Part throttle hiccup

[Dan M]

OK by you?

 

It's all OK by me. Have fun and share your findings, we'll all benefit. Did you buy a chain and gears too? If you need them once things are apart, are they available? ...just thinking about down time, best laid plans and all of that.

[Guest ratchethack]

Did you buy a chain and gears too? If you need them once things are apart, are they available? ...just thinking about down time, best laid plans and all of that.

Well, no, Dan. I'm not concerned about the need for new sprockets and chain wotsoever. As Pete has explained so well previously, and as I thought I'd repeated several times in this thread, at 34K miles, based on the well known history of many hundreds of Guzzi's -- dare I suggest into the thousands? -- and the credible opinion of at least one expert well-placed enough to know with a high degree of certainty, the probabilities of an appreciably worn sprocket and chain set would seem to be slim to ZIP -- and would be something of an extremely rare anomaly, no doubt accompanied by a set of additional easily identifiable symptoms, of which I don't have a single trace.

 

Of course, without having the patient on the operating table with chest cracked and retractors screwed fully open, it's impossible to know exactly wot we'll find once we get in there. But lacking an X-ray machine at our remote frontier operating room, but carefully weighing the symptoms before going in, we're pretty confident about managing the known probabilities and keeping the liklihood of surprises to an absolute minimum before we put the poor bugger under anesthesia -- again, simply on the probabilities, of course.

[Dan M]

Yea, but, but, in Pete's initial posts on the matter he states that the scatter you are observing is a sign of a worn chain. The soft tensioner can give scatter on the overrun, but as Pete put it, that doesn't matter a tinker's cus. Pete also says that the tensioners can go 200000 miles.

 

good luck!

[Guest ratchethack]

Yea, but, but, in Pete's initial posts on the matter he states that the scatter you are observing is a sign of a worn chain. The soft tensioner can give scatter on the overrun, but as Pete put it, that doesn't matter a tinker's cus. Pete also says that the tensioners can go 200000 miles.

 

good luck!

Dan, you're really gonna make me work for a point here, aren't you? To clarify, I don't b'lieve you'll find that Pete stated that the scatter I observed is a sign of a worn chain wotsoever. (see Pete's post below) I think if you read the following, you'll also discover that the "doesn't matter a tinker's cuss" remark refers to VALVE TIMING (variance of which would NOT make any difference WRT the symptoms I've experienced), not erratic advanced IGNITION TIMING due to a SLACK CHAIN, which WOULD be expected to produce exactly the symptoms I've observed. Again, I think it's worth the small investment of time and negligible cost of opening the timing chest @ $26 USD of parts to discover if it's really a wonky tensioner that's behaving like it's giving up the ghost, and the resulting SLACK CHAIN that's the cause of the symptoms.

 

BAA, TJM, & YMMV

 

Damn! Just wrote this out once and then the 'pooter crashed! Don't ya hate that???

 

Lets we'll try and deal with a few misconceptions about the supposed accuracy of the chain drive system. After this we can look at problems and how they may manifest themselves.

 

Lets first deal with the erroneous idea that chains 'Stretch'. They don't. What happens is that the pins and rollers in the chain wear. The easiest way to see this manifested is to look at the old drive chain off a cahin driven bike and compare it to a new one. If you place them side by side on the bench/floor whatever and try and *bend* them sideways the old chain will Bend* a lot further than the new one. What you are doing is canting the pins over inside the rollers which allows each link to run slightly out of alignemt with the others. The end effect is much the same as stretch but it's important not to confuse the two.

 

OK. So now we need to look at thetining chest and see how the whole sorry business works. From here on I'll be speaking about the engine as viewed from the front.

 

On the right hand side of the timing chest there is a long run of chain thatgoes from the oil pump sprocket, over the tensioner and up to the cam sprocket. It loops over the top of the cam sprocket and then drts right again to circumnavigate the crank sprocket on the right hand side before exiting left again to hook around the left hand side of the oil pump sprocket before once more heading up the RH side of the timing chest.

