750 Breva Engine noise |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8731 |
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Operating the clutch pushes the clutch pushrod forward and hence the pressure plate into the flywheel and in turn tries to push the crank forward. Noisy front bearing? |
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"Chicken nuggets don't dance on a Tuesday."
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rapheal
Senior Member Joined: 13 Nov 2014 Location: west country Status: Offline Points: 573 |
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might be worth checking that the engine mounting bolts are tight, that can exaggerate any noises
my bike thuds a bit under load, but its better when you rev the nuts of it an Italian taught me that this is a thing worth knowing it makes it go faster and it makes the dials whizz around which looks pretty
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NevilleG
Falcone Joined: 07 Nov 2018 Location: Nairn Scotland Status: Offline Points: 72 |
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Which bearing are you referring to Mike ? Nev. |
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V7II Stone
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Chris950s
Senior Member Joined: 03 Nov 2018 Location: Essex Status: Offline Points: 373 |
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It sounds like Mike is suggesting the front main bearing but I would be surprised if it is that on such a new bike. On the older bikes this is a plain bearing which any pressure from the clutch on the crankshaft would have little effect. I am not sure what type the main bearings are on the Breva but would be surprised if it is that. Have you worked out where the noise is coming from?
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Chris and Karen - Essex
2011 Stelvio NTX, 1974 950S (750S replica nearly rebuilt!), 1966 Triumph T100SS 58 years young this year! |
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5572 |
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It could be worthwhile to check the oil pressure,at a dealers If you don't have the gear to do it at home.Any excess radial clearance between the front main bearing and the crank would result in a drop in oil pressure.I don't suppose this is the problem but it would be beneficial to know that all is well in that department and eliminate one possibility.
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
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NevilleG
Falcone Joined: 07 Nov 2018 Location: Nairn Scotland Status: Offline Points: 72 |
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If that was the problem Dave, I think it would still make the same noise without pulling the clutch lever in. As Mike said, pulling the clutch pushes the operating rod onto a cup which in turn pushes the spring loaded pressure plate forwards, away from the friction plate. This action puts a load onto the end of the crankshaft, pressing it forward. I can't see how that would, in itself, induce the noise, unless there was a large amount of end float in the crankshaft, sufficient to put the big-end bearings out of alignment with the con-rods. The main bearings are static, so can't be twisted out of line. Is that likely ? If so, why does it only happen when the engine is hot ? Would the fact that the oil has thinned down allow the crankshaft to move a bit further forward ? |
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V7II Stone
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8731 |
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My BMW R80 once had an alternator brush spring jam - I was camping out Ledbury way at the time. Had the charge light coming and going. Went into Ledbury for food supplies during which I discovered if I pulled the clutch lever, light went out, when I let go, light came on. Thought it was weird but in hindsight I figured the crankshaft was moving forward when clutch was pulled, so the stuck brush touched a bit of the slip ring that was less worn, when released it went back again and the brush lost contact. Strange but true. NB: I fixed the brush on the site - had to smooth one side a bit so it could move again. |
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"Chicken nuggets don't dance on a Tuesday."
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NevilleG
Falcone Joined: 07 Nov 2018 Location: Nairn Scotland Status: Offline Points: 72 |
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Thanks Mike. I am itching to get the covers off the alternator and check out the end float, if any, but at the moment I am resting my hands to try an ease a bout of "trigger finger", which is making some of the joints lock up. My plan is get the bike warmed up so that the noise can be reproduced and, with the covers off, see if I can push the end of the crankshaft backwards, which may, or may not, stop it. It may mean taking the alternator stator and rotor off out of the way, but that seems to be fairly straightforward and the engine should still run without them in place. I should also be able to feel any lateral movement and any vibration that's creating the noise being transmitted at the front end of the crankshaft. As you are showing an interest, I would be happy to send you the two video's I took of this same noise on the first Breva I bought, if you send me a Private Message with your email address in it. Nev. |
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V7II Stone
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theoneandonly
Senior Member Joined: 24 Jul 2014 Location: london Status: Offline Points: 661 |
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what grade of oil are you using ? 10/40 ? or 15/50
i have recently seen a B7 run on 10/40 that had done the big end shells .
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http://baldricksworkshop.co.uk/ motorcycle slut, if it has wheels and an engine , i will ride it . |
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NevilleG
Falcone Joined: 07 Nov 2018 Location: Nairn Scotland Status: Offline Points: 72 |
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As you may know, Guzzi recommend 5w-40 for this engine, so using 10w-40 shouldn't have been the cause of big-end failure. Probably some other reason. I use 10w-60 Silkoline in mine. One thing that can cause a bearing failure problem is that these engines only have a capacity of 1.8 litres, so frequent oil changes are absolutely vital. There is a modification to fit a sump extender, which takes it up to about 3 litres. Gutzibits sell them. |
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V7II Stone
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8731 |
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Just a note, theoneandonly is No. 1 guru expert Guzzi mechanic, usually when he says summat, we prick up our ears. NB: not to be confused with theoneandonlymin (different person) HTH |
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"Chicken nuggets don't dance on a Tuesday."
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Chris950s
Senior Member Joined: 03 Nov 2018 Location: Essex Status: Offline Points: 373 |
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It would appear he has a fan club too
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Chris and Karen - Essex
2011 Stelvio NTX, 1974 950S (750S replica nearly rebuilt!), 1966 Triumph T100SS 58 years young this year! |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17637 |
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He would like to think so.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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NevilleG
Falcone Joined: 07 Nov 2018 Location: Nairn Scotland Status: Offline Points: 72 |
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Ah! Sorry, I didn't know that, so my reply was somewhat out of place ! On a brighter note, I couldn't wait any longer to check for any crankshaft end-float, so I took the alternator covers and stator off and found absolutely no movement at all, hot or cold. In fact I was surprised to find the engine very tight to turn over, almost like it was hardly run-in, despite it's 17000 odd miles, so I would be interested to hear if anybody else has noticed this. When once I have put it all back together, I am going to put a torque wrench on the nut and take some readings of just how much effort is needed to move it, as I couldn't decide if it was easier when hot or cold. Obviously I had removed the spark plugs and had the clutch pulled in to remove any load from the gearbox. After taking the front cover off (shearing a badly corroded bolt off in the process !!) I was disappointed to find quite a bit of surface rust on both the stator and rotor. Looking at the parts list, the cover is supposed to be secured by 5 bolts, but mine only had four bolts in the lower four holes and a plastic stud affair in the top hole. The cover had distorted slightly from engine heat, leaving a gap at the top, which had obvious let some water in. This plastic stud looked very original in its design and fit and there was no evidence of a bolt ever having been down the top (threaded) hole, so I'm confused as to whether this was how Guzzi built it, or if some previous owner had done it. Is anybody else's like this ?? Nev. |
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V7II Stone
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NevilleG
Falcone Joined: 07 Nov 2018 Location: Nairn Scotland Status: Offline Points: 72 |
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Further to my previous post, I forgot to mention that, with the engine hot and the noise evident, it was still there when the crankshaft was pushed backwards, so I am now fairly certain that it isn't an end-float issue.
Using the "screwdriver in the ear" listening technique, the noise was very evident as being transmitted from the crankshaft, so still needs more investigation. One thing I haven't checked is if the noise disappears above tick-over revs, if it does, then the tight engine/hot oil/lower oil pressure/no load on the engine combination, might be causing bearing knock ? Dunno ! Nev. |
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V7II Stone
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