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PostPosted: Fri May 04, 2018 10:43 am 
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Joined: Thu Apr 10, 2014 3:32 pm
Posts: 31
I simply cannot find the bolts that attach the tank on my MR175. I have tried every motorcycle-related bolt I can scrounge up in my shop and nothing fits. I looked up what I thought was the size on the parts fiche and bought some, but the thread pitch seems to be different. WTH do I do? The fiche only says they are 6-32 bolts... I guess I am not even sure how to interpret that. I think they are still available from Honda but surely there is another way.


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PostPosted: Fri May 04, 2018 1:56 pm 
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Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1010
Location: Connecticut, USA
All three MR175 tank bolts are M6x1.0 thread, 32mm long (Honda p/n 92101-06032-0A). Most hardware stores should have something similar. 1/4-28 bolts will also fit.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric


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PostPosted: Mon May 07, 2018 10:26 am 
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Joined: Thu Apr 10, 2014 3:32 pm
Posts: 31
I found some at a hardware store, so thank you. But after putting them in, I see that the bolt hole threads are pretty messed up on one, and the other has a significant amount of rust. I think I need to tap them, which I have never really done before. The rusty one just needs to be cleaned out, the other is more to fix the threads. Any tips on this?


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PostPosted: Mon May 07, 2018 1:26 pm 
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Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1010
Location: Connecticut, USA
You can try cleaning up ('chasing') the threads with a bottoming tap like the one below:

https://www.ebay.com/itm/M6-x-1-00-HSS- ... SwHjNWAGS1

Your hardware store may have one that's similar, but make sure you get one with a blunt tip (bottoming) like the one above, and not the standard pointed tip. The store should also have a tap holder, which you'll need to drive the tap in straight. You didn't mention the rear bolt hole threads, hopefully they're just rusty too.

This tap should clean up the rusted threads easily, just use some oil on it first, and clean the hole out well after. This will also give you a feel for how much resistance the tap has with undamaged threads.

With the damaged threads, I'd measure how deep the hole is first (with a short rod, Q-Tip, whatever), then oil/grease the tap & run it straight into the hole as far as possible until you start to encounter greater resistance, back it off 1/2 turn, turn it in a whole turn if possible, back it off 1/2, etc. until you've gone as deep as you're comfortable with (and hopefully nearly as deep as the hole; the blunt tip allows you to go extra deep). If it starts getting real hard to turn, do NOT force it, just back it out and call it a day. Then, you can use an extra-long stainless bolt that can be screwed in deeper to engage the new threads you've cut (and hopefully also some damaged ones you've cleaned up). A stainless bolt can be shortened if needed without rusting up afterwards.

If this doesn't work, the hole will probably need to be drilled out and a Heli-Coil insert installed. I've done this many times, but IMO the above is definitely worth trying first, you might get lucky with the damaged threads.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric


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PostPosted: Tue May 08, 2018 3:06 pm 
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Joined: Thu Apr 10, 2014 3:32 pm
Posts: 31
The rear mount hole is just rusty I think. One of the fronts is definitely damaged, right from the start, but the other is fine. I have a tap set that I have never used, but it's probably standard. I have a holder, so I'll just need to track down the tap. Thanks for the advice. I'll let you know what happens.


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