 

The crank rotates clockwise and the cam is towed round by the chain, but between the crank sprocket and cam sprocket there are only about three links and maybe four pins/rollers. Now given that on anything other than a feathering throttle that four links is always going to be in tension the only thing that will be able to retard the timing is the wear in the pins and rollers. Even assuming a whopping 3 thou clearance betwixt pin and roller with four pins that will give you 1/4 of a mm of increase in *length* of that bit of chain. I can't be bothered to do the sums but 1/4 of a mm at the circumfirence of a 720 degree camwheel is not, I'm sorry to say, going to retard your timing to any noticeable degree. when you are on the over-run it's a different story. Then, unless you have a decent tensioner that will 'Take up the slack' in that long run up the RH side of the case, the chain may well try and 'Bunch up' between the cam sprocket and the crank sprocket but there will still be variable loadings being imposed by the valve train and it is at this point tat the scatter will be most evident when examined with a strobe. The important thing to remember is that unless you are running such a radical cam that your piston to valve clearance is super-critical, And no road-going Guzzi cam is anything like this!) It doesn't matter a tinker's cuss what the valve timing is on the over-run as the engine isn't producing power, exactly the opposite in fact! Certainly if the chain is really badly worn you will eventually damage the sprockets but as far as valve and piston damage is concerned? Don't even think about it!

 

Now the last example, and this I think is probably relevant to Ratch's observations of his bike's behavior, is what is happening on a light or feathering throttle. Here too is a situation where the scatter WILL be apparent. IMHO though the hesitation that he's experiencing is probably much less to do with any variance in cam timing per-se, (Although the observed scatter will prove that the timing is shifting about a bit.) but is Far more likely to be the result of instability in the signal from the 'Phonic Wheel' due to the 'floatation' of the timing due to the slack chain. This may well confuse the ECU so that it periodically says 'F@ck it! and givs up the ghost for a revolution or two until it can get it's bearings again.

 

As has been observed the later model Guzzi tensioner has a pissweak little spring and IMHO it probably won't have the strength to combat the chain-flap on the over-run but I know of CAlis that have done best part of 200,000 miles without replacement of the chain or tensioner so?????????

 

The Valtech/Stucchi type 'Blade' tensioner is in some ways a lot more robust than the Guzzi item. Yes, I know that some people don't like 'em and I know that some people have reported breakages of both blade and spring. I've had one broken spring on dozens I've installed and generally prefer them to the later model Guzzi item but both are a HUGE improvement over the original 'Foot' type tensioner from the early chain drive models. I think like most things both have advantages, both have disadvantages. When the chain or tensioner becomes a problem on my Griso I'll probably install a Valtech type as I think these work better at their true task of tensioning the chain but I certainly have no intention of doing it pre-emptively.

 

As many people know I'm not a fan of any of the available alloy or composite gear sets available for converting to gear drive. I'm not willing to embark on another long and tiresome debate on the subject here. If you want to see how the other half thinks, if somewhat irrationally, go and have a look on the timing gear thread on Guzzi Exchange. I can't be arsed going through all that shit again!

 

Anyway, my

 

Pete

[BrianG]

OK Zebra fans........

 

Intake spigot boots checked and no leaks found.

Compression checked and 110/105 psi rt/lt found

valve lash rechecked.... 0.006/0.008 retained since adjustment last week-end

 

 

I chose the "TPS from the closed throttle" parameter as the sensible baseline parameter.... mostly because it's pretty much a useless number for anything else.... and that in itself is enough to make an engineer pick it. Given this assumption I manipulated the mechanical issues to get the throttle place on the bore wall (closed).

 

Initial reading was 106 mv......... final adjusted reading was 156..... (crap that thing is position sensitive!)

 

Then I set Idle to somewhere between 1000 - 1100 Vague-alia RPM...... so it sounded right, ticking over nicely but not quite doing the Harley "potato - potato - potato" thing.

