Compression Release

[ThumpNRed]

I picked up a head cover off of a '93 XR600R to enable a compression release on my XR650L "frankenmotor". Here's the question:

I have a Xl600 clutch cover (for the kickstart) so I have the choice of running the XL600 comp release that is triggered by the kickstarter or I can run a manual release off of a handlebar lever (like an XR600R).

Pros and cons of each? What say the braintrust?

Sidenote: FYI... you apparently cannot heliarc a shifter wound on an XRL stator cover. Took mine to the welder today and he gave it a shot with the heliarc. Said there's too much magnesium in the alloy Back to the JB Weld fix?

[Beyond The Pale]

I doubt you can use the XL kickstarter actuated cable. You would need the matching XL cable attachment at the head. My old 81 XR500 had two cables at the head decomp lever. One cable attachment was above the shaft and was actuated by the kickstarter. The other was below the shaft and was attached to the handlebar decomp lever. That 93 XR600 head only has the one cable attachment designed for the cable to come in from the front and above. Not sure how you would connect that to the old style kickstart cable that goes backwards.

If you can get the cable attachments from an older head you might be able to run both cables.

The only reason to run the kickstarter decomp would be if you run a non OEM cam that doesn't have the decomp and anti-kickback. That cable would be redundant with the OEM cam. However, you have a Hotcam that cable should restore an automatic decomp system.

[HeadTrauma]

1.)I have a Xl600 clutch cover (for the kickstart) so I have the choice of running the XL600 comp release that is triggered by the kickstarter or I can run a manual release off of a handlebar lever (like an XR600R).

Pros and cons of each? What say the braintrust?

2.) Sidenote: FYI... you apparently cannot heliarc a shifter wound on an XRL stator cover. Took mine to the welder today and he gave it a shot with the heliarc. Said there's too much magnesium in the alloy? Back to the JB Weld fix

1.) Fun RFVC fact: The XL600 has a different automatic compression release and head cover than the twin carb XR600. The XR600's kicker cable was tied to the manual release over an exhaust valve, but the XL600's actuated a fifth valve in the combustion chamber instead. In order to use the kicker cable, you would need the associated parts from a twin carb XR600. You also need the cam that slides onto the kickstart shaft in order to actuate the kicker cable.

2.) I don't know why he couldn't weld aluminum with a lot of magnesium in it. The stator cover on my father's XL600 had the clutch cable tab welded back on at some point and it is magnesium.

[AZRoadRunner]

Just curious, do late-model XR650Ls have a compression release?

The only bike I ever had with one was by 1972 Yamaha XS650, which was used in tandem with the starter since the starter was not quite up to the task.

[HeadTrauma]

Just curious, do late-model XR650Ls have a compression release?

All 650Ls only have the automatic one on the cam.

[AZRoadRunner]

All 650Ls only have the automatic one on the cam.

That must be what I hear sometimes for only the first second while starting - a sharp metallic hammering that disappears almost instantly?

[HeadTrauma]

Eh, it shouldn't be making any noise at all, let alone a "metallic hammering."

[ThumpNRed]

Thanks HT and CL. I suspected there was probably more to it. The search begins for the lever, cable and other bits & pieces.

Cleonard... The engine build plan:

Adding a kickstarter

Swapping in an XR600R flywheel (half the weight of the XR650L)

E-Start delete (I know, I am nutz )

XR600R counter and main shafts; XR600R 1-2 gears; XR650L 3-5

High comp piston

HotCam

Reworking the electrics will come later in the summer once we get her back up and running and I am settled on losing the e-start. I would like to investigate a more compact battery that will run the lights (no need to crank the starter that's no longer in the circuit)that I can easilly tuck into the airbox.

If the XR600R flywheel yields the desired result, and I actually miss the e-start, I have thought about having a machinist carve five pounds off of the XRL flywheel. I'll then have to figure out a starting drill that uses the bar mounted comp release and the e-start together.

HT... I'm not sure why he couldn't get the side case to weld. He tested it on the inside of the case. He said as soon as he hit it with the heliarc, it just boiled up, started splattering and made a mess. I've never heard of anyone welding magnesium. As flamable as magnesium is, I can't imagine getting it to weld. No biggie there though... I was looking for a more permanent fix than the JBWeld patch... I guess I'll have to harness the OCD tendencies and get good with the JB Weld fix.?

