Let me just start off by saying that I have a 98 Superhawk with Two Brothers pipes, K&N Filter, and a Factory Pro Jet Kit. The Two Brothers pipes that are on the bike have selectors to open and close baffles at the beginning of the pipes. I am currently running the baffles closed.

I have a couple of questions dealing with the Factory Pro Jet Kit.

I had this kit installed by a shop. They never gave me the stock jets and the needles they took out, or the remainder of the jets and needles from the Factory Jet Kit. So, I had no idea what was in the bike. A word of advice for anybody in the Northeast, never go to Cycle Design in Philipston MA. After battling with the shop on poor performance, I finally gave up and tore into it my self.

When I opened the carbs up, I found a 175 Front Main Jet, a 178 Rear Main Jet, and a 50 pilot jet. For all I know the main jets were the stock jets.

I had been chasing a dead spot at 6000 rpm at operating temperature. So, per Factory's customer service I went down a size on the main jets to 172 Front and 175 Rear. This did improve the situation. Not cure it, but improve it.

Finally here are my questions.

I thought the whole point of a jet kit was to richen the fuel air mixture up to combat the lean condition caused by increase air flow of the aftermarket filter and pipes?

If this is true, then why is my bike running better with smaller main jets then what came stock in the bike? I see most people on this site using a 180 front and 185 rear.

I have noticed that the bike becomes a buzz box at around 5000rpm. Could this be a combination of a high flow air filter and the baffles being closed on my pipes?

If I open the baffles on the pipes will that require another rejetting? I would assume this would give me some performance gains as well.

Could somebody tell me the size jets that are included in a Factory Kit?

Thanks for the help.

 

Hi Clogee,
That sounds a bit suspect. With the storm, airfilter and pipes makes her go lean, especially up top. Most folk need to rejet richer as you said.
First off many people go dynojet main jets which are different to the keihin-factory ones and the Factory one also, but I ma told the keihin and the Factory are very similar in the way the flow fuel for any given size, what I am saying is a 180 keihin is different to a 180 dynojet, i understand that the keihin will flow more fuel for a given size. Did your mains have keihin written on the side?

Unless you live at high altitude, for airfilter and pipes you would still be wanting to go 180 or maybe 182 Factory or keihin main jet rear and 178/180 front. Under the needle have two shims if you are using the std needle ( thanks to the shop ) of if a Factory needle is installed then this is the area to play with if the main jets didnt clear up the midrange. I would suggest running 182 rear 180 front, then playing with the clip under the needle for midrange, if you loose the plot like I have done have your best go and then run it on the dyno too see where you need more/less fuel.

Make sure the airfilter has been oiled correctly as this is crucial too.
Regarding the vibe at 5k, if your neihbours can hack it run to 5k o the side stand and see if you can pick up a vibe from a loose bolt or something rubbing, it may be a coincidence.

Also, we will need to know if the flat spot is at 1/3 1/2 or full throttle etc

Have fun!

 

Do you have the TBR full system or slip-on?

 

Rufion:

The jets I took out did not say Keihin on them. They just had the numbers. I have no idea if they were the stock honda jets or jets from the jet kit. Thankfully, the shop did put the needles from the jet kit in. So, I am able to adjust needle height via a clip.

I noticed the flat spot at 3/4 to full throttle. It is temperate dependent. Cold bike, no flat spot, Hot bike flat spot. Based on this Factory Pro recommended going down on the Jet sizes.

Interstingly enough the vibration seems to be temperature dependent as well. This morning when I rode to work, it was 41 degrees out. So obviously the bike was not very warm. Did not notice much vibration. Only normal V-twin vibration. This almost makes me think the vibration is linked to carburation instead of loose parts.

If it helps, I live in Granby CT which is about 300-400 feet above sea level.


HawkRider:
They are just slip ons, not the full system. The whole selectable baffle thing is strange. On one pipe the mechanism that holds the baffle in one position shook apart. So, I had to bolt it in place.

