hey guys just did a bit of an overhaul on my 850,
1.5"carb
new radiator
generator conversion

it was over eating before which is why the rad went in. took it for a spin and i swear no less than 2 minutes later steam was coming out of it,

seemed to run ok, mixture isn't right yet and need to redo timing anyone ot any ideas on what the cause would be

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1962 850,Frog

You converted to a generator?

Have you got a temperature gauge connected? If not connect one, as you can get what looks like steam from the coolant even though it is not boiling.

2 minutes is very quick for it to overheat from cold - unless you mean 2 minutes of driving after having warmed it up. I would look for any blockages or perhaps a dud thermostat (is the top radiator hose hot, and have coolant in it?)

I would also recommend you check the timing and tune the carburettor properly - a mixture of incorrect ignition timing and lean carburettor can make the engine run artificially hot and cause all sorts of problems.

you could have a airlock in the head...Run the engine and pump the top heater hose from the thermostat once it has opened. Did you also change the thermostate as it could be stuck

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Stop Licking the Dog...I Don't Care Who Started It

It must be overweight and the engine has to drag too much weight around

overheating that quick is most likely a timing problem, second to that is a stuck thermostat, and no impellor on the water pump

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did I tell you that I won a trophy?

I`ve had a mini recently that had a blocked bottom rad hose & blocked water pump,,, old gungey corrosion inhibitor all caked up & solid.

My bet with this one is on the thermostat being stuffed tho

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.