Hiccups at idle

[Guest Brent]

Not having had, or been around, Moto Guzzis, I don't know what to make of this little quirk that my bike has. I can only describe it as a hiccup that occurs while idling. When it happens, I can sometimes see exhaust shoot out from a joint in the exhaust pipe, usually on the right side of the bike.

 

I've been told that this is to be expected during the break-in period, and that it should go away after the 1000 mile service. I have no reason to doubt the person that told me this, but if it's normal, then most of you have probably experienced this. If you have, has the quirk/hiccup gone away, and was it the 1000-mile service that did the trick?

[RichMaund]

Very common problem with this bike. Make sure your idle isn't too low and it will go away. Here's another quirk though... The Tach will lie to you. They generally read low. When mine reads 1100 rpm at idle the idle speed is actually 1000 and the dreaded hiccup will occur. If I set up the idle to an indicated 1200 rpm, it really idles at 1100 and the problem becomes almost non-existent.

Another important point is to ensure your FI system is set up well. A good Dealer can take care of that. And make sure the throttle bodies are well balanced! They are very sensitive to this. My Dealer proved to me that my mercury manometers weren't completely accurate. I set it up with my mercury sticks and it ran OK. The Dealer used a "Twin Max" electronic balancer and found they were slightly off. After he set it up with the Twin Max, it ran even better! Very cool tool. I plan to buy one.

The problem was worse during break-in. If I follow my own advice above, it almost never happens. Maybe once a month when hot at a long light.

Guzzi's definately improve with miles and good service! Hope this helps.

[Guest Brent]

My idle is usually at or below 1000, so it sounds as if I need to increase it a little. The owner's manual says to use a vacuum gauge when adjusting the idle screws. Is this necessary, or will it be OK just to turn each screw the same amount?

[RichMaund]

You need to use an accurate set of manometers, guages or best yet a Twin Max.

All machined parts have tolerance variations when manufactured. Just because you set the screws the same, doesn't mean they affect the system by the same amount! Good tools are the key here.

[dlaing]

If you don't have the best quality vacuum gauge, you may be able to alternate the left and right gauge and average out the difference to get the proper reading.

I have no name brand mechanical dial gauges, they are terrible. It takes me five minutes to synchronize the gauges, and then I have to synch the throttle bodies and then re-synch the gauges and then double check the throttle bodies and if they are off re-synch the gauges, etc. etc. etc.

I sucked in mercury once, so I second the recommendation for a twin max, although I have not tried one.

The dealer saying that it is a break-in issue is all the reason to invest in a twin max. The bike should survive till the first tune up with no harm done, and then he can make a few bucks off of you. If it was my bike, I would not wait. Yes it is a normal problem, but it is a problem, especially if you are going around a slow speed turn and the bike hiccoughs. Hiccoughs are normal, but you should minimize or ideally eliminate them. I recommend you get a power commander. If your dealer can't get rid of the hiccup, I reccomend you get a power commander now, and have the bike dyno tuned.

[Guest JohnInNH]

IMHO... If you are just wanting to raise the idle, and you are not balancing the Throttle bodies, is it no big deal if the balance is off some at Idle. As soon as you twist the throttle the throttle stop screws do nothing.

 

Soooo . Just turn the throttle stop screws 1/4 turn each till ya get to 1100 or so. Then if you want turn one side in and out till it is as smooth as you can get it. Being >perfectly< "balanced" at idle is not all that important.

 

Now balancing the throttle bodies so they are equal at TPS settings over 10% is a different story. That is what is so critical, and reduces vibration, and gives you smooth power etc.

 

I found driveablity was MUCH better with an idle of 1000 rpm or over because the transition from on throttle to off throttle was MUCH smoother. FI bikes need a higher idle than the carbed bikes.

 

The dealer said a lot of FI guys like to set the idle lower than the better 1000-1100 because they like the sound of a low idle, or are used to a low idle from the carb days. Try the higher idle and see how much different the bike is. You may like the difference.

[Guest HI-TECH-CHECK]

I have used mercury sticks and Twin-max for syncronization. I currently use the Cabrtune II . It utilizes stainless steel instead of mercury and is much more stable. It is also small enough to fit in the fairing pocket of my BMW. it is availiable through their website and they have exceptional customer service.

 

www.carbtune.com

[RichMaund]

If you are using the linkage stops to set idle speed, you aren't doing the job correctly. You set TPS with the TB's completely closed, then set the stops to crack them open until the TPS reads a slightly higher value. (Sorry, I don't have the tech manual here at the computer.) Then you use the air bleed screws in the TB's to balance the system at idle as well as set the idle speed. Once that is all satisfactory, rev to about 4000 rpm and set the TB balance at that speed with the adjuster on the linkage. Once I do that I often rev slowly to a higher number just to watch how the balance tracks from side to side.

The factory tech manual is in three languages and has excellent photos to work from. I highly recommend it.

Yesterday, I bought a CD containing the full parts breakdown of a V11S from a seller on EBay. None of my Dealers have been able to get the book for me, so I hope this will do me fine.

When it comes in, I'll check it out. If it's good, you see a post here on the forum and the contact info to buy your own.

You can never have enough info on your bike!

