1986 Honda XL600R Camshaft


32 replies to this topic
  • valvesrule

Posted November 10, 2010 - 07:41 PM

#21

The 101mm piston gets you about 600cc even. The 11-1 actually will only give around 9.8-10 or so. That's not a bad thing though. Mine has the 102.4 Wiseco and it's only about 10.2 with a smaller chamber XR500 head. The 105mm pistons need the main cases and cylinder both bored and a much larger sleeve installed. It's pretty expensivebut the only way to get over 620 cc. I don't know just who it is that makes these kits but the pices are available. Captain Midnight (on this forum) can refer you to the right company for this mod. I don't believe you could modify stock guides enough to work with the x12 and I'm positve it wouldn't fly with the x35. I estimate my 620 is 48-50hp using all comparable stuff except a stock XL cam. Even the dropin Webcam is good for a couple hp and it's far less money. The big tube headers look cool but don't make much difference in power unless you go big on all the other aspects (big cam, ports, carbs etc). I have the WB S/S header and can hardly tell any difference at all from a stock XL header (which is already bigger than an XR header). The lighter flywheel is a real good idea if you want quicker responce.

  • biker1ktm

Posted November 11, 2010 - 08:28 AM

#22

Yeah the guy i bought the bike from had turnded the flywheel down on his other xl and it helped a lot.

Do you have the specs for the RD guides? I am going to talk to a local flat track engine builder and see if he has any ideas. I am also going to talk to someone at webcams to see if i can some details on the springs to see if the kibblewhite ones will work.

Thanks for all the info its a big help. deffinately giving a lot more to think about.

  • valvesrule

Posted November 11, 2010 - 01:19 PM

#23

The early 83 XR500 has the lightest flywheel. 83 1/2 up XR500/600 are slightly heavier but much lighter than the XL. More expensive to machine yours down than get one on ebay. You may actually prefer the heavy XL flywheel for ice racing. KW 30017 and RD1010 springs are campatible for both open pressures and lift capacity. I'll try to post dimensions for the RD guides tonight.

  • joeskiguy

Posted July 24, 2014 - 08:31 PM

#24

Has anyone ever entertained the idea of installing an xl to end on an xr bottom end? That would increase the stroke from 75mm to 80mm. Fabricating a riser plate for the bottom end of jug to accommodate the longer stroke. With a longer sleeve the riser plate would be only acting as a spacer. Just curious. Then at a 101mm bore you could squeeze out about 640cc.

  • valvesrule

Posted July 25, 2014 - 12:13 PM

#25

Has anyone ever entertained the idea of installing an xl to end on an xr bottom end? That would increase the stroke from 75mm to 80mm. Fabricating a riser plate for the bottom end of jug to accommodate the longer stroke. With a longer sleeve the riser plate would be only acting as a spacer. Just curious. Then at a 101mm bore you could squeeze out about 640cc.

No riser plate needed. An XL 600 cylinder bolts on with an aftermarket XR 100mm piston for dual port engines while an XR650L cylinder and the same piston does it for single carb 600s. Height of the wrist pin is different so spacing the topend up isn't required. With an XR crank and 102.4 wiseco you can get 660cc. The JE 105/106 pistons can get you +/- 700cc.....without any spacer plates.



  • joeskiguy

Posted July 25, 2014 - 12:17 PM

#26

I like.
Very interesting!

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  • joeskiguy

Posted July 25, 2014 - 12:34 PM

#27

So if the extended stroke is added at the bottom and not at the top, doesn't the piston protrude past the sleeve at bottom of stroke? Or are the aftermarket sleeves longer to accommodate this?

  • valvesrule

Posted July 25, 2014 - 12:49 PM

#28

So if the extended stroke is added at the bottom and not at the top, doesn't the piston protrude past the sleeve at bottom of stroke? Or are the aftermarket sleeves longer to accommodate this?

You have a fundamental misunderstanding of how the stroke change works. No the stroke is longer both up and down. The wrist pin is just higher in the piston to compensate. With the 650L they shortened the rod but that isn't the only place you can adjust. Most pistons do indeed protrude some amount from the bottom of the sleeve at BDC even on stock engines. Clearly less is better. aftermarket pistons almost always have smaller skirts to reduce metal to metal friction but as a side effect reduce the concern. More stroke also brings up the consideration of clearance with the crankshaft and cases which these pistons also compensate for. Engines are nearly always designed with the possibility of larger bore/stroke combinations in mind later in the production cycle. Internal dimensions are chosen to give the extra size changes that might be needed. A notable exception is the CRF450 engine. There's very little room for any expansion without major changes.


Edited by valvesrule, July 25, 2014 - 12:53 PM.


  • joeskiguy

Posted July 25, 2014 - 12:57 PM

#29

Copy that. You're correct. I want thinking that the stroke is divided between the 180 degree to and bottom. So it's only 2.5mm each way. But if the jug is the same and the piston or rod is modified to fit same jug, doesn't that in effect bring the entire additional stroke to the bottom of the jug, thus creating a need for clearance or accommodation of the entire extra 5mm at the bottom end?

  • valvesrule

Posted July 25, 2014 - 01:26 PM

#30

No the stroke is evenly divided top/bottom regardless. If you have to clearance the bottom (below the crank)it's still only going to be half the stroke difference. The other half of the stroke is accommodated by rod and pin length/dimension changes. The extra stroke will all be apparent at the bottom of the cylinderand piston not the crankshaft. It's rare cases where engine height is changed with spacer plates, deck heights or other. Guys in the XR80/100 and XR200 forums do these mods all the time but that's a lot of trial and error if you don't have the budget of a major manufacturer. The XR200 is a great example. This engine started out as the CB/SL100. Over years of evolution both the factory and aftermarket developed 125, 133, 145, 175, 185, 200cc versions. The 200 is pretty tapped out at 205cc without a stroker crank. This required a shorter rod to fit it in the package or a taller cylinder/spacer plate. Problem solution from the factory? CRF230F engine. Taller cylinder/deck height to allow use of the longer stroke AND long rod. Other than the longer stroke crank and taller cylinder this engine is basically the same as an XR200. The electric start was added not so much as a convenience but rather a necessity for reliability since the original SL100 kickstart mechanism was too small to depend on anymore.

Edited by valvesrule, July 25, 2014 - 01:29 PM.


  • joeskiguy

Posted July 30, 2014 - 08:15 AM

#31

Copy that. Any advice on how critical it is to re-cut valve seats on an xl600? The seats on the on the head I'm about to install are a little pitted and when I blued the valves there were a couple that seemed to not be seating perfectly with my old valves, even after lapping. I found an old jobs Honda oem valve cutting tool with the pilot and 3 different angled cutters. Says it's for cr250. Would it work for my xl600.

  • joeskiguy

Posted July 30, 2014 - 08:34 AM

#32

? It was a question about the cr250 valve cutter writing on my head, but now that I'm thinking about it the cr 's were two strokes and had reed valves. I'm going to have to look that eBay cutter up again to verify.

  • joeskiguy

Posted July 30, 2014 - 08:36 AM

#33

Found one for a cb125 and another for an xl250. The cutters look to have about1/2" if cutting surface, so I'm thinking that they have a range of valve seat sizes they would work on, no?





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