Kick-back

Hi chaps,
There is undoubtedly a very simple answer from the more knowledgeable
amongst you, but here's the question:
As some here will know, I recently spent several arms and legs on a Norman
SC - and very nice it is too!
When I received it, it obviously had not been run for a long time and needed
all manner of cleaning and tweaking to get it running.
One thing I thought odd was that initially it was kicking back a lot. I had
decided that the stupid cranking handle was going to do me an injury before
the thing ran so I attached my high torque drill to the flywheel nut to give
it a good spin. The thing was kicking back so hard that on the odd occasion
when it actually fired it stopped the drill dead (or rather it tried to turn
my arms into something resembling a twisted rope). The obvious thing, I
thought, was ignition timing. I checked and found that it was spot on. I
decided that, in the interests of science and a broken forearm, I would
retard the ignition to the point where it would fire just after TDC, after
all, the thing couldn't possibly kick back in this condition - could it? It
bl***dy well did! In fact it made no difference.
Anyway, after working my way through all the normal things (points, ignition
timing, valve timing, valve clearances, fuel supply, carb. jets etc, etc),
it now runs superbly and I've now returned the timing to the correct setting
(it's still a bu*
**r to start using the wholly inadequate cranking device
though)
So, the question: how can an engine, retarded to the point where it is
firing after TDC kick back? I guess that when its cranking over and not
firing properly there's all sorts of undesirable conditions going on in the
fuel department but that doesn't seem to account for the kick back.
Reply to
mark.howard10
Loading thread data ...
Mark, SC's and the Alco Featherweight engines are notorious for this - the problem lies in a lack of inertia in the engine itself, hence no great urge to keep rotating in the correct direction. Your SC is also virtually a new engine IIRC, so may improve when run in. Normans supplied, as an alternative to the handle, a rope-starting pulley that bolts on in a similar fashion - it may be worth considering converting to this set up before you damage a wrist or finger. SC's also get a lean mixture for starting due to the long induction tube and no choke, so this probably doesn't help matters.
Regards
Dan
Reply to
Dan Howden
Sounds very reminiscent to my Witte. Its one of the smallest engines I own, yet ive never known an engine kick back so visciously. Luckily I am able to hold the inlet valve open to get speed up before starting, so it doesnt prove to be such a problem for my arms.
Mike M
miley snipped-for-privacy@hotmail.com
Reply to
miley_bob
"Dan Howden" wrote
My T600, which Kim now has, surprised me several times and felt quite capable of delivering a 'chauffeur's fracture'. Wico A mag with impulse so plenty of retard on starting, but it is another engine with a very long, cold, induction tract.
Reply to
Nick H
Dan, ISTR a certain Wade dragsaw engine which I saw at a big rally back in June. Compared to this the SC or Alco is a pussycat :-)
Regards
Philip T-E
Reply to
philipte
I don't know this particular engine but here's my 2P worth.
The obvious answer is that it can't kick back but it is. So when the first obvious doesn't apply, look for other obviouses.
To kick back, something must be igniting the mixture. Is there an auto advance? Is the compression enough to produce Dieseling? Did you check for TDC when timing the engine or use the timing marks? These can be wrong. I know little of mag ignition but on coil ignition, there is a small spark when the points make as well as the better one when they break. I've certainly known engines run when timed on the make rather than the break. Could this be the case here? Were the points clean? If there was some dirt on the faces. some vibration or movement could cause a slight break in the contacts that causes a spark.
Finally, which way was the engine facing when it kicked back? If the crankshaft was aligned North/South, it's rotations would be cutting the earths magnetic field. This combines with the Corriolis effect of the rotaing flywheel and magneto to generate a positive self compounding EMF. Under certain circumstances, this can be sufficient to provide a false trigger of the mag. The effect varies with latitude and which hemishere you are in. There was also some concern in the early days of motoring regarding the interference effect of passing cars and the direction of engine rotation. Conclusions were never finalised but as a result, some countries now drive on the wrong side of the road. At least with a stationary engine this is not a consideration.
John
Reply to
John
"John" wrote (snip):-
What are you on and where can I get some ;-)
Reply to
Nick H
Nick,
Share it with me :-))
Martin P
Reply to
campingstoveman
I'm sure you guys are right about the long induction tube thing and cold starting, it's a lot better once warmed up. And, Dan you remember correctly, the engine is still like brand new, very sweet, very nice.
I've only started my T600 once, just to try it out when I bought it. It's now waiting for it's shiny new fuel tank and governor linkage to be made and fitted before I run it again. I'm not now looking forward to it! I thought it was a bit of a beast before you warned me that the bu***r could well kick back!
A tight 6HP engine with an awkward cranking handle (too short to get it over compression and too long to spin the engine properly) and an attitude problem to boot doesn't make for an enjoyable experience in my book!
Being a wimp, I might try my high torque drill system with a torque tube stuck in the ground next time I give it a go (I'm allergic to physical pain, you see)!
I once had a well tweaked Triumph Bonneville chuck me several feet in the air and deposit me in a crumpled heap through kicking back, and I can tell you now, I didn't like it!
Maybe I'm in the wrong game, perhaps I should take up origami or something similarly innocuous.
Reply to
mark.howard10
I checked the calendar - but no, it can't be April yet.
I love the deadpan tone & I am now leaning it rote fashion in order to deliver it to an unsuspecting audience ......
Regards,
Kim Siddorn
Time flies like an arrow Fruit flies like a banana
Reply to
Kim Siddorn
wrote (snip):-
What, and risk a paper cut ;-)
Reply to
Nick H
The Wade needs another dose of looking-at on the mag trip - the kicking on that is purely timing related. It can't be too bad - I've still got all my fingers... ;-)
Regards Dan
Reply to
Dan Howden

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.