Gradual power loss cally stone

[Exmembers]

Easy I think maybe someone has got mm and “thou” mixed up here. as Mike says Tonti 2 valve bikes are .22mm =0.0085 " I too do em at a loose 9 thou, YES they rattle BUT the engine will love you for it.

I would bet if a home mechanic goes for .22mm they will be within the tolerance zone, nice thing about Guzzis is they are very forgiving.

When you effectively have a tolerance zone of .05mm it is pretty easy to get a comfy .22mm guzzibear2013-04-12 07:59:50

[Exmembers]

@guzzibrat

From the Raceco websiteTappet clearances for two and four valve enginesTwo valve enginesTappet 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.

It’s actually worse than that because the figures quoted are for the ‘World’ models not the US specific ones.For a period in the late '90s onwards the US specifications called for valve clearances of 0.05/0.10mm (2/4 thou)!And yes, the specified valve clearances for two valve engines from the Sport 1100 onwards, including the Tonti framed Calis are 0.10/0.15mm (4/6 thou).I use 0.15/0.20mm as a compromise.Back to the OP’s original query - I’m with Mike on this. The balance pipe is there for a reason and running straight through pipes will have an effect on performance. I once tried to set up a Sport1100 injection that had straight through pipes and it was a nightmare and almost impossible to achieve a decent balance at anywhere above idle.Be interesting the hear what the outcome is.

guzzijack2013-04-12 09:37:59

[Exmembers]

I found out on the V11 Le Mans they even added a 2nd balance pipe as per the org Le Mans across the front of the down pipes.

[italianmotor]

Funny, I worked as a lackey in a Guzzi place many moons ago and I was always taught tight 9s…

[QUOTE=Mike H]

Crikey yes 0.1mm is < 3 thou, nearly closed up. It depends which bits expand / contract more than others, but obviously enough clearance ensures valve will be properly shut when it’s supposed to be at all foreseeable operating temperatures. From my MG manual: page 30"If the clearance is too much, there will be noisy valve operation, if too little, the valves do not close fully causing inconveniences such as: Loss of compression; Overheating of engine; Burning of valves.“ A Tonti is 0.22mm (0.0085”), I was told very early on to make it a loose 9 thou (0.009")     [/QUOTE] italianmotor2013-04-12 20:59:37

[guzzibrat]

Oxford Motorcycle Engineers (a blast from the past) used to recomend “tight 9’s” for thye Tonti framed 850/950 motors too.Steve

[Mike_H]

Whatever, mostly ‘9’ just has to do