Getting ready to rebuild engine

[51Hog]

Description: I am starting to research rebuilding my 51 Pan engine.

Hi guys-n-gals--
I am starting to research rebuilding my '51 Pan engine.
Eventually, the ol' gal will be doing duty pulling a side car through the mountains. Can't go anywhere in Alaska with out crossing serious mountains.
First question is:
Will the stock 72" engine handle the extra weight of the Hack with a rider and my 280 lb. body? And stay at highway speed of 65?
If not, any internal mods that will do the trick? Stroke? Cam? 80 Cube Jugs + Cam?
I am not looking for a race car. Just want to keep up with traffic and still want to look original.

It looks like some of the vibrations that I have been having are caused by a bent crank. Crank wobbles at the drive gear.
Does anyone know of a machine shop in Alaska that speaks old Pan Head?
As a last resort, I could send out the flywheels to have a new crank put in, aligned and balanced.
I am still undecided if I will set up the case with rollers and install the crank myself, or have it assembled by a pro. I am not even thinking about having timkins put into the case.
Who would you recommend I ship to, to have the work done?
Thanks in advance for the help and advice,
Dale

[fourthgear]

I'm not a race head but upping the cubic inches and a mild cam will make a big diff. on pulling riders or side hack and its stock 74 ci (well close to it anyway 73
. something or other ). I would have someone with a lot of experience do the lower end, just my two.

[Skip]

66tintop lives in north pole AK...he may be able to help...

[51Hog]

Just talked with a machine shop in Anchorage.
Anchorage Drag Bike.
They tell me that they can:
furnish the parts for and replace valve guides and seats and valves.

check and repair rods
assemble flywheel assy with new parts and dynamically balance assy.
new pistons
Either clean up or replace races.
new properly sized bushings and bearings.
bore and hone cylinders.
ready for me to assemble.
$1800 - $2000
How does that sound to you guys?

[Jack_Hester]

Talk to Cotten about what you need for a sidehack. He's well versed on the world of sidehacks, and their needs. As to the wobble, if you can see it, it's really bad. Take it off the road. Your flywheels are shifted. No telling what the bearings or races look like. No new flywheel assembly should be necessary, unless you are going to increase the stroke. Some new shafts, races, and bearings may be in order. They are not terribly expensive. As far as I'm concerned, your engine is one of the easier models to rebuild. That is, easier to take apart and put back together.

If the prices you quoted are for turn-key, parts and labor, go for it. I charge $750 + parts + machine work. Most come out to about that price range. Maybe closer to the low end. But, those are very reasonable. Check references if any are available. They sound thorough.

Jack

[Cotten]

Since my name has been invoked here....

I shall put it straightforward that my theory is by no means original, unique, nor a secret. Yet it contradicts the approach of most shops in the modern industry.

A survivalist service scenario dictates that all vanity performance mods are a liability.

Avoid high compression.
Mountains? Avoid anything but an FLH cam. Even that's rad compared to what your machine left the Factory with.

Inches help naturally, but not at the expense of flymass.
Stock wheels actually pull better than lightened S&S stroker wheels.
T&O heavy stroker wheels are a dream come true, and not unreasonably priced either.
Anything up to 88: (and maybe more) can be efficiently aspirated with a stock valvetrain and carb for sidecar duty.

(And adequately as well for solo service, although any shop with a dyno can milk it for all the horses you're worth.)

The success of a "built' motor depends entirely upon the 'wherewithal' of the builder.
Even those of us in the lower '48' cannot conveniently find a builder with 'wherewithal'.
(I have a completely outiftted shop sitting idle waiting for a builder with 'wherewithal' to take over.)

So Dale,
since it looks like you are facing a total overhaul,
research in depth, as your best insurance is your own familiarity with your machine. Particularly when crossing a mountain pass can become an adventure.
We all take an interest in your project, so let us know what you discover. (It is always something new, as no one has seen it all)....

....Cotten

[51Hog]

Thanks to all for their replies.

Cotten---
In your opinion, Would the 51FL Stock motor have enough Poop to handle a Hack, 350 lbs of meat bone and fat, and still handle the hills at about 60mph without burning her up?
You mentioned the FLH cam--Would that cam work on a stock FL Motor? Would it increase upper, middle, or lower end grunt?
Thanks

[Cotten]

The Factory designed a motor that would pull full tilt without blowing itself up. They are made to be geared lower and rev higher than most riders feel is comfortable.
But 'performance modifications' often shorten the fuse. An "H" cam is as rad as I would suggest, ... only to accent highway service.

