Crank appears to be seized on a forty plus model??

[headdownarseup]

Looks like you're making some good progress there.
Patience with the last screw in the pumphousing. (heat and soak, and if all else fails give it a wack with a decent hammer and impact driver) sooner or later it'll go.
As a last resort you might end up drilling or cutting the pumphousing away as Oyster mentioned previously, but stick with the heat and soak method first (it usually works for me with an impact driver)
The replacement crank and rod sound to be from a motor that is slightly younger than yours, not that this will make much difference to how it will run.The number 2 conrod is a slightly re-designed version of the number 1 (and by all accounts has a bit more meat on it so it won't distort quite as easy as the earlier ones)

looking good so far, well done

jon

[MorrisMan]

I have purchased an impact screwdriver, which is in the post. I guess the removal of the top makes access to the screw a little easier, especially hitting the impact screwdriver directly.

[Stelios_Rjk]

Heat and quenching heat again and then try with a screwdriver or the impact one. But don't be gentle when applying heat!

[MorrisMan]

I hacksawed the gasket but chose not to cut through the screw, I can now swivel the gear casing halves slightly. Hopefully the oil can now reach the thread a bit easier, as I sprayed it through the gasket gap.

I have also cleaned out the waterways on the cylinder, Do I just need to give this a good scrape out with a thin screwdriver and rinse or maybe let it soak in something?

[headdownarseup]

Little tip with rusty seagull screws that refuse to come undone (easily)
Arm yourself with a decent blowtorch, a typical plumbers torch is fairly ideal.(and an absolute must if you intend to work on seagulls in the future)
As you already have the impact driver, the only other thing you'll need is some courage!

As Stelios has just said, dont be scared about heating the aluminium pumphousing or the gearbox. This will take some pretty fierce heat before it will start to distort.(i've done loads of them like this)
Heat the bejeeesus around the area of the screw from underneath,(we're talking BLOODY HOT) then using your impact driver give it what for! DONT BE SCARED TO HIT THE SCREW ****ING HARD!! Before you get carried away,take a moment to check for adequate clearence when using your impact driver. I ended up having to buy some longer bits so the tool wouldn't end up smashing the casting at the base of the torque tube (you'll see when you start)
One way or another it will come out.If after all this it still refuses to budge, drill the head of the screw out (but be carefull not to drill into the aluminium of the pumphousing) what's left sticking out you should be able to get some vicegrips (molegrips/locking pliers) and remove the rest of the screw that way.

Cylinder cleaning is up to you how clean you want the waterjacket to be. Scraping and poking the crud out will get some good results. You could also try some caustic soda mixed up really strong and soak the waterways in the stuff for a day or two. Rinse out with plenty of water afterwards.It's been covered fairly well here in the past,have a look through some of the older posts.

Best of luck

jon

[MorrisMan]

I ran into a small problem in that my shiny new impact driver fouls on the pinch bolt fixing, so I bought a socket extension for it. Although my socket set has a 1/2" drive handle, it has only 3/8" drive extensions. I decided to go for a second hand Proto branded 5" extension as I thought this might be more robust than the set of of 4 new "no brand" drive extensions that can also be found on ebay for about the same price.

I have cleared out most of the gearbox gasket with a hacksaw blade, and the fixtures rotate against each other slightly, so the screw is free in one of the halves of the gearbox. Strangely it feels like the thread end is free, but the screw head is stuck in the top half... Anyway hopefully a good hit from the impact driver will loosen it up regardless.

I have not had any luck with the flywheel yet, I should have some free time next weekend to attack both problem areas and maybe assemble it with the replacement cranshaft to do a test run in the wheelie bin

[Stelios_Rjk]

Heat it hard and quench. The impact driver won't do anything if it is badly seized.

[MorrisMan]

Progress!!!

