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GT6MK3

The SS Minnow - Vespa PX200E

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It looked so pretty, sitting in the dappled shade, as I rode down a few hours of back roads to the Drop Zone.

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Then I wen't a little too hard down the freeway, and coasted to a stop.

 

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The plug did not look good

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And this shadow on the piston looked ominous

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For good reason

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Mmm, toasty

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And for good measure I've killed the cylinder too.

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Oops.

 

 

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It could be lean, or possibly timing, maybe a bit of both.  

Was just before the end of a 10 minute WOT run on the freeway - was planning a plug chop and inspection to check the jetting.

CHT was hot but not stoopid hot (426F).

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4 hours ago, GT6MK3 said:

was planning a plug chop and inspection to check the jetting

Well, you got your plug chop.......  I'd say marginally lean and heat built up to the point where pre-ignition took over and killed it in seconds. Did it not start to get a bit sick first?

If it's an iron barrel can you not dunk it in caustic to remove the aluminium deposits then hone?

Looong push home either way!

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Hello All

                2 Strokes! 

Looks lean to me!

I think they set chain saws etc a bit rich at top end for this reason(and cheaper than pistons?)

Roger

ps just go for a bit more smoke and a touch less BHP!

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Flecks of ali on crown suggest detonation to me. If the hole is close to the plug maybe the plug was running too hot and acting to trigger detonation. But it would have run rough...

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On 7/20/2019 at 3:26 PM, GT6MK3 said:

CHT was hot but not stoopid hot (426F).

426!?!?!?!?!?!?!?!?!

Just what the devil DO you call 'stoopid hot' then??

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On 7/22/2019 at 2:06 AM, thebrookster said:

426!?!?!?!?!?!?!?!?!

Just what the devil DO you call 'stoopid hot' then??

450ish.  A mate took his to 496F without it failing.  We like to (ahem) push things a little...

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A poster on one of the Vespa sites has decided to name the PX.

His inspirations?

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And

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As he put it "White barge, 3 hour tour, hole..."

So it's been christened "S.S. Minnow".

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Pulled the engine Saturday night.

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It was filthy, so I took it down to the local car wash and blaster it with the high pressure cleaner.

Sunday morning I headed down the road to Michael's evil lair for a rebuild session.  About an hour into the drive I was banging along on cruise control in the bogan van, when the  back of the trailer of the truck in front of me got bored with the lane it was in, and headed into the one I was in, independent of the truck pulling it.  I don't think it's driver was expecting to hit slushy snow, and I know I wasn't.  Luckily he got it under control, and pulled over (I suspect for a trouser change).

I barrelled on, albeit a lot slower, and the snow in the fields told the story of the road conditions.

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Michael and I broke the motor down,

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then I got on with marking it up for porting and plugging for the Malossi Sport 210.

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The outside of the motor still needs some more cleaning, but we made sure the inside was spotless.]

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Then we installed the gearset Michael had re-shimmed back to tight spec, and built her back up with new bearings where needed and new seals throughout.

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I'm not certain that this will cut it in place of a split pin though.

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It's well and truely possible I was over agressive with the porting, so the 1.2mm sealing lip I left wasn't quite enough.

I finally got the cylinder to seal, but the test plate that goes on it kept leaking.  Temps in the garage haven't helped, no sealing compounds have wanted to cook off.  I've also been making the mistake of leaving the test kit sealed while using a heater to try to cook of the sealeants.  Heat plus a semi-sealed area equals higher pressure, so that pushes the uncooked sealant out...  

Lesson learned, don't leave the thumbscrew tightened till the test.

It was still leaking (fuck fuck fuckity fuck!) when I got home from work at about 1am last night, and the problem was getting the temp test plate to seal to where the carb box normally goes.  The metal to metal connection wouldn't seal despite a few attempts this week, so I got medieval.

Grabbed a spare gasket to bridge the gap, and trowelled on a pretty much rediculous amount of rtv (I also stuffed a tiny bit of rag down the inlet so the RTV couldn't drip in there and give me trouble later).

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Then I torqued down the plate (again), pointer a heater at it, and left it to cook off with the pressure valve undone.

This arvo I too it up to 6ish psi.

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30 minutes later the pressure loss was negligable

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Took almost 3 hours to lose 1/3rd.

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And after 9 hours it still had over 1/3rd.

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User acceptance testing complete...

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Hello Craig

                     I like a challenge but you seem to be a B*****r for punishment and I hate to say it but like our Triumphs they were built down to a price that would sell!

Still makes me laugh at my own struggles!

I have a few pre war Motorcycles that have given the same troubles(still have them) still beats the hell out of Scuby Do puzzles?

Roger

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More work on The Minnow today.

Cleaned up and offered up the rear wheel.  The new tubeless wheels and tyres available are great, but the short studs only just hang on to the flanged, serrated nuts they use.  A mate had a wheel come off at speed last year, so I'm a little paranoid.

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These nuts are good and tight, and have a visual mark for me to check so I can know thay havent moved

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Next up was to install a RPM gauge.  This should let me see what's happening with the adjustable CDI, to see if the rev range is improving.

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Onto an adjustable clutch lever

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A clear 2 stroke oil line

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An adjustment to the exhaust mount so it doesn't need the wheel to come off to install/uninstall it

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and a slot cut into the rear brake pedal so it will accept a modern adjustable cable

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This was followed by the dissapointment of finding broken fins on the flywheel

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So I'll be spending again..

But, after a fight

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In it went.

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Time for a rest.

 

 

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More work.

Which takes way too long, and too much lying down

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But in it went .

Exhaust was adjusted so it fits without rear wheel removal.

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And the rear brake pedal was slotted to take an adjustable cable

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This was a nasty discovery, will need replacing, but will do for running in

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Timing time.

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Then final hookups

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And away we go...

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Currently going through the running in heat cycle process, but signs are good.

Pulls like a train, hits 8500rpm at 1/2 throttle if you hold it.  Hasn’t been over 90kms/h yet, but a few more hours of running in coming tomorrow.

WOT run is coming soon...

 

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