Engine overheats after rebuild

[sashkar2000]

Hi guys. I took off the head and cylinder block end to replace broken intake valves. Finally put it all back together. It starts easily but the left cylinder heats up within a few seconds and exhaust gasses come out of the exhaust port. Id think its a simple exhaust leak because I didn't replace the exhaust gasket, but the rest of the exhaust pipe is also very hot.

Dieing to know What could be the problem?

Thank you!!

[sashkar2000]

Actually it looks like the colder cylinder wasn't running. I swapped the exhaust gaskets and the leak is gone but  it still heats up extremely quickly. Is it normal for the engine to heat up to where its uncomfortable to touch it within 30 seconds? Meanwhile the exhaust pipe is scorching hot but i imagine that's normal.

Compression on both cylinders is 100 psi which sounds ok considering the rings got disturbed and havent seated yet, though maybe that's wishful thinking.

[adidasguy]

Balance the carbs. if you don't have the tool, do a search for "hill billy carb sync". It will get you really close.
Do that then report back.

[sashkar2000]

i definitely need to get the other cylinder running, and it's probably a carb issue. but can you elaborate on how disbalanced carbs or a non-firing cylinder would affect engine temperature?

[Big Rich]

Well, a non-firing cylinder won't get hot ......

And if your carbs are out of sync, then one carb can be running the engine at idle - the other carb isn't doing anything.

[adidasguy]

If one side is doing all the work and the other side is doing nothing, then one side will get very hot while the other stde stays cold.

If both cylinders working, then, basically average the hot and cold and both sides will be very warm, as opposed to one side hot and one side cold.

[Janx101]

.. and now we wait for a 'thermal' engineer ..  

[adidasguy]

Surprised Sledgey hasn't jumped in to say I'm all wrong......

[radodrill]

Only one cylinder firing you'd expect one hot cylinder and one warm cylinder due to the thermal conductivity of all the cylinder block.  Both running they'd both get hot, though there can be some temperature differences based on variations between air/fuel mix, oil flow path and temperature, etc.

The engine/exhaust can certainly get hot quickly when you aren't moving; and the exhaust will invariably be hottest.

[Janx101]

20 mins.... a bit tardy!! .. 

[yamahonkawazuki]

Balance the carbs. if you don't have the tool, do a search for "hill billy carb sync". It will get you really close.
Do that then report back.

^^^ agreed ^^^^