Author Topic: long bolts in crankcase  (Read 364 times)

Offline Brett72

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long bolts in crankcase
« on: March 23, 2021, 09:12:45 PM »
Hi, can anyone tell me if they have ever fitted a slightly longer bolt in the crankcase. I was just torquing down to do a plastigauge test and what is no.2 bolt on the diagrams will not tighten down. The bolts are M8 x 140 1.25 pitch. If i put the bolt in the top half of the casing without the bottom fitted it bites fine and i think it would torque down ok.  I was thinking about putting a bolt 145mm long in and see what happens. Has anyone got any thoughts on this? Thanks in advance

Offline K2-K6

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Re: long bolts in crankcase
« Reply #1 on: March 23, 2021, 10:02:23 PM »
Can you measure the depth of the hole in top case with the "wrong" end of vernier caliper, then stick the bolt through the lower case to measure how much is going to go into the upper case, then compare the two to assess.

Offline Brett72

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Re: long bolts in crankcase
« Reply #2 on: March 23, 2021, 10:08:01 PM »
Great idea Jedi. Thanks for the idea. I will give it a go in the morning

Offline K2-K6

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Re: long bolts in crankcase
« Reply #3 on: March 23, 2021, 10:13:45 PM »
To emphasize the need for caution as most of the holes on these engines will have something very close by in proximity.

See what you get and if you've clearance room for using alternative. 

Offline Brett72

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Re: long bolts in crankcase
« Reply #4 on: March 23, 2021, 10:19:29 PM »
Thanks for the advice

Offline Oddjob

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Re: long bolts in crankcase
« Reply #5 on: March 23, 2021, 10:53:32 PM »
Surely a parts book will tell you the correct length?
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Offline Brett72

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Re: long bolts in crankcase
« Reply #6 on: March 25, 2021, 04:50:49 PM »
Thanks for the replies.  As it stands on further investigation it looks like the threaded hole in the top half of the crankcase has had it :-[
Has anyone ever tapped it out to an M10? If so did it go ok?
Thanks in advance

Online hairygit

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Re: long bolts in crankcase
« Reply #7 on: March 25, 2021, 05:30:18 PM »
No! Get it helicoiled or better still a Wurth insert fitted, that will sort it and keep all the volts standard size and thread.

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Offline K2-K6

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Re: long bolts in crankcase
« Reply #8 on: March 25, 2021, 05:57:37 PM »
No! Get it helicoiled or better still a Wurth insert fitted, that will sort it and keep all the volts standard size and thread.

I like all my volts the same size too, else they get stuck in the electric string if you get a chunky one  ;D and then all the smoke falls out.

Auto correct, predictive text, don't you just love it.  :)

Offline Nurse Julie

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Re: long bolts in crankcase
« Reply #9 on: March 25, 2021, 06:28:58 PM »
No! Get it helicoiled or better still a Wurth insert fitted, that will sort it and keep all the volts standard size and thread.

I like all my volts the same size too, else they get stuck in the electric string if you get a chunky one  ;D and then all the smoke falls out.

Auto correct, predictive text, don't you just love it.  :)
That made me laugh 😂 😂 😂 😂 With my limited knowledge of all things electrical, thats just how I would explain a problem.
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Offline K2-K6

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Re: long bolts in crankcase
« Reply #10 on: March 25, 2021, 07:26:15 PM »
Reminds me of this

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But on a more serious note for the OP,  generally wise to go with and insert/repair on these engines to preserve original bolts and thread sizes.

It shouldn't be difficult to complete either. 

Offline Brett72

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Re: long bolts in crankcase
« Reply #11 on: March 25, 2021, 07:51:21 PM »
I have used helicoils before and they are obviously the cheaper option but will they withstand the bolts being torqued into them?

Offline Nurse Julie

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Re: long bolts in crankcase
« Reply #12 on: March 25, 2021, 08:02:54 PM »
Which one is it exactly that has stripped?
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Offline Brett72

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Re: long bolts in crankcase
« Reply #13 on: March 25, 2021, 08:08:35 PM »
The thread in the top crankcase for bolt no.2 in the picture at the start of this thread

Offline K2-K6

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Re: long bolts in crankcase
« Reply #14 on: March 25, 2021, 08:40:23 PM »
Properly installed the helicoils are fine for torque rating.

Some high use structures in aluminium use them routinely as the threads are more durable to multiple use, they don't get anything like that in this application as so infrequently removed.

 

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