I'll still have to run pod filters. I have used an XL600 cylinder on a '96 XR600 before so it shouldn't be a problem on the 650L engine.

I'm pretty sure the 102mm bore only makes 657cc, at least according to the JE website. I've seen massive gains in CCs on XRs Only website and I'm not sure how they come up with those numbers. I do know compression could be a bit of a problem. We'll see what happens. I will get some pics going too. Bruce

Well. I took the affected cylinder to another machinest friend of mine and he said don't use it. This guy has been machining and building race thumpers for 30+ years, so his word is as good as it gets for me. So, he's boring my only other XL600 cylinder now. Hopefully I'll have it back in a couple days.

Cleonard I stand corrected.:busted: I had him calculate the displacement increase with the 102mm bore and 82mm stroke and he came up with 670cc. Obviously my way of calculating the numbers is wrong.:banghead:

Here's a couple pics of the "guinea pig".DSC01203.jpg

DSC01202.jpg

And test fit of the cylinder I'm not using and head/camshaft.

DSC01209.jpg Check out the clean work area! LOL

Hey................me wonders if the XR650L motor will bolt into the XL600R frame....hmmmmmmmmmmmmmm

Motosprtman, look REAL HARD at the engine in the XL600 in the previous pics. :banghead: LOL Bruce

LOL!

it fits!!

I got the cylinder back tonight. Shot a few coats of paint on it and I'm letting it dry overnight. Installed the rings on the piston and the piston on the rod. Reassembly begins tomorrow morning.:busted:

On a side note, we cc'd the heads and came up with approximately 54cc on the 650L head and 52cc on the 500. That's good for about a half compression point or 11-1 on my application. I have run 11.5-1 in a Yamaha TT600 on premium pump gas with no detectable detonation, we'll see how the Honda does. If I end up having to run race gas or a blend, no biggie. This isn't my daily rider, just a fun project.:banghead: Bruce

OK, here's a few pics.DSC01217.jpg This shows the difference between the 600 cam chain on the right and the 650L on the left.

DSC01218.jpg The cylinder torqued down. DSC01220.jpg Ready for installation.DSC01219.jpgDSC01222.jpgDSC01221.jpg Back in the bike.:banghead:

Initial impression is this is a strong engine. I have a couple of issues to address. One is the carbs. They have been sitting awhile (dry) and the o-rings that seal the crossover tube evidently have dried up and shrunk giving me a nice fuel leak.:D The other being battery strength. I am using a Yamaha WR450 battery housed in the air box, it's the largest that would fit. It spun the stock engine over fine with the auto decomp. Now, with 11-1 compression and no auto decomp, it doesn't get the job done.:banghead:

I did get some detonation at about half throttle in the upper gears but I only have 87 octane in the tank right now, leftover from before the build. Overall, I'm pretty happy. Just need to get the bugs worked out.:busted: Bruce

very cool bruce! good power huh?

very cool bruce! good power huh?

Hey Rich! Yeah, good power. I just got back from a 6 mile ride. The fuel leak healed itself, the seals must have swelled up over night.:busted: I got on it a little harder in the lower gears and wound her up a little farther in the upper gears...this thing pulls hard. I can't weight to get some higher octane fuel and get it somewhat broke in and then HAMMER IT! See what she'll really do.:banghead: Bruce

Awesome project!Keep us informed.Are you going to get it dynoed?I'm curious to know how much power it's making.

Awesome project!Keep us informed.Are you going to get it dynoed?I'm curious to know how much power it's making.

Thanks Frank! I'd like to get it dynoed. Our local Harley/Buell dealership just built a new facility complete with a chassis dyno. When I get some available "disposable" income I'll see about gettin' 'er in there, if the Harley boys will let my lowly Honda into their building LOL! Actually I know most of the people there and they're a good bunch, so it shouldn't be a problem.:banghead: Bruce

Any update???

Hey everyone! Been off the site for a while "takin' care a business." Had a couple other projects to attend to most notably getting my '90 Mustang back on the road.

Regarding the XL600, this thing's fast. I still don't have but probably 100 miles on it but I couldn't wait to open her up any longer. My buddy Davey stopped by yesterday on his 2005 650L, (having just got back from vacationing in Jamaica, mahn). His bike has a jet kit, K@N and an FMF slip on. We took a short ride and did a couple 4th gear roll ons. My bike pulls him by about 2-3 bike lengths and stayed there until we had to shut down. My bike is nowhere near broke in and it was detonating like heck. I only had 87 octane in it from before the build. I filled it up with 91, which is as high as is sold here, on my way home yesterday. We're supposed to go for a ride today so I'll see if the 91 helps. I'm probably going to have to play with the main jets a bit too. Once I get the detonation under control we'll do some true drag races from a dead stop. The next thing I'm going to attempt is to install a kick starter to this thing. With this much compression and only a manual decompresser, this thing doesn't always start when it's cold. I run out of battery. You have to hold the compresser just right, not so far open the engine just free spins and not so little the engine barely turns over!LOL It usually lights right off when it's warm. I'll keep ya posted. Bruce

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