|
|
| Author |
Message |
| Flatbadger |
This post is not being displayed .
|
Flatbadger
World Chat Champion
Joined: 07 Apr 2012
Karma :  
|
|
| Back to top |
  |
You must be logged in to rate posts |
|
 |
| Andy_Pagin |
This post is not being displayed .
|
Andy_Pagin
World Chat Champion
Joined: 08 Nov 2010
Karma : 
|
|
| Back to top |
 |
You must be logged in to rate posts |
|
|
| Flatbadger |
This post is not being displayed .
|
Flatbadger
World Chat Champion
Joined: 07 Apr 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Alpha-9 |
This post is not being displayed .
|
Alpha-9
Super Spammer
Joined: 19 Jan 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma : 
|
 Posted: 17:40 - 03 Oct 2012  Post subject: |
 |
|
Phisics?
Newtons laws of motion mate. Forces create acceleration. A body subject to a force is accelerated, unless balenced by an equal and opposing force.
Stalling is when the load force put on the engine is greater than the motive force the engine is delivering.
Unable to shift anything, crank goes round, bang goes off, piston comes down, tension is put on all the parts of the transmission..... but cant 'quite' make anything shift.... and force spent, winding up cogs and chains and things, comes to a complete halt.
CONKING OUT Engine is ticking over on a wiff of throttle burning JUST enough fuel to make enough force to ONLY over-come the internal resistance of all its own bearings and oil and 'stuff'.
Bang happens pushing piston down, charging up the fly wheel with energy to keep it spinning through the unpowered strokes, and being wasted, elsewhere.....
Kinetic energy is mass x speed, so kinetic energy in the crank is proportional to how fast its spinning.
At some speed, kinetic energy it gets on each bang is insufficient to keep it spinning through unpowered strokes.... and the bike will 'conk' piston coming down on power stroke, probably making it up again on the exhaust, struggling on the drag imposed by the suction of the induction stroke, then completely defeated by the force of the compression stroke.
At low revs and small throttle opening, the idle is likely to be a bit 'lumpy', tiny changes in air intake temperature or density having much bigger effect on the size of bang in the pot. BUT a healthy idle speed setting, will keep the idle high enough that you dont get a 'conk-out'. But as the idle speed drops beneath that, it only takes a few 'weak' pops in a row to depleat the flywheeel energy and the engine stutters, slows and conks...
In other words.... you aren't STALLING... because the engine is dying without you applying any load to it.... you are 'conking out', symptom of a low idle poor spark, dirty plug, incorrect tappet adjustment, dirty air-filter or other service item!
GO SERVICE YOUR BIKE
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
| Back to top |
 |
You must be logged in to rate posts |
|
|
| weasley |
This post is not being displayed .
|
weasley
World Chat Champion
Joined: 16 Oct 2010
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Flatbadger |
This post is not being displayed .
|
Flatbadger
World Chat Champion
Joined: 07 Apr 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Lord Percy |
This post is not being displayed .
|
Lord Percy
World Chat Champion
Joined: 03 Aug 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma :
|
Posted: 20:16 - 03 Oct 2012  Post subject: |
|
|
| sa1988 wrote: | | Teflon-Mike wrote: | Phisics?
Kinetic energy is mass x speed,
GO SERVICE YOUR BIKE |
Sorry. This has to be done because I learned it only last week, and I'm feeling incredibly smug.
Kinetic energy = 1/2 mass x velocity x velocity
(Ek= 1/2mv^2)
Your formula, mass x speed, is actually representative of momentum,
momentum = mass x velocity,
(p=mv)
which is probably also applicable to engines in some way, but I just felt like being snooty and pointing out that your specific formula for energy was wrong 
 |
I know.
Chap doesn't know the difference between Stalling or conking out, and is blissfully aware what a tappet is, let alone they need adjusting....... even the simplified 'piston go up get bang' explanation was a little heavy going for him....... so I thought that a few points of higher differential calculus would be rather err..... irrelevent!
