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Alright guys and gals, I can really use some help here.

Judy did a rebuild on the topend of my '92 FXDC.

Brand new cylinders, pistons, rings, valves, springs, cam, lifters, etc..

Before completing assembly, I would stop every so often and make sure everything would move freely along the way.
After full assembly, I go to crank the bike and nothing. The engine wouldn't even spin.
I take it all apart again, thinking that maybe a lifter got jammed and wouldn't allow the cam to spin, so I remove the cam and lifters and spin the engine by hand again.. EUREKA! IT WORKED! Put everything carefully back together.. Now it won't spin again.

Now, once again I take everything apart and work my way back. This time I have everything assembled except the heads. I spin the engine by hand so I can see the pistons moving and it spins easily with no binding.

I torque the heads on (to service manual specs) and it no longer spins again. Take the heads off... It spins.

What am I missing here?
Why would the engine not spin if the heads are bolted on and spin when they are not?

This is my first time doing my own rebuild to this extent.
I've followed the service manual word for word. I'm at a loss and could really use some help.
 

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Just Ride
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Cam timing off or pushrods in wrong holes. Does it spin without the sparkplugs installed? Certain on the correct pistons.
 

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Discussion Starter #3
Cam timing off or pushrods in wrong holes. Does it spin without the sparkplugs installed? Certain on the correct pistons.
Appreciate the response.

At this point, the pushrods are not installed. No rockers either. Simply just the head bolted to the jug.

Head off: spins
Head on: no spin

Each time, I follow the torque sequence exactly while bolting the head on.

When I installed the cam, I rotated the engine until the timing mark on the pinion gear was facing up, then aligned with the cam, followed by the breather gear.

Edit: plugs in or out doesn't make any difference.
 

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weird member
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I have an Evo motor that I upgraded. Now, I sent my stuff off to Hillside for machining and they installed the springs and valves and everything.

But considering the pushrods aren't in and it stops spinning when you put the head on, I really can't see what it could be at all. No rods, cam can't be binding and stopping it, plugs out can't be air pressure.

It has to be the con rods binding, maybe when you torque it down and the jug gets pulled fully into the case, the rod is hitting the bottom of the sleeve or something? Because that's the only part that's changing that I can think of, but you didn't have the jugs honed or anything right, no new pistons/rings, etc? You sure you got the cylinder base gasket on? I still can't see with only the top end being changed would do that, valves should be closed and not moving with no pushrods so can't be that. And when I did mine, it was the whole motor with a lot thinner, SLS base gasket and my rods didn't hit the jug cylinder.

And you're absolutely sure the piston isn't maybe catching and kinking in the jug or something?
 

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Discussion Starter #5
I have an Evo motor that I upgraded. Now, I sent my stuff off to Hillside for machining and they installed the springs and valves and everything.

But considering the pushrods aren't in and it stops spinning when you put the head on, I really can't see what it could be at all. No rods, cam can't be binding and stopping it, plugs out can't be air pressure.

It has to be the con rods binding, maybe when you torque it down and the jug gets pulled fully into the case, the rod is hitting the bottom of the sleeve or something? Because that's the only part that's changing that I can think of, but you didn't have the jugs honed or anything right, no new pistons/rings, etc? You sure you got the cylinder base gasket on? I still can't see with only the top end being changed would do that, valves should be closed and not moving with no pushrods so can't be that. And when I did mine, it was the whole motor with a lot thinner, SLS base gasket and my rods didn't hit the jug cylinder.

And you're absolutely sure the piston isn't maybe catching and kinking in the jug or something?
All the parts are brand new. The jugs pistons, rings were a complete new kit from Vtwin Mfg.

The piston definitely isn't catching anything. It moves very smoothly until i bolt the front head onto the jug. Even without the head torqued down (bolts only finger tight) it doesn't move. I thought maybe I had it over-torqued, even though I followed the specs in the manual and double checked with online results.

