Running Hot

[Stu55Flash]

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

[chaterlea25]

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

[Stu55Flash]

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

[wilko]

Too retarded is the usual reason for overheating.

[BSA_54A10]

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

[Triton Thrasher]

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.

[A10Boy]

Agreed, too rich = Soot. Too Lean = Flames

[beezalex]

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