Modern Vespa

Okay,

Must be unlucky second seize in two years from something to do with the oil pump.

Well this time the circlip that holds all that in place snapped and destroyed the teeth on the oil pump worm gear. (See photo)

Close up

Anyway,

Hard seized pretty good.

I have a pinasco 225 cylinder that is nikasil and has some scuffs and what not on it.

Need advice on if it can be saved.

Cylinder

Piston

Piston_2

"If it wasn't for bad luck, I wouldn't have no luck at all"

Looks pretty bad. How does the cylinder feel? Can you catch any grooves with your fingernail? If yes then plenty of people will tell you it's had it. But it's worth trying to revive, you really don't have anything to lose.

If you're having trouble removing the rings from the piston, try a little hydrochloric acid where they are stuck... let it fizz for a little and use the wire brush on it. That did it for me.
I also used the same method on the cylinder itself to clean up any smeared aluminium with good results.

Oh, and pre-mix. Everyone needs a hobby.

Yeah I definitely don't have anything to lose.

I had a bit of luck with the acid removing some of the aluminium from the wall of the cylinder.
I ordered a new piston and rings in the hope that the cylinder will be ok.

What's the best way of cleaning it up aside from scotch brite and sandpaper?

I would use wet and dry but not regular sandpaper.

The other thing to watch out for is how long has the flywheel side bearing and small end bearing been without oil? Easy to replace the small end now.

Yeah it's all in pieces so I can do it all.

There was heaps of ground up teeth in there so I pulled the engine and cracked the cases.

At least I have been here before and I know how it all comes apart.

Worst case scenario if I use the not so great cylinder? Excessive ring wear?

If it's not useable I'll go the malossi 210 with my old crank.

It's pretty annoying.

Well you won't have any ground up teeth in the cranckase so that's good. Just the bearings including big end running without oil for a bit which could be bad depending on how long it went for. Check it for play.

Aside from bearings worst case is the compression is not up to scratch (if you'll pardon the pun) due to poor ring sealing... but still worth a go. Especially if you've already ordered a piston.

Ok I'll check all that.

Theses are the measurements for the crank:

I was thinking of the other method where you hang the crank from your finger through the small end, make a fist and sort of whack one fist with the other... if there is play it should cause a kind of ringing sound, Not a great description, but it's easy.
But if you are able to check those other measurements somehow then it's probably a lot more accurate.

Is there not that method where you use your feeler gauge and measure the space down there?

If you know what I mean.

I have done it with a yz85.

I'll give the tuning fork method a try.

You screwed the cylinder stud in too far, or someone else did, and it fouled on the gear. As the engine ran, the gear teeth wore away unril it stopped working.

I bet if you looked at the end of the stud that was screwed in to the case there will be visible damage.

A feeler gauge will measure side to side clearance. That's going to be unchanged... what I'm suggesting is trying to see if there's any play between the bearing, pin and conrod journal in an up and down direction.

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Had a look, stud is about 5mm still inside the casing so doesn't look like that has happened.
Cheers[/img]

How about this:

Someone screwed it in too far. Maybe you didn't do it, but someone did. I've seen this a bunch of times. There aren't many ways for that sort of damage to happen. The fact that ALL of the teeth are worn down is a sign it was turning, otherwise only a section of the teeth would be messed up. The likelihood that the circlip piece snapped off and was flung up into the oil gear is slim, as the piece would have been more likely to have fallen down into layshaft. I would expect both the oil pinion gear and the drive gear on crankshaft gears to have been damaged, but it is only the pinion gear.

Yeah it makes sense that it would have happened but it's not here.

The stud is too far up to hit anything. It's 5mm up inside the case. I was the last person to disassemble everything.

Oh well no matter it's bad now

Hi there,

The comment about the stud being screwed in too far makes perfect sense: it happened to me too; except that I was lucky enough to realize it right away, when the kick pedal was stuck, and unscrew it straight away. In your case, it may have been screwed in in such a way that it didn't completely block the cogs; or maybe the guy who had it before simply didn't see the kick being blocked as a red flag, and just went ahead and forced it.
About the stud being back in place: if it moved being screwed in, it likely moved in the other direction being unscrewed. In any case, better to glue the studs with Loctite (medium or strong), and to check the clearance while doing so. It's pretty much a permanent repair from then on.

The cylinder itself is fine. Just have it honed with the right material (nikasil requires a specific type of hone); the wrong material will either damage the plating, or not disturb it at all. The piston needs to be changed, as well as the rings (which is already in the process of being done, so all's good).

Here's a Malossi 172 cylinder of mine (T5) which was a little more damaged (20 kms going full blast on the freeway, with the oil pump inadvertently cut off).







I thought it was toast, but a buddy who has access to a workshop told me to send it to him so he could hone it. Got it back like this:



Absolutely no discernible loss of power; I can hardly feel the remaing marks with my nails. No doubt yours will come out even cleaner...

I'm interested to know what kind of hone was used FNS? I keep reading that they can't be honed, so therefore what do you have to lose if you do? Obviously worked out well in your case.

Not sure exactly. There are different procedures to get the aluminum deposits off the nikasil bore: lye, deglazing, proper diamond honing. The guy who took care of this job is on vacation till 2017, so no hope for details until then. Also, there's no single solution for each and every case. In my case, just eating up the aluminum deposits with lye wouldn't have sufficed, as the nikasil lining had been damaged. In your case, a shop that specializes in 2 stroke MX repairs will be familiar with appropriate techniques for the specific job required (they'll need to have direct access to it, not just an over-the-internet appraisal). Maybe check Australian MX forums for a reputable workshop in your area, and see what they say when they have a chance to check it out in person.

Oh, and although I have the same 225 kit, I didn't notice a grade on it when installing, so I don't know if grades apply here. But for the Malossi, they have several grades to adjust to manufacturing clearances, so if your cylinder is an A, you need to get a corresponding (A) piston.