Throttle bodies and breather hoses.

Well yesterday we got in a Stelvio, must be a 2011 or early '12 as from our records we rollerised it a few years back.

Anyway at that time it was living in Sale in Victoria but subsequently got sold and moved to Darwin in the Norther Territory. Now it's been bought by a long time customer from down the South Coast and he bought it up to us because it was "Running like a bag of shit."

This was a pretty accurate description but close examination showed that the throttlebody screws hadn't been molested either by Harry Hometune or a Shaved Ape. Sadly though closer inspection showed that not one of the hoses to the airbox was attached! Not the drain hoses, nor the breather hose or the stepper hose and this thing, although in seemingly very good condition, has been sucking Northern Territory dust for a couple of years.

The TB's are buggered. It's a great shame. Michael will try and compensate with CO trim after a thorough cleaning but I fear the only 'Cure' will be new TB's.

I really can't stress strongly enough the importance of making sure the breather and drain systems are correctly connected and, in the case of the drains, capped or plugged. Hoses and caps are very cheap. Throttlebodies? Not so much......

How're ya? I hope i'm in the right place. Greetings from Ireland.
I have an 08 1200 8v GRiSO with 35000 kms. My first Guzzi. I've put 14.000, trouble free klicks on this beauty in 4months. (I was told it had been rollerized as well)
She stopped picking up at the 5000 rpm band recently, feeling like a ' i'm not going any quicker' flat spot, for all the world. That went on for a bit.
Later as i'm changing down, instead of the usual popping, i heard a bang. No internal damage, thankfully.
I made it home, 20kms by tickling the throttle, at about 30kms/hr.
She would tick over, just wouldn't take juice.
She swung over there now, no start though, followed by no more swinging, and more head scratching for me.
Could you steer me in some favourable direction, please and thanks.
Sincerely, Martin.

I'd start by replacing the fuel filter if it was me

Martin Cummins wrote:

How're ya? I hope i'm in the right place. Greetings from Ireland.
I have an 08 1200 8v GRiSO with 35000 kms. My first Guzzi. I've put 14.000, trouble free klicks on this beauty in 4months. (I was told it had been rollerized as well)
She stopped picking up at the 5000 rpm band recently, feeling like a ' i'm not going any quicker' flat spot, for all the world. That went on for a bit.
Later as i'm changing down, instead of the usual popping, i heard a bang. No internal damage, thankfully.
I made it home, 20kms by tickling the throttle, at about 30kms/hr.
She would tick over, just wouldn't take juice.
She swung over there now, no start though, followed by no more swinging, and more head scratching for me.
Could you steer me in some favourable direction, please and thanks.
Sincerely, Martin.

OK, Martin. Can we get a few things clarified please?

You've owned the bike for 14,000 Kms. You say that you were told it was rollerised? Have you confirmed this? If you have adjusted the valves in this time the roller tappets would be obvious but it's important to KNOW, not guess or suppose that it does in fact have roller tappets.

Secondly. The issue of it not revving above about five grand? Was this sudden? Or is it possible you only started noticing it as you became familiar with the bike and started to try and use the motor above that five K mark?

You say you heard a bang but there was 'No internal damage'? How was this lack of damage ascertained? How deeply did you dig into the motor?

If you can expand on these points I would be grateful.

Oh, and this is actually a lousy place to post this question as it isn't relevant to the thread subject. That's fine, I understand it's probably just unfamiliarity with the board but I did have trouble finding it again to reply after my usual morning scan of the board for new messages.

It might be worth copy and pasting the original question into a new message in the Grisology section with an unambiguous title so it's easy to find again. Even if it only helps my tiny brain! If it's under its own topic though it may be easier for others to reference if they encounter the same or a similar problem.

Just as important, what was done on the bike in the period before it stopped revving past 5,000 (assuming it was before...)?

Getting back to the original topic here we've found that unfortunately while we could get it to run pretty much acceptably up on the tablelands when I rode it down to the coast it got very temperamental. There's simply so much air slipping past the butterflies that the altitude/density compensation can't cope.

Shame.

Just say no to aftermarket air filters and make sure ALL the airbox hoses are connected and the drains capped.

Arse!

New TB's required?

It's the only solution I can see.

The real problem is that the dirt and grot going through, along with the oil residue, (which is probably excessive because most owners try to do the 'Right Thing' and keep their oil at the 'Full' mark on the stick.) combine to make a 'Grinding Paste' that then gets fed into the engine via the TB's.

This muck will cause wear in the throttle plate spindle bushes and that means that when the plates are closed, (At idle.) the plates fret against the inside of the throttlebody choke. This causes wear of both the alloy of the choke and the plate itself.

