Mk 2 vs Mk 5 le mans ?

Hi,advice appreciated ?
I am making a ‘special’ based on a tonti frame from a mk 2 le mans and up until now I had intended to use a round barrel mk 2 le mans engine.
however I have been offered a good condt mk5 le mans engine and I am wondering just what the differences are ?
ok the square barrels jar a bit when you’ve been used to looking at the round older type.
but are there technical differences and horse power differences that would make the mk5 choice better in some way ? is it a more powerful engine ? is it more reliable ?
any advice or experience with the mk5 le mans engine would be appreciated.

You can use round rocker covers on the later square fin heads with an intermediate plate and a square gasket below and round one above.
The Mk V has a larger capacity engine, bigger valves, higher lift B10 camshaft and high domed pistons to achieve better compression in the larger bored combustion chambers. Plus of course 40mm carbs.

very similar to what I am doing, though mine has a le mans 2 engine, 950cc though,

the mk5 engine will be more powerful, but no more or less reliable,

I would be tempted to use the mk5 engine with the round barrel covers, and adjust the barrels to soften the square bits, if I had access to one,

not that I need the extra performance!

Found this: Google books search

Interesting to know I can use round barrel rocker covers !
That would look much better thanks !
I think from other research I’ve done that the mk5 engine
Has an up rated oil pump compared to earlier models .

Mk 5 the last evolution before emissions etc killed it…superb thing but lumpier than the 850 s…if its the right money you wont be dissapointed with the performance…I have one done by Raceco…out to 1150…awesome performance but still a well mannered roadbike…this has old v7 rocker covers fitted using Gutsibits adapter plates…
I speak from experience…we have a Mk1…2 Mk2s, a Mk4 and a Mk5/1000s hybrid…

I have a 950 G5 which has had a bit of work on , Cams - Heads - Saches Ign , carbs + light flywheel , it picks up really quickly and is really quite smooth low down , smoother than my T3 , so i reckon the flywheel makes a fair bit of difference to how it will feel , i rode a 1000 a fair while ago when looking to get back into Guzzis and its lumpiness put me off .

My G5 has a down side at the moment tho , its a bit juddery on the take up with the clutch , not sure if this is down to a really light flywheel or a clutch fault , otherwise all tickety boo .

This is just my findings with my two bikes , i’m no expert , especially on Guzzis , but i like em .

From Ian Falloon’s book Sport and Moto Guzzi Le Mans bibleChris950s2014-09-29 14:43:29

That’ll be the centre boss Chilly…

Just for your info the Finebau Forge Head Protectors for square barrel motors (as mentioned in Gambalunga last year) have now been modified to enable the fitment of round barrel rocker covers.Cheers

Good one Ray ! X

I’m ignorant of the technical differences, but think that you are right to be concerned about the loss of round fins purely from an aethestic stance.

Seriously though, round head with adapters, and grind the corners off just a little, and you’d have something that might be very very nice.


I have seen a article somewhere about actually having the later square barrels machined to look like the rounds

Thanks - whats it mean

The splined clutch centre on the input shaft of the gearbox…my Mk 1 clutch was orrible…I managed but Guy hated it…we had it down twice b 4 replacing that with a new part…voila ! Cured…

Thanks Kate , was it the splines that caused it , thought mine were ok when i rebuilt it ?

How long ago was that? But yes can have like notches worn into it, what happens then is the friction plates ‘drop’ into the notches in the driven direction, causing the them to ‘grab’. Think that’s what Kate means. I had it much worse on the original boss, bike would creep forward albeit with clutch lever fully pulled in, can’t push it backwards in gear and lever fully pulled in, even if engine not running, although could push it forwards; impossible to get in neutral if engine running, ditto.

Ohhhh ! That sounds interesting :slight_smile: any ideas where to find out about this ?

Not long , did it more or less on initial runouts from rebuild .

Maybe i didn’t look at it carefully enough , i’ll have look in the winter shutdown

Thanks for reply .