old K&B 7.5.... .45 cu in....starter motor ?

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old K&B 7.5.... .45 cu in....starter motor ?

Postby frd1952 » Mon Feb 23, 2009 1:03 pm

Does anybody know if I need any special starting motor when I try to start this motor (once I make sure it is not frozen from 25 yrs sitting) ? Here is the motor... http://www.modelengine.org/gallery/deta ... ode=search .... Will the starter motor at http://www3.towerhobbies.com/cgi-bin/wt ... XJC35&P=ML work as it is or do I need special cones, inserts, etc like it talks about at the bottom of the specs, tech notes about the starter ?? I just do not know how the starter will actually turn the metal cone flywheel on the top of the motor without some type of locking/catching pins or something...or does a rubber cone come with the starter that creates enuff "grip" to turn the metal cone flywheel ?? The holes on the metal cone also tell me MAYBE there are pins or something that grabs the flywheel there?? Obviously, I have never had one of these before, and this thing is so old it is hard to find stuff about it...thanks.
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Postby SteveM » Mon Feb 23, 2009 1:24 pm

The electric starter you linked to will work fine to spin the K&B outboard. All K&B outboards use a reverse rotation crankshaft so when looking down on the K&B the crank needs to spin clockwise. When using that electric starter you will need to connect it to a 12V battery backwards. The red lead on the electric hand starter needs to connect to the negative terminal on your 12V battery and black to positive.
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Understood on the reverse crank/flywheel....can I turn it?

Postby frd1952 » Mon Feb 23, 2009 1:37 pm

Good info on the reverse crank/flywheel Steve...understand to hook to battery in reverse and the crank/flywheel when looking from above should spin clockwise...thanks.

If I pull out the little glow plug, should I be able to turn the top cone/crank/flywheel (all the same correct?) or the prop by hand, IF neither the piston and the drive shaft is not frozen up ? Is there any reason to NOT pull out the allen screws and pop the head off of the cylinder to check on the inside ?
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Postby SteveM » Mon Feb 23, 2009 3:09 pm

Your motor is ABC construction (aluminum piston, brass sleeve that is chrome plated) and the sleeve tapers towards TDC. If you remove the glow plug and squirt some Wd40 in you could probably rotate the crank as long as the bearings haven't seized.

You can remove the motor from the lower unit with those 4 bolts no problem. The power take-off (PTO) can also be removed to expose the insides of the motor. It may need to be de-gummed and WD-40 works fine.
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Piston OLD K&B 7.5

Postby frd1952 » Fri Feb 27, 2009 5:15 am

Steve, is there really a need to take out the piston and the cyl sleeve if they look clean ? I have popped the head off, looks very clean lubed and moves easily, back end by the piston arm also looks good>>>do I need to get the piston and cyl wall out to look/clean if needed ? IF yes, how do you get these parts out since it is tapered and will not come out the head hole, and do not see how to get to pins to take off the arm ?? Thanks, Frank
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Re: Piston OLD K&B 7.5

Postby SteveM » Fri Feb 27, 2009 6:14 am

frd1952 wrote:Steve, is there really a need to take out the piston and the cyl sleeve if they look clean ? I have popped the head off, looks very clean lubed and moves easily, back end by the piston arm also looks good>>>do I need to get the piston and cyl wall out to look/clean if needed ? IF yes, how do you get these parts out since it is tapered and will not come out the head hole, and do not see how to get to pins to take off the arm ?? Thanks, Frank


If the piston and sleeve look good then there isn't any real need to remove them. If you would like to disassemble and check then you need to remove the sleeve first.

A trick I use is to have the motor partially assembled with the crank connected to the piston and the flywheel attached. Rotate the piston to BDC and drop a brass washer from a glow plug onto the top of the piston positioned at the exhaust port. With that washer just peeking over the edge of the piston slowly rotate the crank to move the piston up until the washer is pinched between the piston and the edge of the sleeve. Gently continue rotating the crank to lift the sleeve out. The brass washer is soft enough not to damage anything. Once the sleeve is removed you can disconnect the connecting rod from the crank and then the piston assembly can be removed.
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Postby frd1952 » Fri Feb 27, 2009 6:47 am

Wow...pretty slick idea Steve. If I get it, you assy the parts like u said, then thru the exhaust port on the bottom side (so you turn the whole thing "upside down" to drop in the washer and to see/work inside the cylinder ??) with the piston all the way "back" towards the crankshaft end, you drop in the washer from the glow plug thru the exh port and then with that washer laying on the real "top" side of the cyl (which is now actually closest to the floor as you do all this) you slowly turn the flywheel to have the crank/piston to wedge the washer between the piston head and the notches in the cyl wall sleeve. The washer will push the sleeve out of the head area. Then you can see the pins holding the piston to the arm and can remove the pin(s) and then remove the arm and the piston head...do I have this correct Steve. Sounds pretty tricky, but makes sense...Is this how they meant these parts to come out, or were they never intended to come out without wrecking them and putting in new parts? just wondering..is BDC when the piston is at the full "back" position closest to the crank, and TDC is when it is closest to the glow plug ?...thanks again.

Frank
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Postby SteveM » Fri Feb 27, 2009 1:04 pm

frd1952 wrote:Wow...pretty slick idea Steve. If I get it, you assy the parts like u said, then thru the exhaust port on the bottom side (so you turn the whole thing "upside down" to drop in the washer and to see/work inside the cylinder ??) with the piston all the way "back" towards the crankshaft end, you drop in the washer from the glow plug thru the exh port and then with that washer laying on the real "top" side of the cyl (which is now actually closest to the floor as you do all this) you slowly turn the flywheel to have the crank/piston to wedge the washer between the piston head and the notches in the cyl wall sleeve. The washer will push the sleeve out of the head area. Then you can see the pins holding the piston to the arm and can remove the pin(s) and then remove the arm and the piston head...do I have this correct Steve. Sounds pretty tricky, but makes sense...Is this how they meant these parts to come out, or were they never intended to come out without wrecking them and putting in new parts? just wondering..is BDC when the piston is at the full "back" position closest to the crank, and TDC is when it is closest to the glow plug ?...thanks again.

Frank


BDC = Bottom dead center when the piston is at the bottom of its stroke
TDC = Top dead center when the piston is at the top of its stroke close to the head.

It's best to have the motor with cylinder pointing up. Re-attach the flywheel so you'll have something to grip with your hands. Re-connect the nose piece with the crankshaft to the main case with the piston & sleeve. Be sure the piston rod is connected to the crank pin. Leave the PTO off as it isn't needed. Take off the cylinder head and gasket and set aside. Rotate the crack until the piston starts to move up the sleeve and stop before you close off the exhaust port. From the top of the cylinder, drop in the washer and use a popsicle stick or similar to move it so that it protrudes slightly out in the exhaust port. Gently continue moving the crankshaft moving the piston up so that the washer is pinched between the top of the piston and the edge of the sleeve and then continue rotating and watch the sleeve rise out of the case. All you need is a few milimeters so that you can use your fingers to remove the rest of the way.
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ahhh...

Postby frd1952 » Fri Feb 27, 2009 1:24 pm

very clear...understood Steve...thanks.

F
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