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Tiger cub dies on open throttle. #696345
05/24/17 12:03 pm
05/24/17 12:03 pm
Joined: Jan 2012
Posts: 12
Gloucester , uk
C
cragrat73 Offline OP
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cragrat73  Offline OP
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Joined: Jan 2012
Posts: 12
Gloucester , uk
Hello I have a 1955 tiger cub and it has ran well until recently where it now idles okay but when throttle is opened quickly, it coughs and dies. If you carefully open throttle gradually it revs up okay. I have cleaned the carb, used ignition/plug leads and coil from a known good bike and no difference made. I have set the carb at factory setting which worked well before and the plug is very lean and it runs hot. Checked for air leaks (spray carb cleaner on joints while running) none found. I will admit that I have got myself chasing my own tail trying to sort it out. So I'm hoping someone can offer some advice and help me out.
Thanks in advance.

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Re: Tiger cub dies on open throttle. [Re: cragrat73] #696350
05/24/17 1:06 pm
05/24/17 1:06 pm
Joined: Jul 2001
Posts: 12,934
Central Virginia
Lannis Offline

Life member
Lannis  Offline

Life member
Joined: Jul 2001
Posts: 12,934
Central Virginia
You've come to the right place ... I just had a similar problem that was running me in circles and the list was a great help. I'll be really interested in seeing what the solution is.

One thing you might do is to check the compression and the valve clearance. Something may have changed there and masquerade as a fuel problem.

Troubleshooting Rule Number One is "Compression - Ignition - Fuel" in that order.

Good Luck!

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: Tiger cub dies on open throttle. [Re: cragrat73] #696362
05/24/17 2:45 pm
05/24/17 2:45 pm
Joined: Nov 2005
Posts: 7,457
Back on the mainland!
JubeePrince Offline

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JubeePrince  Offline

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Back on the mainland!
Rolling open the throttle only to die can be a symptom of lean running. (As evidenced by your plug) An easy test would be to try closing the air screw an 1/8-1/4 turn and see if the problem goes away....

Cheers,

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: Tiger cub dies on open throttle. [Re: cragrat73] #696370
05/24/17 4:57 pm
05/24/17 4:57 pm
Joined: Jan 2012
Posts: 12
Gloucester , uk
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cragrat73 Offline OP
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cragrat73  Offline OP
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Joined: Jan 2012
Posts: 12
Gloucester , uk
Okay checked compression and it was 90 psi. Checked valves at TDC and they were correct. So a put a little oil in spark plug hole and checked compression again, 130 psi. Started bike after, started better and ran better but still sputtered and stopped when throttle opened quickly but revved up better then got worse till it struggled to tick over and was very hot. I only last year rebuilt the engine with a newly rebored barrell 0.20 thousand over with new piston and matching rings, so expected it to be okay or is it having oil starvation issues. I checked the oil return in the oil tank when running and it was pumping oil back into the tank.

Re: Tiger cub dies on open throttle. [Re: cragrat73] #696415
05/25/17 12:36 am
05/25/17 12:36 am
Joined: Aug 2010
Posts: 588
Toronto, Canada
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Bola Offline
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Bola  Offline
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Joined: Aug 2010
Posts: 588
Toronto, Canada
Main jet. Check to see if your main jet has come undone or plugged up.

Re: Tiger cub dies on open throttle. [Re: cragrat73] #696636
05/27/17 12:59 pm
05/27/17 12:59 pm
Joined: Aug 2001
Posts: 1,139
Lucan ON Canada
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jfligg Offline
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Posts: 1,139
Lucan ON Canada
Hello my cub does the same. I did read somewhere I think it was the Hughie Hancox tales of Meriden that there was issues with the distributor and the shaft wobbling around. Jeff

Re: Tiger cub dies on open throttle. [Re: cragrat73] #696673
05/28/17 1:54 am
05/28/17 1:54 am
Joined: Sep 2001
Posts: 527
Great Southern Land
tridentt150v Online content
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tridentt150v  Online Content
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Posts: 527
Great Southern Land
Did you do the compression test when the bike was hot??? Results look like a cold compression test, if it was cold then I wouldn't be too concerned about the numbers. But hot you should see the dry and wet test results get much closer together, maybe 110-120 psi.

Re: Tiger cub dies on open throttle. [Re: cragrat73] #696689
05/28/17 1:13 pm
05/28/17 1:13 pm
Joined: Dec 2013
Posts: 4,293
ohio, usa
kevin roberts Offline
fefsa
kevin roberts  Offline
fefsa
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Posts: 4,293
ohio, usa
does the carb gave a choke slide? warm it up, drive up to cruising speed, drop the choke slide and open it up. if it runs better, then part or all of the problem is lean running. if it's worse, then the problem is probably not mixture.

but it really sounds like tbere's a restriction in fuel flow. petcock? blocked tank vent? plugged lines? goo in the tank?


