Author Topic: Running Hot  (Read 1699 times)

Offline Stu55Flash

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Running Hot
« on: 26.09. 2010 16:57 »
I finally started the plunger flash and its running hot. Both headers have blued after being run for about 2 minutes in the garage (with the door open). It revs soothly but back fires when settling down to tick over. It fires on kick over and runs for about 5 seconds then cuts out when cold. I have to do this several times over until it warms up. It then runs and gets hot. The plugs look OK. The timing was done before I put the head on, I had it spot on.

Any suggestions what to check first?

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline chaterlea25

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Re: Running Hot
« Reply #1 on: 26.09. 2010 18:01 »
HI Stu,
Sounds as if the carb mixture is really lean??
check for fuel flow at the bottom of the carb
then check the fuel level in the carb before altering anything else
I'm assuming the carb is thoroughly clean and that the pilot air and fuel passages are clear
Is the petrol "new" and fresh ????

HTH
JOhn O R
1961 Super Rocket
1963 RGS (ongoing)

Offline Stu55Flash

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Re: Running Hot
« Reply #2 on: 26.09. 2010 18:34 »
Thanks John

The carb is a 389. I've striped it and replace the washers only so I'm not sure how good it is. The needle is on the second from top. On strip down it was blown out with an air line and was all clear. There was nothing obviously worn. It is new petrol. I did think about the fuel level when it wouldn't run from cold.

I will order a repair kit.

Cheers

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline wilko

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Re: Running Hot
« Reply #3 on: 27.09. 2010 00:09 »
Too retarded is the usual reason for overheating.

Online BSA_54A10

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Re: Running Hot
« Reply #4 on: 27.09. 2010 00:59 »
Blue pipes at low revs = fuel still burning as it comes out of the head.
So from that.
Too much fuel to burn before the valves open.
Valve opening too early.
Spark happening too late
Bike Beesa
Trevor

Online Triton Thrasher

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Re: Running Hot
« Reply #5 on: 27.09. 2010 07:56 »
Blue pipes at low revs = fuel still burning as it comes out of the head.
So from that.
Too much fuel to burn before the valves open.


If you're saying a rich mixture blues the pipes, you're wrong.

Offline A10Boy

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Re: Running Hot
« Reply #6 on: 27.09. 2010 12:31 »
Agreed, too rich = Soot. Too Lean = Flames
Regards

Andy

1960 A10 - Black Golden Flash
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Offline beezalex

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Re: Running Hot
« Reply #7 on: 27.09. 2010 14:12 »
Yup.  Too lean and/or too late.  Do a search on reading spark plugs with "mixture line" in the search to educate yourself on how to properly read plugs.  Here's a link that should get you started:

http://www.strappe.com/plugs.html
Alex

Too many BSA's