Author Topic: 79 RD200 head stud thread size.  (Read 374 times)

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Offline Dgree234

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79 RD200 head stud thread size.
« on: May 16, 2021, 02:22:09 PM »
Have some damage on the thread of the head studs and need to run a die down the stud but struggling to get one to fit nicely. Does anybody know the correct size and thread pitch. Surely it can’t be anything other than a metric thread!!!

Online Gr8uncleal

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Re: 79 RD200 head stud thread size.
« Reply #1 on: May 16, 2021, 02:33:03 PM »
I would imagine standard (ie coarse) M8.

Presumably if the thread is damaged, the need for a little bit of effort is expected?!  ;)
Yam RD200DX (Gr8auntiepat's)
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Yam RD400C slowly getting back to standard
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Offline Dgree234

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Re: 79 RD200 head stud thread size.
« Reply #2 on: May 16, 2021, 02:39:17 PM »
The pitch looks to be 1mm but an M8 is a really loose fit. The stud OD measures 6.5mm


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Online Gr8uncleal

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Re: 79 RD200 head stud thread size.
« Reply #3 on: May 16, 2021, 03:04:27 PM »
Sorry, my bad for skimming your original question (I read it as exhaust stud)!  :-[ ::)

The parts list indicates that it is M7.
Yam RD200DX (Gr8auntiepat's)
Yam FZX700 Fazer
Yam RD400C slowly getting back to standard
Yam RD350B rough
Yam RT2 almost finished
Yam DT360A almost finished
Suzi GT550J just started
Suzi 1250 Bandit regular rider
Yam RD125(A?) in the kitchen being reassembled
Yam RD250E just started
Yam DT3 just in

Offline Dgree234

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Re: 79 RD200 head stud thread size.
« Reply #4 on: May 16, 2021, 03:21:24 PM »
You got it. M7x1
Wow never used that size before.
Cheers


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Offline Alistair64

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Re: 79 RD200 head stud thread size.
« Reply #5 on: May 16, 2021, 06:12:01 PM »
Daz, firstly yes M7, a very weird size!
If in any doubt about the threads on the studs, I would replace.
Well, this is what I did as they were corroded and probably stretched.
I found M7 studs easily enough on Ebay, so if you decide to get a new set. No need to buy genuine ones but make sure they are designed to be used as cylinder head studs on bikes (i.e high tensile).
I think I found a set for another bike which I sawed down to the correct length for no more than £7 or £8.
The old ones were easy enough to remove by locking two nuts together or using mole grips.
Having said all that, yours may be ok, but it's just a thought.
1983 Candy red RD200DX Fahron-tuned Special with one-off Swarbrick pipes
1986 White/red Stephens-tuned RD350F1 YPVS - owned since 1987...yes, honestly!!

Offline Bluehaze

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Re: 79 RD200 head stud thread size.
« Reply #6 on: May 17, 2021, 12:05:14 PM »
7 x 1 mm threads are not unusual on Euro vehicles.
Try Renault for example.

Offline Dgree234

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Re: 79 RD200 head stud thread size.
« Reply #7 on: June 12, 2021, 01:31:15 PM »
Sorry, my bad for skimming your original question (I read it as exhaust stud)!  :-[ ::)

The parts list indicates that it is M7.
So studs all sorted, heads are on. Just have a bit of conflicting info on the head nut final torque. Haynes manual states 15 ft-lb (20 Nm) but the online RD200 A service manual states 1.0 m-kgs which I believe is 7Nm!


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Online Astute Greaser

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Re: 79 RD200 head stud thread size.
« Reply #8 on: June 12, 2021, 02:17:01 PM »
Throw the Haynes in the bin its full of errors  >:( >:(
Read this link
https://www.aircooledrdclub.com/smf/index.php?topic=59242.msg469127#msg469127
86.8 - 130.2 in lbs (1.0 - 1.5 m-kgs) is the conclusion
But if your bike is a 79, that is not an RD200A  ???. The head nut is a totally different beast on the 2R7.
The figure I could find for DX as attachment

I found that you will need to retorque 2 - 3 times before the figure stays static after rides out.
-Mike
« Last Edit: June 12, 2021, 02:27:00 PM by Astute Greaser »

Offline Dgree234

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Re: 79 RD200 head stud thread size.
« Reply #9 on: June 13, 2021, 07:05:53 AM »
Just digested your reply. Very interesting. 5 ft-lb of torque sounds a bit low but I will go with that as I don’t want to over tighten. Many thx again Mike for the help.


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Offline Dgree234

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Re: 79 RD200 head stud thread size.
« Reply #10 on: June 13, 2021, 08:36:12 AM »
One more thing Mike...
Can you direct me to the correct owners manual. I was using the RD200A as I couldn’t see one for the DX.
Cheers
Darren


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Online Gr8uncleal

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Re: 79 RD200 head stud thread size.
« Reply #11 on: June 13, 2021, 09:15:34 AM »
Try this.

Yam RD200DX (Gr8auntiepat's)
Yam FZX700 Fazer
Yam RD400C slowly getting back to standard
Yam RD350B rough
Yam RT2 almost finished
Yam DT360A almost finished
Suzi GT550J just started
Suzi 1250 Bandit regular rider
Yam RD125(A?) in the kitchen being reassembled
Yam RD250E just started
Yam DT3 just in

Offline Alistair64

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Re: 79 RD200 head stud thread size.
« Reply #12 on: June 13, 2021, 11:59:47 AM »
5 ft-lb is clearly nonsense for a M7 stud.
They've got it wrong, so if the earlier models also use M7 I would go with their quoted figure (assuming they've used higher than 5).
I use about 13 which feels about right to me.
1983 Candy red RD200DX Fahron-tuned Special with one-off Swarbrick pipes
1986 White/red Stephens-tuned RD350F1 YPVS - owned since 1987...yes, honestly!!

Offline pidjones

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Re: 79 RD200 head stud thread size.
« Reply #13 on: June 13, 2021, 01:47:11 PM »
120 inch pounds would be 10 foot pounds.

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