Thanks again!

[AZRoadRunner]

Eh, it shouldn't be making any noise at all, let alone a "metallic hammering."

Oh well, I have 11.5 months of warranty left. ?

[HeadTrauma]

He tested it on the inside of the case. He said as soon as he hit it with the heliarc, it just boiled up, started splattering and made a mess.

Yeah it started spitting, the pores on the inside of the case are full of oil! Aluminum has to be spotlessly clean and he probably wouldn't have had a problem if he tried the outside. Also, magnesium is indeed flammable, but it won't burn if there is nothing(like oxygen) to react with. Titanium can be welded too.

[ThumpNRed]

Yeah it started spitting, the pores on the inside of the case are full of oil! Aluminum has to be spotlessly clean and he probably wouldn't have had a problem if he tried the outside. Also, magnesium is indeed flammable, but it won't burn if there is nothing(like oxygen) to react with. Titanium can be welded too.

Yea that makes sense. I don't know if I should dick around with another welder or just JB Weld it. I am afraid of someone screwing it up.

[ThumpNRed]

Would someone mind posting a picture of the compression release cable on their XR600R where it mounts to the valve cover. I have collected most of the parts and pieces (I think), but must be missing a mounting bracket of some sort. I don't have a frame of reference, so I can't tell for sure what I am missing.

Thanks much! ?

btw... I did search first

[HeadTrauma]

[ThumpNRed]

Crap that's what I thought. I have the wrong bracket! No wonder it's not obvious how the one I have works.? It doesn't!!!?

First EBay swing and miss yet... guess I am doing well If I have only missed once.?

Thanks for the picture ?

[tractor4play]

1.) Fun RFVC fact: The XL600 has a different automatic compression release and head cover than the twin carb XR600. The XR600's kicker cable was tied to the manual release over an exhaust valve, but the XL600's actuated a fifth valve in the combustion chamber instead. In order to use the kicker cable, you would need the associated parts from a twin carb XR600. You also need the cam that slides onto the kickstart shaft in order to actuate the kicker cable.

2.) I don't know why he couldn't weld aluminum with a lot of magnesium in it. The stator cover on my father's XL600 had the clutch cable tab welded back on at some point and it is magnesium. ?

hi there ht,i think it was just the 1983 xl 600 head that came with the 5th valve.all others have the cable to the exhaust valve including the euro model (lm).they kept making them with the decom chamber for some reason.maybe for somewhere to keep a spare set of keys...ha

[tractor4play]

Crap that's what I thought. I have the wrong bracket! No wonder it's not obvious how the one I have works.? It doesn't!!!?

First EBay swing and miss yet... guess I am doing well If I have only missed once.?

Thanks for the picture ?

i might have the parts you need exhaust rocker,shaft and double sided cable bracket which should fit on your cam cover.i need to check plus i live accross the pond in belfast..

[ThumpNRed]

i might have the parts you need exhaust rocker,shaft and double sided cable bracket which should fit on your cam cover.i need to check plus i live accross the pond in belfast..

In my tinkering the other evening, I discovered that the cable assembly I got though fleabay is the cable that runs from the Kickstart up to the valve cover. The bracket is a perfect fit for the side cover bolt holes. ?

I discovered that the bracket that bolts to the valve cover is only $9.00 from the dealership, so I think I will pick up a new one. The cable that I have might actually be long enough to run from the bars down to the headcover.

Building a frankenstein motor is so much fun...

[HeadTrauma]

hi there ht,i think it was just the 1983 xl 600 head that came with the 5th valve.all others have the cable to the exhaust valve including the euro model (lm).they kept making them with the decom chamber for some reason.maybe for somewhere to keep a spare set of keys...ha

XL600Rs all have a manual release cable going to the right exhaust valve. As far as I know, '87 was the only year XL600R in North America that did not have the fifth valve. The XL600LM/Paris-Dakar also appears to have come with an XR600-based engine with the matching small-port XR600 head with a cast XL600 compression release chamber cover instead of the XR's stamped steel cover. The stamped XR600 cover was merely cosmetic since the chamber did not function. The XL600R needed a stronger cast cover that could withstand significant pressure. From what I can tell none of the XR600s had a fifth valve, so that would explain why the XL600LM doesn't have one.