Cam or head pipe?


33 replies to this topic
  • Frank ZX

Posted October 23, 2007 - 12:11 PM

#1

I have a couple hundred dollars saved for engine mods on my XRL.I have a homemade Yoshumura slip on,so I think a cam would give me the most bang for the buck.I have also though about a FMF or XR's only head pipe.What do you guys think?Also what cam should I get,Hotcam's or other?
I can pull the front tire in second by loading the forks,then slamming the throttle.Will a cam swap make the front lighter?Thanks :crazy:

  • martinfan30

Posted October 23, 2007 - 12:27 PM

#2

I have a couple hundred dollars saved for engine mods on my XRL.I have a homemade Yoshumura slip on,so I think a cam would give me the most bang for the buck.I have also though about a FMF or XR's only head pipe.What do you guys think?Also what cam should I get,Hotcam's or other?
I can pull the front tire in second by loading the forks,then slamming the throttle.Will a cam swap make the front lighter?Thanks :crazy:




if you dont have a hicomp piston, dont do a cam. i have heard of guys detonating with just a cam. i would recomend the hicomp piston, then head pipe.

  • Frank ZX

Posted October 23, 2007 - 03:13 PM

#3

if you dont have a hicomp piston, dont do a cam. i have heard of guys detonating with just a cam. i would recomend the hicomp piston, then head pipe.


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

  • Frank ZX

Posted October 23, 2007 - 03:15 PM

#4

XR's only has a piston kit,but it's 100.5mm.I'll have to rebore the cylinder right?I was hoping for a direct swap.

  • martinfan30

Posted October 23, 2007 - 04:22 PM

#5

XR's only has a piston kit,but it's 100.5mm.I'll have to rebore the cylinder right?I was hoping for a direct swap.


if stock bore is still 100mm , then ya rebore to 100.5mm.

  • tobinbakner

Posted October 23, 2007 - 06:25 PM

#6

I don’t understand. I know that a high compression piston can cause detonation, which is why you have to use higher octane fuel when you raise the compression ratio. I haven’t heard of a cam change causing it. It’s common practice in cars to change cams without changing to higher compression pistons. Can you elaborate further why a cam change could cause detonation?

Thanks

Tobin

  • martinfan30

Posted October 23, 2007 - 06:57 PM

#7

sorry, have to revise my post once i found the thread i was mentioning.
a hi comp piston was added and stock cam left in. increasing effective compression. see this...

http://www.thumperta...ight=detonation

  • Frank ZX

Posted October 24, 2007 - 01:33 PM

#8

I'm thinking about a cam and head pipe for right now,and then after a few thousand more miles getting a hi comp piston.Any advise?

  • martinfan30

Posted October 24, 2007 - 01:38 PM

#9

I'm thinking about a cam and head pipe for right now,and then after a few thousand more miles getting a hi comp piston.Any advise?


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.

  • Denn10

Posted October 24, 2007 - 01:45 PM

#10

yeah i think your ok with a cam and stock piston, down the road when u get a hi comp piston youll get even move out of it

Got any pics of your homemade yoshi?? Sounds cool

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • stepho

Posted October 24, 2007 - 01:51 PM

#11

interesting old post that happened on a cam change on our bike. With the FI i had to take 5 degrees of timing out of it to stop pinging. still trying to figure out why a slightly different cam could cause such a major detonation problem

  • martinfan30

Posted October 24, 2007 - 02:01 PM

#12

interesting old post that happened on a cam change on our bike. With the FI i had to take 5 degrees of timing out of it to stop pinging. still trying to figure out why a slightly different cam could cause such a major detonation problem


SEE! i know i had read it somewhere! thanks stepho!:crazy:

  • Frank ZX

Posted October 24, 2007 - 04:18 PM

#13

[IMG]http://http://i201.photobucket.com/albums/aa281/FrankZX/Picture166.jpg[/IMG]

yeah i think your ok with a cam and stock piston, down the road when u get a hi comp piston youll get even move out of it

Got any pics of your homemade yoshi?? Sounds cool


I'll take $100.00 for the slip on plus shipping if anyones interested.Then I'' have to get a FMF titanum:applause:

  • Frank ZX

Posted October 24, 2007 - 04:20 PM

#14

Posted Image
Posted ImageI'll take $100.00 for the slip on plus shipping if anyones interested.Then I'll have to get a FMF titanum:applause lol

  • stepho

Posted October 24, 2007 - 06:58 PM

#15

Sending some dyno results to Jim at megacycle should get an answer tomorrow on why detonation occurs just on a cam change while still having the same compression ratio:excuseme:

  • martinfan30

Posted October 24, 2007 - 07:40 PM

#16

Sending some dyno results to Jim at megacycle should get an answer tomorrow on why detonation occurs just on a cam change while still having the same compression ratio:excuseme:


ya that is the best choice for diag. this issue. in my best guess it comes down to a needed richening of the jetting with the more aggresive cam. more fuel can solve the prob.

  • XR650L_Dave

Posted October 25, 2007 - 06:03 AM

#17

Sending some dyno results to Jim at megacycle should get an answer tomorrow on why detonation occurs just on a cam change while still having the same compression ratio:excuseme:


I don't know the tech terms for it, but anything that gets you 'too much' cylinder filling for whatever specific head shape you have, will cause trouble.

I could see this happening (but I'm speculating) at maybe very specific RPMs where the cylinder filling just happened to peak, so if you jetted for just that peak point, elsewhere you'd be too rich.


Dave

  • Frank ZX

Posted October 25, 2007 - 07:11 AM

#18

I found the exhaust I want in the TT store,but it for the XR600.Will it fit my XRL?FMF muffler p/n 27-3438 header p/n 27-1197,and mid pipe p/n 27-3208
Please help.

  • martinfan30

Posted October 25, 2007 - 08:02 AM

#19

I found the exhaust I want in the TT store,but it for the XR600.Will it fit my XRL?FMF muffler p/n 27-3438 header p/n 27-1197,and mid pipe p/n 27-3208
Please help.


yes. it will fit.

  • Frank ZX

Posted October 25, 2007 - 09:28 AM

#20

yes. it will fit.


Thanks man!:crazy: Why don't they list it to fit the XRL?





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