If you like our site, please consider joining our club!
By joining you will help ensure that we can continue to provide this service
JOIN HERE!

A question about spark plugs

User avatar
vechorik1373
Posts: 260
Joined: Fri Oct 27, 2006 3:00 am
Been thanked: 15 times

Re: A question about spark plugs

Post by vechorik1373 »

I told all my customers, and anyone else that will listen, the following:

One should avoid heavily tickling the carbs. If you must tickle, a quick "blip" on each one should suffice. If you hold the ticklers down until gas pours out, you can get the plug wet with gas. My experience has been, and I have told owners this, (always carry a spare set of new plugs with you) You can pull them, dry them, put them on wires, lay them on the head, shove down the key, and see the spark, but many times (not 100% but many times) you can re install them, and it will NOT start. You will kick your brains out in frustration. Put a fresh set in, and BINGO! It will start on the first kick. That is why I tell you to carry a spare set. Why does this happen? Why won't the dried off plug fire under compression? Another unsolved mystery of the universe! I don't have a good answer, except my 40 years experience starting them. But it appears to be true, put in two new plugs, it will start on the first kick.
Another thing you must realize when starting.. The Bing slide carb is basically a variable diameter venturi with no accelerator pump. It draws fuel from the vacuum created by the piston in the cylinder. Air rushing through the restricted neck down, creates a vacuum in the neck down, which draws the fuel off the needle jets, and idle jets, into the engine .
I have watched people heavily tickle the carbs, causing raw gas to flood the inlet to the head, (which make the mixture WAY to rich, and then OPEN the slides, (to get more air, but virtually eliminating the the velocity of the air through the neck down and thereby causing the needle jet, and idle circuit, NOT to put a mist of fuel into the carb. So if it does start, it may or may not keep running, but you may have gotten the pug wet with fuel and it won't start at all.

You know, you have to learn what it likes, when starting, and always do it that way, because it won't do what you think or like.....
Next time you start one dead cold, on the center stand, try this.
1. turn the gas on, count to 5 1001, 1002, etc 5 seconds
2. Shove the key down.
3.Do NOT touch the throttle simply kick it.
one or two kicks max, it should take off running. but do NOT touch the throttle, let it idle until it warms up some.
If you open the throttle, when it is dead cold, idling, the engine will quit.
Generally speaking, in warm summer weather, a cold R50 - R50/2 R60 - R60 /2 R51/3 R67 will start without tickling doing as I described.
Now, the R68, R69 and R69S are a little different. When dead cold, they require a tickle a SHORT tickle, a "blip" on each button as I described. but when they start, don't open the throttle, let it warm up first.

Restarting a hot engine, slightly different procedure.
Turn the gas on, count to five, put the key down, and this time, have you hand on the throttle grip. Don't open it, but as your foot hits the bottom of the kick start stroke, crack the throttle open simultaneously. It will start on one kick usually.
Vech
Technical Adviser, Former owner, Bench Mark Works
662 312 2838 cell 9 am to 4pm CST PLEASE!

Bob Allan
Posts: 38
Joined: Tue Jul 25, 2017 10:09 pm
Has thanked: 1 time
Been thanked: 4 times

Re: A question about spark plugs

Post by Bob Allan »

Interesting information on starting twins. What would you advise for the singles?

Post Reply