"Are bikes so nice as all that?" asked the mole, shyly...

"Nice? They're the only thing," said the Water Rat Solemnly, as he leaned forward on the handlebars. "Believe me, my young friend, there is nothing -- absolutely nothing -- half so much worth doing as simply messing about with bikes."
Re: Tiger cub dies on open throttle. [Re: cragrat73] #696755
05/29/17 11:32 am
05/29/17 11:32 am
Joined: Jan 2012
Posts: 12
Gloucester , uk
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cragrat73 Offline OP
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cragrat73  Offline OP
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Joined: Jan 2012
Posts: 12
Gloucester , uk
Okay had a few minutes to work on the bike. Removed and clean main jet, all secured and clear. The fuel flow is good from the tap, no restrictions. The distributor does have some play in the shaft, but not a big amount. The cam is solid and has no play on it.
I redid the compression tests. Cold test dry = 90 psi, cold test wet = 100 psi. Hot test dry = 110 psi, hot test wet = 110 psi. So as you said readings much closer. The carb is a AMAL 332 and has no choke slide or any choke mechanism,
I will try to gp for a ride to see how it's behaves. Thanks for responses.

Re: Tiger cub dies on open throttle. [Re: cragrat73] #698336
06/13/17 2:52 pm
06/13/17 2:52 pm
Joined: Jan 2012
Posts: 12
Gloucester , uk
C
cragrat73 Offline OP
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cragrat73  Offline OP
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Joined: Jan 2012
Posts: 12
Gloucester , uk
Sorry for delay in replying, I had to fix the family car (dpf problems). I have managed a ride and it ran rough and stopped after 1/2 mile. Upon inspection at home, I found the spark plug very sooty. Also found the needle clip has split and the needle has moved upwards out of all notches, so that would seem to be the issue there. I also checked the needle jet for wear and there is a slight bit of play between needle and jet, about 0.010 ish play. What should I expect and how much would be too much. I have ordered a new needle jet and clips.
Thanks again.

Re: Tiger cub dies on open throttle. [Re: cragrat73] #698370
06/13/17 8:48 pm
06/13/17 8:48 pm
Joined: Oct 2003
Posts: 11,264
North Georgia, USA
RF Whatley Offline
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RF Whatley  Offline
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Joined: Oct 2003
Posts: 11,264
North Georgia, USA
Some finer points.....

► Before you can start any carb repair it is mandatory that you thoroughly inspect and repair your ignition system, and set the ignition timing. If you don't and later find out that your timing was off, then you have to go though all the steps on the carb again.

► 90 psi is minimal. Poor. Barely adequate. Not good. Bad boogie.

Carb needles and needle jets are replaced as a pair. They are both brass, so how can one wear without the other wearing an equal amount ? It is also important that the float level is checked.

► Friend, some inkling of which one of the 41,396 carbs fitted to Cubs since 1955 might be nice to share if you really want detailed help.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Tiger cub dies on open throttle. [Re: cragrat73] #698428
06/14/17 10:15 am
06/14/17 10:15 am
Joined: Jan 2012
Posts: 12
Gloucester , uk
C
cragrat73 Offline OP
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cragrat73  Offline OP
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Joined: Jan 2012
Posts: 12
Gloucester , uk
The carb is an AMAL 332/3 no choke mechanism. The float level has been checked right height and float is not punctured.
The ignition has had a contacts cleaned, new condenser, points and timed. The distributor rebuilt.
True about the carb needle and jet, will order new carb needle.
Will do a leak down test as yes the compression is pants.
Cheers.

Re: Tiger cub dies on open throttle. [Re: cragrat73] #698551
06/15/17 12:08 pm
06/15/17 12:08 pm
Joined: Oct 2003
Posts: 11,264
North Georgia, USA
RF Whatley Offline
BritBike Forum member
RF Whatley  Offline
BritBike Forum member
Joined: Oct 2003
Posts: 11,264
North Georgia, USA
Originally Posted by cragrat73
The carb is an AMAL 332/3 no choke mechanism. The float level has been checked right height and float is not punctured.


Thanks for that info.

Originally Posted by cragrat73
The ignition has had a contacts cleaned, new condenser, points and timed. The distributor rebuilt.


Those items constitute about 1/3 of your ignition system. How old is your plug wire ? Is it metal core ? Do you have a resister plug or resistor plug cap ? What plug are you running ? How old is it ? Are you running ethanol fuel ?

Originally Posted by cragrat73
Will do a leak down test as yes the compression is pants.


Why don't you start by detailing how the compression test was done.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

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