I took apart my 1981 Lowrider to fix a leaking rocker box gasket and now it is back together and runs like crap! It will not idle right no matter how I adjust the carb. Giving it gas causes it to smooth out some, but occasionally it will bakcfire. If I try to ride it will miss sometimes.

PLEASE HELP ME!

Obviously, it is a shovelhead motor. It has no modification (stock). I know that there are probably 100 things that it could be, but I will start with what I think is going to be the most obvious.

I did not replace the cylinder head gaskets (O-shaped). I re-used the old ones. Will this cause it to run like crap?

I am also thinking that it very likely could have something to do with the pushrods and valve timing. Now, I did not disassemble the valves and springs, I just left them in the head and them reassembled everything. I am thnking that maybe I somehow messed up when I reinstalled the pushrods. I followed the directions, but I don't think that the timing is correct.

I pulled the tanks, carb, exhaust, and then cylinder heads and rocker boxes attached together. I took off the rocker boxes, and took them apart (rocker arms) and cleaned them. I then scraped all of the carbon from the heads and valves. Then I cleaned all of the gasket surface between the rocker boxes and the heads, reassembled them with new gaskets and some sealant and then put everything else back together.

Can anyone help point me in the right direction? Or at least any direction. I am not sure what to do next.

 

Always use new gaskets just cheap insurance.
Did you installed the push rods in the right order?
Check your timing?

 

I did onstall them in the right order. How do I check the timing.? Do I use the timing marks when I install the pushrods?

 

It's not timing Do you have hyd or solid lifters ? are they adj correct ? How about carb manifold air leaks ?

 

I have solid lifters. Where and how do I check for carb man air leaks?

 

The manifold that goes to the front and back heads usually for an 81 shovel has flat rubber bands under the clamps to stop air leakage Where these rubber bands replaced ? I usually use brake clean start the bike up (if possible ) when running spray the area around the rubber bands See if the idle comes up or the engine dies leakage is there Did you adj the solid pushrods correctly ? When you put the heads back on did you position the intake manifold for proper clearance before tightening the head bolts ?

 

I did not replace the rubber bands, but I now plan on it.

I believe that I adjusted the pushrods correctly. I turned the engine until both the intake and exhaust lifters were at their bottom point of travel. I them adjusted the rods so there was no slack up and down, but they still spun. Then I tightened the lock nut. Then I turned the engine over and did the other two pushrods.

Please let me know if I did anything wrong with adjustment.

As far as the intake manifold went. I tightened the cylinder head bolts and then put the manifold back on. It was difficult to get back on, but I managed. I could have definitely stretched out the rubber bands by doing this.

I am thinking that I might pull the engine apart again and replace the cylinder head gaskets. Then I can also use your tip of putting the manifold on before the cylinder heads are attached and tightened.

 

You did the solid pushrod adj properly New head gaskets/ manifold rubbers a must Keep us posted

 

When installing the heads do a mockup of the intake before torqueing the heads.
there is enough play in the heads to make a difference in how the intake mates.

The shovel intake design was... er... less than perfect.
If the intake is sucking air you will never be able to tune it.
To check for leaks spray wd40 around the intake to head mating area while the engine is running. If it is leaking the engine rpms will change.

You may also want to read up on the pushrod adjusting procedure. And the static timing procedure.

Shovels rock, ya gotta be a wrench to own 1!

 

Check the intake for leaks before you tear it down. If you used old seals there, thats a problem area.