1980 CB750 Custom - Running Hot

[tketter]

I've recently acquired this bike.  I've removed the airbox, replace with velocity stacks, cleaned the carbs and installed the Dyno Stage 3 Jet.  I've also installed a 4 to 1 exhaust.  

I went with the suggested (no airbox, 4 into 1 exhaust) jetting that was suggested in the instructions.

Notch (3) on the needle, (75) main jet..  I think...

The bike seems to run good.  Starts, idles good!  Very responsive throttle..  

I have not synced the carbs..  only bench sync! (Visually)

Here's what it does....

After about 15 mins of riding the bike shuts off..  I think this is a vapor lock due the gas cap.  I had to replace the gas cap and I'm not sure it's venting properly.  This isn't the biggest issue..  

What concerns me is that there is a lot of smoke coming off the engine and out of the air vents (one has a filter, and the other is a hose near the starter).  

I checked the oil level.. spot on..  looks good!

The bike seems to be running HOT!

I'm thinking it's running too rich..  I might need to adjust the needle height.

Any thoughts...??

I'm new to this so thank you for all your input.  

Best!

[Hoosier Daddy]

Couple of things...

tketter wrote

there is a lot of smoke coming off the engine and out of the air vents (one has a filter, and the other is a hose near the starter).

Smoke out the breather / hose is a sign of blow-by. How many miles? Have you ran a Dry / Wet compression test? Dry is the way it sets cold, Wet is a small squirt of oil down the sparkplug holes to seal the rings. A low "Dry" reading that has a signifcant increase in numbers "Wet" indicates worn rings.
You also say you recently acquired the bike and you have a lot of smoke coming off the engine. Was it freshly painted when you bought it? Is there oil leaks at the head or cylinder base gasket? either of these will cause an engine itself to smoke.

 

tketter wrote

The bike seems to be running HOT!

I'm thinking it's running too rich..  I might need to adjust the needle height.

a LEAN engine runs hot, rich is cool. How is the exhaust..
Does it look blue? (indicates running rich or burning oil)
How are the head pipes up by the engine, is their chrome blue ? (indicates lean)
Are you thinking it is hot purely because of the smokeing? Do you have a way of measuring the temp? You can pick up a infra-red thermometer pretty darn cheap nowdays. But a good old fashioned dial thermometer for a bar-b-que grill can work in a pinch.

[Piute]

    Can ya get N give a n oil temp ,Need to understand what you are considering HOT,
   My F2 runs best hot but not good for it/oil at over 250deg

[Larry spillman]

Since you altered so much The first thing you need to check is that you dont have a vacuum leak at intake.also check nothing was left off carbs such as o rings or metal washers under screws,If you are running rich your plugs will be black.If timing is too late you wont get a full burn either and fuel can pop in exhaust being too rich.If you are lean again it may be a vacuum leak as a leak will lean out a motor to the point it can melt pistons and valves edges.You are stuck checking everything now since you altered soo much.

[TOOLS1]

Lean will make them run hot, not rich. Check for air leaks, and do a compression check.
TOOLS

[shinyribs]

A blued exhaust pipe is a sign of overly hot exhaust. Either retarded ignition timing or a lean mixture,not a overly rich mixture. Not trying to be fussy,just saying