Main jets!

[jefflanthier]

I have an 85 vmax and just wondering what would be the best all around jet size. I currently have a pair of 320,s in it and the engine is bored 20 thou over ....I,ve seen anywhere from i think 260 to 320 jet sizes shown in all the information i,ve read. The altitude i ride in is under 1000 ft. I also ride in air temp between 0 degrees celcius to minus 30 degrees celcius . 0 is the freezing point and i,m not sure what - 30 eqauls but its damn cold lol. My spark plugs are burning tan, light brown. right now but everything i read says to use smaller jets. Any ideas would be appreciated, tks. Jeff

[tyler440]

ive heard that every engine will need slightly different jetting to run at it best, and i know no better way to fine tune jetting that to read the plugs... if they are light tan i wouldnt go any leaner

[Vmax540]

Jeff, I agree with Tyler if it's running good, not fouling plugs, and the plugs look decent don't mess ! You're running fairly low temps and altitude ! Ps. Any 540 with jets that are smaller than necessary is headed for a tear down and good cylinders are hard to find !

[Undertaker#13]

I run 270's in old Maximum Overdrive

[Vmax540]

I run 270's in old Maximum Overdrive

But, you only run it in 1000' (?) bursts and you don't trail ride it at 1000' in low temps do you ?

[Undertaker#13]

I run 270's in old Maximum Overdrive

But, you only run it in 1000' (?) bursts and you don't trail ride it at 1000' in low temps do you ?

But ?? I do trail ride it some I do other little things, but I don't let out info

[Undertaker#13]

Vmax540 , race or Trail ride as you know you can't do both If I did trail ride, I would run 290's all Day long. I have the Max fine tuned for 1000FT. I have many hours of field testing and clutch work. I would love to trail ride it, but I have two problems. 1. I premix my Fuel because a factor Yamaha Rep told me not to trust the oil pump. 2. Ice picks are expensive and roads dull the picks!

[Chris]

Im running 300s right now and it has a bog at low end , , ,the slid needle is at the top grove , what should i try 270s and move the needle to the middle clip ? Does it matter i have hex mains in it now will it hurt if i put rounds in it ?

[jipcee]

Im running 300s right now and it has a bog at low end , , ,the slid needle is at the top grove , what should i try 270s and move the needle to the middle clip ? Does it matter i have hex mains in it now will it hurt if i put rounds in it ?

1. Who put and why is the jet needle in the top grove (might be too lean)
2. I wouldn't try 270 until you fix the low end bog.
3. Hex jets are mains and the round jets are POWER JETS

Is your sled totally stock?
What pilot jets are you running and what is the pilot air screw set to?

[jefflanthier]

I dont race this sled , i,m a trail rider. the mountains around here arent very big so high altitude jetting isnt an issue. I will just keep an eye on the plugs and the way it preforms and make adjustments as necessary in all the ranges of the throttle. Tks. for your input

[Chris]

I did the porting as listed in the arcticals , I will run good but i cant get past 5000 rpm if the needle is in the middle grove , put it to the top grove i can get over 5000 rpm , and it flys after it gets over 5000 rpm , But it will bog till there it has 130 piolets i belive

[tyler440]

chris, where is it engaging at?

[Chris]

Hey tyler sorry for the slow reply ive been busy , But its ingauging at 4500 after it bogs for a second it has TONS of power to spare

[srxvmax50]

Hey, make absolutely sure your belt sits at the top of your TC. The vmax does not have alot of power down low, so move shims 'round and get that belt on top. Good luck. MJD

[Chris]

Belt sits on the top TC ? ? Sorry im kinda new at this im 17 still learning