Jump to content
Sign in to follow this  

Need help preliminary jetting a fcr41 on a xr600r

Recommended Posts

Motor isnt even finished but I would like to jet my pumper so the bike will atleast run SAFELY.

1997 XR600R

JE 10.6:1 4mm over (what does that make it in cc's anyways)

Pro-X rod

Megacycle Cam (dont have the cam specs off hand)

Open Uni Air filter (no airbox)

Unknown header pipe (fmf hi flow possibly)

FMF power core cut in half and packed with stainless scotchbrite (it does not burn so do not tell meit will melt and shoot out the end thanks)

Not sure what else I should list?

Maybe that it is going to be professionally jetted at factory pro in a few weeks, I need some in the ballpark jetting so its not running terribly lean so it can start, run, drive for a few miles and get its virgin oil changed :smirk:

Share this post


Link to post
Share on other sites

Try doing a search in this forum to see what others have used.

I can answer the cc's question though. It's just a hair under 641 cc's, up from the stock 97mm piston size of 591 cc's.

Share this post


Link to post
Share on other sites

Thanks for the cc's :smirk:

I see a ton of threads on xr650L's and some on xr600r's

I think having a no airbox will be throwing a huge stick in the wheels....I do not want to run the stock carb, but maybe for firing it up I will.

Share this post


Link to post
Share on other sites

run the stock for 400 miles them go dyno. than put your carb on dyno with air fuel meter to jet in right. dont blow it up jetting it in on brake in. my .02

Share this post


Link to post
Share on other sites

Unfortunately the stock carb wasnt jetted the best, and with all of the changes I made...I do not think it will run too swell. :smirk:

Share this post


Link to post
Share on other sites

Jetting the stock carb is not difficult. You could probably start with jetting as fat as what my bike is running (68/170/3rd groove) and be pretty close.

For future reference, the formula for cylinder volume is πr²h.

π = pi = 3.14159. This symbol doesn't look like the classical pi because of the font this forum uses.

r = cylinder radius

h = cylinder height.

The result is cubic volume in whatever units you used. Using millimeters will give cubic millimeters; divide by 1000 to get cubic centimeters.

Share this post


Link to post
Share on other sites

I may just run the stock carb with your listed jets, just to make it run and for break in. Then take it to the professionals, dont want to hurt my 5000$ xr600 LOL

Share this post


Link to post
Share on other sites

How do these FCR41 carbs work for restarting if one stalls engine during a crash? (the one thing I like about the quicksilver, restarts are excellent)

Share this post


Link to post
Share on other sites
How do these FCR41 carbs work for restarting if one stalls engine during a crash? (the one thing I like about the quicksilver, restarts are excellent)

I have never had a problem refiring my pig with the FCR... of course I have not yet had any epic crashes so I cant say for sure how it would do if I went @$$ over teakettle in a grand fashion.:smirk:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×