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86 Rebel 450
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Discussion Starter · #1 ·
Hello! So I took the tank off the 450 to replace the cdi. I’m having problems with the bolts screwing into the frame now. I see the bolts on the parts diagram. Not sure of the thread or pitch to replace them. I’m pretty sure the threads on the frame are mangled up pretty bad and stripped. The (side holes). Does anyone know the exact size and pitch thread? Is it 8x1.25 metric? Or is it a sae thread. I went to lowes and got 8x1.25 bolts but they do not thread in. Maybe 2 threads go in then stop. It would be great if I can find or you guys know what size tap I would need to chase the threads or do I need to retap the holes? Thanks in advance !
 

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1987 CMX250C AC
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I know of no Japanese bike that used SAE size bolts or screws..
Or Japanese automobile for that matter.
it's 8mm that is for sure, you might take your bolt to hardware store and use their pitch gauge.
 

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i would be cautious too, but that's the next step - if you bugger the threads too much you will have to go up a few sizes or other measures

use only hand pressure - if you're lucky the tap will find the old threads and clean them out

otherwise - the tap will take out what's left of the old threads and clean the bore

there are a number of options to fix the latter so don't fret too much

 

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86 Rebel 450
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Discussion Starter · #6 · (Edited)
I may just leave it alone. When the tank is on I can catch a couple threads on each side. The frame hole by the seat is fine. It’s the 2 side ones that are the problem. I may just leave them. Everything I try to do to this bike turns into a disaster as far as screws and bolts. The easiest screws to remove seem to break or strip so easily. Even with the correct fitting Phillips heads. Even going gingerly and cautiously. So far the left headlight screw that holds the headlight lens in stripped. The actual threads. The 2 speedo screws that you would unscrew to change the speedo light both broke. I had to silicone the speedo back together.
 

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1987 CMX250C AC
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Honda never used Phillips head screws..
They are a US invention designed to cam out if to much torque is used..

Japan used JIS (Japanese Industrial Standard) screw heads which will take more torque as the cross head design is different but the phillips driver cam out will destroy a JIS screw..

I own 2 Vessel JIS driver sets that also include Pozidrive and flat bits

I also have 8mm (5/16") shank JIS driver bits for use in impact driver..
 

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I have to fuss with the front gas tank screws to align them up so they don't cross thread..
Wouldn't think on not screwing in fully myself, it's not that difficult to set tap strait and slowly work it back and forth to clean up threads imo..
 

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The CMX 450 OEM front tank bolts have a hex head, not JIS. When threading a bolt or screw, begin by slowly turning it in the direction for loosening it (counterclockwise for most bolts). Listen for a faint "click" and a slight movement. This is where the threads on the bolt and nut align. Once it clicks, slowly tighten by hand until threads engage fully. If a tap is needed, it will usually, but not always follow the old threads. Use the above method to start a tap too.
 

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86 Rebel 450
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Discussion Starter · #11 ·
I was able to run a m8x1.25 tap in both holes. Caught the threads on both sides and the bolts went in easily. The tap worked good. I used different m8x1.25 bolts though. I’m not a fan of the chrome plating on the original bolts
 

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'86 FoFity
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Hey there -- I'm in a similar situation, would love advice (re posted pics):

A few weeks back, I noticed while at the gas station that my tank (not stock) was loose, so I finished filling the tank, finger-tightened the two bolts, immediately went home to re-tighten them with a wrench. Everything seemed fine, until two days ago.

Two days ago, I noticed these bolts were loose again. Why?! (I believe this MIGHT be due to the fact that every time I finish filling my tank, I end up wiggling the tank a bit because the cap isn't the easiest to refasten.)

This time, I tightened one side with a wrench without issue. BUT when I tried to tighten the opposite side (brake side), as I tightened the bolt, the bolt would get tight, then it would be loose again. Why is this?! Right now, I have it moderately tightened because I don't wanna push it/wrench it.

I think I need two new bolts to make sure my tank is secured. Right? My questions:

1) Where can I purchase these two new bolts? They must be stock, correct?
2) How can I ensure this doesn't happen again? What am I doing wrong with this?
3) Is there a workaround to this, so that I don't need new bolts?
4) Someone mentioned backing the bolt all the way out, then re-wrenching again?

I'm just afraid of messing with it/wrenching it any more right now, unless I have two new bolts on hand to replace them in case something goes wrong. I don't wanna be without a bike for too long.

Thank you, thank you for your thoughts and suggestions. (I don't have a garage, not a mechanic.)

=
 

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1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
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I don't know where you're from, but near me, Menards has a very good selection of metric bolts, including chromed, (although you said that you don't like the originals). They are supposed to be tightened snug, but leaving the rubber mounts with some ability to absorb vibration. IF...notice the all caps, IF YOU USE some kind of thread lock, (I've never needed it), make sure it is the blue, NOT RED. I'd expect that the engine mounts are shot. Being a 1986 CMX450 means that they're around 36 years old, & if not periodically oiled with boiled linseed oil, they've most likely dried & cracked to smithereens.
 
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86 Rebel 450
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Discussion Starter · #14 ·
Probably just need a longer bolt. In my situation I do not care if the bolts are stock or not. I picked up Allan heads with the same thread m8x1.25 bolts. After I ran the tap in they threaded fine. If you don’t want to run a tap into your frame you can probably just put blue loctite on the bolts or get a tad longer bolts. The threads in the frame are probably cross threaded or stripped.
 

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'86 FoFity
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UPDATE: I took the bolt out, and it turns out the threads on the frame itself are bad, but the bolt looks OK.

I had some threadlock (orange) on hand, so I used it on the bolt and just wrench it back in softly. Now it hasn’t fixed it completely, but it is a tad tighter than it was.

I guess I will just wait to see if it loosens again in a few weeks; if it does loosen, then:

My neighbor (who also has a bike) suggested I buy a threader from Home Depot, re-thread the frame to coarse — instead of fine, which is what it probably has been? — then return the threader back to Home Depot.

Does this sound like a solid, wise plan?

Thx again!
 

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Discussion Starter · #16 ·
There is fine sae thread, and course sae thread then there is metric thread. It’s metric thread that we have. Try the m8x1.25 tap to chase and clean out the threads. That’s what I did and it worked. I would definitely not try to change the threads. You would have to drill it and retap it then and go up in size of the bolt.
 

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UPDATE:
My neighbor (who also has a bike) suggested I buy a threader from Home Depot, re-thread the frame to coarse — instead of fine, which is what it probably has been? — then return the threader back to Home Depot.

Does this sound like a solid, wise plan?

Thx again!
Your neighbor is unethical, to say the least. If you use a tool, it shouldn't be returned as unused.
 
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