[Guest IanJ]

I'm experiencing the hiccup right now, with 1200 miles on my Le Mans, and Micha at Moto International explained that he thinks it's the crankshaft timing sensor being set up incorrectly -- the sensor gets a pulse off teeth that are arranged around a wheel on the crankshaft. There's one tooth missing, and that's the computer's signal that the crankshaft is at some point (probably TDC in one cylinder or the other). The ignition computer uses this missing pulse to time the spark to each cylinder. Unfortunately, every other manufacturer does this the other way 'round, and has one tooth at the correct point, and then no teeth anywhere else, providing one pulse at the right time. Micha theorizes that the "missing pulse" signal isn't as clear as the "single pulse", which causes problems at low speeds, when the sensor isn't getting as much electromagnetic effect. I don't know how much I buy that, but I thought I'd pass it on. He says that MG's approved fix is to raise the idle by 50-100 RPM and stop worrying about it.

 

Regarding manometers, I use a water manometer that I constructed out of about $1.50 worth of plastic tubing and 5 feet or so of PVC pipe I had lying around. It is more sensitive (read: easier to see small differences) than a mercury manometer, and has a TwinMax beat on sensitivity, reproducibility, and price. The serious disadvantage? It's over 5 feet long, and doesn't travel well. (Well, and it's not a cool gadget.)

 

To make a water manometer, get about 20-25 feet (6-7.5m) of clear vinyl tubing which has the correct inner diameter to go over the vacuum nipple on your bike's throttle bodies or carbs. Fold the tubing into a thin U shape, but don't pinch the bottom -- it needs to allow water to flow freely to work right. Attach the bottom 5 feet (1.5-1.8m) of the U to some kind of stiffening structure. PVC pipe, wooden dowel, piece of lumber, the wall of your garage, the choice is yours. I used nylon zip ties to attach mine to a thin PVC pipe. The main thing is to have a length of tubing with this U shape, ideally with the sides of the U lying right next to each other for comparison. There should be enough tubing coming out of the top of your manometer to reach both carbs or throttle bodies on your bike -- mine has about 6 feet on each side.

 

See this drawing of a manometer for a visual representation of what I'm talking about.

 

Now, add water to the tube. You need to fill it up so there's water up to about 3 feet (1m) inside the U, so you have a foot or two of clear air above the water when it's at rest. That gives you enough room for the cylinders to be significantly out of balance and still not suck in any water (when the water reaches the top of the U and starts down toward the carb, you'll get a quick cleansing burst of water through that cylinder and have to refill your manometer). I found that using a vacuum pump (or sucking on the tube) with one end submerged in clean water works alright, although I spent about 20 minutes getting bubbles out of the tube on mine.

 

Attach the sides of the manometer to each cylinder and test away. A higher level in one tube or the other indicates that that side of the engine is pulling more vacuum than the other side. The only important difference between the water and mercury manometer is that this simple model can only compare two carbs at a time -- not an issue on two-cylinder bikes, though, and three- or four-cylinder bikes can just compare carb 1 to carb 2, then carb 1 to 3, etc. Oh, and sucking water through one cylinder won't cause any harm or mental degradation, unlike vaporizing 300 ml of mercury. Water also doesn't run out of batteries.

[Guest HI-TECH-CHECK]

Rich,Can you give us the TPS value and what wires you measure it at?

[RichMaund]

Actually I gave up setting TPS when I bought this bike. I let the Dealer nail it for me. Once done, you just do valve adjustments, oil changes and TB balance checks to keep it in tune. The wires aren't accesible for milivolt checks like they were on the huge connector of the computer of my 1997 Cali 1100. On that bike I set the TPS to 150 mv.

On the V11S there is no good place to just check the TPS setting w/o the factory software and computer interface.

I will try to remember to look it up in the tech manual sometime this week. Then I'll post it for you.

Sorry, I'm spoiled with this bike. I have the regular maintenance memorized. So I don't crack open the tech manual as often as I probably should.

[dlaing]

Great instructions for the manometer, Ian!

My dial gauges are so outa whack, I must seriously consider making a water manometer. I was thinking of using slightly larger tubing to reduce bubbles and the overall size of the unit. The drawback would be less accuracy, but it only needs to be as accurate as I can adjust it.

As for the mV reading for the TPS, it should be 150mV with stop screws out and throttle closed, At an idle of 800-1000rpm, it should read 500-525mV. I got this information from

http://www.geocities.com/guzzitech_pages/t...ne-brannen.html

Which has pretty clear instructions.

As for probing the wire, I think it might be a good idea to splice a wire inline for probing.

I have not done it, but if you look at the wiring diagram there are three wires coming out of the TPS. The violet should be 12V+, the grey goes into the ECU but because of the grey color it is most likely the ground-, the violet/black wire is the wire that I suspect carries the control voltage. You could use a cheap crimp type splicer, but those can damage the line. A better idea would be to shave off some insulation, solder on a wire that you can probe, seal with liquid vinyl electrial sealant. Or alternately, cut the line, add shrink tubing, resplice the line with the new test lined, solder, seal with shrink tubing. If it turns out I was wrong and the grey line was correct, repeat the process for the grey line! Warning what is in the wiring diagram or what is on someone elses bike may vary.