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Discussion Starter #1
Hello All,

I have a problem that has me quite a bit frustrated.

Last year I starting having problems with the bike running rich/stalling out at idle after long rides in 80+ degree temps. After reading here, decided that it was the TPS sensor.

I replaced the sensor, and the intermittent problems have gone away (have had lots of 90+ degree rides to confirm!), it's just consistently bad now!

At the last service I did (around 46000 miles), I checked the valves (in spec, on the tight side), TBS, plugs, air filter, etc. I've synched the secondary plates. Bike has 50k now.

About a month ago I replaced the faulty TPS sensor, and I haven't been able to get the bike to run right since. I've set the secondary TPS, checked the boots and hoses for vacuum leaks, reset the TPS a dozen times. When the TPS is adjusted in spec (-C00, bumps up around 2k), the bike runs like crap, bucks like a horse under light throttle between 2k and 4.5k rpm. Runs great at >60% throttle or above 5k rpm. If I have the TPS adjusted out of spec, so that it is always just on the high side (dash up above the C00), it is tremendously smoother, but sometimes hiccups at idle.

The map I have on the PCIII to get it rideable is +13% or so from 1.5k to 4.5k, in the 5% - 50% throttle range (of course that's an approximation, it's curvey. :) ). Outside that set, all points are within a couple percent of the stock map. I've been using an O2 sensor as a tuning aid, and am quite confident at my ability to interpret fuel mapping symptoms. fwiw, I'm quite good at tuning carbs (multi weber setups, carters, holleys).

I've had a PCIII on it for the past 25k or so, and had tuned a lot of the rough running out with it. About the same time the PCIII happened, I had put on a single exhaust.

I don't know how I've missed it in the past few years, but I finally saw Service Bulletin 35 on the vsri forum, and guess what? My VIN indicates that my bike falls under that service bulletin!

I'm wondering if a faulty ECM really is the root of my problems. Even before I did the TPS replacement, I had to work pretty hard to eliminate the 2k-4k lean surge/stumble.

I'm guessing with the modifications to the bike (single exhaust, PCIII, -1/+2 sprockets) and now 50k miles I'm going to have a hard time convincing a dealer get an ecm under the service bulletin. I'm not too keen on spending a saturday putting everything back to stock to find out if the dealer is willing to help or not.

Any suggestions on something I've overlooked? This is really getting under my skin. It's been a great 50k miles to this point, and I'm hoping for another 50k.
 

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Discussion Starter #3
Running perfectly again!

The bike is now running beautifully again! It's back to being the bike I've loved for the past 50k miles.

So here is what I did that wasn't the problem:
-new plugs
-TB sync
-TPS adjustment
-air filter
-bench tested fi sensors per service manual (iaps, iats, tps, stps)
-disconnected and reconnected PCIII
-dealer performed service bulletin 35
-adjusted STPS per service manual

What was the problem?
TPS sensor I had replaced was bad out of the box; had a crack in the housing and read erratically on the bench test. Also, I was an idiot and didn't remove the TPS seal from the TB when it was replaced; looked but didn't see it in there.

Solution:
Replaced TPS with a new sensor, with only one TPS seal in place. Problem solved. :) And the bike runs better than ever!!


See thread below, from another guy who made the same error:
Wrong conclusion - broken TPS & symptoms
 

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I am suspicious that the tps is a simple potentiometer and they do wear out and/or get dirty

Do us a favor if you have the old one take apart and show whats inside. A simple pot has the habit of wearing out where the arm rests most of the time
 

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Discussion Starter #6
Pics of TPS

Included are pictures of the TPS with the seal installed and removed, and then the internals of a bad TPS. The dissasembled one has roughly 50k miles on it; i replaced it because it would cause the bike to stall when hot.

You can see the wear bands on the potentiometer. It was a bugger to get into, very well potted.


TPS w/ seal installed


TPS w/ seal removed





 

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Interesting...... I thought of cutting mine up... what a diff it made with the running......
 

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Thanks

Mystery solved

It is a potentiometer and looks like high quality.

So it IS a wear part.

It appears so well potted that you couldn't get in there with a spray to clean her up. It looks like you might get good cleaner in where the leads (plug) goes. MIght be worth a spray of brake cleaner when she's acting up.

So when it gets funky or sooner than it has to be replaced. Probably a PM like when you do the chain

Chain and sprockets
Cush hub bearing and maintenance
TPS pot
 
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