Hi all,

My MC16 (with MC18 carbs, heads and barrels) has siezed!
Coming back from the MOT as well . I wasn't even goin that fast - I noticed it started to slow a bit, pulled the clutch and the engine died. Coasted to the side of the road, and the kickstart was solid.

The rear piston is now knackered, and the barrel has some smeared piston on it.

So I'm in need of some new parts. Please see my post in 'wanted' section if you have an MC18 (or 2x MC16) barrels/pistons for sale.

Well I've been thinking about pulling the crank out as it's been making a bit of noise, and changine it for another one I have.... might as well do that while it's apart.

Thanks, Mat Grant.

Sorry to hear that Mat. Must of been a tad lean on the needle/mj hey.
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If I have to take the carbs off once more...

Hi,

Having stripped it, and looked closely, I think what happened is it has lost coolant, the MC18 head water outlet is smaller than the MC16, and I think it has got loose and lost the coolant - DOH! Although the temp guage didn't go up much, it was about 1/3 up the guage. But the exhaust side of the piston was melted away.

It's got standard airbox and jets, so I don't think it was too lean.... I'll check though....

Cheers, Mat.

Standard MC16 airbox/jets, or standard MC18 airbox/jets? What exhausts?
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Andy.
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the airbox is MC16 with a new filter from apex leisure - the carbs are MC18 with the standard MC18 jet sizes - can't remember but I've written them down somewhere....

I think I see what you're saying - have I done something really dumb???

Cheers, Mat.

If you lost coolant, over heated and seized then chances are the piston would show signs of grabbing all around the skirt.

With the front side of the piston melted away, this would suggest a lean mixture.

It's very possible to be rich on the main jet, but lean on the needles (as Steve suggested) and nip up.

Mine let go due to a coolant pipe split, and that melted the front of the piston crown. Jetting was already a bit on the edge though, so that would've accellerated failure.

I have a set of stock MC16 carbs somewhere (everything is "somewhere" at the moment!) and a set of MC18 carbs... I'll see if I can find them and compare the needles. I would imagine the "washer under the needle" trick will do, but you may find a set of HRC needles better.
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Andy.
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Andy wrote:Jetting was already a bit on the edge though.

Define "a bit"
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fontyyy wrote:

Andy wrote:Jetting was already a bit on the edge though.

Define "a bit"

Right on the bloody edge, everything comes out white and you get 200mpg, seizes at every hill but goes like the clappers. Thats "a bit" lean.
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If I have to take the carbs off once more...

Don't be a girl Steve....That's bl dy perfect that is