Idle Ajustment

[Bruno]

I have a little problem. I adjusted the valves last weekend, after torquing the heaqds... this was essentially the first service. I set the valves to .004" and .006" and everything seemed fine, that is until the engine got to operating temperature. Now it simply stalls every time I stop at a traffic light, unless I keep the throttle open a little and slowly reduce it. It idles at around 750 RPM. It will start right away, but if I keep going this way, I'll end up shmokin' the starter.

 

I read some of the previous posts but can't find the ones talkin about this. Obviously, I'm missing something. Should I be adjusting something on the throttle bodies?

[Mike Stewart]

Bruno,

 

The idle spec. for the bike is 1000 to 1100 rpm. The idle speed adjustment is on the left throttle body (left side sitting on the bike) and you will need a 2.5mm allen wrench to make the adjustment. The adjustment screw or stop is just about under the air intake tube to the throttle body.

 

If raising the idle does not help, try loosening up the valve specs to .006 intake and .008 exhaust or even Raceco's specs of .008 intake and .010 exhaust. By using the Raceco spec, the bike will idle very strong and much smoother. Also, everytime you adjust the valves, the throttle body sync. should be checked as well as idle speed. Just by going to the Raceco valve specs on my 00 V11 Sport raised the idle speed by about 300 rpm.

 

Good luck,

Mike

[Bruno]

Well adjusting the valves really isn't a big deal, and doesn't sound like the idle would be any trouble either, but how do I set the throttle body sync?

 

Amazing how simply changing the valves clearance, the idle should go up nearly 30%? Any idea why?

[Mike Stewart]

To sync. the throttle bodys, you will need a mercury stick or equivalent. Remove the evap hose (going from throttle body to throttle body) and hook up the mercury sticks to the throttle bodys. Start the engine and raise the engine speed with the throttle to 2500 rpm., watch the mercury stick and if they are not equal, adjust the knob on the left throttle body linkage (screw in and or out) till the mercury in the columbs are equal. Now let the engine idle and recheck the balance on the mercury stick. If it is off, you will need to adjust the air bleeds on the throttle bodys to make them equal. After this adjustment, you should recheck the 2500 rpm. sync. once again and readjust if needed.

 

The theory in high preformance cams is that a high duration cam produces more horsepowere in the upper rpm range. This is true with the Moto Guzzi engine. With a larger valve lash, the duration of the cam is changed. With the larger lash, the duration is lowered. The opening and closing of the cam is slighlty changed (with the extra clearence) and the opening is slowed by the clearence. Thus, the bike feels like it has a less duration cam and will then have less overlap and a stronger idle. I and a few others out there have noticed the difference in idle after opening up the valve lash.

 

Mike

[Guest IanJ]

Definitely true -- I got my 02 Le Mans back from the warranty engine swap, and it basically wouldn't idle at operating temperature. It turned out that the valves were adjusted so tight I couldn't get a feeler gauge of any size in there (probably because the shop didn't have a chance to actually run the engine and retorque everything). Adjusting to .008 and .010 solved that, brought the idle up from ~500 RPM (where it would quickly die) to ~1100, right where it should be.

 

As far as balancing, like Mike said, you can get mercury sticks, or a TwinMax, or you can build a water manometer for less than $10:

 

How to build a water manometer

 

You can also use oil or transmission fluid in that manometer if you want more damping in the movement of the balance fluid. Water manometer is a good choice if you're not sure you want to drop the cash on a more "professional" setup. I have used a water manometer as described for years, and find it to be quite sufficient for my occasional throttle balance needs.