Newby with a throttle position sensor / carb tuning question

[supersonictoys]

I have a 2000 Katana 750 complete engine car kit which has carbs with a throttle position sensor mounted on them. I was curious what this sensor actually does and what would happen if I install an aftermarket set of carbs without this sensor and just left the plug for this sensor disconnected? I would assume this sensor has something to do with ignition timing? I am actually installing this motor in an atv chassis and am just about finished but since my application required elimination of the factory Katana airbox for fittment reasons , I am having the usuall "cv carb/ no air box" tuning issues. or if somone can give me some info on how to jet and tune the factory cv carbs for individual filters this would be awsome. it currently idles fine and runs ok to about 1/4 throttle but anything past 1/4 throttle just doesnt happen. sounds totally lean. anyway, alot to ask for a first post I know but I really like this motor and would like to make this work. I will post some pics of the bike later today and sure would appreciate any info you guys can share with me.

[The CyberPoet]

The Throttle Position Sensor:

http://katriders.com/wiki/index.php5?title=Throttle_Position_Sensor

Yes, it can be obsoleted.

The lack-of-airbox problem: not readily correctable on the 98+ Kats. My advice would be to reinstall the airbox, even if you have to use modified velocity stacks to position it elsewhere.

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[supersonictoys]

so I can just unplug it and run? or is there anything else that has to be done to delete the TPS? it will stil run normally or close to it? and would you also know if anyone makes an aftermarket set of carbs that will work on the katana 750? if not I will most likely have to build an aluminum airbox from scratch using the factory carb boots and the intake air pipe from the factory box but with an external filter.. what a nightmare.. thanks for sharing your knowledge with me ! Gregg

[The CyberPoet]

Yes, you can just unplug the TPS and it'll run just fine. It's just a modifier signal that changes the spark timing minorly based on throttle position (whether you're full or part throttle).

Aftermarket carbs: If you are serious about obsoleting the airbox for a 98+, look for a set of (non-CV) direct-slide Keihin carbs. These won't adjust for altitude (you have to do that manually by rejetting), but should take care of your no-airbox issue, and let you jet them correctly. Because of the lack of an airbox, you're going to need a smaller carb opening (29 to 31mm) instead of the OEM size range (34 to 36mm). How much space do you have for velocity stacks?

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[supersonictoys]

well here is a pic to give you an idea of what I'm up against . so you are talking about an old set of CR keihins or some rs series flat slide smooth bore mikunis? I can build an aluminum air box which will use the factory rubber velocity stacks and still have probably 3 inches of open space inside behind the stacks and then have only one air inlet on the back. I would then mount the plastic air inlet tube from the factory box to the back of my new aluminum box with this tube pointing out instead of in . I could then install a much larger aluminum tube over top of the plastic tube and mount a large clamp on free flowing filter over the tip of the aluminum tube. I think the important thing about the air box is this plastic 4 inch long intake tube. it has a very small inside diameter and must restrict the flow of air at higher rpm's which would richen things way up. without the box it seems extremely lean...

[The CyberPoet]

Yes, I was talking about an some flat-slide or CR keihins...

Yes, the OEM airbox is necessary to getting the right vac levels at the carbs to getting the fueling right, and after many, many riders have attempted jetting to compensate for the lack of the airbox (without success across the board -- you can get one RPM right but then have it muddle in some other RPM zone), we've all come to the conclusion that the airbox is pretty necessary with these particular carbs. I have zero clue how far back you could extend the airbox via ducting and still get the vac levels right, but it might be worth a try.

Good luck!
=-= The CyberPoet

[tone]

Mostly good info on the TPS cyber but do you know its actual funtion eg what it means for us when riding our bikes ?

Clue ..... its got very little to do with emission controls

[The CyberPoet]

Mostly good info on the TPS cyber but do you know its actual funtion eg what it means for us when riding our bikes ?

Clue ..... its got very little to do with emission controls

On a bike like the Kat, where the system only has control over the timing (and not over fuel injection), tt should have to do with part-throttle timing advance for maximum fuel mileage.

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.