Motorcycle and Scooter appreciation

That is Italy for you. You are a new comer, and don't speak the dialect or comprehend the dialect.

Or worse your family left and then came back.

Am having a rather thin skinned day. Or better put would be either looking for an argument or feeling hard done by.

EDIT Also getting a bit tired of people I deal with getting more and more fascist about clandestine people in Italy.

It’s the typical north vs south banter and to be completely fair, I have no right referring to it whatsoever as a foreigner.

It’s something that’s used quite often here when people do something that’s not exactly in line with the rules / expectation. It’s always entertaining for the locals however whenever I use it as they don’t expect me to.

That banter is jus not northern and south, it is the whole city state history.

Not sure if it more offensive or justification when non Italians use it. But think that this is a Lega discussion...

Yea… but Ducati rattles….

Certain ducati engines...even some with wet clutches ;)

Often wondered if the rattle coulbe tuned, like the F1 engine playing 'when the saints come marching in'
https://www.youtube.com/watch?v=434SLnbyRrQ

Anyone ever knurled a piston or expanded a skirt in a vice?

Ok need more information, what piston...I'm hoping not an engine piston.

New knobblier tyres were a game changer today, real confidence inspiring. Coming from road cycling I'm always paranoid of falling off the shoulder but switching lines between ruts was a lot more sure-footed.

Was probably way off, but felt like I was getting somewhere near the CRFs performance when the trail opened up and I could safely crack the throttle. Bike felt great even at crazy hi psi from the garage.

Having said that, got a little too adventureus in some somme-spec claggy mud, almost thought I might have to abandon the bike. Thankfully the trail gods were looking down on me and somehow made it out exhausted but lesson learnt, don't push your luck when riding alone.

Went down a rabbit hole regarding piston slap.

The Rotax 237 inside the Scorpa Easy (project bike... btw I have a project bike) is rattly as hell. I expect it is piston slap, because it is top end and metallic.

Need to order fresh gaskets before I open the top and investigate, but I am expecting to see a big gap in the piston vs cylinder.

Reading online, back mid-20th century, there were two 'old school' methods to reduce piston slap before going down the bore/hone/piston route. One was to knurl the piston, and the other was to clamp the skirts in a vice to spread them slightly. Both achieved a greater circumference to reduce slap.

I am expecting the 'no no no no no no nope nope noooop don't do it' but I also wondered if anyone was old enough to come across a mechanic who had done it.

The Scorpa's Rotax engine is just short of obsolete anyway.

Edit: https://www.practicalmachinist.com/vb/general/knurling-pistons-384013/

Nice! Did you actually drop the PSI or did you feel the full wrath of running hard pressures?

I think probably yes. Was a big improvement on the oe dual sport rubber though, even at full pressures. Will experiment with dropping it and see how things change.

Lower pressure will be more squirrelly on harder stuff and more grippy on softer, so go easy on tarmac!

Don’t do it! You measure piston to bore clearance with a Micrometer and internal Mike. It varies depending on air / water cooled / iron / coated sleeve and cast or forged piston. If it’s a little over, either live with the noise if the compression is still OK, or get it rebored / replated.

So just leave it sounding awful and excessively rattly until something goes pop?

No, you should rebore and new pistons with new bottom end bearings.

or wear earplugs :)

Is it possible to adjust the timing and get it running quieter?

So the engine is a Rotax 237.

My next question would be, how interchangeable are pistons?

I am lead to believe this piston is the original spec, but I am struggling to see/understand what my next size up option would be.

The ideal would be a rebore and new piston, but will a shop be able to find me a suitable not-rotax that will work? Or am I limited to a Rotax shape that may be £££/impossible to find?

This is why I wondered about spreading the skirt a little and getting some more life out of the current arrangement before paying sums beyond the value of the bike.

Re: timings, you mean like retard the ignition?

As @jung and @airhead advise.

Open the engine up, and see what the problem is. Find the right engineering shop to do the bore find the parts.

Not sure what it is like here and now, in the past when I have had work the machine shop doing the work sorted all the stuff. But that was two decades ago.

Sigh. Guessed as much.

Still need to do some other basic things to get it running and riding. Once it works as a whole, I’ll strip the engine and see how much it’s gonna cost for the top end to be sorted.

It is only a single cylinder so not that expensive as it just one cylinder. ;)

Sometimes you can adjust it to a slightly more sympathetic timing. It's not F1 after all.

Find out what’s up with it first. I’d start with compression, if that’s low it could be ring sealing or just the bore getting a bit tired. Pull the top end off and inspect and measure. There’s generally some degree of cross compatibility on two stroke pistons, but before you get into that, see what OEM / aftermarket ones are available. If there’s no damage, measure the bore and order the next oversize. They generally come in increments of .25. Then take the new piston and barrel down the machine shop and get them to bore it. Cast pistons need less piston to bore clearance than forged - so make sure they know what you have.

Old air cooled two strokes are pretty rattly even when they are fresh. The couple of Rotax engines I’ve played with also had straight cut primaries that make a racket.

If it’s been sat unused for a long time, the crankshaft oil seals are often suspect. Just go slow - two stroke engines are mostly a doddle to build.

The bike is affectionately nicknamed ‘dog’. 1995 Scorpa Easy 250. I bought it from someone at the local trials club as a fixer-upper but it wasn’t quite as cheap as it should have been.

When started there was gear oil dribbling out the wrong cap, and coolant sizzling from the exhaust/rad. The lower fork clamp also had a crack in it. The fan was a big 12V job but poorly fitted. Wiring had come loose too. It became apparent it will be a labour of love.

The bike has spent the last couple weeks in a friend’s garage while I made space in my shed, so I’ve only had a few hours across two days to work on it.

So a friend in Shepton Mallet had a spare front end (forks, clamps, wheel, radiator, fan), rear suspension, Ducati stator and CDI, from a 2000 Sherco 2.5 Graham Jarvis.

We fitted the Sherco clamps and fork, original wheel, and replaced a few bolts. Fitted a correct size plug for the gear oil.

I syringed maybe 30ml or so of 2T oil into the plughole and cycled it a few times, then left it for the week, I hoped at least a little would seep down toward the mains. I was recommended “soak it in diesel” by an old 2T rider but didn’t have the guts.

Ordered the correct radiator from a breakers, fitted the Sherco fan, refitted and filled with coolant. New brake pads front and rear. Rear was bled but wasn’t necessary. Front was bled but needs more work still.

Clutch master appears to be leaky. Pressure one minute not the next. Going to rebuild, but have an Amazon special that should get me by, at least to test the clutch action.

We have a new front tyre to go on, and a near-new rear. That’s an impending job. Also need new unworn snail cams, fabricate a kickstand mount and kickstand, and some other bits and pieces I guess.

So yea, about 4 or 5 hours in and we finally kicked over the bike to make sure nothing was leaking out. It’s rattly and noisy.

I could live with the noise, so long as it doesn’t seize the engine the first time it gets used for more than 5 minutes.

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Got my engine back yesterday - the sprag clutch assembly wasn’t broken in the traditional way (failed spring) but rather the sprocket had a big chunk and around 4 teeth taken off.

I imagine this originated when I once fitted the ignition coils in the wrong order and the engine kicked back pretty hard after failing to start.

Also a little worrying: the mechanic warned me that the main clutch plate is only held on by 4 of 5 spring and bolts. I’ve probably put 5000 miles on the bike since buying it, without that being a problem, but definitely going to be fixing that!