Cam or head pipe?

33 replies to this topic
  • martinfan30

Posted October 25, 2007 - 09:30 AM


prob. because the heat sheild is different.

  • tobinbakner

Posted October 25, 2007 - 10:14 AM


Here is a link to website about about Dynamic compression ratio.http://e30m3performa...comp_ratio2.htm
If I read it correctly putting in a high performance cam will lower the dynamic compression ratio. This should reduce the chance of detonation. I could imagine if you were running on the ragged edge of detonation before a cam change you might get some detonation when the cam reaches it's peak cylinder filling area. This would increase the pressure and heat at that rpm perhaps causing detonation. This problem would actually be increased by going to a higher compression piston. I don't think the Hotcams stage one cam for the XRL with the stock compression ratio could get anywhere near that. Hot cams does not say you need to use a high compression piston with their cam.
A question for Stepho. Did this engine use the stock compression ratio? Did you retard the cam or the spark? I’m assuming FI stands for Fuel injection. How did you fuel inject it?



  • Frank ZX

Posted October 25, 2007 - 10:51 AM


Just ordered a FMF factory 4 titanium slip on and mid pipe from the TT store.I'll get the head pipe and cam next.I hope it's possible to get 40-45 HP from these mods.I had a KTM 625 SM pulling away from me out of the corners at Road Atlanta.I hope this don't happen any

  • martinfan30

Posted October 25, 2007 - 11:19 AM


i think you will be right between 40-45 HP. MAN i cant wait for my cam! its going to be a LONG 3-5 business days!LOL!

  • SniperTeamBravo

Posted October 25, 2007 - 12:50 PM


I was afraid someone would say that.I don't want to get that far into the engine yet.Any other thoughts?

Do a stage 2 hotcam, and make sure you do a pipe and jet it correctly, itll come up in third. But thats only if you trade me wheels!

  • crmc33

Posted October 26, 2007 - 03:27 AM


I dont think a stg 2 hotcam exists for the XRL

  • martinfan30

Posted October 26, 2007 - 06:45 AM


I dont think a stg 2 hotcam exists for the XRL

if there is, i havent found it yet!

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  • SniperTeamBravo

Posted October 26, 2007 - 09:59 AM


if there is, i havent found it yet!

I mihgt be thinking XR600R but thought there was a stage 2 for the XRL and only stage one for the 600, might be reversed. Either way, any hotcam is great in an XRL!

  • martinfan30

Posted October 26, 2007 - 12:03 PM


I mihgt be thinking XR600R but thought there was a stage 2 for the XRL and only stage one for the 600, might be reversed. Either way, any hotcam is great in an XRL!

you have in your xrl? how many miles on the cam? any issues?

  • stepho

Posted October 26, 2007 - 06:44 PM


Hey Tobin
yes, FI stands for fuel injection we have had it on an XR706L motor with 12 to1 compression since 2000. I am building another coustomers motor right now after i get the perfect cam grind figured out. I will send some pics, sorry guys does not fit in any stock frame. 61.1 hp and 47.8ftlb to the rear wheel 320lb dry weight amazing jetting/ mapping= 140mph! It sure is good to make old technology haul ass:crazy:

  • Frank ZX

Posted October 27, 2007 - 02:12 PM


OK,I'm going to order the head pipe Monday.Is the Powerbomb worth the extra $35.00 over the high flow header?I have the feeling the Factory 4 muffler is going to be loud and the powerbomb is supose to be a premuffler to lower the sound.

  • Frank ZX

Posted October 28, 2007 - 07:04 AM



  • Frank ZX

Posted October 30, 2007 - 03:38 PM


after re reading that old post, i went ahead and ordered a hotcam for my xrl. i still have stock piston(ill do a hicomp piston when it comes time for rings).
i will be running a fcr 41 , hotcam(using stock rockers/springs), stock head pipe and e2 slipon.

if you can do cam and headpipe at same time, sweet. maybe just do a cam and grind down the header welds for now, then get a head pipe in a couple months. this way you can enjoy each individual mod and appreciate the power incease each is responsible for.

Hey,Did you get your cam yet?I ordered my Hotcam stage 1 today.Let me know how the install and power are.

  • martinfan30

Posted October 30, 2007 - 08:44 PM


just finished the install of the hotcam. was pretty easy except getting the tensioner for the chain back in. there is a special tool but can be done without it. i am DYING to start and break it in but its 945 right now! so i will rush home tommorrow and hopefully it wont grenade!lol

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