 

Then I balanced the TB's at 2200 RPM and then at idle I adjusted balance with the air-bleed screws that started at 1/2 turn out (we are at 3500' MSL)

 

Then I checked idle TPS output and I see 485 at that nice slow tick-over with no apparent desire to change directions.

 

ROAD TEST

 

No real change in power.

 

VERY real change in drivability...... NO hickups at idle..... NO chuffing at part throttle.... Positively Honda-like throttle response, and immediate starting when hot (which was a minor concern before this event)

 

So... A cigar is really a cigar......... and resolving the problem is, for some, simply a matter of normal procedure. I'll count myself lucky in that regard......

 

Back in school one of the clinic supervisors said "If you hear hoofbeats.... think "horse", first..... not "zebra"!

[Dan M]

Dan, you're really gonna make me work for a point here, aren't you? To clarify, I don't b'lieve you'll find that Pete stated that the scatter I observed is a sign of a worn chain wotsoever. (see Pete's post below) I think if you read the following, you'll also discover that the "doesn't matter a tinker's cuss" remark refers to VALVE TIMING (variance of which would NOT make any difference WRT the symptoms I've experienced), not erratic advanced IGNITION TIMING due to a SLACK CHAIN, which WOULD be expected to produce exactly the symptoms I've observed. Again, I think it's worth the small investment of time and negligible cost of opening the timing chest @ $26 USD of parts to discover if it's really a wonky tensioner that's behaving like it's giving up the ghost, and the resulting SLACK CHAIN that's the cause of the symptoms.

 

BAA, TJM, & YMMV

 

 

Hey, I'm just hackn' at the ratchet. It's been a brutal couple of weeks here so maybe I'm feeling ornery.

I was referring to Pete's first post:

 

To answer the questions.

 

1.) As Orson suggested if you stick a strobe on it and watch the timing mark on the flywheel this will give you a pretty good indication of how worn the chain is. If the mark appears to jump about, (A phenomenon known as 'Scatter' then it's a good idea to do something about it.

 

2.) Ypu don't have to remove the engine to do the timing chain. Just pop off the fron't cover and everything is easily acessible.

 

Pete

[Guest ratchethack]

Hey, I'm just hackn' at the ratchet. It's been a brutal couple of weeks here so maybe I'm feeling ornery.

I was referring to Pete's first post:

 

To answer the questions.

 

1.) As Orson suggested if you stick a strobe on it and watch the timing mark on the flywheel this will give you a pretty good indication of how worn the chain is. If the mark appears to jump about, (A phenomenon known as 'Scatter' then it's a good idea to do something about it.

 

2.) Ypu don't have to remove the engine to do the timing chain. Just pop off the fron't cover and everything is easily acessible.

 

Pete

Looks like Brian got fixed with a regular tune-up. Congrat's to Brian.

 

Pete's evidently avoiding this thread now (not that I blame the man ), so I don't expect anything like a repeat of everything he's already said a few times over any time soon. Yes, he also said scatter would be an indicator of a worn chain, but I reckon he meant a worn chain with a worn tensioner, since a worn chain with a functional tensioner wouldn't throw a jumpy strobe signal. Now how many worn chains are you going to find in the field with a tensioner that works like new?! (CORRECTION: like a tensioner should?) I reckon slim to ZIP, heavy on the ZIP, but that's just me.

 

Here's one more clarification that I hadn't made before. I'd noted that the scatter I'd read with the strobe was erratic and showed up on the flywheel by a movement of a static mark on the flywheel by anything from 1 mm to up to 6-7 mm. I should have noted (because this is where it indicates an advanced signal, and excludes a retarded signal): The signal had a spot that it hit most of the time. Every time the signal strayed from that spot, it strayed on the UPSIDE of that spot on the flywheel, never on the DOWNSIDE. This is consistent with scatter from TIMING ADVANCE ONLY.

 

Make sense?

[BrianG]

That was a great ride. Everything seems nominal and drivability is excellent!

