Steve,

As you requested via email, I'm listing my issue/problem here. I've got a '99 Roadstar that I bought last year used. I've got the original paperwork with it that says the dealer installed the Cobra pipes (not slipons) and put in a jet kit. I'm in the process of removing the original stock air box and installing the MaxAir Roadie Air box (an oiled foam filter). The bike now runs horrible...thought it was running rich because of gas smell, but I have to run with full choke to get any pickup at all, else when I twist the throttle it just bogs down. I've put the old airbox on for testing purposes, and it runs great. I now have the carb opened up, and I see a 165 jet in there. Don't know any settings, as I've not played with them.

I have a jet kit, a Cobra Stage 1 kit with DJ155, 160, 165, and 170 jets in it. Can I possibly use this, or do I need to go to something else? I really need to get this thing running! I haven't looked to see if I've got baffles in...I assumed I did, but I'll need to take a look. What else do you need to know?

Thanks so much,

Pete

It sounds like you might have the stock needle in there too Pete.

You are going to need to rejet. You are flowing a lot more air than you did before the new airbox, and the stock jet and needle aren't going to do it.

I would really recommend that you try and find an aftermarket jet kit, hopefully one that has a 170 mikuni main in it. If you find out that you have an aftermarket tapered needle in there, then you just need to find a 170 main to put it all together.

There is a possibility that you might need to get 167.5 main, but I would bet that a 170 would do better.

With just about any aftermarket needle, you will need to go with the fourth clip using a 170 main with your setup. Then you will need to dial in the PMS, per one of my posts on the Road Star Riders.

If you find out that your baffles have been removed, bump that main to a 172.5.

It will take a while to get it dialed in. After changing out the main and needle, you will need to get the PMS set to about 2 1/2 to 3 turns out, then start dialing it in.

Expect to have to readjust the PMS a couple of times, but it might just do great straight out with these settings. Look for backfire on decel (lean PMS, bring out in 1/8 turn increments - riding between each adjustment), and problems with pause on initial throttle engagement.

Let me know how it comes out.

Jet Kits: I recommend the Baron's because it comes with the mikuni jets that you will most likely need, but just about any aftermarket kit with a new needle will work.

If you find a Dyna kit, use the 180 main with baffles, 185 without.

Sorry to take so long to get back to you. I had a family gathering today away from home.

GRAM

Gram,

I'm going to stick to corresponding with you from here, as between the MaxAir Garage and Roadstar riders, I'm getting confused! You mentioned ported manifold. Where do you suggest purchasing one? I have the stock that I can trade if necessary, because I don't have the tools to try porting it myself. Also, do you know where I can get a 37.5 pilot jet?

Thanks!

Pete

For the 37.5 pilot (if you can't find it in a local harley or Yamaha shop) try www.sudco.com

Ported manifolds are available from a few sources. Dynamic imports, Nopork.com and Phat performance all have them (look in the vendors folder on Road Star Riders).

Some of them will port yours, others only carry new.

Let me know if you have a problem finding the pilot. I have few other places we can look.

BTW... The pilot is the same style used in the Mikuni HSR42. If you call anyone but a Yamaha dealer they will need to know this. Our carbs are made by mikuni, but are OEM to Yamaha. That means that no one will have cross reference charts for them.

GRAM

GRAM,

Well, the Baron's kit came in, and I'm headed to the garage. I'm going to use your advice:

"I would really recommend that you try and find an aftermarket jet kit, hopefully one that has a 170 mikuni main in it. If you find out that you have an aftermarket tapered needle in there, then you just need to find a 170 main to put it all together.

There is a possibility that you might need to get 167.5 main, but I would bet that a 170 would do better.

With just about any aftermarket needle, you will need to go with the fourth clip using a 170 main with your setup. Then you will need to dial in the PMS, per one of my posts on the Road Star Riders.

If you find out that your baffles have been removed, bump that main to a 172.5.

It will take a while to get it dialed in. After changing out the main and needle, you will need to get the PMS set to about 2 1/2 to 3 turns out, then start dialing it in."

I'm going to use the 170 and the fourth clip. I don't have the 37.5 pilot yet, do you think I ought to attempt using the stock pilot, or wait until tomorrow and find a 37.5 or 40?

Pete

You can change the pilot without removing your tank Pete, so I would say go ahead with the stock pilot for now. If it takes more than three turns to dial it in, then you are going to need to exchange it with a 37.5

GRAM

GRAM,

I completed the task. I set the clip on 4, used the 170 main, and turned the stock pilot exactly 3 turns out. I put everything back together, and she runs like a scalded dog! I'm getting a wee bit of popping, but nothing serious. Now I need to re-read your articles, because I'm not sure what to do. It can't be that easy! Something must need adjusting! I do have a size 40 pilot if I need it. My aluminum manifold will be here Monday or Tuesday. I'm hoping I can leave my jets/setting as is when I install it. What do you think?

Thanks for all your help.

Pete

Is the popping backfire?

Also, I forgot, but do you have your AIS removed?

Aluminum manifold... A nemesis?

If all the above is yes, then it will most likely even out when you get the manifold on. Go ahead and put the #40 pilot in. Your nearly maxed out on the pilot circuit, and still getting backfire on decel, so we need to increase it. If the manifolds evens it out, the 40 will just be for good measure.

Popping (backfire) on decel is caused by a lean idle circuit. If you want to go after right now and see if you can resolve it, follow my procedure in one of my posts about dialing in the PMS. It needs to balanced out to the other circuits in the carb to most effective, and that will do it.

Did you do a WOT test to verify that the main was not too lean?

If you did, and it was boderline, you should not have to change the main. If it passed, you are going to need to drop that 170 to a 167.5 main for the new manifold.

Let me know, sounds like we are in range of a bullseye here.

GRAM

Hi GRAM,

Well, here's where I'm at: I installed the Nemesis manifold, the 170 jet on the 4th clip, and the MaxAir filter. I put 440 miles on the bike. It is running pretty good, but I'm getting popping on decel. Currently I've got the 35 pilot installed, set to 3 turns. The 40 I got from the dealer is the wrong jet for the roadstar (you'd think they'd know that...)

Can I go out 3.5 turns on the 35 to see if it eliminates/minimizes the popping?

Do you have the "dial in the PMS" listed somewhere?

Thanks yet again for your help.

Pete

The article on dialing in your PMS is under Articles -Carbs/intake. Is on the second page of the list of articles (look for the nav bar at the bottom of the list, it will take you to page two). Its also listed in the far right column of every page on this website, under "newest articles".

You can go out to 3.5 turns on the PMS. Just keep an eye on it, as some have lost the screw (fell out) when it was too far out.

GRAM