A stocker will not set any land speed records, but then how heavy is the traffic up there anyway?

A thorough and proper rebuild of stock hardware today should be better than what the Factory put out. And the Factory produced very durable machines.

...Cotten

[51Hog]

what does "Full Tilt" mean?
does it mean High RPM--What is normally max loaded RPM for these great engines?

or does it mean

Pulling hard at heavy throttle for long distances?
Or does it mean something else?

The more I investigate, the more I think that I will be going back with a stock engine. Maybe the H cam.

As far as traffic goes, There are about 600,000 people in the whole state year round. But in the summertime the traffic increases greatly due to tourists.

Our area only has approximately 200-250,000 people year round.---And it seems that all of them want to drive on MY roads!!!!---All at the same time!!!! LOL

When the traffic is flowing well, it flys, even on the two lane roads. which is why I want to be able to maintain highway speeds. It is not good to be the one holding up traffic on a mountain road--Especially on a bike.
On the few 4 lane hwys that we have, I just take the right lane and do my own thing.

[51Hog]

Well, I disassembled the top end and the cam chest. It Does not look as bad as I expected. There was so much carbon in the head and on the top of the piston, that there could not have been any air space when the piston was at tdc!!! There was at least 1/8 inch of carbon built up on the head, and the same on the piston.
Pistons are marked 60 over. Not galled at all.
Jugs re not pitted or scored too deeply--Just scratched.
Ring groove at the top pf jug maybe 1/3 of the circumference approx .005 deep.
Largest spot in the cylinders with the exception of the
above ring groove is 3.493-3.494". Looks like the cylinders will clean up at 3.5"

Any one know if there is a piston that will fit that hole,
and if the jug would stay in one piece running a piston that large?

The engine goes to the machine shop on Mon. to have the crank and wheels checked/repaired/aligned/dynamically balanced/and re-installed into the case.
While he has the engine, he will check out the cam chest.
Rod bearings are marginal (3/16" side to side check per book)

Everything in the cam chest needs attention.

[sleeper]

51Hog-

"Rod bearings are marginal (3/16" side to side check per book"

I always spray 'carb- cleaner' or (brake-cleaner) or similar at the Crank pin & rods while rotating wheels , thoroughly washing out oil, prior to measuring for side-play & up & down slop...

Because oil has viscosity=thickness & your readings will be more accurate when washed off & re-checked.
aka= they most always read looser !! I'd check while ya got her down..

[Cotten]

By "Full-Tilt", I refer to the typical sidehack mode of operation where the throttle is thrown wide open through every gear up to cruishing speed. If you follow packs of modern solo machines, you'll soon understand.

As far as your lower end,.....
Leave no stone unturned, cut no corners. You cannot truly inspect a crank assembly without disassembly, and by that time you are going to fix it anyway.

Your cylinders have plenty of life left in them, but please ask your boremeister to use at least a base torqueplate for the final hone-fit.

Good luck,

...Cotten

[51Hog]

I am going to completely rework the engine, and check every tollerance.
As far as trying to keep up with the modern machines----I wouldn't even try.
If they want the pleasure of riding with a great bike, they can slow down.
So far, they dont like stopping at gas or rest stops with me, cause everyone wants to know about the great old bike----not the newer ones. LOL

[51Hog]

Finally finished the rebuild.
Machine work:
Bore and Hone to .070 2 jugs $ 130.00
Assemble crank $ 200.00
Balance crank $ 150.00
Spacer washer $ 5.00
Parts $1300.00
Total $ 1785.00
Installed engine and fired her up.
After 5 minutes of running poorly, rear cylinder intake valve stuck open.
Removed rear head. Very little oil in the top. Valve was dry. Top of valve stem at guide was scored.
I cleaned up guide. Checked clearance-still within tolerance. Pre lubed new valve and re assembled everything.
Oil pressure was great even the first time around.

Engine running smoothly a Little solid lifter noise-- need to re-adjust lifters.
A small oil leak at rear lifter block.
All in all----Very happy!!!!! ;D ;D ;D

[jellero]

do yourself a favor and do tranny too. check for leaks while things are apart... j