Jackpiner revving out with fuel shut off.

[KJDonovan]

Greetings,

It was rainy day here in RI so I figured it would be a good day to work on my Jack Piner and I ran into kind of bizarre problem.  Here's the deal.  All year the bike has been idling lousy, basically if I was not feathering the throttle it wouldn't idle. So I figured, I would try messing with the jetting to see if I could improve things.  I'm running a Bing carb and it had 150 main, 30 pilot, 2.73 needle with the jet needle clip on the very top notch.  I swapped this out to a 155 main, 35 pilot, 2.76 needle and set the jet needle clip on the 3rd notch down.  I put carb back on and left the air boot off, started it up and adjusted everything out until it was idling fine.  Next, I figured I would just burn off the rest of the gas in the bowl so I shut of the petcock and slowly but surely the bike starts revving higher and higher.  I hit the kill switch and nothing, next I take a screwdriver and pop off the plug cap and it still doesn't shut down.  I had spark literally flying out of the plug cap dancing all over the head.  It finally died after another 20 seconds or so but what the heck?  Did the idle climb like that because I leaned it out shutting off the gas?  Or, do I have some other issue I should be looking into?  If anyone has any ideas I be happy to hear them!

Thanks,

KD


Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner (My Ride)
72 Six Day (Wifes Ride)

[john durrill]

KD ,
 Yes they do rev up as the float bowl dries out.
Sounds like you had a head or a plug with a hot spot . That gives you a 2 stroke diesel chuckle chuckle!!!!. Hand over the air intake or a rag in the end of the exhaust pipe will kill one like that quick.
Last bike i saw do that was an Ossa 250 .
john d.

[KJDonovan]

John,

Thanks for the info, that was new experience for me and caught me off guard to say the least!

Thanks,

KD

Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner (My Ride)
72 Six Day (Wifes Ride)

[cubfan1968]

My Six Day does this every time I try to run the gas out. I usually keep it in gear and ride it out. Makes it so it doesn't rev as high.

Rod Whitman
Omaha, Nebraska
1972 Six Day (Rider)
1972 Six Day (Project)

[tomale]

I don't think I would have change so many things at once... I would have started with the pilot jet and see how that works, then if if it felt sluggish in the mid range I would have lowered the clip a notch. and then if it felt sluggish or flat on the top then I would have changed the main....I have always been told when it comes to carbs that you chance one setting at a time.....

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[Bob Bean]

KD,
Many Many years ago, when I was about 15, I worked at Burroughs Cycle shop.

My main job was sweeping, cleaning bikes, etc..
Of course I got to test ride the bikes after checking the air in the tires, to make sure everything was good on them

Once time after testing this one particular Zundapp out for about 15 or 20 minutes, I had 2 things happen all at once.  I jumped a little jump in back of the shop and had the chain pop off.  I couldnt seem to get it out of gear to stop the chain from turning, so I shut the bike off...  

Only problem was, it wouldnt shut off ?  I lay the bike over on its side and it started to rev up even more ??  I was panicked by now.  
 
What do I do?  

Like a moron, I tried kicking the chain back on the sprocket to kill it, not realizing how dangerous that was...
It didnt work any way and by now the bike was in full song, screaming
about 8,000 RPM's...  

So I did the first thing that came to mind.
I yanked the plug wire off...!   BUT STILL IT RAN... ?
How the heck??  
What demon is in this Zundapp ?

Finally, I yanked the air boot off the back of the carb and stuck
my hand over the back and choked it to a stop...
Whew !
Tic, tic, tic..

Pulled my hand away, and off it went again... ?
What the ?
Now I was really perplexed...  
Back went the hand over the carb...

I must have sat there 5 minutes with my hand over the carb...

Finally, I worked up the nerve to take my hand away and thank God,
it didnt take off again....

So I pushed the bike back up to the shop and was met by Ira Burroughs and a couple of other customers who I then proceeded to tell, them about this possessed Zundapp...

Well after about 5 minutes of laughter died down, I found out about
hot carbon and dieseling.....


Bob Bean