I am absolutely certain about everything being in place as it should be, including gaskets. I pulled it all apart and reassembled 3 times now.
This is just absolutely mind boggling.

The pistons claim to be 10:1 compression. That's the only major change that I can think of, once the head is bolted on. However, I have tried to move it without the spark plugs, to relieve some compression.. Still nothing.

It literally seems as if the engine is seized when it's completely assembled but, moves as smooth as silk when the front head isn't on.
 

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It moves when the rear head on though?

I still can't understand how just the addition of the front head would lock it up when it was otherwise moving without rods unless somehow the piston is catching in the jug, like the jug can move enough for the piston to move until the head is put on and keeps the jug from moving so the piston catches and binds. But you would think that even with the head loose on it and not torqued down, that if what I said were the case, the jug could still move enough to not maybe be the piston binding.

And you tried moving the engine with the front head on and the rear off?

When you put the front head on and it stops moving, where is the piston located in the jug? Near TDC or BDC? Have you tried moving it where the piston is half way down the jug before putting the head and seeing if it would move?

Because otherwise, I am stumped as to how simply putting the head on locks it up if there's no pushrods in it, because the only place it could be binding is between the piston and the jug that I can think of.

Where's @SCHMIDTY ? He's one of the ones that might have a better idea.

Also, as to compression, it's not just in the piston height (it's also the gaskets involved and any clearancing on the bottom of the head that all add up to the volume change).
 

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Might be a dumb question, but which way did you put the notch at the bottom of the cylinders? Facing each other, or facing away?
 

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Please confirm the "kit" you purchased from V-Twin Parts includes their Jugs ( Barrels/cylinders) With their " matching" pistons set. Confirm they sent the correct one for your model/cases etc. You sent them to be honed and fitted at a machine shop. Do they know how to do HD work? (using torque plates etc) ..It seems to be a FITMENT interference problem in my opinion. As one poster said, the notch in the cylinders and pistons (install direction) need confirming. And V-Twin Parts may have a tolerance/fitment problem. It is a close one since installing the head bolts is snugging down and reducing the fitment. (even if finger tight) . An incorrect base gasket for that VTwin kit may be the problem. Was it supplied with the kit.? You may have to blueprint all the parts to insure they work together. No offence but it V-Twin stuff ...not always known for the best quality.
 

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One other thing should be considered. It spins freely with heads off..the Interference fit may be with the pistons hitting inside the head too..are they domed/ notched correctly etc. ( although you have not installed the pushrods and valves are always closed- that eliminates valve to piston Clearance in a static situation ) You had the valves done too..so something in fit Tolerance has changed. You had it all together and cranked it with the starter? Or did you only roll it over by hand (turning rear wheel/ wrench on drive sprocket etc) . Especially if you used the starter, Inspect the heads. Make sure a valve wasn't bent and now open slightly. (Pretty doubtful.. but you may have missed it) . Think of every close tolerance fit that has been effected by simply hand tightening the head bolts.
Compare all V-Twin parts to your old stock parts (Jugs especially) you took out for height, profile / con-rod notches and all interference dimensions Etc. Mic them for total clearance requirements. Especially any relief notches on lower cylinders , piston skirts etc.
Let us know what you find- no matter How embarrassing ! We have all done it.
 

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Any clearance issues with the head gaskets . . .
 

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Interesting ... everything moves freely until the front head is installed loose and bolts just finger tight. If the piston is half way between TDC and BDC the gaskets wouldn't come into play. The cylinders are located on the case by the cylinder studs. Hmmm, the cylinder studs ?
 

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I have to second what someone else said too about the problem may be the brand. I've never once gotten a good part from that brand (V-Twin Manufacturing). There's a reason their stuff costs half what everyone else's does. Maybe they're fine for non critical parts or something, but based on my personal experiences, I would never use their engine parts.
 

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Just Ride
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Does it lock up totally or if you reverse direction it moves then stops again.
 
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