So... my H300 Accolite..... over to you to explain tappets.........
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Lord Percy |
This post is not being displayed .
|
Lord Percy
World Chat Champion
Joined: 03 Aug 2012
Karma :
|
| Posted: 20:26 - 03 Oct 2012 Post subject: |
|
|
Haha! I think I learned about tappets from you! I learned everything from this website alone! Oh and my Haynes manual.
Here's where I monumentally fuck up with my explanation...
The tappets are the valves in the top end of the engine. I guess they're called tappets because they tap against the valves as they open or close. I have no idea though.
Anyway, checking the valve clearances is best done with a Haynes manual as it will undoubtedly have all the info there, along with instructions on how to do all the other various service checks.
Differential calculus is only necessary if you want to find the rate of change of something at a given point, where the rate of change ins't constant, usually a force or measurement, over time, amongst other things. I differentiated something today actually, for the sheer hell of it, to see if I could apply my knowledge to a given situation without being asked to. I felt like a genius. |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Flatbadger |
This post is not being displayed .
|
Flatbadger
World Chat Champion
Joined: 07 Apr 2012
Karma :
|
| Posted: 20:47 - 03 Oct 2012 Post subject: |
|
|
Calculus indeed - the only time I brushed with that is when we had to bring something to school beginning with 'c' - I turned up with a calculus book from home at age 5! I can make as much sense of it now.
I've a mate who's done an engineering course and knows his way around engines, I'm sure I can save your fingers and do a bit of research or its total overload!
What snobbery I'm being subject to - from a grease monkey as well! I'm having chicken and chips and intend to enjoy it with salad cream, is that working class enough? My tappets might need adjusting but not as much as your attitude Mr Mike - as Donald Rumseld once said, there are things we know, things we know we don't know, and things we don't know we don't know.. 
What things don't you know that you don't know eh?
____________________
If you can keep your head when all about you
Are losing theirs and blaming it on you,
You're in ISIS |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Lord Percy |
This post is not being displayed .
|
Lord Percy
World Chat Champion
Joined: 03 Aug 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma :
|
Posted: 21:42 - 03 Oct 2012  Post subject: |
|
|
| Flatbadger wrote: | What things don't you know that you don't know eh? |
There's lots of things I don't know. In fact how much I dont know is one of the things that I dont know. What I do know is that the more I learn, the more I know, but the more I do know that I dont know.......
No snobbery, there's ignorance and there's inteligence. Inteligence is recognising your ignorance. And not necesserily being RUDE about it:!:! Geez you look to take offence easy! Your not related to Dilly by any chance? It was comment to Sa explaining I wasn't getting TOO bogged down in accademic pedantry JUST to explain your bike was conking out, not stalling! ANYWAY....
TAPPETS:-
The tappte the thing that adjusts the gap or clerance between a valve (its not the actual valve!) and whatever opens it.
https://i4.photobucket.com/albums/y105/mattay_anderson1/fordlaser/parts/B6-tappet.jpg
This is the more conventional, 'Screw & Lock-Nut' tappet arrangement on a 'Rocker' actuated valve.
This is possibly no longer the most common tappet arrangement; but certainly the one you are most likely to come accross, as it is 'User-Serviceable'.
Pic is actually showing a direct acting rocker, bearing directly on the cam-shaft; as it rotates, lumpy bit (an eccentric, like me, in technical terms) pushes the rocker up.
This is probably the most common arrangement in modern engines, and the cam-shaft is located in teh cylinder head above the combustion chamber, and is known as 'Over-Head-Cam'. Older or less sophisticated engines (CG125 springs to mind) iuse the Over-Head-Valve' arrangement which puts the cam-shaft down some-where close to teh crank-shaft, and there is a 'Push-Rod' between the cam-shaft and the rocker.
There HAS to be some 'clerance' between the valve stem and whatever opens it. this is to allow for any expansion or contraction in the metal fo the variouse whirly bits, so that the cam, at no time holds the valve slightly 'open' stopping the valve sealing.