Remember that problem I've seen with when you recalibrate the TPS with the engine off and then when the engine is started the TPS reading jumps? Well that must be due to wear in those components and air pressure pulling the plate round further than where it settles with no pressure on it from the atmospheric side.

That means that the fueling is already way outside the '8 Ball' of where it should be. Then you add the worn choke and plate and the idle mix is going to be shitful. When we do your gearbox Mark you can dig through our pile of dead TB's and see for yourself. You need to compare them to a new set and it's not something you can easily take a picture of but the light that passes the butterflies and choke on a set of worn TB's is quite obvious, and wrong.

As I said you can compensate for this, at least a bit, by playing with the CO trim. The bike mentioned ran *OK* on the tablelands but down at the coast, only an 800 metres difference, it had turned into a spitting, coughing, farting monster!. Could you try and compensate, at least in early stages of wear, by playing wth the 'Sacred Screw/s'? Possibly. But what happens if it just makes it worse or leans out the mixture to such a degree you hole a piston or shed a valve head? If you want to experiment please! Bring me your bike! But you'll be signing a waiver before we lay a screwdriver on it!

Once you have throttle plates so worn and chokes so eroded that you can see light glinting past the full circumference of the plate it's all over red rover. As this wear occurs, if you are running a closed loop map, the ECU seems to be able to trim to a point. But if you clear the trims it all turns to unfixable shit in an instant. I know. I've had several Stelvios that did this to me. Subsequent examination showed badly worn TB's.

I've considered seeing if Mark could work some sort of map compensation magic but I don't see how it could be done simply because once the wear occurs the stepper can't do its job. Also every set of TB's would require a different baseline. Nah. It's just not a viable solution.

Look, if anyone can produce a 'Magic Bullet' I'm all ears. The problem though is that I think anything offered, other than sleeving, full refurbishment and recalibration by flow bench, (And even then you'd need to know the original MM baselines!) would be more 'Magical Thinking' than 'Magic Bullet'.

I wish it wasn't so.

And of course once you'd much off idle it doesn't really matter a bean!

In this particular case, we could probably tweak the pressure-air-temperature correction table to minimise the affect you mention at sea level, but I fear it's simply treating a symptom, not curing the disease.

It would never be right.

Exactly. We can philosophise in Coonamble but I think it's a dead end.

FWIW I think the continuing high idle I have on the 'Soon to no longer green' Horror is also symptomatic of the condition. It's not bad enough to cause the 'I'm going to behave like a huge bell-end when I'm away from home' but the recent map tweak works to lower the idle when cold but once hot it's back up to 1,400. The idle is though a lot steadier. Which is good. I'm more than happy with it but it's not *Right* and given I had a hose off the airbox for a while, (Mea Culpa!) it's almost certainly a contributory factor if not a cause per se. Perhaps I should swap the TB's off the Tenni Shitter? They have a lot less km on them. While we don't know Michael and I did a bit of chin-rubbing as he was going through it and after looking into our Scrying Bowl and examining the entrails of a few chickens we decided it was actually quite a low KM bike. Our guess is about 25K. It may of had a lot of 'Toad Crap' on it but it didn't have a K&N type filter and all its hoses were correctly connected.

I wonder how the 1,400's with their one huge TB and throttle plate go after some wear and tear from a load of grit through them....

Quote :

I wonder how the 1,400's with their one huge TB and throttle plate go after some wear and tear from a load of grit through them....

Same issues, I would think. Labyrinth filters, air leaks (disconnected or misplaced hoses), plus blow-by (and we know how much the 1400 has) would no doubt have the same affect.


Charlie had a pretty good result having his 1100 TB's rebuilt. Worth pursuing?. Maybe not as good as a brand spanking new set, but as they soon will be made of unobtainium, might end up being the only solution.

The people who rebuilt Charlie's declined to entertain another such job. I asked..

Pete Roper wrote:

The people who rebuilt Charlie's declined to entertain another such job. I asked..

Ay, Caramba!

That doesn't bode well.

Apparently setting them up in the mill is a fucking nightmare and the chances of cracking the castings are extreme. This was on the 45mm ones (?) on the 1100. The 1200 50mm ones are more delicate and the machining would need to be more exact.

Setting up for thousands with blank castings would be one thing. Recovering worn ones? Awful! Look at how many firms re-sleeve or refurbish carburettors? A handful in the world and most of their work is on really old, queer shit like Lctron's and vintage oddballs. What makes it worth their while is rarity and the consequent incredible costs and, while I've never had to do this sort of thing, I'll bet there is an 'All care, no responsibility' clause in the contract.

Arse.

Shitting arse & hole!


How many kilometreges on the soon-to-be-another-colour horror now? If your TB's are starting to wear, there's no hope for the rest of us. Or is it a case of YMMV? No pun intended.