Gearbox halves separated

I have managed to undo the screw, in the end it had become stuck in the top non-threaded part, so I changed tack by using the impact driver with the screwbit missing, to push the top half downwards and break the seal. Still required lots of blowtorch. When it was finally loose it actually came out easily. I had to purchase a 1/2" extension, as others have stated, a standard impact driver fouls on the driveshaft clamp.

The impeller looks to have survived intact surprisingly.

My final task before reassembly can take place is removing the flywheel, I am debating whether to reassemble it, as I may have made it harder to remove without the weight of the whole thing pulling it down when hitting it. It seems like I could place the assembly over a workmate vice and hit it, but I think this may distort the crankcase half still stuck inbetween.

Flywheel still attached

[MorrisMan]

Ok I managed to remove the flywheel by heating it a bit and then just dropping it onto a concrete floor.

With my new crank installed, it looks like the crank cases are distorted, it will spin freely until I tighten up the bolts that hold the two halves together. Also it appears the crank has no float, e.g. it cannot move up and down on its axis at all.

I guess replacing the crank cases is the only sensible option?

[headdownarseup]

Well done on getting this far with it, i was getting a bit concerned that this was going to get "binned".

Have you removed the ignition baseplate yet? (makes things a bit easier for later)
With the crankcases assembled with all of its internals in place and the case bolts nipped up,try spinning the crankshaft--- if it's tight/seized then maybe the case halves are indeed distorted as you say.
There should be some end float on the crank,a lot depends on the individual motor. I have a couple of old 102's with a heck of a lot of float in the crank (around 4-5mm as best as i can see with the naked eye) but yet some of my 40's have got a lot less (1-1.5mm thereabouts)
It might not be the cases that are distorted but the crank bushes themselves. (just a thought)
There's often a couple of cases for sale on fleabay, but i'd be wary that you might end up getting something that's not much better than what you have already!
Try JOHN @ SOS, he might have what you need, either new or secondhand.

If you get really stuck,i have a complete 40 powerhead that looks alright taking up room in one of my drawers!

jon

[MorrisMan]

Yes I have the baseplate off now. When I assemble the crankcase with the bolts fairly loose, the crank spins freely by hand. When all the bolts are done up it can only be turned by attaching the dome nut to the crank and turning with a socket wrench.

I have sanded the inside mating surfaces of the two halves slightly at one angle, which has improved the alignment a bit, bit still no good if the bolts are done up.

On further observation it looks like I have about 3mm of end float. I have a friend with a lathe and likely a suitable reamer, so I will try bolting the halves together tight and reaming them both. When it is spinning freely there is less than 1mm of space between the two halves, so I am hoping the reamer can fix it without boring out the bearings to a strange shape.

I guess the damage that bent the crank also bent the crank casings. The car boot sale seller assured me it ran beautifully But for £15 I knew I was getting myself into trouble

[headdownarseup]

sounds like you might be wasting your time with all that machining.

Spare powerhead in my drawer taking up room if ever you feel the need.
Spins nice and free,nominal amounts of end float although the head needs to be removed to clear out the waterjacket. (although you could just use the crankcase with internals and use your cylinder/head combination.) Would also save you a lot of time and effort.

jon

[MorrisMan]

So I tried to true up the two halves on a lathe, but for whatever reason it still did not turn when bolts pinched up. I am just annoyed at having been defeated...

Anyway, I have purchased another pair of castings, that appear to run freely, I will begin assembly tomorrow, and see how far I get, I think I have all the parts I need now.

[headdownarseup]

That's half the problem with buying from a carboot sale.
You have to ask yourself why the owner is selling in the first place?
Always look before you buy. Some things are easily sorted, other things not so easy. (good idea to have a few spares of your own.you never know when you might need them)

Should be straight forward from here on.

jon

[MorrisMan]

Yes I was a bit unlucky, but learnt alot about 2 strokes and engines in general, and if I sell it fully working I will probably about break even, and had a fun project.

Any issues if I fire this up briefly without any of the base attached? Without any water I will run it only briefly, so it does not overheat.