To 'tight' a tappet clerance, and the valve wont seal properly. Too 'slack' a tappet clerance, and the tappet has to move a long way before the valve starts being moved. This is not good.
Wide tappet clerances mean that the valve doesn't get opened as soon, or as far by the cam, meaning you loose possible power, it effectively changes the cam profile. But also, as the cam rotates it accelerates the tappet on teh opening ramp... wider the tappet clerance, the further the cam will accelerate the tappet before any load resists it, like taking a longer swing with a hammer, rather than little 'taps', and the bigger forces can 'pean' or litterally 'hammer' the end of the tappet,deforming it, and making the gap even bigger!
So, important to keep tappet clerances in check. Good for engine power, good for throttle response, good for ecconomy; good for engine life.
And screw & lock-nut arramgement, its PRETTY simple, we could ALMOST even trust Smiler to do it.
You need to remove the rocker cover; usually a couple of bolts, probably 10mm AF spanner on most little bikes.
Then you need a spanner, probably an 8 or 10mm AF to undo the tappet lock nut and allow the tappet to be screwed in and out of the roicker to change the gap between rocker and valve.
You may need a special 'square' spanner, or improvise with a GOOD flat beak adjustable.... NOT mole-grips or pliers! If the tappet has a square head. Some though have conventional flat screw slots, or even allen key slots.
And a set of GOOD feeler guages. These are little blades of metal of known thickness, that you can put between the tappet and valve stem and feel for any movement. Get some, the gaps bigger. Cant get the blade 'in' gaps too tight... pretty simple stuff.
So; you get the Haynes manual; find out what the tappet clerances ought to be; and find the right size blade
You then follow the instructions to rotate the engine through the cycle, to get teh cam-shaft, what they call 'on the rock' which is normally the piston Top Dead Centre on teh combustion stroke, when BOTH inlet and exhaust valves OUGHT to be fully closed, and the tappet gaps at their widest.
Then you unwind the tappet,m insert feeler guage into gap, and wind teh tappet back in until it 'just' nips the blade. Give the rocker a wiggle make sure it's on the cam, and the blades 'just' nipped and not holding the valve open or slopping around in the gap....
Hold tappet with apropriate tool, wind lock nut down against rocker and nip with spaner to hold tappet in place.
Repeat for all valves, winding engine round cycles in necessary, then one more cycle to be sure and without undoing anything, CHECK the gaps and make sure you got them right and nothing has slipped.
When happy..... replace rocker cover.... put tools away, Job done.
On a 125 single like a CG125 or something ought take less than ten minutes.
For illustration, though, done HERE on a CB125-Twin. (if you like it, give Snowie Khama SHE wrote it, not me!)
Accademic interest:-
https://t1.gstatic.com/images?q=tbn:ANd9GcR8cB8-XbG9kEawpyrBKMtlrazJ8QXnVXKw-dBAHF6b5_1q8vp-a9ksfaCaNA
This is a Bucket and Shim 'Tappet'. Its an Over-Head-Cam engine with DIRECT acting cam, the bucket over the top of the valve stem is the actual 'cam-follower' pressed directly by the lobe of the cam-shaft.
Still needs a tappet clerance, SO the gap between teh bucket and the cam is 'set' by putting a thin sliber of metal, ground to a known thickness under the bucket, on top of the valve stem. Neat, and simple hugh?
Arrangement means that there is basically NOTHING unnecessary between the cam and the valve, which means that the valve 'train' is very light. This means that thecam-profile can be very agressive and a lot hotter and the engine can run to much higher rpm, and make more power. So its a common arrangement on higher performance engines.
Its ALSO pretty robust, and doesn't need THAT much maintenence. So few parts theres little to wear out, and they can go many miles without needing attension..... but utter bastard to do when they do!
You have to measure each gap before you take the cam-shaft out to get at the tappets, remove each bucket, marking which valve it came from.
