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Engine basics => Engine set up tips => Topic started by: Bill Barber on September 05, 2010, 05:14:29 PM
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My Brodak 40 that has run very well for the last 18 months is starting to give me fits . Inconsistent runs and gray exhaust residue are the symptoms , the front shaft has about 1/8" play in it . Other than replacing the whole case is there another way to replace the bushing ? The motor still has good compression .
Bill Barber
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The grey is likely aluminum, probably from the backplate. Stop running it! Check inside. If it's eating the backplate, you'll burn out a lot of glowplugs. You're better off replacing the case or other needed parts, at the current price of glowplugs.
I think your 1/8" estimate is probably much exaggerated, but I'd fix it or send it to be fixed, or better yet, just buy a new one. I know they're hard to find, but sometimes they can be. Keep your old one for spare parts, just in case you (or somebody you know) needs what's left. I had two NIB, but sold them a few weeks ago. H^^ Steve
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Steve , your right the 1/8" play is exaggerated but the backplate looks ok . Piston & sleeve look good and the motor had good compression so I just plan to buy a new case .
Bill
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Just got an email from Brodak , they are out of Brodak .40 cases . So I will have to find someone to replace the bushing .
Bill
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Bill...Check the crankshaft OD for out of round/taper before you get too serious about the bushing job. If the crank isn't good, the bushing doesn't matter. Were you using a shaft extension, by any chance? ??? Steve
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Steve , not using a shaft extension , haven't measured the crankshaft , but did put it a drill press and spun it .
Crankshaft appears to be true . IIRCC other Brodak.40 users had issues with bushings wearing out .
Bill
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Just got an email from Brodak , they are out of Brodak .40 cases . So I will have to find someone to replace the bushing .
Bill
Given the length of time that the Brodak 40 has been unavailable and not privy to whats happening at the source I'd say that the Brodak 40 is in trouble. I like this engine but the supply has been choked off for over 2 years with no news from Brodak or any other source as to ever having these in stock again.I sincerely hope that they become available again because there is no comparable engine in it's price range to take it's place
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Had an engine builder put my Brodak -40 crankshaft on a dial indicator and found the crankshaft was machined .0035 off center .
This caused the egging of the front bushing . The con-rod at the wrist pin is also egged shaped . Steve Helmick was right , time to get a new motor .
Bill Barber
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I went on the Brodak web site today and the B40 is listed as being IN STOCK! #^
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<the crankshaft was machined .0035 off center>
I heard that others have had the same problem.
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"the crankshaft was machined .0035 off center"
I'm not sure I understand. Off center from what? Do you mean out of round?
It's not that hard to re-bush the engine. I will do an article in the next CL World.
Bob Z.
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If the crankshaft was ground on a centerless grinder, it is eazy to see how the crankshaft prop shaft could be off center from the bearing area. When the shaft is heat treated, it probably takes a bannana shape due to the timing cutout in the shaft. and on the centerless grinder it might tend to take more off the side with the timing cutout before it is ground round. If you looked at other makes of crankshafts that were ground on a centerless grinder you would probably see the same thing.
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Bob if the crankshaft is off center or out of round , what is the point of putting in a new bushing ?
Won't it just wear out in a relatively short time the new bushing ?
Bill
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Well..I've had a few B-40 come through my shop for a new front bushing. One of them is my B-40 First Run. After about 100 runs I had about 1/4" end play on my prop...tip to tip. Taking the engine apart and noticing the front bushing is egged shaped I took the crank and my dial indicator and found that the crank not machined with the tolerances that a precision engine should be. Yes mine was out of true .0027. Some even more. Enough to cause viberation and wear.
Scott
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<Yes mine was out of true .0027>
I still don't understand. 1). The crankshaft is not round. 2). The crankshaft is not centered on the counterweight. 3). The propshaft is not centered on the crankshaft......???? I guess it really doesn't matter in all cases it will be a problem and cause uneven wear on the case bearing.
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3). The propshaft is not centered on the crankshaft H^^
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Thanks for clearing that up Scott...........Sounds like something that could also cause the engine bolts to loosen up or the muffler to fall off or a prop to develop fractures or even a crummy engine run due to vibration and/or foaming in the tank. Now I understand why my friend was having so much trouble with that motor.
Thanks again
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Any Time Greg. ;D