sods law - engine seized?

[Hutchysrs50]

sooo

went to put £5 woth of petrol in my bike.

went for a little ride because its so hot out! after about 40 minutes, i started to notice the revs going a little funny, like it i was slowing down and put it into neutral the revs would stay really high, untill i set off and then they would take ages to pick up.

so i was on my way home and the back wheel just locked up without warning, leaving me to come to a skidding stop.

i sat at the side of the road for 10 minutes and started the engine again, and it started again, enough to get me home.

why would this happen?
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Gilera SC 125 - Current

[Kickstart]

Hi

Idling high can be a sign of an air leak, which means it is also running lean. Running lean can cause a seizure.

As such check the simple stuff, like the carb being sercurely mounted and no cracks in the rubber intake manifold.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Hutchysrs50]

[Hutchysrs50]

ok, so the radiator was bone dry

i checked the exspnation bottle and it was full to the rim!

i only filled it up half way last night, whats gone wrong


i took the spark plug out (was quite black)

put the jumper pack on with the plug out and the engine was turning over fine, but im going to take the cylinder head off and check anyway!
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Gilera SC 125 - Current

[Hutchysrs50]

just the usual update!

the wierd smell was the gaskets cooking away, great.

the cylinder seems perfectly fine, but the piston has grind marks down both sides.
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Gilera SC 125 - Current

[spitfire123]

[Hutchysrs50]

[Kickstart]

Hi

The bit beside the cap just looks like a clip to stop the cap coming off when you don't want it to.

Person first guess would be that the head gasket leaked, compression then pressurised the cooling system (hence the header tank getting fuller) and either leaked the excess liquid out of sucked it into the combustion chamber.

Think the head gasket is a rubber O ring, in which case check it hasn't cracked.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Hutchysrs50]

[Hutchysrs50]

right.

iv checked the crank and it all felt ok.

i put a new cylinder head on with new gaskets.

filled it up with hot water and reved it for a while untill there was alot of presure in the radiator, couldnt see any leaks at all, so that is probly fixed now.

i still dont understand why all the water went into the exspnation bottle and didnt come back out.....

what would happen if i filled the radiator up to the top, and filled the water bottle to the top, would that stop the problem or cause havok elsewhere.

also, i bought the water bottle and it came with no lid, i just put like bag over with a cable tie, do the exspantion bottle lids have to be a special type with a hole in the middle to let air escape or just seal it off compleatly?
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Gilera SC 125 - Current

[Kickstart]

Hi

Expansion tank is just basically a catch tank on most bikes. Somewhere to catch any excess coolant and to allow it to get suck back when pressure in the cooling system drops (probably when it gets cold). However some like the RS125 it is a pressurised part of the cooling system. Not sure of the style on the RS50.

If a head gasket goes then one thing it can do is pressurise the cooling system, pushing coolant out.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Blue_SV650S]

[Hutchysrs50]

[Hutchysrs50]

also, the radiator cap and exspnation bottle are both new
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Gilera SC 125 - Current

[Blue_SV650S]

[Hutchysrs50]

[Hutchysrs50]

also!!!

not long ago, i cleaned the radiator out and put mesh over the front, think that could be helping it over heat faster than usual?

it still has ail holes etc but obvs not as much as if it was off
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Gilera SC 125 - Current

[Blue_SV650S]

[Hutchysrs50]

so if its all sorted, its gona be ok to sell?

what are the chances of there being any other damage?

melted some internals or oil seals or somthing, i dono.

i want to sell the bike in good condition, not for the person to buy it and then break down 2 miles from my house.
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Gilera SC 125 - Current

[Kickstart]

Hi

Head is the hottest part by far. Biggest risk is that you have warped the head.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Hutchysrs50]

[Kickstart]

Hi

In which case that isn't a worry. It is possible you have done other damage (eg, possible to warp the crankcases, and also possible to damage the big end from seizing it), but probably fairly unlikely.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Pete.]

It's normal for the level in the expansion bottle to go up when the engine is hot and back down when it cools. The radiator cap will let water by when the pressure gets to about 1.1bar on most bikes, about 16psi. There's not much restriction the other way so it pulls water in from the expansion bottle easily when cooling down, this is a normal process. Your bottle should have a min and a max level on it, you should fill it to between those marks when cold.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Blue_SV650S]

[Hutchysrs50]