Well, that's weird
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From: Pip Luscher on 29 Jul 2010 03:04 Guzzis. As I've been assembling the V11 engine I have had to make sure that the flywheel was properly aligned on the crank so that the timing marks are positioned correctly. Now, both my Guzzi flywheels have three timing marks: an arrow; an 'S' and a 'D'. I always thought these were: full ignition advance on one cylinder; left TDC and right TDC respectively. The Guzzi manuals don't actually call these marks TDC marks, however, the Moto Guzzi Twins Restoration book does. Diagrams for the older Guzzis show S & D strobe marks for various amounts of ignition advance, so I guess they must be 90deg apart for the two cylinders. Except... As a final sanity check, I turned the assembled crank so that the S & D marks aligned approximately against where the reference mark would be if the gearbox were fitted. For each mark, I looked down the cylinder bores to check the position of the big end journal. Upon checking the LH cylinder mark I thought "Huh?" and double-checked the marks. And a third time. I've found that the 'S' & 'D' marks o the V11 flywheel are about (at a guess) 155deg apart. It's a 90deg Vee twin engine. Only one mark matched a TDC, and that's the 'D' mark. As all the marks are on the same bit of metal - the flywheel itself - and I took care to put paint blobs on the crank & flywheel before I dismantled them to ensure I assembled them correctly, I'm sore confused. This doesn't actually affect engine operation; there are no sensors that trigger off the flywheel, unlike a Quota's engine, but it is a mystery as to what the marks actually mean. -- -Pip
From: Krusty on 29 Jul 2010 04:07 Pip Luscher wrote: > As a final sanity check, I turned the assembled crank so that the S & > D marks aligned approximately against where the reference mark would > be if the gearbox were fitted. For each mark, I looked down the > cylinder bores to check the position of the big end journal. Upon > checking the LH cylinder mark I thought "Huh?" and double-checked the > marks. And a third time. > > I've found that the 'S' & 'D' marks o the V11 flywheel are about (at a > guess) 155deg apart. It's a 90deg Vee twin engine. Only one mark > matched a TDC, and that's the 'D' mark. Are you sure you're not getting confused between the angle of the cylinders & the angle between the rods? The fact that it's a 90deg V-twin has no bearing on the angle between the timing marks, so I'm not sure why you mention that. 'D' (dextrous) should indeed be TDC for the right cylinder, & 'S' (sinister) TDC for the left. If they don't match the TDCs according to the journals, I'd suggest you need to check again with a clear head. -- Krusty Raptor 1000 MV 750 Senna Tiger 955i Tiger 885 Fantic Hiro 250
From: platypus on 29 Jul 2010 04:11 On Jul 29, 8:04 am, Pip Luscher <plusc...(a)live.invalid.co.uk> wrote: > Guzzis. > > As I've been assembling the V11 engine I have had to make sure that > the flywheel was properly aligned on the crank so that the timing > marks are positioned correctly. > > Now, both my Guzzi flywheels have three timing marks: an arrow; an 'S' > and a 'D'. I always thought these were: full ignition advance on one > cylinder; left TDC and right TDC respectively. The Guzzi manuals don't > actually call these marks TDC marks, however, the Moto Guzzi Twins > Restoration book does. Diagrams for the older Guzzis show S & D strobe > marks for various amounts of ignition advance, so I guess they must be > 90deg apart for the two cylinders. > > Except... > > As a final sanity check, I turned the assembled crank so that the S & > D marks aligned approximately against where the reference mark would > be if the gearbox were fitted. For each mark, I looked down the > cylinder bores to check the position of the big end journal. Upon > checking the LH cylinder mark I thought "Huh?" and double-checked the > marks. And a third time. > > I've found that the 'S' & 'D' marks o the V11 flywheel are about (at a > guess) 155deg apart. It's a 90deg Vee twin engine. Only one mark > matched a TDC, and that's the 'D' mark. > > As all the marks are on the same bit of metal - the flywheel itself - > and I took care to put paint blobs on the crank & flywheel before I > dismantled them to ensure I assembled them correctly, I'm sore > confused. This doesn't actually affect engine operation; there are no > sensors that trigger off the flywheel, unlike a Quota's engine, but it > is a mystery as to what the marks actually mean. I've got a nold T3 HBoL to hand, and it describes the timing marks on the flywheel as S for the LH cylinder and D for the RH cylinder - which makes me think they mean "sinistra" and "destra". Maybe your flywheel is twisted...
From: Pip Luscher on 29 Jul 2010 14:40 On Thu, 29 Jul 2010 08:07:53 +0000 (UTC), "Krusty" <dontwantany(a)nowhere.invalid> wrote: >Pip Luscher wrote: > >> As a final sanity check, I turned the assembled crank so that the S & >> D marks aligned approximately against where the reference mark would >> be if the gearbox were fitted. For each mark, I looked down the >> cylinder bores to check the position of the big end journal. Upon >> checking the LH cylinder mark I thought "Huh?" and double-checked the >> marks. And a third time. >> >> I've found that the 'S' & 'D' marks o the V11 flywheel are about (at a >> guess) 155deg apart. It's a 90deg Vee twin engine. Only one mark >> matched a TDC, and that's the 'D' mark. > >Are you sure you're not getting confused between the angle of the >cylinders & the angle between the rods? Quite sure. As I said in my OP, I was looking at the big end journals, not the rods. In fact, the rods weren't even fitted when I first checked. Also, if I mark the ring gear by the S mark and again by the D mark and look at the flywheel from the end, they are clearly not 90deg apart. As a further check, there are eight evenly-spaced bolts that hold the flywheel assembly together, so 45 degrees between bolts. One mark is close to a bolt, the other is midway between two. >The fact that it's a 90deg >V-twin has no bearing on the angle between the timing marks, so I'm not >sure why you mention that. I'll explain: on older engines with points, the left & right cylinder timing can be checked individually and the engines thus have individual timing marks for each cylinder. These marks must be at 90deg to each other otherwise one cylinder would have different ignition timing to the other. I did also consider that there might be some illusion caused by a desaxe offset, but again, if both cylinders are to have the same timing, the timing marks on the flywheel would be the same. -- -Pip
From: Pip Luscher on 29 Jul 2010 14:43
On Thu, 29 Jul 2010 01:11:41 -0700 (PDT), platypus <monotreme(a)blueyonder.co.uk> wrote: >I've got a nold T3 HBoL to hand, and it describes the timing marks on >the flywheel as S for the LH cylinder and D for the RH cylinder - >which makes me think they mean "sinistra" and "destra". Maybe your >flywheel is twisted... Heh. Or maybe one of the timing marks was mis-stamped, or maybe they aren't both used as TDC marks on the FI motors. This is a possibility because they only have the one common timing system. For the purposes of doing valve clearances, I've painted an extra mark on the flywheel. I also can check against the Quota when I find a tuit. All I need to do is remove the alternator cover and turn the engine by spanner to check the marks on that - it should be pretty obvious. -- -Pip |