pete roper Posted January 8, 2008 Share Posted January 8, 2008 OK, I'll try again and attempt to behave meself this time. This argument is an absurd storm in a tea cup. Everybody will have s different idea of what the correct *feel* should be. As long as the guage isn't flapping about between the bits being measured and you don't have to brace your leg against the cylinder head to yank it out it will be fine. The amount of difference the change in the valve timing is going to make to the way the engine behaves as long as the gaps are set moderstely accurstely id going to be so small as to be virtually undetectable, especially on a horrible old ditchpump like the Guzzi donk. Using a DTI to measure the clearance is the sort of thing I'd expect the very worst sort of Ducati owner would insist on doing You know the type? They buy 25mm M6 bolts and insist they come in a bag with 'Ducati' written on them. the only point for having a clearance is to allow a period of rotation of the cam where the valvetrain isn't under load so that oil can get between *bits*, (And it's not strictly the cam/follower interface that is going to suffer neccessarily.) and that the valve isn't held off the seat and that it isn't so large that the cam has the opportunity to turn past the point where the follower should be lifting, (on the ramps.) and slamming it into a more agressive part of the opening flank of the cam. Why do I say that th actual cam/follower interface isn't neccessarily the part most at risk? Well, firstly I've seen lots of burnt valves but I've never seen a cam lobe or follower destroyed even if the clearance has closed right up and the machine has been ridden for ages in this condition, (Yes! People do this! They ride around on a 500cc air compressor and think it should feel like that!!!!!) and secondly it is the pushrod tips and the bottom of the inside of the tappet wher they sit which is going to take more of a beating as they will be revolving and rubbing together but no oil will be able to ge between them. The cam and follower don't have this issue, the cam rotates in a a molecular fog of oil. Unless you've seen it with your own eyes you have no idea how much oil there is being sprayed around inside a motor! Everything is happening very fast and great streamers of oil, globules and droplets, are bouncing off everywhere. In this the cam is rotating and rotating fast! 30 times a second at 6,000RPM! I'll get coated in enough oil every time it rotates to form an *adequate* wedge betwixt the cam and the follower. It is certainly BETTER that there should be a period where the tappet is un-loaded but it is NOT in my opinion as super-critical as many people imagine. No doubt this will lead to enraged screams of 'Burn the Heretic!' from people who don't actually want to think about what is occuring and don't have a particularly good grasp of how lubrication occurs but follow the logic and you'll see it stands up. Working oneself into a lather over whether a valve clearance is set at 5.5thou or 6 thou is a waste of time, bandwidth and inteligence. Go and have a beer or something useful!!!! FWIW and just to agravate people I'll tell you that all my roundfins, regardless of cam, run a tight 5 and 7 thou when the factory used to specify much bigger clearances, especially on the loops, (8 and 10?) and all my squarefins run a tight 4 and 6. The Racebike uses ChrMo pushrods and they're set at 2 thou inlet and exhaust and it runs a silly cam! OK, now have another pointless fight over that Pete Link to comment Share on other sites More sharing options...
Dan M Posted January 8, 2008 Share Posted January 8, 2008 Working oneself into a lather over whether a valve clearance is set at 5.5thou or 6 thou is a waste of time, bandwidth and inteligence. Go and have a beer or something useful!!!! Pete Come'on Pete, it's not about .005". We all know it makes no difference (well, at least 50 of us anyway) It's about crappy weather, can't ride and nuthin better to do, so might as well break Dave's balls. Sorry about the wasted bandwidth though. And what makes you think nobody's having a beer already? Link to comment Share on other sites More sharing options...
pete roper Posted January 9, 2008 Share Posted January 9, 2008 Kevin, the modern Duc motors, (At least the 2V ones.) are a lot easier. You have to take the shock out to get to the rear head but the closing rockers are now spring loaded and just pull to one side rather than you having to go through the awful embuggerance of the early system. They still shag out their valve guides like a priest with a novice choirboy though! Pete Link to comment Share on other sites More sharing options...
