Hey guys,

I recently picked up a project 93 fxdwg. The previous owner put a narrow glide front end on it. Makes me think they were bent as he did not have the original forks. I am planning on a full rebuild, I have already pulled the motor and Tor I to it. I found some goodies, s&s breather Andrews ev27 cam and adjustable push rods. I pulled the top end as I am planning to put new valves and springs in there. I am also concerned about the piston. The front cylinder has a lot of carbon build up. Do you think I should replace the pistons as well? I figure I am already in there, so I might as well, but if I do, do the cylinder have to be rehoned? And if rehoned will that require a larger piston? I have rebuilt 2 stroke dirt bikes and always ran them without doing anything to the cylinder and never had an issue....this is my first Harley complete rebuild.....thanks in advance.

Rear cyl.

Front cyl.

Push rods

Andrews ev27

 

Personally I see no reason to replace the pistons.
How did the motor run before you pulled it apart?

 

I have never heard it run. There were some electrical issues. I managed to fix up the wiring to get her cranking, but that was it. Crank but no fire. I'm going to replace the electrical system as well, I have a new harness on the way and I'll be ordering a stator/regulator/coil...

 

I agree with TH, and your carbon build up "ain't bad".... I see its a head breather, and the engine when stock is vented to the air filter which sucks up that oil/water vapor-mist from the engine giving you some carbon build up over long term use. It's and EPA thing.

Some will vent those gases "outside" or to the ground so to speak, so it will cut down on the carbon build up from that point forward.

A common problem with the evo is the cylinder base gasket leaks, so you need to decide if your going to deal with that, even if you don't do anything with the pistons..

Also, it might have been been dealt with if your cam has been replaced, but the cam bearing if stock should be replaced, it is another known issue.

The base gasket and cam bearing are often talked about here so lots of info/reading...if it were me, it would be a new koyo-torrington b-138 cam bearing, and Cometic metal base and head gaskets.

Here comes the question...do you leave the pistons in the cylinder by removing the pin so you can replace the base gaskets, or do you pull the cylinder leaving the pistons and rings as is, put in new gaskets, then re-install, or do you lightly hone/dress the cylinder walls, install new rings on the pistons then reassemble...or pull pistons and cylinders, have cylinders honed or bored and bases of cylinders trued by a machinist, new pistons and rings to match the hone/bore then reassemble. Opinions on this will vary.

I will always suggest having the cylinder bases trued up flat by a machinist. It is part of the reason the base gaskets leak. The other reason is the low quality gasket used originally.

The rub is, can you find a machinist who will do the work right now because of the Covid stuff. YD

 

Me, being it’s opened I would change to high compression pistons and have the cylinders honed to the new pistons

 

You really should back off a bit and tackle one issue at a time, since you are learning as you go.

You should have left the engine alone unless you know for sure it must be rebuilt, but its too late now to go back.

Remove the cylinders, pistons, and take them to a qualified Harley machinist, and have him check them out.

Make sure you cover the openings on the crankcase as soon as you start to lift the cylinders.

Fix the existing electrical problems for now, get the engine back together and running, then start the next project.

 

Man you seem to like throwing parts at a problem.
The only thing that could cause a no spark situation from the list above is the coil.
The most common thing I've found that causes a no spark condition is the cam sensor.
The other possibilities are ignition module, coil, wires, and spark plugs.
If you do decide to change to change the cam sensor I recommend the Dynatek 2ki.
It makes cold starts way easier!!!!!!!!!!!!!!!!!

 

I noticed that there was rtv at the base gasket, that was the reason for teari g into it. My plan was to find out the condition of the motor, what was in it (upgrades) and to replace all the gaskets...

 

FWIW
I bought a '93 Evo engine...awhile ago... did hear it run previous to purchase, idle and some walk around for "noises"
Dropped it into an FXR chassis, had some smoke from rear pipe...turned out to be oil in the [purchased separately] Pipe...
That was over 3 Years ago...last year she attained a ton inside the 1/4 mile, poor ET because of Rusty Rider!!! so I suspect Non-Stock
Wouldn't dream of tearing it apart "just because" as I do Not think it is Broken... don't know what is In it...and do Not Care... I'll find out soon enough if I keep taking it to the Harley Drags!!!! LOL
Got an Extra layin in the corner... I should Bust that one out... May be more Good Surprises!!!!
Edit; Geeze time flies... that was 5 years ago!!!!!

 

I think this is a hobby project and someone looking for some fun when we are locked away.

Good luck and please post a ton of pix. How do the cylinder walls look? Smooth? See any cross hatching? Any lip? I wish you would have done a compression test with and with out oil. Did you?