 

I'm fixed, and the process was really quite easy!

[dlaing]

I thought I would throw a wrench into the works Feel free to ignore as this is stuff that few will ever encounter, but I find it is interesting, and POSSIBLY relevant.

Thinking that if the state of tune at idle was off a little, you might get scatter as the ECU map moves from between cells.

But I don't know if the analog output is averaged between cells or if the changes are sudden. I am sure someone here knows.

Check out the ignition advance curves for the standard map and the Ti ECU map.

It looks like with the Ti map one might get some advance surges from 12 to 15° as the idle drops towards 900RPM. The stock ECU does not do this till it approaches 700RPM, but it does transition from 9 to 12° at 518° X 1300RPM. I suppose one might hit this transition if the idle and TPS are both set too high.

Note: idle is not in the bottom row of cells, but rather it should be about 3.4-3.8

 

EDIT here is the fuel chart

FWIW I looked on the map for the point that I thought a mis-set TPS would show the worst change and all I could come up with was the transition shown above from 10.43 to 11.84 which equates to about 175mv. So if you set the TPS and were off by 175mv at 3200RPM at those that throttle transition, it would go up 8 units which corresponds to Air Fuel ratio change of about 12%. So, if you were at an A:F of 14.0:1 it might drop to about 12.3:1, which would not be so bad, but it was already at 13:1 it might drop to 11.3:1. Worse of course would be the other direction and it were too lean.

But that is a worst case scenario. The average cell transition is 275mv, not 175mv and most cell transitions are much less than 12% change in fueling per 175mv of TPS. Nobody should be setting there idle TPS to 350 nor 700mv. Most TPSs will be set within the recommended range so the variation will probably only be about a seventh as bad as that so, equivalent to a less than a 0.2:1 air:fuel ratio difference between maybe 500 and 525mv. Most map cell transitions are much milder.

This of course does not take into account the other tables in the map, and as always, my math and theory may be way off

Still I think some will be able to detect a difference in how the engine feels from just a 10mv change.

Also, I think anyone who splurged for a custom PCIII map should be a bit more diligent at setting the TPS and other settings very close to how it was when dyno-tuned.

[pete roper]

Brian. Glad it's fixed. My apologies for not responding to your PM but things have been very busy around 'Chez Roper' for the last few weeks due to a number of factors I wouldn't dream of boring you with.

 

My experience with V11's and the like is stumbles and hiccups are almost invariably the result of the ballance being out coupled with incorrect idle adjustment and failure to *correct* the TPS after linkage adjustements are made.

 

Thing is you can set up the idle to *roughly* 900-1000RPM using the throttle stop screws. If the one on the left is used it is best as when the ballance is adjusted using the knob on the linkage the rod will remain under tension. When you alter the idle speed using the stop screw this will also alter the TPS setting. Once the ballance is done then the TPS should be re-set to whatever you think works, (I don't use millivolt readings and a multimeter 'cos I've got an axone which tells me it's opening in degrees.) and then the idle speed can be bought up to 1200 or so using the air bleeds.

 

Sometimes you may need to raise the idle speed a bit more with the stop screw and then re-set the TPS again to get a good, steady idle using the bleed screws. I know that many people say that you have to set FI up *exactly* to book specs for the best results but the more I play with it, (I'm a novice with FI.) the more I'm finding this to be bullshit. there are just too many variables in a mass produced engine for there to be an *ideal* that can simply be applied. Ideally a dyno would be the best sollution I suppose but i find that simply test riding and analysing the results before and after making adjustments works just dandy!

 

Pete

[pete roper]

I respect Pete's experience with the MG mill, and he's likely to have most all of the answers, but I'm sure he'd agree it's tough to diagnose a problem over the internet.

 

Don't respect me too much. at the end of the day Dan I'm just another prole with a box of spanners There are MANY here who have a lot more FI experience than me so on any issue like this its probably wiser to listen to them than to listen to my ramblings.