mike wilson Posted January 9, 2008 Share Posted January 9, 2008 It just means that when used correctly, feeler guages enable the trained user [eg: everyone who just read & understood my instructions above] to generally achieve a clearance within plus or minus .0005" of the selected guage. If you had a guage set w/ a .0005" leaf, then I expect that would enable the average user to achieve plus or minus .00025" accuracy, but there's a limit to how accurate & small you can take this: fortunately, we don't need to go to those extremes on our "old ditch pumps." I'm not sure that's entirely correct - because in this application, as has been pointed out above, we are not dealing with prefectly flat and parallel surfaces. Therefore the absolute accuracy of what we are measuring by inserting flat pieces of metal will always be in question. What I think is true is that you can acheive _consistent_ results from measurement to measurement. Link to comment Share on other sites More sharing options...
docc Posted January 9, 2008 Share Posted January 9, 2008 And so ,Pete, what would be the advantages of 0.004/0.006 versus the widely held view that 0.006/0.008 is altogether 'better?' Link to comment Share on other sites More sharing options...
Dan M Posted January 9, 2008 Share Posted January 9, 2008 The rest of you are off by an order of magnitude with reference to half a thousandth of an inch. It should be .0005". Good thing you aren't machinists. Who? When? Where? Regardless of all of the other blather I think everyone here knows .005" is 5 thousandths of an inch and .0005" is 5 ten thousandths of an inch. Link to comment Share on other sites More sharing options...
pete roper Posted January 9, 2008 Share Posted January 9, 2008 And so ,Pete, what would be the advantages of 0.004/0.006 versus the widely held view that 0.006/0.008 is altogether 'better?' The smaller the clearance you can run the less it will rattle and you're less likely to be getting the follower lifting on the flank rather than the ramp. To be honest though it probably won't make a ha'porth of difference. The biggest advantage of closing up the clearances a bit comes with the roundfins which all tend to rattle like a sack of chisels with the stock clearances. Throw in a bit of rocker spindle and bush wear and a bit of tappet bore wear, (Which for some reason never seems detectable by feel but going to oversize followers helps!?!) and these will make a deafening racket! Newer squarefins don't seem so prone to being noisy. I assume because they are manufactured to slightly less sloppy tollerances. pete Link to comment Share on other sites More sharing options...
dlaing Posted January 9, 2008 Share Posted January 9, 2008 Ratchet (and other than actually being a professional mechanic; myself) and the 50 others are satisfied at within .001 as Ratch said +/-. That's +/-. Did he say +/-? I'd interpret that as no more than .001 greater or .001 less than spec. That's a .002 spread my friend. No my Guzzi Brother, the argument started over my stating: One man's 6 thou could be another man's 7 thou, so try looser than what you have it set to now. Skeeve and Ratchet challenged the statement. For the statement not to be true, both man's (or woman's) 6 thou would have to .0060" ± .0005". I am simply saying that if you took the more accurate half of forum members that do there own tappet adjustments, that not all of them would be in that range, while Ratchet and Skeeve are saying the contrary. But it appears that Kevin is spot on when he somewhat humorously says, OK professor, so our variable in this algebraic equation would be the undefined (by you) "within .001"? I'm no military genius or global warming expert, but I do know that algebraic equations must have a variable by definition. The rest of you are off by an order of magnitude with reference to half a thousandth of an inch. It should be .0005". Good thing you aren't machinists. This was a reply to Ratchet saying, Um, Dave. This (again) is yet another example of exactly why the obvious needs to be repeated so very very often. . . [sigh] . . . <_> You've made the same critical mistake as GuzziMoto. It's a margin of error of 100%. Please review post #24. Maybe a very very simple algebraic expression will help. (within .001") x 2 = (+/- .001") or (within .001") = 1/2 x (+/- .001") Where he seems to be backing out of the claimed accuracy necessary to make my original statement untrue. A forgivable mistake...a mea culpa from Ratchet and Skeeve is anticipated. So, Kevin's statement was spot on! Link to comment Share on other sites More sharing options...
