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Yamato 80 break in procedure

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  • ZUL8TR
    commented on 's reply
    Brass but if you can get aluminum has better thermal conductor and best. I was given steel from Tom Cronk and required 1 range colder plug since less thermal conductivity much less than brass or aluminum. Make sure final 14mm plug threads are level with end of adapter (I trimmed adapter 18mm end) and the adapter fits in the head with same plug reach as the OEM 18mm plug. To achieve this I used the thick copper spacer from the OEM 18mm plug on the trimmed adapter into the head and no squish gasket on 14mm plug into the adapter. I am using NGK B10EGV fine wire gold palladium tip electrode, NGK part #5927. The adapter you get might require different trim adjustment and spacer(s)?

  • Steven27jack
    replied
    Looking into 18mm to 14mm spark plug adapters, brass or steel?

    Leave a comment:


  • dwhitford
    commented on 's reply
    15 cubic-inch engines could also run in the RB class almost without any restrictions. For example a 20 ci RB engine could have only one carburetor, and that one was restricted in size. Mike Schmidt was quite successful in RB running my 15 ci Quincy Z engine with two 36 mm Mikuni carbs on it. Mike won with my engine most of the time.

  • raceright
    replied
    Break in race motor. Squeeze throttle.

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  • DeanFHobart
    replied
    Originally posted by Steven27jack View Post
    What does RB stand for? These are the only good pics I have, and they're not great, but the pistons are not flat top, they're a little round
    If I am not mistaken, RB stood for ‘Restricted B’… The ‘Restricted’ part meant that the power head remained stock, except the block could be blueprinted to max / min specifications, meaning the head could be machined to minimum CC’s to increase the compression, and the ports could be machined to max specs. Also, the motor could be converted to run on Methanol. That is why there is a Bing carburetor on it. The ‘B’ means 20 cubic inches or in metric 350 cubic centimeters. This was in the ‘Pro / Alky’ outboard division of APBA.
    Yamato later on would also manufacture total complete ‘Alky’ motors without any Restrictions except cubic centimeters.

    Some of the other guys here should be able to add more information on this.

    Leave a comment:


  • Steven27jack
    replied
    What does RB stand for? These are the only good pics I have, and they're not great, but the pistons are not flat top, they're a little round
    Attached Files

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  • Beaverman
    replied
    I also agree you have an old RB motor. This engine may be set up to run on Alcohol. Just wondering if you have any pics of the pistons when you rebuilt it. I have a Y-80 RB motor with two pipes rotated power head and a Bing carb. I will take some pics and send post them later. I am wondering if your set up is the same.

    Leave a comment:


  • ZUL8TR
    commented on 's reply
    Stock port timing on the Y80 is 62 intake and 83 exhaust Degrees BDC measured from bottom dead center from open to close. The exhaust is open a total of 83 x 2 = 166 crank degrees from open to close. The 88 Timing stamp I think references increased exhaust port open to close of 5 x 2 = 10 degrees more crank rotation or total 176 degrees, done by raising the exhaust ports. Done for a mod engine as well as the 0.120 stamp on the head.

    The stock head gaskets come in 2 thicknesses 0.5 and 1.0 mm and they are aluminum.

    How thick is the gasket that came with the engine? Is it aluminum?

    You can do a compression check to see what the engine is making just for reference with that gasket it came with. Will change with break in but at least you know where you are starting at. Lots of oil in the cylinder will boost the test compression. Check after break in. I do cold compression tests to keep temp variable about the same - compression is just a relative measure so always do it the same way and with the same gage. Stock Y80 with 18mm head will pull at 150psi compression. Your mod Y80 will be different.

  • Steven27jack
    replied
    Any idea as to what 88 degree stamped on cylinder block would mean, or modified .120 on cylinder head? Would that mean exhaust timing is at 88 degrees, and the head had been shaved .120 to increase compression ratio? The head gasket that came with the engine is thicker than the new head gaskets, any rhyme or reason to that? I'm thinking the thicker head gasket may lower the compression ratio of the shaved head closer to the stock compression ratio, should I go for that or try to keep compression ratio as high as allowed?
    Attached Files

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  • ZUL8TR
    commented on 's reply
    For the stock Y80 that diameter is about right and maybe just a bit too small but pitch will better zero it in as well as other things on the prop like blade shape, cup, rake, blade thinness, etc.

  • Bob Rusnak
    replied
    Jim McKean passed away several years ago. His son Sean is on FB.

    Leave a comment:


  • Steven27jack
    commented on 's reply
    The diameter is 6 1/2". Have to get protractor to measure pitch

  • ZUL8TR
    replied
    It might run without the stock Megaphone? But power would be down. Try to get the stock Megaphone complete and the 3 tapered seat Philips head bolts. The shims can be easily made from aluminum cans. There are 2 parts: per the parts manual the exhaust megaphone holder #6 and the exhaust megaphone #7. Forget the mod stinger pipe setup and get used to the stock Y80 on the hydro.

    Measure the diameter of that 2 blade, would be nice to know the pitch, great if a pitch gage is available . There are simple methods to get average pitch with basic tools if interested. That just may be a mod prop and a bit too much pitch and diameter for the stock Y80?

    Leave a comment:


  • Steven27jack
    commented on 's reply
    Success, got the propeller off with help from a friend

  • Steven27jack
    commented on 's reply
    I guess it's time to start Facebook stalking Mr. Jim McKean? Lol, see if I can find him and if it belonged to him
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