2 Stroke Engine won't turn over

[Ol]

I'll start by saying in writing this sat in a field at the bottom of a mile long steep hill procrastinating as much as possible before having to push my bike home!

So....

The bike is an old 125 2-Stroke 1986ish Cagiva Crosser, there's no kick start so I've been jump starting it for the past 18 months.

The bike was running ok last time it went out 2 weeks ago, but this time whilst trying to jump it, as soon as I let the clutch out the rear just locked up. I took the plug out, pushed it as far up the hol as I could before thinkin I was going to have a heart attack, and the engine would turn over ok, but as soon as I put the plug back in the rear just locks up again.

I don't imagine it's seized as said before, it was running no problems on the last outing... Any ideas??!

A very tired Ol.

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If it turns over with the plug out, maybe it's hydrolocking? Take the plug out and kick it over a few times.
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[temeluchus]

wrong plug?
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[MarJay]

I don't think it's easy to hydrolock a two stroke as the fuel will escape out of the exhaust port...

Sounds like something is very wrong though. As Temeluchus says it could be that the new spark plug is too long and is fouling the piston?
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[Ol]

I put the same spark plug back in, and its been running ok with that plug for the last 6 months or so.

I doubt it's hydrolocked - The bikes only ever been out in the wet / rain once when i first got it, and i thought hydrolocking was from riding through streams / big ass puddles etc? Hell, i've only cleaned it once in the last year or so too so couldn't be from a jetwash etc.

After a bit more through, i'm genuinely stumped with it - only other thing i could guess at is if one of the ports has got too much carbon / crap on it and has stuck??
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[Ol]

I have no idea if it has a power valve - the engine is an early mito lump that claims 25bhp so I presume it's got a power valve...

Flooding the crank with fuel makes sense, but the bike hasn't moved since it was last out, and was literally ridden up to the garage door after the last ride so hasn't been thrown about in the back of a van etc.

Think I'll start stripping it down at the weekend and have a look!

Thanks
Ol.
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Previous: Cub50, NRG50, TS50, YB100, CB125, NSR125, ZZR600, CBF1000, SV650s, ZX6R B1H, XT250, Mito Powered Crosser, WRF450, , FZ600, VN800, GSXR600 - Currently CB1000R

[stirlinggaz]

Hi,
easy way to tell if you have CTS (cagivas powervalve system), is simply by turning the key.
does it make a sound, like a motor whirring when the power is turned on? from under fuel tank or a bit lower down.

of course, being the older engine (pretty sure its NOT the mito engine : does it have 7 gears? but still be good for around 25-30bhp) it may have a non electric pv.
easy way to check what/if powervalve system is fitted is to lift the tank.
if you see 2 cables connected down on the cylinder (right hand side) going up to where it joins the loom then you have CTS the more modern pv system.
if you have just a rectangular alloy box, it may well have a pneumatic version. it should have cagiva cts stamped on it btw

so.....lift the tank + see whats fitted!

would be good to know the following :
1: cylinder head code, should be something like 2O0H
2 : what cylinder is fitted? should have a code cast onto side of cylinder, something like 73037
3 : what exhaust is fitted, especially the expansion chamber. there is a code engraved on the belly of the exhaust system, but might be hard to see if its rusted &or been painted over.
4 : what carb is fitted? standard dellorto 28mm? or 34mm or mikuni 35mm?
all these thing will tell you a lot about the bike.
doesnt the crosser have the full engine |+ cylinder painted black?
the lack of plastics will make identifying engine parts easy.

us cagiva owners are pretty obsessive about the codes, because the correct combination of head,cylinder,expansion chamber + carb can make a VERY good bike.

now the spark plug : what are you using? i'd be looking for a BR95EGV

so......tell us some more....please?

+ it might not be as bad as you think, pretty sure it wont be hydro-locking.
but i've had 2 strokes randomly go into a REVERSE gear, when kicked over at the wrong time.
seriously....kick started my mtx when it stalled at a busy junction + when i let the clutch out, the bike shot backwards, gave me + the car driver behind me a bit of a fright.
sorted itself out + never done it again.

cheers,
GAZ

[Robby]

Your terminology and spelling in the first post makes all of this a bit confusing.

When you say jump start, do you mean bump start? Jump starting is using another battery to start it, bump starting it running alongside and hopping onto the bike.

When you say you took the plug out and pushed it up the hol as far as you could, did you mean you pushed the plug into the hole, or you pushed the bike up a hill? Two very different things.

As far as I can tell, you have an engine where you're been bump starting it, and it won't turn over with the spark plug in but it will with the plug removed. In that case, the issue is likely to be with the clutch, or failing to get it into neutral. The fact that you're been riding it for months with a broken kickstart suggests that the whole thing is a bit knackered.

[Kickstart]

[nathan k]

big end, or main bearings could be shot.

The added compression from having the plug in would make it too hard to turn over but do-able with it out.

How does the engine sound/feel if you turn it over by hand with the plug out?

[stirlinggaz]

[Kickstart]

Hi

The early Rotax engined Aprilias used a pneumatic power valve, and the same system is still used in the Rotax Max kart race engines. Aprilia carried on using the system in their race bikes for quite a while after they stopped using it in the road bikes. Advantage was it was lighter and didn't need a battery / charging system.

It was the early Freccias that had the mechanical system. The late C12R had the electronic system (and just like the Mito, it toasts the control unit occasionally ). Can't remember off the top of my head which of the C10 / Anniversary and very late C12 had electronic or mechanical systems. The very late C12 was a bit of an oddity, seemingly built on the cheap (C12R bodywork but early wheels and a 6 speed gearbox - in France they were punting them out new for about the same price as the normal kickstart TZR125)

There was also an aftermarket power valve system sold for a while that worked off exhaust gas pressure.

All the best

Keith
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