Then, having measured the gaps, you need to measure the shims, and work out what the gap would be without it..... THEN what size shim you need to fit to bring the gap back into service spec....
Little bit of muggering around you may be able to get a couple of valves into spec using shiums removed from other valves... but other wise, you then need to go order shims of teh correct thickness to set each valve...... wait a week for them to arrive.... put them in teh respective buckets, HOPING you have remembered where everything belongs.... THEN you can re-fit the cam, and check them, and wo-behold you have got ONE wrong, and have to do it ALL again!
This is not generally considered 'User-Serviceable' and normally left to professional mechanics and 'experienced' ameteurs to do. Its NOT a nice job, or 'cheap'.
Last one? automatic or Hydraulic Tappet.
https://4.bp.blogspot.com/_t3BkJYs_Pvc/RpdM7YWp2uI/AAAAAAAAAMc/8Mw4kJfts_U/s320/Hydraulic+Lifter+.jpg
Best I can do for this one; they sound and LOOK complicated, but actually, they aren't!
Small telescopic arrangement, with a spring in the middle to keep the two ends apart, fills with engine oil through a hole in the side, and sits between the cam and valve some-where in the valve train.
During the 'On the Rock' period, the spring between the two parts pushed them apart, taking up valve clerance, essentially to zero, BUT the spring is deliberately a LOT softer than the valve spring so it will never open the valve, and oil is sucked into the cylinder.
When the cam comes round and threatens to swuash the tappet, instead of opening the valve..... the oil resists being forced out the hole that fast, and 'locks' the tappet (there is sometimes a self compensating valve as well, so its not just viscouse resistance holding the tappet open, but the resistance closes a valve 'locking' the tappet until pressure is released)... so the valve gets pushed upen.
These are WONDERFUL... completely service free, you dont have to worry about them almost NEVER.... unfortunately very few bike engines use them, but ...... mine does 
But they aren't so great for high performance engines, its a heavy arangement at they dont like wild cam profiles, and you HAVE to change the oil frequently or they gum up and stop working.
So, there you have it, the three more common types of 'tappet'.... the bit that controls the clerance between valve and the valve 'gear' in an engine.
AND how the tappet clerance is commonly adjusted.
HINT: On screw and lock-nut tappet engines; books usually reccomend tappet adjustment every other oil change, or so, typically every 2ooo miles or so!
This DOES need doing often; if you never done it;l do so, its probably due, and you are likely to be AMAZED at how much more powerful it feels and how much more quietly it runs.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Flatbadger |
This post is not being displayed .
|
Flatbadger
World Chat Champion
Joined: 07 Apr 2012
Karma :
|
| Posted: 23:00 - 03 Oct 2012 Post subject: |
|
|
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma :
|
| Posted: 23:45 - 03 Oct 2012 Post subject: |
|
|
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| ajbsmirnoff |
This post is not being displayed .
|
ajbsmirnoff
World Chat Champion
Joined: 09 Dec 2009
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| cimbian |
This post is not being displayed .
|
cimbian
World Chat Champion
Joined: 27 Sep 2012
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Matt B |
This post is not being displayed .
|
Matt B
World Chat Champion
Joined: 01 May 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Alpha-9 |
This post is not being displayed .
|
Alpha-9
Super Spammer
Joined: 19 Jan 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Matt B |
This post is not being displayed .
|
Matt B
World Chat Champion
Joined: 01 May 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Codemonkey |
This post is not being displayed .
|
Codemonkey
Crazy Courier
Joined: 18 Oct 2009
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| cimbian |
This post is not being displayed .
|
cimbian
World Chat Champion
Joined: 27 Sep 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Alpha-9 |
This post is not being displayed .
|
Alpha-9
Super Spammer
Joined: 19 Jan 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
 |
Old Thread Alert!
The last post was made 13 years, 360 days ago. Instead of replying here, would creating a new thread be more useful? |
 |
|
|
Help & FAQs
Search BCF
Members
Groups
Events Calendar
rating
rating