TPS-Jetting issues
 

Ok, So I just rejetted the bike again, probably like the 11th time now but at any rate I noticed in the service manual that the TPS has to be adjusted between 490-510 ohms. Well the only way I could get 500ohms out of the TPS was adjusting it all the way up and turning the idle screw out to achieve 500 ohms. Well When I started it up today it wouldnt start unless I adjusted the idle screw back in.

When driving the engine bucks and missfires from 1-3k rpms but drives rather nice throughout the power band. So what do I do now? I know it sounds weird but do i adjust the TPS back to its original position which was like 750ohms... I dont know what to do..

Thanks Guys!

The TPS adjustment does alter the timing but I'm surprised you're getting such a significant change that it won't run well @ 1-3K.

Where are the needles set?

Needles are set at 2 notches...

You know come to think of it i did have a problem with one of the rubber seals that go around one of the needle carriers.. It was stretched out and I was going to get another one for when I decided to pull it back apart. Do you think that could cause it to run this rough?

2 notches from the bottom or top?

If it's 2 notches from the top then you may very well be running lean and you'd need to raise the needle one position. I remember a similar running problem when I setup mine and tested the 2nd clip position (from the top).


Did you reset it yourself to that position or was it already in that position when it ran well?

yes, if the diaphrams / cap don't go back together right then you'd expect problems. Make sure you hold the slide open as you put the cap back into position.

Well if your looking at the needle and the tip is the top and the flat portion is the bottom then its 2 positions from the bottom..

Well it ran fine before when the TPS was ohmed at around 800 ohms and i looked at the manual and it said it should be at 490-510 so i dremeled the screws and changed the TPS to 500ohms. Well kind of, I got it close and i adjusted the idle screw down to get it to 500 ohms.. (my mistake) Im an idiot. But the main thing is what I have been researching is that the TPS doesnt control the ignition but the advance of the ignition. So... would this cause it to run like a POS from 1-3K rpms? Or would the needle be the problem. Another thing is it gets worse as it warms up...

I ordered a new gasket set for the carbs today just to be on the safe side.

I guess ill adjust the TPS back to the original position or as close as possible but the only thing I dont understand is how come nobody knows the exact position it should be in for the ICM to take its readings from? If it does advance timing in the upper RPMs then you would think that the TPS would need an exact reading to tell the ICM to advance the timing right?

Thanks guys!

OK,
So the clip is at the second 'most rich' position. If it ran there well before I doubt the needle is the problem but you mentioned a problem with the diaphram during some part of your jet changes. The obvious question is 'did it run OK anytime after the last time you put the diaphrams back in' ?? Maybe there is a sealing problem on one of them. Or worse yet maybe one now has a defect .... $$:(

I'd try to get back to square one and reset the TPS to whatever it was - just to see if the dang thing will run right .... I still doubt the TPS is the reason it won't run from 1-3K though. I messed with various TPS settings between 900 and 450 as I rememeber and I ended up at 600 but there wasn't a huge difference across the range.

The bike ran fine around that range before. This is probably the 4th or 5th time the bike had that needle height before and so far this is the first time I have ever felt this before. At any rate I am going to hold off on pulling the bike apart again untill I get that seal/gasket set in and replace the seals on the bike.

The only thing I still dont understand is the TPS sensor. Why does the manual say 500 ohms when in reality it really doesnt even matter what setting it is at then? Whats the point of it then?

Thanks

99,

Are you refering to the black diaphrams (surrounds the squarish black plastic the needle sits in)). The best way I've found to replace them un damaged is to have the sealing area extended down so it looks like a bell.

Lift the slide up and place the butt end of a small fat handle screw driver in the carb throat to hold the slide up a bit. The sealing end of the bell shape will seat easily and then lower part way so there is a hump in the ruber part all the way around and the squarish black plastic area is sunk in a bit making sure the needle gets properly located in the needle jet(hole).

Scrunch the spring using fingers from both hands onto the underside of the carb cover until there is about 1.5 inches of spring extended. Then get as close as you can and release the spring onto the locator in the black plastic without moving the cover away. The spring should seat well. Move the cover the rest of the way on making sure the diaphram is still seated correctly. Tighten the 3 screws (not over tight). Lastly remove the screw driver handle and you should hear the diaphram sucking air as the slide drops. Lift the slide if you did not hear it and release again to make sure you hear the sucking sound. No sound could mean a torn diaphram.

Sorry I don't know all the proper names of the parts but it should all be very apparent when you have the carb ends open.

Most of what controls your carburetion between 1000 and 3000 rpm is the idle circuit. This includes the emulsion tubes, the mixture screws, and the idle jets. Check those. What are your mixture screws set to?

"the engine bucks and missfires from 1-3k rpms but drives rather nice throughout the power band"

I experienced this when making some jetting changes. I changed back to the #45 main jet (from Factoy's #50 main jet) in search of better fuel economy. With the needle clip at the 2nd position (from the top) it preformed exactly as you described. I dropped the needle to the 3rd position from the top, the bike ran perfectly. I was surprized that one clip position change would make such a difference.

-Actually I was talking about the little rubber seal that goes around the needle holder that you insert into the ... SON OF A B----!!

I think I just found out what I did wrong! God damnit I need to stop drinking. I cant believe I messed that up.. I installed the needle into the diaphragm instead of installing it in the needle holder, then I installed the needle holder ontop of the jet.. Shit. At least thats what I am picturing in my mind anyways... So that would mean that the bike is running way way to lean. Shit i hope i didnt damage the needles..........

Do a search on TPS, there is a lot of info on here.

It controls the ignition advance, and from memory, you need to have your carbs synched and idling nicely to set it properly. Mike from CTSMoto has dynoed about 30 VTR's and this is what he found. As you have found yourself, the idle will effect the TPS reading.

The TPS may not effect the engine at idle, but after that it is definately possible. If you test the TPS you will note that it provides a different reading at idle compared to just off idle, so it MAY effect things at very low revs.