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Old 11-06-2011, 10:24 AM   #4996
HeadTrauma
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Originally Posted by Mopowa View Post
Yes, the skirt is coated. The thing that steered me away from the Wiseco was everything I read saying that the actual compression was less than 10:1 on the advertised 11:1 piston. Having said that, I have not done my own homework and measured my actual compression. I will be replacing the headgasket next weekend, so if someone wants to give me a bulletproof method of measuring this, I may try it for everyone's info.
I don't have any compression height info for the XL600 piston made by JE (or any others made by Venolia or Arias, for that matter). I can tell you that neither the Wiseco nor JE pistons for XR600s and 650Ls make the advertised compression ratio. It's a catch-22 in that it makes them seem deceitful, but these engines would ping like crazy on pump gas if they did have 10.5:1 or 11:1 compression.

What I did with my XR was measure how far the piston was below deck to figure the volume of that dead space and used a "fudge factor" on the piston's valve reliefs(two to four ccs?). Then I measured the head gasket thickness and bore to get that volume. Then I CCed the chamber(my XR came out at 56cc, an '83 XL600 head I have came out to 57cc, and I have heard reports of 650Ls being ~58cc). Divide the swept+unswept volume by the swept volume and you have a compression ratio.

Quote:
Originally Posted by Carter Pewterschmidt View Post
I didn't want to run the Wiseco because I thought the compression was too high. I'm running that piston now and it will detonate at high RPMs. I'm hoping a cooler plug, some more carb tuning, and maybe an oilcooler will reduce the problem.
If your plug isn't too hot now and the carb is already well-tuned, then neither of those are likely to reduce the pinging from parts that demand more octane. Been there, done that. The oil cooler may help. A more aggresive cam would probably help, too.
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HeadTrauma screwed with this post 11-06-2011 at 10:34 AM
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Old 11-06-2011, 12:31 PM   #4997
cynicwanderer
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gasket material

any idea of where I can find metric sized gasket material like the green stuff used on the cylinder base and crankcase center gasket ? I'm rebuilding a xr350 and it uses the same type of gasket material for the center crankcase gasket as the xl600. the thickness is 0.5mm, which is right between the 1/64" and 1/32" material sold here. it looks like it's a rubberized fiber gasket.
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Old 11-06-2011, 05:42 PM   #4998
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Quote:
Originally Posted by HeadTrauma View Post

If your plug isn't too hot now and the carb is already well-tuned, then neither of those are likely to reduce the pinging from parts that demand more octane. Been there, done that. The oil cooler may help. A more aggresive cam would probably help, too.
Im running the 9 heat range plug, I emailed NGK about a cooler one and I bought the JR10B they recommended but I've yet to install it. I know the fueling won't help but I get decent stumble when wide open in 5th gear so I know I'm rich yet. I wasn't aware an aggresive cam would help detonation, but it makes sense. The higher duration keeps the valves open longer so the cylinder must cool better when the larger charges pass through it, therefore reducing the chance of detonation. Thanks for telling me that. I just had myself convinced to keep this bike stock and now you got me thinking of a big cam.
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Old 11-07-2011, 11:00 AM   #4999
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Quote:
Originally Posted by cynicwanderer View Post
any idea of where I can find metric sized gasket material like the green stuff used on the cylinder base and crankcase center gasket ? I'm rebuilding a xr350 and it uses the same type of gasket material for the center crankcase gasket as the xl600. the thickness is 0.5mm, which is right between the 1/64" and 1/32" material sold here. it looks like it's a rubberized fiber gasket.
I bought a whole gasket kit, for pretty cheap off ebay. Don't ask the specifics; Doesn't take long for me to forget details. Sorry.
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Old 11-07-2011, 11:06 AM   #5000
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Cams with more duration and overlap actually work by reducing dynamic compression at lower revs and moving peak cylinder pressures(torque) to a higher rpm where the engine is less likely to ping. I fought pinging with my XR and a DPR9 plug made no difference at all. The ground electrode still indicated too much spark advance and since it is not technically adjustable, that meant changing something else. It liked 93 octane gas and really liked 96, but the 100 I was using to mix it costs 7.59/gal out of the pump here. I had already planned on installing a cam and hoped that it would negate the need for race gas. Fortunately it did the trick and I can run 91 again.
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Old 11-07-2011, 12:52 PM   #5001
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yes, I couldn't find an aftermarket gasket set that fits that particular model. I'm only asking on this thread, because it uses the same gasket material/thickness as the XL600 (and xr600/xr650l) and thought someone might have found a source for the material used.

