[troyslap]

I recently added header to my 99 M900 and it already had Remus highs. It has the airbox removed with Uni filters on carbs. Has anyone got a similar setup and if so, What main jets, idle jets are you running? I put 230 mains in and it seems OK, but haven't done an extensive ride yet.

 

[dj]

230 mains? Really? Have you had any head work done? What do your plugs look like?

Check out Chris' FCR site for some info on tuning those suckers.

 

[chris]

I'm told that 200 main jets in 2 FCR 41 carbs are enough fuel to make 100hp. Without doing head work, you shouldn't need over 162. Really, I'd be surprised if you needed that much.

Guy Martin gets ~95 hp out of his Testarosso modified heads with 162 to 165 mains...

Chris

 

[troyslap]

I had 178's in before headers and it ran OK when warm, but was really cold to start, much more so than when they were on my 900ss with 158's and airbox with cut lid. They required several ((10+) times hitting start button after turning idle all the way in. Another guy I know with full system and filter pods was running 220's and that is why I went that high. I have not had the chance to do a plug chop but will this weekend. It does start better when cold. Has anyone changed the idle jet and/or needle and if so to what?

 

[chris]

The "I know this guy" part kinda scares me. Ever seen what happens to the piston crown when you pour 100+ hp worth of fuel into an engine that's making 75~80? You get carbon build up REAL quick. I learned this the hard way... with 180 main jets. And I've still got those pistons with roughly 2000 miles and .200" of carbon burnt toast on them.

You're trying to use the main jets which affect WOT to compensate for the idle circuit?

How about reading the webpage linked to above to sort out the circuits which affect idle?

Chris

 

[Norm]

I have 2 sets of FCRs & while I don't remember what size main jets I have in them, I just checked my jet box & the biggest size that I have is 175, sooo.....................you're a touch over jetted!!!!

 

[troyslap]

Norm, do you have stock airbox and headers?

 

[Norm]

I don't have a stock airbox or headers on anything I own!! I have a habit of taking perfectly well engineered products & hacking them to death until they run worse. It's a curse.