Hey all. Here's another thread like the mc21 nearly killed me one. I need help diagnosing whats going on.

I was giving my '21 some go today and was at around 170 when she seized, locked up the back for at least a second - couldn't tell cos I ripped the clutch in - it just felt real loose and it happened so fast. Anyway I rolled to a stop with engine dead.

I proceeded to kick the bike over - it turned over as if nothing had happened. The only problem was that it wouldn't start. I proceeded kicking it over with with only signs of life being tiny splutters now and then and even tiny backfires coming out the back which i have never heard before. After about 50 kicks, it started but sounding really weak and funny and wanting to die. I kept the revs up and proceeded to put my gear back on to limp home.

Before I was fully suited, the bike starts smoking like a bitch from the engine with burning smell and then coolant starts pissing out the bottom. I think that i lost all my coolant in a steamy puddle. That was that - shut engine off and called a friend, being all dejected.

I'm wondering - what has happened here? Okay - perhaps the engine seized, but why would the coolant piss out? Why would the engine seize only for me to find that i can kick the engine over straight after? Why did the engine not start again (straight away) eventhough I could kick it over freely?

I'm thinking rebuild time but I need to find the cause of the problem first. Any thoughts would be much appreciated.

I'm getting withdrawal already

Is it running too lean and overheated? So an over expanding piston caused the seize but then cooled and contracted while not running and by the time you started kicking it over it had freed but lost most of its compression because of internal damage so wouldn't start easily and ran badly. The losing coolant sounds like excessive heat is making it expand too much in the radiator and its running out of the overflow, though not sure about that.
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After years of moaning about immigrants now i am one...

They will often kick over with ease after seizing. Poping and back firing is also a sign. I'm afraid your in the world of exspensive rebuild.

Best pull the heads and pipes off and find out whats happen the the cylinder(s) and go from there.
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If I have to take the carbs off once more...

Cheers. I'll post some good pics when I get round to it.

It could of been worse, you could of owned a Seizeuki.
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If I have to take the carbs off once more...

Hey I'm just trying to get the engine out and theres this bolt that requires a 12mm hex key. Does this sound right? I got the 27mm nut off which goes over the bolt but now i have to buy a 12mm hex key to get the actual bolt out?

Admin: Non-working link removed. Do not link to sites that require registration.

Yep, that's right. They're not much though...
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NSR300R - Why did i ever have a 250...

[quote="StephenRC45"]It could of been worse, you could of owned a Seizeuki.[/quote]

well, mine partialy seized last week also,

... i had a mc28 , that took 8 hours of consistant thrashing at high rpm (200kms)
at a race track with NO problems wat so ever....

mc21 may have a bit more balls, personaly i think the mc28 was much more reliable and dependable bike, hows that for confidence in your bike if you dont even know when or wats going to happen...

and did you splice your bike before it seized? or any mods done recently?

Mine seized last year. I removed the cylinder, cleaned it up with muriatic acid, and then installed a new top end on both sides. Runs like a charm now. Not always necessary to replate or buy a new cylinder as long as the nikasil is in place and there are no gouges. A light seizure often just leaves aluminum from the piston on the nikasil and the acid takes it off. If you need help with how to use the acid and clean the cylinder, I'm sure that there are many besides myself that can guide you through it.

Best,

Joel
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1994 MC28 Rothman
TSR250 AC28M

Hey okay I'm have trouble removing the cylinders.

Each one has 4 nuts. On each cylinder, the nut next to where the powervalve cables connect is in a really crap position. I can't get a socket onto it and can't even get my ring spanner over it. I can get a normal spanner onto it but that's dodgy and it was starting to strip.

How the hell do I get it off?!!

here it is. Seriously man I can't fit a socket in there!

A ring spanner should fit with easy as long as its not some cheap monkey metal one.

If yours doesnt fit the I would go and buy another, it will come in handy for the other cylinder
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If I have to take the carbs off once more...

Get yourself a good quality 12mm spanner and grind it until it fits That's what I did. If it's a cheap and cheesy wrench then expect it to break, or round off the nut. It's worth sacrificing a quality tool for the job.

Never use the open end of the spanner unless you have no choice. People have been whipped and hanged for lesser crimes

OhOh

Clean everything BEFORE opening. Look at all the dirt around that hole in the case and around the cylinder. You don't want that in the crankcase.
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

How you get that nut out is not the question, how do you torque it up is....
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Please do not PM me technical questions, if you can't find it on the Forum start a thread