TPS and tuning

[PhillipLarsen]

@docc appreciate the suggestions.

i agree something does not seem correct as discussed perviously.

All sensors were replaced during last winters 20 year overhaul.

Guzzidiag was used to set Co trim to 0, also tried + 10 and + 5, but the current set up is TPS at 285, air screws 1/2 out, CO trim =0, idle 1250 per Guzzidiag. 
No play in TB shafts, Ballanced TBs, No leaks intake or exhaust. New gasket/ sleeves in crossover, bolts with copper gaskets in intake ports, intake rubbers all good, have spares, didn’t need them  

currently only at about approx 18,500 miles (quite low for 20 year old bike)

I did spend two full days doing runs on dyno and street trying to find the lowest combination of TPS setting, co trim and air screw setting to eliminate the misfiring between about 1800 and 2800 rpm, as a temporary fix until can change fuel filter and get injector cleaned / serviced. 

As you suggested I am going to change the fuel filter (have one waiting) as soon as gasket arrives and last item will be to have injectors serviced at a shop this fall. I am hoping one of these will turn out being what is causing the lean running with TPS at 157. 

Sure appreciate yours and the many others help in trying to solve this 

Also happy it is running so nice right now even though it probably should not be!

[docc]

17 hours ago, PhillipLarsen said:

@docc appreciate the suggestions.

i agree something does not seem correct as discussed perviously.

All sensors were replaced during last winters 20 year overhaul.

Guzzidiag was used to set Co trim to 0, also tried + 10 and + 5, but the current set up is TPS at 285, air screws 1/2 out, CO trim =0, idle 1250 per Guzzidiag. 
No play in TB shafts, Ballanced TBs, No leaks intake or exhaust. New gasket/ sleeves in crossover, bolts with copper gaskets in intake ports, intake rubbers all good, have spares, didn’t need them  

currently only at about approx 18,500 miles (quite low for 20 year old bike)

I did spend two full days doing runs on dyno and street trying to find the lowest combination of TPS setting, co trim and air screw setting to eliminate the misfiring between about 1800 and 2800 rpm, as a temporary fix until can change fuel filter and get injector cleaned / serviced. 

As you suggested I am going to change the fuel filter (have one waiting) as soon as gasket arrives and last item will be to have injectors serviced at a shop this fall. I am hoping one of these will turn out being what is causing the lean running with TPS at 157. 

Sure appreciate yours and the many others help in trying to solve this 

Also happy it is running so nice right now even though it probably should not be!

You are definitely ticking all the boxes!  

Makes me ponder the condition of your charging system . . .

edit: @PhillipLarsen, out riding mySport, it occurred to me to ask if this is the original TPS and if you have hooked a sensitive Ohm meter across it and watched the resistance change (smoothly) while very slowly opening and closing it . . .

[docc]

[Moved posts from "cam chain tensioner" thread.]

[PhillipLarsen]

@docc appreciate the follow up. 
During 20 year work last winter / spring replaced cam chain and the tensioner foot and spring. The cam chain had no measurable wear, tensioner foot barely showed wear, just did it as was replacing gasket and to be sure it was not causing any issues. 
With stator out checked carefully, looks good and measures correctly, replaced zip lock as you recommend ( it was broken), the yellow leads at the bullet connectors looked like they has been warm enough to discolor at some time. and the white plug with two yellow static wires has some melting and on wire as well. Removed all that and went spade connectors (soldered to yellow wires covered in shrink tubing ), with just the one joint instead of two places. 
Also had put ground wire from regulator to timing case a few years ago and cleaned and monitor original ground to back of gearbox. 
Battery ( matgas ) was new last year and kept on tender if not using more than a couple days. Charging system and battery show numbers per specs. 
Replaced TPS during 20 year work, had checked before replaced and appeared to function correctly with no jumps, but to eliminate as cause of issue replaced it. Made no difference to missing issue.

Really the only things I think remain to verify is fuel filter, injectors and fuel pump, and remembering it is running great right now with only the TPS at not standard setting and air screws at 1/2 out. 

[PhillipLarsen]

Took the Ballabio on a spirited ride this evening for about total 2.5 hours, from Vancouver up the Sea to Sky twisty highway towards Whistler and back. 
Filled fuel before and after. Fuel mileage was 38 miles to US Gal or just over 42 to Imp Gal. It does top appear that it is running rich, looking at fuel mileage and plug colour. 

[audiomick]

On 7/24/2025 at 5:16 PM, docc said:

... hooked a sensitive Ohm meter across it and watched the resistance change (smoothly) while very slowly opening and closing it . . .

Or with Guzzidiag. There is a function in there that makes a nice graph that shows what the TPS is doing.

[docc]

30 minutes ago, audiomick said:

Or with Guzzidiag. There is a function in there that makes a nice graph that shows what the TPS is doing.

Much like Guzzidiag cannot be used to set the TPS baseline I did not think it sensitive enough to detect subtle failures in the TPS progression.

[audiomick]

22 hours ago, docc said:

...I did not think it sensitive enough to detect subtle failures in the TPS progression.

Guzzidiag is reading out the values that the ECU is recieving, which is also the information that Guzzi's own diagnosis program sees. I'm assuming that if Guzzidiag cannot see a glitch, it is also not significant enough to affect the engine, because the ECU would not be seeing it either, and that Guzzi's own program also wouldn't register it. And the graphic that Guzzidiag generates is very nice to look at and easy to read. 

[gstallons]

To the best of my knowledge , any glitches that occur in that pot (TPS) will be transmitted to the ECU and there is no dampening built into the program .