Author Topic: RD350 Rotor Bolt spec  (Read 197 times)

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Offline Fredswat

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RD350 Rotor Bolt spec
« on: February 14, 2020, 04:56:00 PM »
Anyone know what pitch the M7 Rotor bolt is? (the one that holds the generator onto the Crankshaft) Is 1mm a pitch fine or not? I am trying to procure one through a fastener supplier and want to get the right thread pitch.  It is obviously a fine pitch but I am not sure what fine means. My original is bent beyond straightening.   
« Last Edit: February 14, 2020, 05:00:05 PM by Fredswat »
74 RD200a
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Offline G Jones

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Re: RD350 Rotor Bolt spec
« Reply #1 on: February 14, 2020, 05:09:34 PM »
Anyone know what pitch the M7 Rotor bolt is?
Pretty sure M7 X 1mm standard 7mm pitch...
https://en.wikipedia.org/wiki/ISO_metric_screw_thread#Designation

Offline 5port

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Re: RD350 Rotor Bolt spec
« Reply #2 on: February 14, 2020, 05:10:41 PM »
Just put a ruler alongside and count how many pitches to 10mm, then divide.  ;)  Thread gauges are also good.  The actual thread spec is not easy to find, even going back to the R5.  Cheers

5port
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Offline Fredswat

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Re: RD350 Rotor Bolt spec
« Reply #3 on: February 14, 2020, 05:20:52 PM »
Just put a ruler alongside and count how many pitches to 10mm, then divide.  ;)  Thread gauges are also good.  The actual thread spec is not easy to find, even going back to the R5.  Cheers

5port

Looks like 12/13 which would be 0.75 pitch I think?  .  Really hard to find an M7 X 0.75 x55mm long Hex/socket  head bolts anywhere.   I know 1mm sounds sensible but is that going to be too coarse?
74 RD200a
74 RD350A
77 RD400c
81 RD350LC
89 TDR 250
72 Kawasaki H1d
75 Kawasaki Z1b 
06 Kawasaki Z1000
71 Suzuki T500R
76 Suzuki Gt750
89 Suzuki RGV250 Vj21
76 Honda cd175 
85 Honda c90
03 Aprilia RS125
48 Royal Enfield J2

Offline Fredswat

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Re: RD350 Rotor Bolt spec
« Reply #4 on: February 14, 2020, 05:37:42 PM »
Right crisis over.  I realised I have a thread gauge in my tool box. Just been up the shed in the pouring rain to measure the bent one.  I can confirm it is an M7 1.00mm pitch 55mm hex head bolt :D
74 RD200a
74 RD350A
77 RD400c
81 RD350LC
89 TDR 250
72 Kawasaki H1d
75 Kawasaki Z1b 
06 Kawasaki Z1000
71 Suzuki T500R
76 Suzuki Gt750
89 Suzuki RGV250 Vj21
76 Honda cd175 
85 Honda c90
03 Aprilia RS125
48 Royal Enfield J2

Offline 5port

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Re: RD350 Rotor Bolt spec
« Reply #5 on: February 14, 2020, 07:21:11 PM »
Sounds good!   :)  I did find a supplier a few years ago, but got a few NOS since.    Not sucking eggs but, just make sure your replacement bolt does not bottom in the crank nose thread.  There can be an issue where, if the bolt bottoms during tightening, it overstresses the waisted part of the crank nose and fatigue fails it (snaps it off) after a while!  Cheers

5port
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Offline G Jones

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Re: RD350 Rotor Bolt spec
« Reply #6 on: February 14, 2020, 08:11:44 PM »
Sounds good!   :) it overstresses the waisted part of the crank nose and fatigue fails it (snaps it off) after a while!  Cheers
5port
55mm hex head bolt ??
Yep - had crank break due to that - attached rotor made a pretty good missile when it parted company with the crank...
I had some M10 socket cap screws turned down and threaded with the M7 - many years ago - better quality fastener & decent size socket head for tightening...

Offline Bluehaze

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Re: RD350 Rotor Bolt spec
« Reply #7 on: February 14, 2020, 09:59:19 PM »
There are lists that show a 7mm thread as either 1mm or 0.75mm pitch.
I've only seen them at 1mm, common on Euro cars and some bikes.

Describing fasteners using the term "metric fine" can be unsafe, not taking into account that there might be more than just a couple of pitch number variations for the same diameter.

Owners of early (pre-1968) Japanese bikes should be aware that these used the JIS range of pitches.
Seemingly identical parts at the changeover period to ISO standards, can catch you out and cause you to damage threads. (For "you", read "me".)