Machinist Commission Request

[Pb12]

Hello Folks —

I am in the process of restoring a 1986 Honda CR125 that was not well taken care of. I guess that’s the point! this is my first attempt at a project like this, and so far its gone fine. After all disassembly is somewhat easy….well, except for all the frozen parts. While I am salvaging as many of the parts from the bike as possible in my effort to keep it original as possible, many of the parts from the bike are beyond recover and many of those are no longer available from Honda. Many of the critical parts are available from the aftermarket, but a few things can only be obtained used, and are often in pretty rough shape, as you would expect from a 35 year old dirt bike that has lived its life in the dirt and mud!

So, here is my “ASK” (and please note admins, if this is in the wrong spot, or inappropriate, please let me know. I will take it down or move it); I need a bolt re-created. This is one of those things that is NLA from Honda, and is not available in the aftermarket, and used ones all look like mine.

The bolt is of course unique in its form; It is an M8x124mm bolt With a metric (duh) 1.25 thread pitch. The thing that makes it a bit tricky is that it necks down from 8mm (you can see in the photo it was so badly corroded it is no longer 8mm in diameter!) to 7mm for the middle portion of the bolt. The first 15mm from the head of the bolt it is 8mm and then necks down to 7mm. Then the bottom 10mm it necks back up to 8mm. I need this bolt made out of “steel”…as in not aluminum. Beyond that I am not much help, so I am relying on your expertise to suggest an appropriate material.

So, what do you say, anyone up for the challenge?
I can pay for this work obviously, please let me know what you think is an appropriate fee.

Michael

 

[joe_padavano]

A machinist will require more information than just "steel" as the material. Steels range from low grade **** that is actually weaker than aluminum through exotic high strength, high temp materials. More importantly, bolts like this have precision rolled (not cut) threads to improve strength. It would help to know where this bolt is used. I suspect you will be far better to find a correct original bolt than to try to machine a replacement. The necked down section implies that this is a precision tension fastener, like a head bolt.

 

[Pb12]

Hi Joe -

this is bolt number 15. It holds the motor to the frame.
As far as material, hopefully someone more experienced in this area can chime in.
Michael

 

[VR6ix]

I would start with a 12.9 socket-head bolt and modify to suit, M8x1.25x130 long: McMaster-Carr 91290A474. They don't offer flange hex bolts that long so just use an appropriate washer.

That said... why does it need to neck down to 7mm?

 

[rsanter]

If it was me I would,buy an off the shelf bolt that had the right length and threads and then modify from there.

If that will work for you then the rest is very basic lathe work

 

[The Cobbler]

I'm with Rsanter & VE6ix
the step down is probably just to reduce aluminum to steel contact and corrosion sticking it in place .
I personally wouldn't worry too much about it
and is it that important to recreate that bolt since the bad part won't be seen?

 

[purplezr2]

Depending on the joint, it might have been to increase bolt stretch, that is usually the reason to neck a bolt down

 

[extropic]

@Pb12
Here is another option if you can use a practical fix (rather than a museum quality restoration).
Use a stud, threaded both ends and two locking type nuts. The stud I linked is 18-8 stainless so no rusting and strong enough for that application, IMHO.
It's 150mm long so you'll want to shorten each end.

Mcmaster 6516K329

Regardless of which fastener you choose to use, coat it allover with antiseize compound which should minimize corrosion in the future.

 

[Pb12]

@The Cobbler I think you are dead on re: corrosion resistance. The manual only calls for 17-24ft/lbs so this bolt is certainly not being stretched.

@VR6ix that is a great back up solution, thank you for finding it at MCM-C. I would really like to have the bolt recreated if possible, just seems like it could be a cool project for someone skilled with a lathe. I am certainly not that guy as I don’t even know how to turn one on! But, I’d love to find the guy who is in for a challenge to make something kind of cool, for a really cool (if a bit ubiquitous) old bike. To this point I haven’t had to use anything that isn’t factory or better, and I’d really like to keep it that way.

Thanks for all the input so far, keep it coming!

Michael

 

[The Cobbler]

your location would probably help garner a response for someone offering to help create one

 

[Pb12]

@The Cobbler good idea. I am in the Portland Oregon area.

 

[ItsNemo]

I would start with a 12.9 socket-head bolt and modify to suit, M8x1.25x130 long: McMaster-Carr 91290A474. They don't offer flange hex bolts that long so just use an appropriate washer.

That said... why does it need to neck down to 7mm?

Yup, just get a close bolt...don't even need a lathe, a drill and some sandpaper could neck down a millimeter of material pretty quickly.

 

[mike93lx]

For a one-off, totally custom piece, I bet you would be looking at hundreds of dollars from a shop. Maybe someone here wants the challenge in their home shop and you'll get lucky.

Good luck with the search.

 

[Shiftless]

Yup, just get a close bolt...don't even need a lathe, a drill and some sandpaper could neck down a millimeter of material pretty quickly.

Yeah, if you have a bench grinder, just chuck that bolt in your drill motor, pull the trigger and hold it next to the bench grinder spinning stone. It will only take a few seconds once you get set up.

 

[ZRX61]

It's just an engine mount bolt, just find one the right length & thread etc & don't worry about it being thinner in the middle. If you're worried about corrosion give it a coat of grease before using it.

