Valve adjustment

[Guest jlburgess]

This seems to explain why my bike started idling like crap after the first valve adjustment. Per Raceco:

 

Tappet clearances for two and four valve engines

 

Two valve engines

 

Tappet clearances for the Guzzi big twins should be set to 0.20mm for the inlet and 0.25mm for the exhaust. This also applies to the "modern" Guzzis such as the Sport 1100, Cali 1100i and V11. The factory settings for these bikes are 0.10mm and 0.15mm respectively, but this is to try and reduce engine noise to meet US emissions regulations. With tappets set this tight the engines have trouble ticking over and running cleanly at low revs.

 

Four valve engines

 

These should be set as per the factory settings of 0.10mm for the inlet and 0.15mm for the exhaust. For highly stressed engines in racing applications with borderline cooling to the heads wider settings may be necessary. Please call Raceco on 01728 602101 for more details on this.

[Guest jimjib]

I wonder if this could contribute to the pinging problem.

[Guest IanJ]

At a guess, it wouldn't. Valves that are adjusted too tight will be open for too long, resulting in a loss of compression, and accelerated valve wear. Pinging is also called detonation, which is usually caused by greater than normal compression, combustion chamber temperature, or both. Incorrect spark timing can also cause pinging, by igniting the fuel/air mixture too early.

 

I just found this link, which describes engine detonation pretty well. You'll have to ignore the parts that are more applicable to cars than motorcycles.

[Guest Scura Owner]

Playing Devil's advacate here, but why is a third party's recommendations considered "right" and the manufacturer's "wrong"?

[dlaing]

One theory is based that Guzzi sets it to meet noise emissions while the Raceco, the company that can build 140HP guzzis knows what is best and does not have to answer to petty legal bull like noise emissions.

But I kinda side with the devil on this and say that raceco's .20/.25mm setting is toooo much. (atleast for stock street bikes) Yes, if you use raceco's numbers the valves will run cooler and you will get more compression at lower rpms, but you may be losing top end power by reducing valve overlap and duration. Also you may accelerate wear of the valve train. I say go with .15/.20mm.

Is this based on science? No, just the common sense of making a compromise. And I could be wrong.

What does Guzziollogy say?

[Janusz]

My lifelong rule that whenever in doubt follow manufacturers recommendation did not disappoint me as yet. And I do not think ever will.

 

Just common sense I guess..

 

Ahh, Guzziology. Even the latest edition does not specifically refer to V11Sport/LeMans valve clearances. What it does it though it talks about different specs for US models of Cali 1100S/EV/Jackal/Bassa and Sport 1100, where there was .002/.004 (.o5/.1 mm) or even .002" both valves as opposed to world specs .10/.15 mm for all models. For these bikes author recommends following the world specs.

 

I suspect some less careful reader did interpret that there is a different specs in case of our (V11S, Scura or LeMans) bikes which it is not. I have yet to see other factory specs then .10/.15 mm.

 

So until I do I will set my valves as such and foggetboutit.

[Guest jlburgess]

I just tried the .20/.25 mm setting and the idling problem is gone. However, the pushrods are pretty loud when cold. I think I'll try dlaing's idea of .15/.20 and compromise.

[Frank]

When I had problems with my V11 LeMans, one of the things the MG mechanic did was change the valve settings to .006 inches inlet and .008 inches exhaust. I don't notice any change in engine noise.

 

Frank