Well, I was all set to head out for a nice long ride today and the bike started acting up (losing power while crusing on freeway). It seemed eerily familiar so I turned around and headed home. I suspected a torn fuel pump diaphragm and bingo! This is now the second time I replace it. Oh well, it could be worse and at least I know what it is and how to fix it. Seeing as how I had the tank off (and just bought a dremel and digital voltmeter yesterday), I decided to check my TPS setting. ARe you ready for this? 835 ohms!!! I would say that is a little ways off from teh recommended 500! So, I went at 'er and got it down to 477. I realize the manual says 500+/- 10 but then Greg Nemish recommends 430-440 so I left it at 477 (as low as I could get it without hacking away at stuff). I had to remove the small metal sleeves inside the screw slots to get it below 500 (it only went to 615 with metal sleeves in place). I can't wait to try it out again to see how it runs now.

cheers

 

Fuel pump? What fuel pump? Do you mean a carburetor diaphragm, i.e., the slide's diaphragm?

 

I am referring to the vacuum-assisted fuel petcock.

 

Interested to read your TPS results.

 

hi NOrrTH,

You are eager to read them and I am eager to post them. Unfortunately, my pump/petcock diaphragm parts won't be in until Thursday. I am eager to try it out as the comments I have read have all been very positive (better response, smoother). AS Friday is a holiday here in Quebec and I am heading up to Northern Ontario to visit with friends I may not be able to report back before early next week but I will let you know as soon as I get 'er up and running again. ONce this is done my last hurdle will be getting the jet kit installed.

Incidentally, since I had it apart I decided to reinstall the long intake trumpet on the front cylinder. MY hope is that the smoother running from the TPS will help to "compensate" for the slightly rougher running that occurs when it is on. I cannot wait to try the low and mid punch with the TPS and long runner. Woohoo!!! It should be fun

Are you still happy with the way yours is running?

 

Umm, you mean "TPS reports". Did you get that memo?

 

LOL! Classic... Good call superbling

 

I realize the TPS topic has likely been flogged to death already but I am wondering who all has done this mod and what were your results (in terms of power/throttle response/engine smoothness/mileage)? Also, what was your stock setting and what did you re-set it to?

cheers

 

"...then again, I could burn down the building..."

 

After riding it a fair bit since the upgrades I'm noticing a short flat spot around 6700-7000 which is weird cause this other VTR rider I ride with has the same thing and no K&N and smaller jets.

I'm also getting some popping on decel so I'm thinking she's rich and need to so some plug tests. Prolly have to drop a jet size on the rear - 190 now, try Greg's suggested 188.

Have a great trip.

 

The TPS has a fairly simple job. The only thing changing your TPS setting does is change the changeover point for the ignition advance curve. I suppose it's possible Honda got this wrong, but its pretty doubtful.

It will not, under even the wildest stetch of imagination increase max power or torque.

Of course, specific fuels may benefit from a change in the advance curve, but there would be no way to tune for this on an ongoing basis.

It seems to me that people find them pretty much spot on or somwhere around 850 ohms. I'd sure like to know why. mixtr: was your engine hot or warm when you measured it? Has anyone checked timing after making this mod?

 

[quote]
Prolly have to drop a jet size on the rear - 190 now, try Greg's suggested 188.

Hello NOrrTH,

just bear in mind that Greg uses a Factory jet kit (based on onfo on his site anyhow), NOT a Dynojet kit. The two companies do not measure their jet sizes the same way. Factory uses the same method as Keihin (flow rate I beleive) whereas Dynojet uses the hole diameter. Finally, having researched it in the past, I can vouch that DJ do not make intermediate size jets. In other words, they work in multiples of 5 only (for the mains anyhow).

Finally, and I may be wrong here, but wouldn't a popping condition be caused by a lean setting, not a rich one?

In regards to the function of the TPS, my understanding of it is that it provides a variable (along with engine rpm; not sure if the VTR uses any other variables for this purpose eg. engine temp) for the engine computer to use when calcuclating/setting the proper ignition advance curve. Therefore, if the setting is out, in theory at least, it should cause a shift in the curve such that it is out at all rpm levels. In effect, the curve is calculated/programmed to rely on an expected value from the TPS for a given condition (in this case throttle position), if this reading is out, therefore, the value selected by the computer will be wrong also resulting in a less than optimal running engine.

cheers

 

[quote="mikstr";p="6747"]
I thought the popping was unburned gas in the mufflers - therefore too rich. /shrug This stuff is all new to me.

I didn't realize that jet sizes are different depending on the kit. Thanks for the heads up. I'll have to pass this info along to my mechanic if he doesn't already know.

 

i recently checked my tps readings and found mine to be at 837 ohms. after removal of tps and tps rings i was able to get the reading to 504 ohms....i thought, great more power soon to come. i did notice a very large change in acceleration, at least until 5200 where she fell on her face for a brief moment and then came back to life. very irratating. i checked everything i touched hoping to find what was causing this darn stumble, but found nothing. 4 days and 9 tanks of gas later i put the tps back to where she originally was. low and behold problem went away and never came back. so to those of you who have tried it and it worked great for you! for those of you who it has not worked for i feel your pain, return it to where you found the ohms reading and enjoy the ride!

 

It seems a bit odd that there are only three of us who have tried adjusting the TPS on our bikes?????????????????

Let's try this again, would anyone like to share info about thir experience with this procedure and the results (be they good or bad).

thanks

 

My original TPS setting was over 800 ohms, something like 810 ohms I believe. Even after removing the brass sleves I could only dial the TPS down to 614 ohms. I have no hard data but I don't like the way it runs, specifically the low end. I've been considering going back to the original TPS setting just to see what happens and definitely will do it this weekend considering Phil's response. We'll see what happens.