Jetting question

[Sanders98]

I am new to the site. read a lot of post but new as a member.
I have a blast open lid air box, oil injection delete, stock bore, FMF full exhaust vforce 3 reeds reed spacer k&N filter. looking to see what jets would be best for it I know FMF says 260 but that seems a little small and suggestions?

 

[tbrooks]

Welcome, 260 is just for the pipe by itself. With your other mods it would be best to start with a 310 and plug chop to confirm. It would also be helpful to know your elevation and normal riding temps as well. Usually it would be best to get 270-310, buy individual genuine mikuni jets

 

[Sanders98]

elevation is roughly 0-4500 feet ridding temp 65-85 degrees out side temp.

 

[Herpderplol]

elevation is roughly 0-4500 feet

So you ride anywhere from ocean level to yellowstone park?

That height difference can mean 3-4 jets difference. you need to find something a little more specific.

p.s. google will tell you the elevation of any town

 

[Sanders98]

I ride at the dunes down next to the ocean yes. I live at 1200 elevation I also ride in the mountains that are 2000-4000 elevation ride both 50/50 looking for a jet that would be good mid so I don't have to swap jets every time.

 

[Herpderplol]

well some people say every 500 feet may require a different jet

so maybe you should look into an aftermarket carb with the main jet access on the bottom. 30 seconds and a new jet can be in place

 

[Sanders98]

Thanks I think I'm going to start with the 310 and see how it goes from there I'm working on another engine for it slowly that's going to be a 240 big bore with a 3 mil stroke and waiting to get a different carb for that one.

 

[tbrooks]

You can't get one jet to do different elevations. If it is proper at sea level, it will be too rich at 4500, if proper at 4500, your piston may fry at sea level. If proper at say 2500, it will at the least prematurely wear your engine, maybe worse. It may differ slightly according to your location, but if you plug chop at sea level, you MAYBE can just up one size for every 2000 ft. Actually if it were me, I would up 1 size at 1000ft, and another at 3000 to stay on the rich side. This is a rough estimation though, and as I said may not work as well with your elevation. To really know what jets you need, and to keep your engine running properly, you need to plug chop at your main riding locations

so maybe you should look into an aftermarket carb with the main jet access on the bottom. 30 seconds and a new jet can be in place

It doesn't take long to change jets in the blaster either, loosen the clamps, spin the carb, and remove the float bowl and change it out.

 

[Wifesblaster]

You should either be 270 or 280 on a leak free, clean air filter motor. This is at sea level in 75 degree weather.

 

[Larry's Shee]

You go down on jet as you go up in elevation.
Your dune jetting will have it blubbering like an idiot @4500.
Jet it at the dunes as you would have good long area to do a good pull for a chop/read.
Then just drop 1-2 sizes for higher elev.
If most is about 2000-2500 just go one, if it's just a bit of riding up higher, carry extra plugs.
If your rides go from 2000-4500, might look into a dial-a-jet.
https://thunderproducts.com/product-category/carburetion/dial-a-jet/

 

[Sanders98]

Okay so after plug chopping and do a bite more research to find out what plug chopping really was.
FMF fatty w/pc2, V force 3 reeds reed spacer no lid stock air box k&N with outer wear stock pilot jet air screw 1.5 turns out needle on center clip running a dyno jet 360 main jet at home roughly 600 above sea level the plug seems to be perfect.

 

[Blaaster]

A#360 seems awfully large for your mods, have you leak tested the engine to see if it is air tight?

 

[tbrooks]

A#360 seems awfully large for your mods, have you leak tested the engine to see if it is air tight?

Yes, always leaktest before plug chopping to ensure correct results. VVV that may also be why, because its not a genuine mikuni jet

dyno jet 360 main jet