The current TB's went on when I replaced the whole motive unit after my original motor shat itself due to the flat tappet fiasco. This was, in a way, convenient as just before this one of the ball joints on my original linkage rod had started dropping off its ball on, I think, the LH TB. I'd lashed it back up with a rubber band and cable tie, (Sophisticated? Eh?) because I was hoping to find a cheaper solution than new TB's as the ball joints are not available separately, (More on that at a later date.). Anyway, the purchase of the wreck that provided the new donk rendered this moot BUT the wreck, although very low mileage had had a BMC labyrinth filter fitted.

I know I bang on about this but I'm sure that poor air filtration is at the root of most of these issues and even though I immediately reverted to a paper filter the *New* motor never seemed to behave as well as its predecessor, at least before it's tappets went west.

Having said that, over the 50 odd thousand KM that the current engine, TB's and filtration system have been on the bike nothing has changed to any huge degree. I don't find that when it is serviced and tuned anything ever needs adjusting much. It's fueling 'Oddities' which I've mentioned to you before don't seem to alter in any meaningful way and it's most obvious 'Symptom' of a 1,400 rpm idle worries me not a jot as more revs means higher oil delivery and greater cooling. Something that the oil cooled exhaust valves will surely be grateful for and the maintenance of higher flow and consequently pressure on the lubrication side which can only help in the prevention of boundary lubrication. The slightly higher heat output is nothing to worry about. It's a tiny fraction of what the engine produces as waste when you've got the throttle pinned at 200kph and although the cooling airflow is negligible so too is the energy it it is trying to dissipate.

What 'Hope' do we have? In all honesty lots! If we look after these components they will certainly out live me and probably will out live you! The biggest 'Trick' is to not buy the snake oil about air filters that promise what they can't deliver and to try and chase performance from a motor already close to its thermal, mechanical and volumetric limits!

Keep it clean and mean and all will be good in the world. Or as good as a mechanical device with wear points can ever be.....

Interesting discussion. I like it.
So do you think that the transient high idle issue that people solve by plugging the stepper hose is a side effect of the throttle bodies beginning to wear out? Or that is just an issue of the stepper being too slow/not moving enough?

I'm not sure. In some bikes it may be but my overall feeling is that in many cases this is another byproduct of over filling with oil. That which gets pumped through the breather system into the airbox can then easily end up contaminating and jamming the stepper. That can cause the problem certainly and on some machines there seems to be an 'Early onset' high idle that occurs earlier than one might expect if wear was involved.

In all honesty I have to shrug and say I don't know. Sorry.

No argument from me re filters. I'm constantly telling people that I won't remap their bike until they put a stock filter in. I use the Tuono argument. I might start using the wear argument as well. If they refuse? They get sacked.

They will use the argument that "If they weren't good people wouldn't use them." Or "But they're re-useable". The counter argument is that they are popular because they are 'Money for nothing' for the unscrupulous and as for the 'Reuseable' argument? Let's think this through. Say a K&N filter costs you $140AU, (I have no idea how much one of these POS costs so that's a guess.) and a stock filter costs $18 AU and needs changing every 20,000km how many KM do you have to travel before the shitty 'Reusable' filter becomes economically superior? Then throw in the cost of a new set of throttlebodies and see what that does to the equation?

You can buy 'Reuseable' oil filters too that you're supposed to rinse in the parts washer too if you're that mad! I'd rather stick my dick in a blender personally......

They've tried that on, too. I tell them if they're not prepared to spend a few bucks a year on their motorcycle, they don't deserve to own one. They usually sack me, then. Good riddance.


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My figure of $18 for a filter was a guess but just going to check my costings that's about right if I add in freight to me. I'm making a reasonable profit on that, about $5.00AU if anyone is really interested. The idea that one can save money by using a 'Reusable' filter really doesn't hold much water. I've just checked and TLM sell one for GRiSO/Stelvio for €53.00. If anybody wants to do the sums to work out when you'd start 'Saving' money by using one knock yerself out. I can't be arsed. Actually we have a huge 20 litre 'Junk Bucket' in the workshop that is full of shitty air filters, Fat Duc's, Memjets, Power Commanders and other such dross. It's about time I took it to the dump. Might be a job for this weekend!

I hope to have the gumption to roll in on this tomorrow.
Was running decent compared to when acquired (typical de-mod regime, removing PCV, open element air filter, remap). The became a little rougher, noted that the hoses to the heads have minor cracks and that the breather line to the air box was just cut through. Haven't gotten tank off to view the rest but have parts onhand and the stainless fuel line clamps.
Disappointed to still be cleaning up others' mess, but still appreciate some of the other aftermarket bits that came with it 'free'.