Intake rubber boots: no lip on the pipe to prevent slippage?

[p6x]

This morning, my Le Mans started to run on one cylinder.

In the 87 Octanes topic, I reported that my V11 had a lot of misfiring.

Fortunately, I was less from a mile from my house, on my way back from a run, so I limped back and a quick look at my left intake identified the root cause.

The rubber boot had slipped from the intake pipe, and was no longer sealing around it. I was intrigued to find out there seem to be no lip on the pipe to prevent that kind of mishap.

I have seen similar assembly with the pipe having a lip and the rubber boot a groove underneath the collar recess. Tightening the collar would lock the boot onto the pipe.

But here, it looks the pipe is smooth, so the rubber boot is only held by friction.

If you have not, worth checking on your bike.

 

[docc]

That occurring can be a sign of throttle body imbalance (or imperfections in the tuning parameters, i.e. TPS and valve adjustment variances).

[Scud]

The metal "intake pipe" is not totally smooth, there are some ridges. And the Rubber boot has matching features inside, so it does seat.

In addition to what Docc said about tuning, it's worth inspecting the system for other air leaks - both the boots and the vacuum hoses that attach to the intake port. And since one boot is already off, why not do a quick clean on the throttle bodies?

[GuzziMoto]

Yeah, it is not normally a high pressure situation, so the intake pipe does not need much to stay on. It is actually normally a low pressure / vacuum situation between the head and the throttle bodies. It should not take much to keep it on. But you can see one of the slots in the metal intake spigot that the rubber boot grabs in your picture.

Something went wrong to pop that off.

[Tomchri]

Low idling 

Cheers Tom.

[p6x]

@docc, @Scud:

Agreed. I did check all the collars on both sides.

There is no way I can do any kind of work as long as this extreme heat continues. The inside of my garage is 104 degF.

The vacuum hoses were replaced last year, because the previous ones were all crackled. I did a quick visual check, but did not see anything out of place.

@GuzziMoto

I am going to go check with MPH what they think about that.

@Tomchri

Yes, indeed! my idle is about 550/600 rpm, when Guzzi recommends 1100 +/- 50 rpm.

When I purchased the bike, it was already low idling. Since it never stalled, it was on my contingency list.

All of that tied up to GuzziDiag, which I have not yet managed to connect to the interface.

[p6x]

Just back from visiting MPH (108 degF)

Davey says over time the rubber boots harden and lose their flexibility. That may be a factor too.

In any case, I need to get that sorted by verifying there is no leak.

[p6x]

20 hours ago, Tomchri said:

Low idling 

Cheers Tom.

Low idling no more....

Sorted it this morning in less than the proverbial two shakes of the lamb's tail...

I am now around 1000 rpm give or take 50 rpm....

[p6x]

That new idling rpm has had an effect on my instinctive driving.

I was so accustomed to my low revs, that now, when I stop at a traffic light, I think something is wrong. Like I have not returned the throttle to its back stop.

However, the V11 is easier to ride in traffic as I can let it idle run. No need to touch the throttle. No hiccup as if trying to just run it on a very narrow opening.

It is still 100 degrees F here (38C).

[docc]

17 minutes ago, p6x said:

That new idling rpm has had an effect on my instinctive driving.

I was so accustomed to my low revs, that now, when I stop at a traffic light, I think something is wrong. Like I have not returned the throttle to its back stop.

However, the V11 is easier to ride in traffic as I can let it idle run. No need to touch the throttle. No hiccup as if trying to just run it on a very narrow opening.

It is still 100 degrees F here (38C).

A higher idle is good medicine for the Guzzi Big Block on many levels. It is worth verifying any tachometer error with something like GuzziDiag.  The white face Veglia have often been found to read 300-500 rpm high. This is, perhaps, no consequence cruising at 4,000 rpm, but an indicated 1,000 rpm idle could be an actual (ungood) 700 rpm.

[p6x]

Now that I have put some miles on the Le Mans since the left cylinder boot slipped from the left admission pipe, creating an air gap and ultimately causing the V11 to limp on one side, there is solace.

The V11 runs a lot better through to the 3000 rpm mark. Long runs at 55 mph (3000 rpm) no longer indispose the Guzzi. 

This is a considerable improvement from as long as I can remember.

I am not going to say the V11 is perfect. But the strong coughing I was invariably experiencing around the 3k mark is no longer there. What I get now, are small burps mainly when I am in the city, and while changing gears at low revs; below 3k.

It does seem to indicate I had an air leak for a while. The evidence being the pipe is blackened in front of the rubber boot. The right hand side is not.

You remember that we did have a conversation about rubber boots: Nitrile, Viton, Kalrez...

I don't know what material is used to make those admission boots, but they are exposed to UVs. It is obvious they need to be replaced on a 19 years old motorcycle.

[audiomick]

4 hours ago, p6x said:

 It is obvious they need to be replaced on a 19 years old motorcycle.

Yes, it is. Still, I'll ask: did you replace yours, or just stick them (it) back on properly?

I ask because mine has a nasty cough at about 2,800 rpm, so maybe I need to renew the boots on mine.

[p6x]

On 8/15/2023 at 2:47 PM, audiomick said:

Yes, it is. Still, I'll ask: did you replace yours, or just stick them (it) back on properly?

I ask because mine has a nasty cough at about 2,800 rpm, so maybe I need to renew the boots on mine.

I reinserted the left boot all the way on the left hand cylinder; the adjustable clamp worm screw was the opposite way. In my battle tank days, when using adjustable collars on fuel lines, you would always install them with the worm screw 180 degrees apart to prevent any leak. Mine were not installed this way.

In good mechanical practice, one of the worm clamp access screw should be up, the other down in a 180 degrees fashion.

I am thinking to replace all the rubber parts of the injection system as soon as I complete my 2023 motorcycle grand tour of Texas, and that driving course that I have kept postponing.

[80CX100]

On 8/15/2023 at 3:47 PM, audiomick said:

I ask because mine has a nasty cough at about 2,800 rpm, so maybe I need to renew the boots on mine.

With the bike idling,spray something like WD40 all around the intake boots;if they're leaking you should hear the engine increase in speed.

I'm only a recent convert to Docc's magical rubber restorer aka as Honda's Shin-Etsu grease; I'm now putting a light coating rubbed in with a tooth brush on all rubber pieces I hope to preserve rather than replace in the future;seems good so far,time will tell.

If you do the WD40 spray/idle test and there's no increase in engine speed & no visible cracks or damage; I'd apply some Shin-Etsu & verify fit & tightness & call it good.

A lot of poor running/coughing issues have been cured by doing a decent tune up & making sure all of the vents & plumbing are clear & working properly.

fwiw ymmv 

[audiomick]

5 hours ago, 80CX100 said:

With the bike idling,spray something like WD40 all around the intake boots;if they're leaking you should hear the engine increase in speed.

yes, I know about that one. Here, the spray of choice is brake cleaner. Makes sense to me, as it is extremely volatile.