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Originally Posted by luckychucky View Post
I bought a whole gasket kit, for pretty cheap off ebay. Don't ask the specifics; Doesn't take long for me to forget details. Sorry.
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Old 11-07-2011, 04:04 PM   #5002
Carter Pewterschmidt
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Quote:
Originally Posted by HeadTrauma View Post
Cams with more duration and overlap actually work by reducing dynamic compression at lower revs and moving peak cylinder pressures(torque) to a higher rpm where the engine is less likely to ping. I fought pinging with my XR and a DPR9 plug made no difference at all. The ground electrode still indicated too much spark advance and since it is not technically adjustable, that meant changing something else. It liked 93 octane gas and really liked 96, but the 100 I was using to mix it costs 7.59/gal out of the pump here. I had already planned on installing a cam and hoped that it would negate the need for race gas. Fortunately it did the trick and I can run 91 again.
Nice, what level hot cam did you get? The old XL and XR can only run a Megacycle or Web cam and the higher duration ones require a shorter valve guide along with the standard hard faced rockers and a spring kit. It gets expensive when you add it all up. Just the cam is like $250 alone.
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Old 11-07-2011, 05:55 PM   #5003
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I'm new to the server, but here's my '86 XL600R. It's the gold rim model, currently rebuilding the top end. It doesn't smoke, no oil consumption, but it doesn't have the power that my old '83 XL500 had when I was stationed in Germany. All around, I love the bike though!
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Old 11-08-2011, 10:24 PM   #5004
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Quote:
Originally Posted by Carter Pewterschmidt View Post
Nice, what level hot cam did you get? The old XL and XR can only run a Megacycle or Web cam and the higher duration ones require a shorter valve guide along with the standard hard faced rockers and a spring kit. It gets expensive when you add it all up. Just the cam is like $250 alone.
Hot Cams only make a Stage 1 for the '88+ RFVCs. I'd like to get a bigger Megacycle grind eventually. Luckily I have a stock cam they can weld and regrind to save a few bucks so the whole package will only be, what, $600?
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Old 11-08-2011, 11:06 PM   #5005
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if anyone has any of the cam specs for the "hotter" cams im thinking oregon cam grind in vancouver could likely make cams at a sweeet price
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Old 11-09-2011, 07:01 AM   #5006
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New Bike

I just picked up an 86 XL600 the guy said he put an XR cam in her. one problem is when I get on the throttle (at least 3/4 throttle) she sputters like she is getting starved for fuel. I am not sure if he rejetted the carb. Any ideas? I am the fourth out of my friends to get an XL, I cannot wait till this weekend we are all going riding, 4 of these bikes going down the road into the woods, I hope OSP won't call us a gang.
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Old 11-09-2011, 08:10 AM   #5007
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Originally Posted by bdcorrigan View Post
...
one problem is when I get on the throttle (at least 3/4 throttle) she sputters like she is getting starved for fuel.
...
My XR had a big flat spot in mid-range. It ran OK at low speed, with moderate throttle openings, and it ran OK at full throttle in the highest rpm range, but it was really boggy if I opened the throttle too far in the middle rpm range.

The problem was not that it was too lean, but rather that it was running too rich. I went down one jet size, and now it runs much better.





Hey bdcorrigan, which Portland?



.
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Old 11-09-2011, 09:31 AM   #5008
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[QUOTE=MortimerSickle;17266152]My XR had a big flat spot in mid-range. It ran OK at low speed, with moderate throttle openings, and it ran OK at full throttle in the highest rpm range, but it was really boggy if I opened the throttle too far in the middle rpm range.

The problem was not that it was too lean, but rather that it was running too rich. I went down one jet size, and now it runs much better.





Hey bdcorrigan, which Portland?


Portland Oregon! Sorry
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Old 11-09-2011, 09:40 AM   #5009
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...
Portland Oregon! Sorry
Pm sent.
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Old 11-09-2011, 07:22 PM   #5010
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Quote:
Originally Posted by bdcorrigan View Post
I just picked up an 86 XL600 the guy said he put an XR cam in her. one problem is when I get on the throttle (at least 3/4 throttle) she sputters like she is getting starved for fuel. I am not sure if he rejetted the carb. Any ideas?
FYI, an '85-87 XR600 cam would not necessitate any changes because it is the exact same as an '83-87 XL600 cam. The profile(but not the blank it is ground on) is the same for all the Stateside '88+ RFVC 600s and 650s too.
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