[Grasshopper645]

I inherited a 94 eliminator 250 (same engine as ninja 250 as I understand it)

It had low compression so I replaced pistons/rings, honed cylinder and used a low milage replacement head (couldn't be bothered lapping valves etc)

Got it running perfect, took it for a good 2 hour cruise today and while riding along the highway suddenly got HEAPS of blue smoke and oil coming out the tail pipe. Pulled over and it turns out the lower radiator hose burst and all the coolant leaked out...so I must have overheated it and blown something.

My question is, why did the overheat warning light not turn on to let me know? And shall I now split the case and properly restore it or just take it to the junk yard

[jkv45]

Most likely the head gasket let go, and the head may have warped.

You could refill the radiator, start it, and see what it does. Draining the oil and looking for bronze-colored flakes will tell you if the engine bearing have denigrated from high heat. Depending on how long it ran without coolant, and a few other factors, there may not be significant engine damage.

We had a Ninja 500 that blew a head gasket and pumped coolant out of the overflow bottle. We pulled the head, lapped it on a flat surface, reinstalled with a new head gasket, and all was well.

This is one instance where running a synthetic oil can save you. It gives you extra time before things meltdown because it can withstand extreme heat much better than conventional oil before breaking down.