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Vintage O.S max 21 vz-b(p) Break in method

Vintage O.S max 21 vz-b(p) Break in method

Old 07-01-2012, 08:21 AM
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Default Vintage O.S max 21 vz-b(p) Break in method

Hi guys,

Yesterday at my LHS, I picked up a brand new vzb for the equivalent of 40us$
It's the not the v-spec version, rather the original version with the silver crank case cover.

Having scoured the net for info, it would seem that it had a pretty bad reputation...blowing bearings, breaking con rods and loosing it's compression after a gallon or 2.

But, if it didn't break, it was by all accounts a really fast engine.

My question is how do I go about breaking this engine in?
I have read that if you use heat cycling on this engine, you're stressing the bearings...leading to premature failure.
Instead you should idle it for 3 tanks and then very gently run it for another 3-4 tanks.

If it had been any other engine I would just have used the heat cycling method and be done with it, but with this engine, I'm not sure.

Any help would be greatly appreciated
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Old 07-01-2012, 10:11 PM
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I ran these, and liked them alot. Fuel mileage wasnt that good but eveything else was.

As for as break-in, we just idled a tank and did the usual heat-cycle stuff.

First one we had lasted only about 3 gallons, but then another local who also ran them made up some of their own fuel with 16% oil, and then we started to get about 6-7 out of them.

Once we upped oil content, the rear bearings and conrods lasted much better.
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Old 07-01-2012, 10:20 PM
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Use the heat cycle method and out a vz speed rod in it, it will last a good while. The stock rod does not have an oil hole to let oil onto the crank pin. This caused the crank pin to wear quickly. The vz speed rod solved this issue.
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