Main Jet Question

[Jaoteay]

All, I haven't done too much work on my Carbs yet, so these are going to be real basic questions.

I drilled my stock exhaust and and from my other questions it's probably running a little rich. So it was suggested to drop my Main jets down a size or two...

But I still don't have any idea what size that would be. I have a stock 2006.

I went to the Jetsrus.com site and found where they list the Mikuni jets for the Vmax, but the sizes are from 110-220.

Are Mikuni the right ones to get? I do know that I need to buy 4 of them.

Thanks again guys, if it wasn't for this forum I'd be soooooo lost!

 

[one2dmax]

Mikuni Small Round. Stock is 152.5's - probably 147.5's - 150's would be good.

Sean

 

[Thevmaxrider]

Your stock jets will be Mikuni 152.5's. I would look at buying a set of 150's or maybe a set of 147.5's depending on how rich it is with the stock jets. If you have a shop with a dyno and a selection of jets your best bet would be to tune that way, for accuracy. You can "seat of the pants" tune, but the dyno tuning will be the best method. Whatever you do, make 1 change at a time!!! I cannot stress that enough. If you make multiple changes and the bike runs like doodoo, where do you start correcting the problem. My recommendation would be to put in the 150's and see how it runs, get it checked on the dyno, and if it is good stop there. Should the bike still be rich, drop to the 147.5's (this is where my bike ended up with an HMF exhaust running at ~750ft) and re-dyno/test. Good luck and happy tuning!!

 

[Thevmaxrider]

Mikuni Small Round. Stock is 152.5's - probably 147.5's - 150's would be good.

Sean

Damn, I was too slow LOL. Need to shorten my answers:biglaugh:

 

[Shuriken]

I just installed 147.5s (at 5700ft) and the bike seems to run great. I'll re-check plug color and will let you know....

 

[Jaoteay]

I just installed 147.5s (at 5700ft) and the bike seems to run great. I'll re-check plug color and will let you know....

Do you have a drilled stock exhaust too?

 

[Shuriken]

Do you have a drilled stock exhaust too?

I just reversed the "drilled muffler mod" two days ago. While the mufflers were drilled, I was running stock 152.5s.

The end plates are back on my bike and I am now running 147.5s. So I can't say how the bike ran with 147.5s and drilled muffs, but it runs great now.

I will check plug color and get back to you. I do know how the plugs were with the drilled muffs mod, so I can compare them with how they are now.

I need to do more testing, but I was getting about 28-29mpg (city/hwy) before. I think I'm up to 32 (city/hwy) now - at least it came out to that on the last tank. Will need more trips to make sure.

 

[Jaoteay]

hmmm... So I finally put in the new jets. I put in the 150's - a K&N Filter, removed the Y in the airbox. Synched the carbs. Adjusted the A/F Mixture on Carb 1 (using Colortuen) - then adjusted the other Carbs to match the same number of turns.

I took it out for a short ride (As it was 31 degrees here in Colorado this evening..) - the bike runs well - but seems to be lacking power. I can still feel the vboost - but it just feels weak.

Any ideas?

 

[Rusty McNeil]

hmmm... So I finally put in the new jets. I put in the 150's - a K&N Filter, removed the Y in the airbox. Synched the carbs. Adjusted the A/F Mixture on Carb 1 (using Colortuen) - then adjusted the other Carbs to match the same number of turns.

I took it out for a short ride (As it was 31 degrees here in Colorado this evening..) - the bike runs well - but seems to be lacking power. I can still feel the vboost - but it just feels weak.

Any ideas?

Instead of removing the Y altogether, just shim it higher with washers under the screws. maybe on the order of 3/16" to 1/4"

Stock my bike ran like doo-doo without the Y.

I currently run the Y but its cut way back and the area over the back part of the filter is removed also, I'm running stock carbs other than two coils cut from the slide springs and Dynojet 160's which are smaller than the stock 152.5 Mikunis and I believe are about equivalent to the Mikuni 150's or 147.5S not sure which. Idle mixture is set at 2 1/8 turns out.

My bike loves it lean, and the plugs still look right so it's not too lean...

Bike runs flawlessly

Rusty

 

[Jaoteay]

Hmmm..


SO I have an 06 - and live at about 5,000 feet.

I have a drilled exhaust - K&N Filter, no Y (but may be adding it back). Screws are turned out 4 turns....

Think I should drop down a main jet size to the 147.5? It ran well before this work was done!

 

[naughtyG]

if it ran well b4, just go back to how it was! Classic case of 'if it ain't broke, don't fix it!'

Also 4 turns out sounds extremely rich on the AF screws - usually the 'default starting position' is 2 1/2 turns. If you feel that it ran a bit rich before, rather than changing the jets you could just close your AF screws a little to make it leaner.

 

[speedfreke]

Not to hijack this thread but I also have a jetting question, I live at about 1000 feet here in phoenix, in the next month or so I will be moving up to
prescott valley which is at about 5000 feet, I also have the modified stock exhaust right now until I can afford a kerker system, it runs great here now and I know every bike is different when it comes to jetting but is there a standard that is used for the amount of elevation you go up in relation to how many jet sized you go down? also I will be riding back to the valley(phoenix) fairly often, am I going to run into a lean issue that may be damaging when I go back down in elevation? what do you think

thanks
richard

 

[Thevmaxrider]

If you are running a drilled stock exhaust and the stock jetting you are probably rich at 1000 ft. With my Max at 1000 ft (as per the local airport) I was running 147.5's with an after market exhaust just to get it tuned, I would think that you may be down in that range at 5000 ft elevation. Best way is to go down a size, run it, if rich go down another size. Only make one change at a time though.

 

[naughtyG]

someone needs to come up with some variable size jets for those going up and down on a regular basis..:ummm:

 

[speedfreke]

Okay, I am going to have to check my jetting here and see if I can get it dialed in at 1000 ft. and record all the settings, then once I move I will have to set a day aside and get it dialed in at the new elevation, I suppose if I need to go back down I can swap it all back to the 1000 ft setup since once you leave the town up there you pretty much immediately start dropping elevation, looks like I will become pretty efficient at swapping the jetting around

 

[one2dmax]

There was/is a kit out there that allows adjustments like you are asking about. It's the dial-a-jet kit. I would say to set it up lean and allow the kit to richen to your desires. Essentially it pulls fuel from you bowls and into the top of the carbs using the vacuum created by your intake tract.

Sean

 

[speedfreke]

Sean is that the name of the kit "Dial a Jet",have you ever used them,do they work well, do you know who sells them or where I can read up on the kit somemore

thanks
Richard

 

[one2dmax]

Here's the link:

http://www.thunderproducts.com/dial_a_jet.htm

I have used a similar setup on a set of 41 mm flatslides and have seen them on stock carbs but normally it's never needed once you get the carbs setup right. Most of the time (99%) you'll never need to change your setup for riding around even big climate and or elevation changes. It's only if you are hunting for maximum power at that particular time.

Sean

 

[speedfreke]

so you think if I get it set up for 5k feet of elevation it wil run ok back at 1k feet when I go back down? if so I will save my $250

 

[one2dmax]

If you are just driving through and back then I would not worry about it. If you are going to move there it will still work but you can tune it better with some jetting changes. You can always just get a differnet set of jets.

keep in mind Yamaha sells these bikes all over the world and they only come with one configuration for every climate and elevation.

Sean