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Helpful ReplySize needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaft.

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2018/01/19 21:11:01 (permalink)
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Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaft.

I have a Super Tomahawk 5-8-2G/C chipper from approx 1983. with a Tecumseh 5hp engine Model H50-65484N Ser 4180D sold by W-W Grinder, (who is no longer in business). The crankshaft outside is 3/4", what I need is the correct end bolt size to hold clutch and pulley on. 5/16" 24 3/4" long is too small and 3/8 either 18 or 24 threads per inch will advance no more than a turn. The threads are visible and clean.  This is the bolt that goes into the end of the crankshaft. I have the key and allen head screws. Thanks in advance.
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    AVB
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/20 01:47:54 (permalink)
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    If you have access to tap and die sets use the thread pitch to determine the thread pitch. Might be metric.
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    kshansen
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/20 07:28:53 (permalink)
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    Not to be too fussy but I believe you meant to say 3/8-16.
     
    What happened to the bolt that was used before? 
     
    Is this a new engine to replace the old one?
     
    If this is the original engine and the original bolt fell out and got lost it could be while it was working it's way out it damaged some of the threads causing the problem you are now having. So you may need a tap to clean up the threads.
     
    My opinion, which may be worth what it cost you, is that the threads should be 3/8-24. Should be easy to see difference between 3/8-24 and 3/8-16 just looking at them. 
     
    If you do decide to run a tap in that hole be very careful as taps are very hard and if forced will snap and that is not good!
     
     
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    AVB
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/20 08:57:16 (permalink)
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    Most of the Tecumseh crankshaft specs I looked at had the 5/16-24 or the 3/8-24 (.375-24) threading. I was unable to find drawing on the 34885 crankshaft and this is the reason I suggested the OP to use the thread gauges, you actually find out the thread pitch be it SAE or Metric. This especially true since the OP say threads are clearly visible and in good shape; although, there could be a damage thread further down.
     
    If it happens to be Metric then it would be on the rare side but out the question.
     
    As running taps in you use Tap Magic to lube the tap's cutters and it helps to prevent breakage. Also taps do need to be backed up every so once to break and clean the debris. Start with a taper or plug tap and finish with a bottom tap since this a blind hole.
     
    The follow thread chart should of help. Just remember the 9mm bolt will be very hard to find.

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    kshansen
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/20 12:52:28 (permalink)
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    If no thread gauge is handy one could always try an 8 mm bolt to see if that works. As for a 9 mm bolt one can only hope that is not what someone decided to us as they are probably harder to find than Hens Teeth!
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/20 17:15:40 (permalink) ☄ Helpfulby kshansen 2018/01/21 11:17:39
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    OK, appreciate all the answers. It turns out with the use of the suggested thread gauge I found out 24 was the number of threads. Since I had used a 3/8 16 bolt before even though it wouldn't advance much this had messed up the first 2 threads enough but I didn't realize it was wrong. With the 3/8 24 tap I was able to fix this situation with all your help. Now my 35 year old chipper is restored and I can give it to my son, who needs it. Thanks again.
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    AVB
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/21 06:14:08 (permalink)
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    Ahh, just went that back in December where another tech attempted to screw in a 3/8-16 in place of a 3/8-24 on an Onan engine. On top he had removed the oil pump bypass spring and valve. I just got lucky that he only destroyed the top three threads and I was to cut away the damaged threads; otherwise, the engine would have been a complete lost as the customer would not spend the money for me to disassemble the engine so I could machine in the next size screw threads.
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    kshansen
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    Re: Size needed for end bolt on Tecumseh 5hp engine to hold clutch and pulley on crankshaf 2018/01/21 11:20:18 (permalink)
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    Glad you got it figured out and took the time to let us know the resolution of the "problem"!
     
    Too often someone will come on a site and ask for help then after getting lots of suggestions fail to take the time to say, "Got it fixed and the problem was......... 
     
    Letting it be know what worked can help many people with a similar problem down the road.
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