 

One of the things I've learnt from hanging around Guzzi boards for years on the net is you can never get it right. Invariably any diagnosis you make is bound to be wrong to someone, even if its right! I've got so used to having ranters call me a 'Rhymes with 'Runt'' that its something I now ignore. Any of us who express an opinion are bound to find that there are people who disagree. Thats fine and dandy, especially if it provokes a decent debate. The problem is when it disolves into a slanging match and the hurling of pointless abuse as has happened on Phil's board before now over the whole timing gear issue and regularly seems to occur when enzo sticks his head up anywhere !

 

Pete

[Ouiji Veck]

Ya gotta stick with the pros. I myself am a Guzzi Witch doctor.

I have no idea what Daves' charts say.

[quazi-moto]

I've never had a green haired trombonist work any voodoo on my Guzzi, but the MY15M ECU has cured its ills. I no longer have to ride on gilded splinters.

[BrianG]

Brian. Glad it's fixed. My apologies for not responding to your PM but things have been very busy around 'Chez Roper' for the last few weeks due to a number of factors I wouldn't dream of boring you with.

 

My experience with V11's and the like is stumbles and hiccups are almost invariably the result of the ballance being out coupled with incorrect idle adjustment and failure to *correct* the TPS after linkage adjustements are made.

 

Thing is you can set up the idle to *roughly* 900-1000RPM using the throttle stop screws. If the one on the left is used it is best as when the ballance is adjusted using the knob on the linkage the rod will remain under tension. When you alter the idle speed using the stop screw this will also alter the TPS setting. Once the ballance is done then the TPS should be re-set to whatever you think works, (I don't use millivolt readings and a multimeter 'cos I've got an axone which tells me it's opening in degrees.) and then the idle speed can be bought up to 1200 or so using the air bleeds.

 

Sometimes you may need to raise the idle speed a bit more with the stop screw and then re-set the TPS again to get a good, steady idle using the bleed screws. I know that many people say that you have to set FI up *exactly* to book specs for the best results but the more I play with it, (I'm a novice with FI.) the more I'm finding this to be bullshit. there are just too many variables in a mass produced engine for there to be an *ideal* that can simply be applied. Ideally a dyno would be the best sollution I suppose but i find that simply test riding and analysing the results before and after making adjustments works just dandy!

 

Pete

 

Too true, Pete! But thanks for the belated commentary in any case.... you have nicely confirmed some of my suspicions gathered in this, my forst forray into the MG EFi system.

 

I learned at least ONE very revealing point in this thread.... being that the TPS setting is a rough parallel to the main-jet needel position in our old carbs. I knew that what I had going on was a lean mis-fire situation, but I didn't know enough about the EFI basics to have a clue about where to look.

 

As you and others here have pointed out, the adjustment process is an iterative one that require much circling about the parameters to get it all sorted. When I had finished my first pass through the set-up loop, I ended up with a very rich-smelling idle. Now an old hand like me does not much like the smell of an over-rich mixture, and I didn't know enough about this EFI to understand what might have gone amok...... but as many have stated, the diddling around with the idle stops and balance-nut of the throttle linkage had sure-enough messed up my careful initial TPS idle setting. Resetting that parameter last thing has left me balanced, idling right, and smelling sweet!

 

These forums are almost the best part of the internet!!

 

Here's grist for your grinder, Ratchethack! Why on earth did MG place the TPS on the remote throttle body? Life would be so much easier if it lived on the active TB unit, leaving balancing as the only significant adjustment for the right side and no need for going round and round this silly circle where one adjustment messes up things on the other side.....

 

Maybe this is a good winter project.......

[docc]

Again, I think it's worth the small investment of time and negligible cost of opening the timing chest @ $26 USD of parts to discover if it's really a wonky tensioner that's behaving like it's giving up the ghost, and the resulting SLACK CHAIN that's the cause of the symptoms.

 

BAA, TJM, & YMMV

Ratch, I've lost track. Did you ever actually change your, I mean 'yer', tensioner and recheck the scatter?