Centauro tuning challenge

[BrianG]

A little information.....  I have owned a number of V 11 MG in my time, but never have I had this much trouble tuning one like I am with this Centauro. I have completed the usual tuning sequence,  and replaced the TPS with a known good unit from another bike. 

With weather cooperating today, I went out on a road test and discovered the followin:
1. Idle is good once warm. The "choke" function works properly while cold.
2. Cruising under light throttle AND below 2000 rpm, the engine runs smoothly at any speed.
3. Accellerating from a stop or from any rolling speed or throttle opening is smooth and as powerful as expected.
4. Steady state cruising above 2000-2500 rpm through 4500 (that's as far as I dared go) precipitates extremely rough runnin, and I mean birdering on violent, at any speed in any gear.

To me, the common issue is engine load/throttle position. This critically includes engine rpm (over 2000 rpm). I thought this pointed to the TPS but a new one had no effect on any of this.

Conversation with Will Creedon suggested enrichening the ECU potentiometer setting.  I found that ¼ turn increments, all the way to full rich did not positively affect the issue. (The last 90* of the available 180*, negatively affected idle and low speed running.)

Does this information stimulate anyone's diagnostic ideas?

[guzzigary]

Never have worked on a Centauro, but the symptoms would have me suspicious of the crankshaft position sensor.

[Pressureangle]

Perhaps @pete roper will chime in here. Don't Centauros have the same potential cam issues as Grisos?  Would Griso ghetto be a more knowledgeable forum? 
There's a wrecked Griso nearby for -$1k.... if the price goes down I may have another project

[pete roper]

The first generation Hi-Cams do not suffer from the same flat tappet issues that affect the later 1200 Hi Cams. They can have tappet issues, but they are not the same.

To me this sounds suspiciously like a sudden electrical drop-out. Perhaps caused by vibration or something else. Try running a couple of auxiliary earth cables to the battery negative, including a direct one from the ecu, and bypassing all the strange f*ckery of the standard earth path that probably goes through the pork chops and all sorts of weirdness!

Oh, and Pressureangle? If you do buy the Griso make sure it’s been rollerised or is a post-flat tappet model as I’m hearing reports that the factory has ceased production of conversion kits. If this is the case and the bike you are looking at still has flat tappets it will essentially be a paperweight.

[Lucky Phil]

8 hours ago, BrianG said:

A little information.....  I have owned a number of V 11 MG in my time, but never have I had this much trouble tuning one like I am with this Centauro. I have completed the usual tuning sequence,  and replaced the TPS with a known good unit from another bike. 

With weather cooperating today, I went out on a road test and discovered the followin:
1. Idle is good once warm. The "choke" function works properly while cold.
2. Cruising under light throttle AND below 2000 rpm, the engine runs smoothly at any speed.
3. Accellerating from a stop or from any rolling speed or throttle opening is smooth and as powerful as expected.
4. Steady state cruising above 2000-2500 rpm through 4500 (that's as far as I dared go) precipitates extremely rough runnin, and I mean birdering on violent, at any speed in any gear.

To me, the common issue is engine load/throttle position. This critically includes engine rpm (over 2000 rpm). I thought this pointed to the TPS but a new one had no effect on any of this.

Conversation with Will Creedon suggested enrichening the ECU potentiometer setting.  I found that ¼ turn increments, all the way to full rich did not positively affect the issue. (The last 90* of the available 180*, negatively affected idle and low speed running.)

Does this information stimulate anyone's diagnostic ideas?

Have you replaced the plugs, leads and plug caps yet? 

Phil

[Lucky Phil]

5 hours ago, Pressureangle said:

Perhaps @pete roper will chime in here. Don't Centauros have the same potential cam issues as Grisos?  Would Griso ghetto be a more knowledgeable forum? 
There's a wrecked Griso nearby for -$1k.... if the price goes down I may have another project

Totally different head and cams than a Griso engine BUT the whole valve system on a Dayton/Centauro engine is still a high wear and marginal system prone to flaking lifters and wearing valve guides at a high rate. A 2 valve reliable engine they are not.

