Why different main jet on cyl 1?

[OnDaTrail]

I was looking at my main jets in my 2000 sx700r. Why did yamaha use a different jet (145) in one cylinder and 143.8 in the other 2. Also, I se that Turk recomends switching over to 142.5 all the way accross in another post. Anything to be wary of there? Is it a noticeable gain?

 

[SXlover]

It was because the one side runs a bit hotter, so they jet it higher to run more fuel through it thus keeping temps down. And yes what Turk recommended is safe. We have 2 97 SX 700 triples (same motor basically as yours), and they have both been jetted straight across for years.

 

[Madmatt]

Needle

Wasn't there a safe recommendation for leaning out the needles on the SX'x too? Seems like I used to do that in addition to the mains.

Madmatt

 

[yamaha98sx700]

With the 142.5s what temp should you start to worry about burning a piston?

 

[Mysledblows]

Bout -20F or so is the limit.

 

[yamaha98sx700]

Then this is a pretty safe set up. That is good to know.

 

[daman]

You may want to check jetting now with stock settings and see where your at for your temps and alt. when i got my sxr was going to jet her down too but after some testing and checking jetting i decided not to it looked about right on and anything leaner would have made me nervous.

allot of guys run that jetting w/o issue so just a little food for thought is all,id rather be a little fat.

 

[panteramatt]

Well Im in NJ at sea level and ride my sled in the ny mountains. What would rejetting to 142.5 do for me and would it be safe? At sea level I should already be running lean.

 

[daman]

well 142.5's is good for 40-60 F @ 0-300 ft

or 20-40 F @ 300-1700ft

or 0-20F @1700-3300ft

on and on,,do you know what your alt and temp going to be?

 

[panteramatt]

Well that wont work for me since nj is at sealevel. Dont know about my cabin in NY maybe 1500. Thats why my next one will be efi.

 

[daman]

well if your temp are going to be 20 to 40(1700ft) it'll work but caution if it gets colder.