Cagiva Supercity 2 Stroke - "just died"

[j.o.n.n.y.g]

Hi, well the whole thing has died now, first of all slowed and changed down on approach to a roundabout and engine just petered out regardless of throttling. Switched to reserve just incase (no fuel guage) managed with some effort to get it to fire up again, got over the roundabout and about 500 metres down the road suddenly felt "engine braking" and rolled to a neat stop at the side of the road. Now having pushed it a mile and a half home just wondered if anyone could suggest where to start looking for why this has happened?
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If it flies, floats or f***s, rent it!

Supercity 125 Lucky Explorer R.I.P. - Jinlun JL 125 11..... next.......

[cheekythomas]

Sounds like engine seized chap.

Could be mixture issues, oil wasnt good enough, lack of maintenance or possibly just bad lack... although its very rarely just bad luck, normally there is a reason...

[collywog19]

As said, send engine/whole bike to me, ill sort it

I just been fitting new top end to a mito

Col
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1996 Yamaha YZF750R, 1994 Yamaha YZF750R, 1989 Honda CBR400RR NC29, 1995 Kawasaki GPX 250R AND 1995 Cagiva Mito Evo SP!

[cagiva gezzer]

Seized or dragging up crap fuel.
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"because one stroke isnt enough and four strokes waste two"

[-Elliot-]

when you say it rolled, if you were in gear the engine cant have seized can it??

[lee125]

[AbiJ]

[stevo as b4]

Yeah i'm leaning towards a piston seizure being the most likely culprit.

I don't know why, but in my experience, nearly every time i've had a 2 stroke bike seize up, it's always been when your slowing down for a junction/roudabout etc, or travelling down a long hill with the throttle closed.

When the piston in my KMX200 decided to break up it was just as i was riding it home from some off road MX track use, i was just going slowly about 25-30mph, and slowing down for a junction, when the back wheel momentarily locked and skipped and then i felt a sudden strong engine braking effect for a few seconds and then nothing at all! I knew i'd lost all compression as soon as i tried to kick it over. ( Most of the piston crown was either in the expansion chamber, or the crank case at this point.)

I would'nt worry too much, if your Supercity has only has a piston seizure it won't be that hard to fix, or cost that much hopefully! The worst case scenario is that the barrel is badly scored, and the combustion chamber in the cylinder head is pitted or damaged.

When you get it repaired the bike should once run in feel much more powerful than it used to! I don't think that any performance 2 stroke engine stays at it's best for more than 3-5000miles, even if it runs alot longer than this between re-builds/blow up's/seizures.
2 stroke engines run very hot, and they all eat their piston rings over time. They are usually ready for a new piston and set of rings/small bearing, and a full de-coke by 5-6000miles, regardless of how you ride them.

Hope you get it sorted out without too much expense mate!

[lee125]

[collywog19]

He says it now starts ok etc, maybe nipped a ring?

Id still get it sorted anyway.

col
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1996 Yamaha YZF750R, 1994 Yamaha YZF750R, 1989 Honda CBR400RR NC29, 1995 Kawasaki GPX 250R AND 1995 Cagiva Mito Evo SP!

[j.o.n.n.y.g]

Update.... engine was running at just over 80 degrees, on a day when the temperature was about 30, run downhill, along country lanes and then got stuck in traffic. Ran about 1 mile at a constant 35/40 (under 6000 rpm). Engine died shortly after. Rear wheel nor gearbox locked. freind suggested water in the oil? Local Halfords lacking in the spares department. Have managed to start, idles at 2000/1500 rpm. ran for at least 2 minutes. Haven't had time due to other comitments to do anything more..... will have the whole thing apart and in the "dishwasher" tomorrow.....
____________________
If it flies, floats or f***s, rent it!

Supercity 125 Lucky Explorer R.I.P. - Jinlun JL 125 11..... next.......

[befdelta7]

my supercity has problems similar to yours j.o.n.n.y.g
i get very strong engine braking only when the engines warmed up when coming off the throttle but it doesnt die or cut out just get a very slow idle, but is still ridable. iv had the head off seems a very very little bit of the power valve nipped the piston, but that wouldnt of caused the strong engine braking for sure and the piston isnt even scratched just marked, you cant even feel the mark just see it.
its something else, im thinking crank bearing or something around that area.
im going to get the engine out and head, barrel, piston off and have a shake and a wobble, to try find out what the problem is.

or i might just pay for a full engine rebuild, about £300 with new parts fitted, new seals/gaskets, crank shaft balanced, all labour charges and pick up and drop off to my address. takes about a week.
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Dont do a wheelie in front of a traffic copper... it gets you 3pts and £220 fine.

[j.o.n.n.y.g]

Bit of an udate here, got the bike running - drained petrol, coolant, changed head gaskets, changed exhaust gaskets, new coolant, fresh petrol, new front brake pads and new chain later....... it runs!!

However, now feels a bit more sluggish between 3 and 5000rpm but takes off like a rocket from 8- 10

Still sounds a bit more like a taxi than 2-Stroke, particulary when idling and at low revs. Sound seems mainly to be coming from gear change side of the engine.... could this be a future problem?

Cheers for all the advice on this.
____________________
If it flies, floats or f***s, rent it!

Supercity 125 Lucky Explorer R.I.P. - Jinlun JL 125 11..... next.......

[TUG]

your front sprocket loose? if it s a knocking sound then i'd have a check for scoring marks on the piston and cylinder wall, did you change the piston rings recently?
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Haz ER-5, innit!

[j.o.n.n.y.g]

New piston went in about 400 miles ago, everything seemed alright on and above the piston, small marks from a previous seziure (not mine!) which seems to have been repaired some time ago.

whoever did it though neglected to install any gaskets in the exhaust, only the inner head gasket, left the starter motor half unbolted, missed a bolt out completely from the crankcase cover, left the connecting piece from the airbox to the carb unnatached and left off the split pin on the chain, didnt bolt the seat on, etc....

Don't know if any of them could have caused any new piston damage and could cause long term issues, surely now there is more done up there should be less noise!!

Sproket is tight, new oil went in about a week ago, but sound started about 2 weeks before that?!
____________________
If it flies, floats or f***s, rent it!

Supercity 125 Lucky Explorer R.I.P. - Jinlun JL 125 11..... next.......

[TUG]

did you run the new piston and rings in correctly? premature use causes it to wear down faster by alot mate, possibly you've used it too fast without running in? maybe a bearing has gone? whats on the gear lever side? clutch push rod?
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Haz ER-5, innit!

[TheDonUK]

Sounds similar to my old GS500

It used to drink oil and had near 100k on the clock by this time...

been riding along a fast dual carriageway, it had given out, as if it was out of petrol, gave it a little while, put it on reserve managed to get it started, but it was sounding rough, i reliased it was likely on its way out, but i just wanted it to get me home, coming out of a corner the back locked up hard as if i had just dumped the clutch in first gear doing 50 (gs500). I just managed to catch the clutch before it had me off, and pushed it the rest of the way (only a mile or two).

If the bike is cheap and you been looking for a new one, maybe nows the time...