Phil 

[pete roper]

The early Hi-Cams were a morass of frictional losses. That, along with the twin, and too heavy, valve springs, (2 per valve.)  and aggressive camming is what made them not only prone to lifter wear but also not nearly as powerful as they were expected to be. Hence the return to the tried and tested 2V Pushrod format.

The early engines had belt cam drives at the front of the motor with camshafts that overhung the front bearings by a huge amount, stressing the oil wedge which was already being provided by a barely adequate oil pump.

The second generation Hi-Cam has cams driven by chains up the back of cylinders, single beehive valve springs and the lubrication pump is a larger and much more efficient trochoidal Gerotor pump. There is no doubt that the Gen 2 motor is streets ahead of the earlier one. It is a far, far simpler design and considerably more efficient. It should have been the engine that opened a new chapter for Guzzi but the flat tappet fiasco put paid to that. By the time it was sorted out, five years on, the world was already moving on. It took the ‘Full House’ Piaggio V100 engine design to finally deliver what the Hi-Cams couldn’t. It’s just a pity they are just such a boring and unexceptional engine in technical terms. Oh and ugly! F*ck me drunk the V100 is an ugly powerplant! It gives me a headache just looking at it!

[BrianG]

Thanks, everyone, for the variety of ideas.  Mine is a '98 model year and shows 7600 miles. It has apparently had this problem for a long time, hence the mileage. 

It has the Joe Caruso gears recently installed and new cam belts. The spark plugs are new but not the wires.

pete roper, it feels like sudden spark drop-out to me as well. I'll change out the plug wires, check the connections to the coils, and double up on the ground connections directly from the battery.

guzzigary, is there a way to test the crank position sensor?

Edited October 22 by BrianG

[Lucky Phil]

3 hours ago, BrianG said:

Thanks, everyone, for the variety of ideas.  Mine is a '98 model year and shows 7600 miles. It has apparently had this problem for a long time, hence the mileage. 

It has the Joe Caruso gears recently installed and new cam belts. The spark plugs are new but not the wires.

pete roper, it feels like sudden spark drop-out to me as well. I'll change out the plug wires, check the connections to the coils, and double up on the ground connections directly from the battery.

guzzigary, is there a way to test the crank position sensor?

Not usually because they dont generally fail in a comprehensive way (like going open circuit) they just give running issues esp when the engine is at temperature or the load is high. Just replace it, esp if it's the original 30 year old unit.   

Edited October 22 by Lucky Phil

[Weegie]

I'd definately replace the HT leads caps and plugs (if not new), then go from there.

First I'd heard about the crank position sensor failing causing intermittent and bad running, another school day I guess.

As I recall the CO enrichment pot near the ECU is only in play up to around 3k RPM.

Cannot remember where I came across the info, but also seen it reported that it's in play throughout the rev range.........but I believe that's wrong.

[gstallons]

7 hours ago, BrianG said:

Thanks, everyone, for the variety of ideas.  Mine is a '98 model year and shows 7600 miles. It has apparently had this problem for a long time, hence the mileage. 

It has the Joe Caruso gears recently installed and new cam belts. The spark plugs are new but not the wires.

pete roper, it feels like sudden spark drop-out to me as well. I'll change out the plug wires, check the connections to the coils, and double up on the ground connections directly from the battery.

guzzigary, is there a way to test the crank position sensor?

The resistor in the spark plug cap can fail and become open. The wire (may be ) can be a solid core and should be good. IDK what this bike uses. 

 The crank sensor is (usually) good or bad.  You can test it w/a DVOM for resistance and post your readings. IDK what r value this should be.

[Tomchri]

Sensor shoud read 600-700ohm cold. Warm it up, that's when they fail, watch the reading go to 0.

Cheers Tom.

[gstallons]

IDK if the service manual has specs. on these sensor values or not. I will look and see . If I find anything I will post it.

[BrianG]

The issue is present regardless of engine temperature. The engine is equipped with an oil temperature gauge.

[BrianG]

Can anyone provide a Service Manual pdf link that works?

Also, can anyone provide a list/location of all the sensors on this '98 Centauro ?