SST 250 rebuild

chopper

chopper

Club Member
So as im now getting along with the rebuild i better start a thread showing you nosy lot how it started and its progress:D


Its a 76 SST250 2 owners from new, last owner since 1978 and hasnt run or been on the road since 1980, bought as a complete roller with a seized engine

How it started!

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Re: SST 250 rebuild

Forks - Stanchions were badly rusted and pitted so dropped them at ABE in greenwich and they re-chromed and ground them, forks rebuilt with 5wt fork oil, new oil seals. Forks legs painted black while they were stripped.

Wheels - were badly corroded, rims were long past it hubs were covered in surface corrosion, rims and spokes cut out and dumped, hubs blasted

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and enamelled black along with the rear drum

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couldnt help myself with the rear sprocket:redface:

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Re: SST 250 rebuild

Yokes were sanded, primed and painted a metallic silver as the surface wasnt up to polishing IMO

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All of the switchgear, bars and other small parts just needed a clean up with a wire brush on a drill and a lick of paint.
 
Re: SST 250 rebuild

Back as a roller again with the bottom end of the motor dropped in

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Re: SST 250 rebuild

Good progress Neil - you don't hang about, do you?

Have you had the bottom end down?
 
Re: SST 250 rebuild

My major issue has always been with the motor, the piston rings had rusted into the chrome bore of the barrel and trashed the bore, there were a couple of broken fins already but i managed to trash a few more :redface: when forcing the piston out! so the barrel is IMO past it. So the search began for a replacement barrel and piston, not the easiest thing to find i soon found out! I have managed to get hold of a later Cagiva SS250 barrel and piston which apparently works but as yet I have no guarantees and as my knowledge of the inside of two strokes is limited at the moment im not sure what to do.

The Piston is the same in every way as is the dimensions of the barrel, the head stud pattern is completely different as is the intake and exhaust ports, the fins are also an inch or so wider on either side but i could easily trim these down if need be
I can make or get made adapters for both im sure but im concerned that the thing will ever run once its back together and the barrel and piston i bought were far from a bargain!

I have looked into a complete replacement engine as there are 5 or 6 european brands that share exactly the same engine mounts apparenty but it would be nice to keep the motor as original as possible


Old Barrel

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New barrel

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Old intake

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New intake

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Re: SST 250 rebuild

banquo said:
Good progress Neil - you don't hang about, do you?

Have you had the bottom end down?
Click to expand...

dont do waiting:redface:

its been very straightforward so far but i get the feeling i may slow down from this point on!


Didnt split the cases no, crank seems fine with no play and turns freely and have been told by the couple of experts i have spoken to that they are good and strong so have left it for now.
 
Re: SST 250 rebuild

All the tins went off to paint to a friend of mine that runs a car repair shop a couple of weeks ago and are being treated to a blast first, all were pretty rusty but in good condition, im going red as below

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they are apparently being a pain and have taken multiple coats of high build filler primer to get a good flat surface to paint on, the tank is in need of re-sealing as it is leaking badly apparently, some repairs have been done but i will petseal it when they all come back

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graphics copied and being made ready for the finished paint in a couple of weeks
 
Re: SST 250 rebuild

:) nice to see you breath life back into the old dear neil will it be ready for mersea ?
 
Re: SST 250 rebuild

chopper said:
I have managed to get hold of a later Cagiva SS250 barrel and piston which apparently works but as yet I have no guarantees and as my knowledge of the inside of two strokes is limited at the moment im not sure what to do.

The Piston is the same in every way as is the dimensions of the barrel, the head stud pattern is completely different as is the intake and exhaust ports, the fins are also an inch or so wider on either side but i could easily trim these down if need be
I can make or get made adapters for both im sure but im concerned that the thing will ever run once its back together and the barrel and piston i bought were far from a bargain!

I have looked into a complete replacement engine as there are 5 or 6 european brands that share exactly the same engine mounts apparenty but it would be nice to keep the motor as original as possible
Click to expand...

Hmmm. If it's that far different, what's the chance of getting the right barrel, if you look harder? Or are they just unavailable, period.

I'm assuming your cylinder head isn't going to fit, so you would need the head off the later model too, and then the exhaust from the later, and adapt that to fit the frame and cycle parts, and make up what looks to be a fairly simple flange to stub adapter to take your stock carb.

There's nothing magic about 2-strokes (apart from the fact they're a lot simpler than 4-strokes), and if your piston is matched to your barrel so the porting works, and the stroke is the same, and the deck height is the same, then it will work, providing you can get a head and some way of attaching carb and pipe....

Adapting the wrong barrel is your only choice if there really is no chance of getting the right one, but it sounds like it's going to provide loads of hassle, and if you haven't used, it, probably you can sell it for pretty much what you paid for it?
 
Re: SST 250 rebuild

Chance of a original barrel are not far of Nil, so i am told, they come up once in a blue moon and tend to be knackered anyway so need re-lining or nikosiling, all the Aermacchi 2 strokes with chrome bores had a very bad habbit of seizing due to the chrome bore and them sitting for to long. My head will sit and work perfectly, i just need to create some holes in the correct place in the new barrel, there is room for them and should be pretty straightforward. The exhaust im not overly concerned about as I was going to get the one i have re-made (its very rusty) by a local exhaust builder anyway so adapting it to the different outlet should be no issue, the inlet rubbers are available for the bigger carb from germany so im sure with a bit of a searchi could find something that is close enough to work with a slight bit of modification.

My other concern is reed valves? by the looks of it the original motor has none, but the newer barrel may have (cant find any info on that but i know the newer cagiva's did) would that cause issues??
 
Re: SST 250 rebuild

From your pix, looks like the inlet port is designed for a reed valve.
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You would fit the reed valve into the square orifice, and the correct manifold adapter to whatever carb the Cagiva was fitted with, which may or may not be the same as yours.

I'm assuming there must be a support forum for these. What have others who have taken the Cagiva barrel route done?

I guess the porting in the barrel is not identical to the barrel you took off then?
 
Re: SST 250 rebuild

Yep thats what i thought when i got it, have bought this a few mins ago on ebay, mount plus a reed valve, mount is for a 35mm carb instead of a 32mm but im sure i can make that fit:D if not its a good base to make something

Cagiva carb mount and reed valve, ebay

I need to look at the porting a bit better than i have so far (only got the barrel a few days ago) all i checked when it turned up where the dimensions of the piston and barrel etc, im learning slowly about 2 strokes:D
 
Re: SST 250 rebuild

If it's made for a reed valve it will have deeper/larger ports.The larger the ports,the worse the pick up from low revs.The reed valve cures the problem.
 
Re: SST 250 rebuild

Much simpler in my day; imagine ruining that simple concept by adding an extra valve... even if it is a reed valve...

Good luck with that.

Old article here about the 125. Even that had a 34mm carb.
 
Re: SST 250 rebuild

This is why i am hesitant to even start playing with this barrel, at the moment the supplier will take it back for a full refund once i start playing with it and it doesnt work out im ?400+ down and no better off.
 
Re: SST 250 rebuild

Out of interest Neil what colour red did you decide on? Getting muddled up with Chiefy's Chipper :D

So did you get the original colour?
 
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