superbling

Man, this is getting close to troll territory.

shayne

Try getting some 41mm FCR's. That will solve your problem in my opinion. I know a guy that runs these with pod filters.

Many people have tried airbox modifications with the VTR, but ultimately the CV carbs are just too tricky to get right. I had mine set up to run 205 Keihin (as opposed to DJ or Factory Pro) mains with 50 Keihin pilots and adjustable needles and it produced great power and torque. But it had a small flat spot at constant throttle I could not dial out. Back to a more standard intake set-up (with 170 mains and 45 pilots) and the flat spot was gone.

savdre

Troll Teritory huh... sorry i am not as knowlegeable as you. That's why I came to this forum, becasue it is a great place get some knowledge and meet some cool people. Apparently it is also a good place for people to take pot shots at you when you don't something and ask questions. I would hate to see your reaction if i shot my mouth off about something I had no authority on instead of asking a quesiton... mabey I would be near Oger territory... or even worse Worlock land. I am not a mechanic type, but am trying to learn and do something fun with my bike. Sorry if I did not take my anti -troll meds in the morning, or put enough troll repelent on, or just plane took a worng turn.

With that said time for more trollesk questions.....

I am correct in understanding that becasue the airbox is gone, the CV slides are not even opening.

If i was able to hook the CV diaphram port to the air intake ( i.e. if a had a little port to connect a hose to below the filter) would that create enough vacum to make'em work?

shayne

Ok, first thing is Superbling is a good guy, so don't get too excited. I am sure he was only joking. He knows a lot about the VTR too.

Back to the problem, I think the answer is no. These hoses you are referring to do not provide any vacuum, they are simply there to provide clean air from the airbox to the carb body to allow the diapragm to work. So changing the source should not make any differnce in theory.

Now I am going to speculate a bit, based on my own experiments. So here goes.

I reckon that the reason everyone has problems when they stuff around with the airbox on the VTR, is that when you change the airflow in some way, you create turbulence in the airbox. This then means that the slides are not controlled by the springs, and they jump around. Result is bad running. I found that at WOT (wide open throttle) my bike ran great, but not at constant throttle, which is where the needle and needle jet (controlled by the slides) controls the fuel delivery.

So in your case, having no airbox may mean this is is the problem. The carbs are not designed to run without a controlled air intake, and they cannot handle what you are trying to do.

I think mechanical carbs such as the FCR's will fix your problem. I am sorry I don't have the answer for the 48mm CV's.

savdre

I was jsut playing around with Superbling... Trying to get a laugh.

So, what would FCR's carbs cost.

Is there any data on the volume of air that the airbox pulls? i think with a little math I should be able to size the filters properly. It seems that the main issue is the amount of vaccum creted in the airbox. i.e. how many inches of water is it pulling - deifferential pressure.

savdre

I was taking a look at the original air box and my initial thoughts are that the K&N pods have waaaaayyy too much air flow. If you look at the intake on the box, it has baically 2 open areas that are 2"x2" each.

My next test is to block off the filters to give them an equivilent amount of air flow.

Last night I tested by coveing them up with an abitrary amount of plastic, it seemed to have better throttle response than before. It was on the stand so I do not know how representative that would be compared to when its rolling.

Any comments?

Rassie

Your bike would need rejectting before it will run clean througout the rev range without stuttering (will run either to lean or to rich) when you loose the airbox. I have done this on several bikes. Usually since you get more air you need to go bigger on the main jets. This is not always the case though since on my old GPZ900R Ninja I actually had to go 2 sizes smaller to get it to run right, however I also had hot cams, freeflow exhaust and larger pistons in that paticular case. Still baffled why I had to go leaner on that one.

If everything is stock I would get jets that are the next 4 half sizes up and start playing with it. Go up one half size at a time, ride and see if it will rev all the way through to redline without stuttering. Just revving it when stationary will tell you nothing it needs load on the engine. If you have money to burn take it to a dyno shop with all the flow meters and other stuff they use and they will be able to tell you right there which way to go with jet size, probably needle height adjustment as well. I am about to do the same thing so would be interested in your results..

Rassie

Found this with Google, may be able to add some insight.

http://www.ablett.jp/bikes/vtr/air_box_lid.htm

killer5280

I think Superbling posted that because he finds it difficult to believe that someone would try to do something as radical as remove the airbox from a VTR without knowing what an A/F ratio is; he thinks you're putting us on.
As far as I know, no one has ever been successful in making a VTR run well without an airbox, at least not with stock cams, pistons and carbs. If anyone is aware of someone having success with this endeavor, please let us know. There's no free horsepower in there and the notion that you're going to out engineer the Honda engineers, who had nearly unlimited resources in developing the Superhawk engine, is a bit of a stretch.

superbling

Ding, ding, ding, we have a winner but now I'm beginning to realize he isn't joking.

Savdre, what you're doing is akin to jumping out of an airplane and THEN asking questions about skydiving and parachutes. Good luck.

savdre

I definetly wasn't joking... I have absolutley no idea about what I am doing!

I had just about given up riding. The old hawk was getting dusty I was gonna sell it for next to nothing... what is a 1999 hawk with 10K miles worth $3-4K? At the urging of a friend (and a six pack), I decided to customize...

This is the post for the project:
https://www.superhawkforum.com/forum...ad.php?t=13611


so I hope you now understand why I am getting rid of the air box.... need the room for everything that was in the tail section. I am definetly not trying to gain horse power or out engineer the Honda people. Right now I just want to get it close to the way it used to run.

I do appreciate everyone's comments... I do find it pretty funny you think I was putting you on. This is for real folks.. .no hocus pocus black magik here.

From my observation the main purpose of the airbox is to limit the amount of air comming into the engine, but provide room for a big enough air filter.

As I mentioned earlier, the openings on the front are relatively small... if you tried to put a filter on that area, you would probably be chainging filters constantly... problem is solved by making the sealed airbox... small opening , big body for the filter. At least this is my simplified theory.

thoughts? comments?

killer5280

Good luck.
Airboxes do much more than limit air into the engine. Race bikes wouldn't use them if that were the case.

savdre

so can anyone elaborate on what else airboxes do?

shayne

Only what I have already said I'm afraid. I would be looking to make up a custom airbox in some way. That may provide the type of airfow the carbs need to function properly.

As for the Keihin FCR's, my friend paid $600 for his, second hand. He got them off Japanese Ebay somehow.

Tweety

Basicly the airbox directs the air, giving both carbs equal amount of air at the right velocity... Atleast that's the theory behind it...

FTMS