 

clogee

Where do you have the needles set at this time?
Have you tried more than one setting?
Have you done a good carb sync?
I always found it necessary to resync after each time I pulled the carbs.

I'm not familiar with the selectable baffle TBRs, mine are from the old school I guess .... do you attach a different end plate? I'd try to get the bike working well with the TBRs pretty much wide open .... afterwards play with the baffles....

 

Carbs are a funny thing sometimes.

As it turns out I am doing pretty much the same thing as you at the moment, and my next experiment is to go own on main sizes to about 178/176 or 178/180. My bike has raised comp, full system, billet intake runners and slightly modified intake.

The theory of more fuel is what I was following too, however this has not always proven to be right. I have a mate who has lot of info on VTR race bikes, and he tells me lots of full race 140hp plus bikes are using mains smaller than 180!

All I can assume from this is that the mains will dispense fuel according to the airflow through the carb. By modifying our bikes we are increasing airflow, and this airflow is dragging more fuel from the main jets, so essentially we are getting more fuel in the combustion chamber for an given main jet size anyway.

One guy I know with standard engine internals but a full Exan system, BMC filter & Factory Pro jet kit, had his bike dyno tuned and ended up with 176/178 mains in it. Go figure.

The HRC jet kit has you running mains in the 150's, no kidding. But that is with carby mods to go with it.

By the way, the Factory Pro jets I have seen have "Factory" written on the side and the number on the top.

I will be doing some more jetting this weekend to see if I can get mine right, so good luck to you and me!

 

All Factory Jets Have Factory Stamped On Them.stock HondA Jets Only Have #'s On The.the Shop You Took It To Probably Didnt Do A Whole Lot But Turn The Mixture Screws.the Best Thing You Can Do Is Get It On A Dyno.you Can Do A Load Test At Any Throttle Position To See How Your A/f Mix Is.you Need A Base Line To Start.not All Shops Are Shitty,some Guys Actually Give A Crap!

 

I have the needles set at 4th down from the top (on up from the bottom). When I still had the 175/178 jets installed in it, I dropped the clip to the last slot. The bike ran terrible. It was after that results that I contacted Factory Pro. They said put the clip back to the forth slot and go down a size on the main jets.

I have not synced the carbs. I could give that a shot.

The selectable baffle TBRs are wierd. I have never seen them anywhere else, nor can I find a picture of them. They have a dial on the outside of the aluminum housing where the header pipes come in. If I shine a light down the pipe and turn the dial, I see a donut shaped metal plate turning. One position forces the exhaust to go through the inside diameter of the donut. The other position is wide open. I have been running them closed so I don't upset the neighbors. On one can, the selector mechanism is messed up. I had to drill through the dial and use a self tapping screw to lock it into place. I am considering cutting these things out completely.

The bike is acutally running pretty good right now. Going to a 172/175 main jet help (not cured) the dead spot at 6000 rpm. There is a slight dead spot now at 6000 rpm, but if you stay in the throttle it almost imediately clears after you pass 6000. If I had to guess it is the transition from the "needle circuit" to the main jet circuit. I think I need to get it on the dyno to get a better idea of what is going on.

 

I agree, I need to get it on a dyno. Unfortunetly, there is only 2 Non harley shops in CT that have a Dyno. Of course they are at opposite ends of the state.

 

clogee,

Yeah, that sounds a little like the needle profile is giving you fits. Sometimes changing position will help in one area but then make you rich or lean in other areas. That's the only crappy thing about carbs, is that needle profile needs to be right for your bike or you will have to have custom ones made. I think FactoryPro did a pretty good job with thier needles.

Oh yeah, and earlier when I said that FactoryPro uses Keihin jets, I misspoke. I meant to say they use their numbering system, and except for the name stamped on it, they are the same. BTW, Keihin will have a "K" stamped before the number.