Runs good cold, rough when hot.

[EricG]

I took the poorly done weber carb off today and put the OEM carb back on - freshly rebuilt by Mark's Offroad. Engine is a 75 2F. Starts up great, and runs great when it's cold. When it gets good and warm it starts running rough, particularly at higher RPM or when you get on the gas. On the way out to dinner tonight, it seemed to get really bad after I gave it full throttle to open up the 2nd barrel.

Any ideas what to look at? Will check for vacuum leaks. Haven't looked at the timing or plugs yet. Have a pertronix to install also. But I'd prefer to go at it one thing at a time.

Also can get a *small* backfire or popping through the exhaust is if rev it up and then drop it.

 

[cjgoode]

I would check the choke, that is the main thing that should change from cold to warm. Make sure the choke is going to full open as it warms up.

 

[EricG]

I would check the choke, that is the main thing that should change from cold to warm. Make sure the choke is going to full open as it warms up.

It's the manual, cable operated choke. So I know it's open. I'll take a look at the cable attachment though and make sure it didn't slip.

 

[Bonemaker]

I have the same problem
runs great when cold and continues to run great until I shut it off. When I restart warm even after a few minutes will run rough.
when it cools down completely will run great again
does it have a choke?


92 fj80 3fe EFI 106k miles

 

[Michael Hanson]

Hi, When was the last time you adjusted the valves? Mike

 

[Bonemaker]

I have never had them adjusted
how often should this be performed?
is it difficult and are special tools needed?

 

[thebigredrocker]

Adjusting valves is fairly basic. Just need feelers and a couple wrenches.

Here are some threads Valve Adjustment (FAQ)

 

[cbmontgo]

I’d be curious what your vacuum reading is at startup versus warm.

 

[Bonemaker]

Think I will take it to the mechanic who worked on it last and get the valves adjusted since they are past due
will ask him to check the compression
he works on all my Toyota’s and has had LCs himself

i have had this cruiser for over 25 years and it spent most of its life being garaged
has never been off road ( maybe across a field or two)
never had a problem except fuel pump and MAF replacement
Great vehicle

 

[Bonemaker]

Thanks for all the help from everyone
it’s appreciated!