Guest ratchethack Posted January 9, 2008 Share Posted January 9, 2008 Skeeve and Ratchet challenged the statement.For the statement not to be true, both man's (or woman's) 6 thou would have to .0060" ± .0005". I am simply saying that if you took the more accurate half of forum members that do there own tappet adjustments, that not all of them would be in that range, while Ratchet and Skeeve are saying the contrary. But it appears that Kevin is spot on when he somewhat humorously says, This was a reply to Ratchet saying, Where he seems to be backing out of the claimed accuracy necessary to make my original statement untrue. A forgivable mistake...a mea culpa from Ratchet and Skeeve is anticipated. So, Kevin's statement was spot on! OMG, NO! Somehow I seem to be "backing out of the claimed accuracy necessary to make [Dave's] original statement untrue." Err. . . yes, indeed. But yes, I'm afraid it IS true. . . [sigh] . . . We all knew it was only a matter of time. . . Coherent, rational thinking and Earth logic have once again departed another thread -- along with Earth gravity, air, atmospheric pressure, and the nice, globally warm and comforting, yet ever-so-restrictive natural confines of the blue planet, on yet another wild trajectory into the "freedom" of the icy, trackess void of deep space. . . Well I reckon there's little surprise after all. . . It'd been getting awfully dark and purply in here (again) for quite awhile lately . . . The menacingly alien, dark and foreboding Purple Planet, with its seven-dimension, reverse-polarity gravity wells and toxic nitrous oxide atmosphere, from high orbit approach Link to comment Share on other sites More sharing options...
dlaing Posted January 9, 2008 Share Posted January 9, 2008 Hm. Please note that what you've said is NOT what I've said. You're off by 100%. Within .001" is exactly half the tolerance of +/- .001". A tolerance of +/- .001" provides exactly a .002" range. The Guzzi manual doesn't spec a range for valve setting tolerances (nor does any manual I've ever used, and that'd be a moderately sized stack), but again, if you can't match your valve lash from cylinder to cylinder within +/- .001", IMHO you shouldn't be attempting it yourself. And I reckon this ain't just me. Maybe these ±.001" measurements are the infamous "U.S. Spec"?!? You are correct that the Guzzi Manual does not spec a range. In fact they don't spec in inches! They spec in glorious millimeters down to two digits before the decimal point, although they use a comma <_>Regardless of it being a comma, without a range being specified, following a machinist accuracy standard I think it could be assumed that accuracy should be to within ±.005mm!!!! But I am not a machinist and it really is not that necessary to be that accurate. But I do strive to get the left and right cylinder dialed in to that level of accuracy against my own measurement, not against the golden dial gauge. I am pretty sure that if you verified my measurements against a dial gauge, I can get the left and right to within .0005" of one another. This would mean my left intake could be set to .0061 and my right intake to .0066, so if you round it out, my left is set to 6 thou and right to 7 thou(out of US spec by .0001"), but I am still accurate to within .0005" and it is good enough. If you translate that into metric, the target is .15mm, and my claimed accuracy of .0005" is about 0.013mm so the left intake I might get lucky and set to .151mm and the right to .012mm more, (since I am so unbelievably accurate) and end up with the right set to .163mm. If following the manual to the machinist's rule, I believe I am out of spec, but I am not THAT anal, so I leave it tightened down, give the same treatment to the exhaust valves, but targeting .20mm, bolt it all up, and then I am happy!!!! I am pretty darn sure I am accurate to within .012mm of my own measurement, but no, I have never verified against a dial gauge. Link to comment Share on other sites More sharing options...
Dan M Posted January 9, 2008 Share Posted January 9, 2008 but I am not THAT anal, Um, this opens another whole debate. Measuring the intensity of analness here will require not only feeler gauges and dial indicators but quite likely trucking scales and teams of psychologists. Link to comment Share on other sites More sharing options...
pete roper Posted January 9, 2008 Share Posted January 9, 2008 Jesus H Christ on a bicycle! This one is going to run and run! It might even eclipse the f@cking global warming thread!!!! I was considering finding and linking a nasty pic of an arsehole from somewhere on the net as an indicator of how anal you'd have to be to worry about this stuff but decided instead to try and hijack the thread by asking that wonderful old question........................... Just how many angels can you fit on the head of a pin? Pete Link to comment Share on other sites More sharing options...
GuzziMoto Posted January 9, 2008 Share Posted January 9, 2008 This is so F'd up it's fun. Ilove that expression and wonder where it came from. Wasn't there a point to the thread? Isn't somebodies Guzzi in need of help? Link to comment Share on other sites More sharing options...
mike wilson Posted January 10, 2008 Share Posted January 10, 2008 Are those the goats your new PM promised you? Link to comment Share on other sites More sharing options...
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