& I know all about Honda front engine mount bolts & corrosion, I once removed one from the SOHC CB750 in 5 pieces.

 

[gorilla]

Making that bolt would be about 3/4 of an hour on the lathe and about 1/2 an hour on the mill to do the hex on the end. Material would be about $25.00 so it's a $175.00 bolt. That's assuming machine shop at $100.00/hour.

 

[Pb12]

Making that bolt would be about 3/4 of an hour on the lathe and about 1/2 an hour on the mill to do the hex on the end. Material would be about $25.00 so it's a $175.00 bolt. That's assuming machine shop at $100.00/hour.

Yeah, sounds about right. Its worth it to me.

 

[mike93lx]

The challenge will be finding a shop to do it. I called around recently for some steel forming and was looking at 6+ weeks for anyone that would even talk to me.

Best thing you can do is get the specs written up on a drawing. Lessen the chance of an error and increase the chance someone will take the job

 

[dutchgray]

This is a job for the retired guy in a garage shop.

 

[LeonardY]

Just curious. Is this it?

Honda 1987 CR250 Motor Mount Bolt CR 250 Nut (maybe 125 CR125 500 1984 1985 1986 | eBay

MIGHT fit the 1984 1985 1986 CR250R CR125 CR500. Here is a used Motor Mount Bolt from a 1987 Honda CR250.This Motor Mount Bolt is used and shows use. Good threads; good nut. You'll receive exactly what is pictured.

www.ebay.com

It's used but for $7.99.

 

[gmcgeo]

Hello Folks —

I am in the process of restoring a 1986 Honda CR125 that was not well taken care of. I guess that’s the point! this is my first attempt at a project like this, and so far its gone fine. After all disassembly is somewhat easy….well, except for all the frozen parts. While I am salvaging as many of the parts from the bike as possible in my effort to keep it original as possible, many of the parts from the bike are beyond recover and many of those are no longer available from Honda. Many of the critical parts are available from the aftermarket, but a few things can only be obtained used, and are often in pretty rough shape, as you would expect from a 35 year old dirt bike that has lived its life in the dirt and mud!

So, here is my “ASK” (and please note admins, if this is in the wrong spot, or inappropriate, please let me know. I will take it down or move it); I need a bolt re-created. This is one of those things that is NLA from Honda, and is not available in the aftermarket, and used ones all look like mine.

The bolt is of course unique in its form; It is an M8x124mm bolt With a metric (duh) 1.25 thread pitch. The thing that makes it a bit tricky is that it necks down from 8mm (you can see in the photo it was so badly corroded it is no longer 8mm in diameter!) to 7mm for the middle portion of the bolt. The first 15mm from the head of the bolt it is 8mm and then necks down to 7mm. Then the bottom 10mm it necks back up to 8mm. I need this bolt made out of “steel”…as in not aluminum. Beyond that I am not much help, so I am relying on your expertise to suggest an appropriate material.

So, what do you say, anyone up for the challenge?
I can pay for this work obviously, please let me know what you think is an appropriate fee.

Michael

BOLT FRANG 8X94 for Honda - order at CMSNL

✓ Get the BOLT FRANG 8X94 ✓ Manufacturer Part Number: 90104-KA3-730 ✓ Quality part

www.cmsnl.com

they may get more soon

 

[TXNinAZ]

The head of the bolt looks odd- is it dished out? It may be lighting, but it also looks like a gold chromate finish that's worn away everywhere else, or??? My lathe won't cut metric threads, but a die can cut the threads easily enough. Have to see what sizes of 4140 I have in the garage.

 

[Pb12]

This is a job for the retired guy in a garage shop.

Exactly. That's what I was hoping to find by listing here. I think getting a shop to take such a small job would be a real challenge right now.

Just curious. Is this it?

Honda 1987 CR250 Motor Mount Bolt CR 250 Nut (maybe 125 CR125 500 1984 1985 1986 | eBay

MIGHT fit the 1984 1985 1986 CR250R CR125 CR500. Here is a used Motor Mount Bolt from a 1987 Honda CR250.This Motor Mount Bolt is used and shows use. Good threads; good nut. You'll receive exactly what is pictured.

www.ebay.com

It's used but for $7.99.

Well, We are going to find out! For $13.49 it was worth a try! Thank you for finding it! He makes it a challenge because he doesn't know the part number and the length measurement isn't exact, but looks to be about 4 7/8 which is right at 124mm. I should know by the ned of the week hopefully. I also bought the Mcmaster Carr bolt as a back-up.

 

[Pb12]

@TXNinAZ Don't look too hard, I am putting the project on hold until I see what this bolt that @LeonardY found on eBay looks like. I had been searching by Honda part number, and so had not seen this bolt listed.

Michael

 

[TXNinAZ]

@TXNinAZ Don't look too hard, I am putting the project on hold until I see what this bolt that @LeonardY found on eBay looks like. I had been searching by Honda part number, and so had not seen this bolt listed.

Michael

Sounds good. Send me a DM if you'd like me to make it for you- I probably won't see a reply on this thread.

 

[ZRX61]

Years ago we needed some engine mount bolts for the R2800's on an A26.

There aren't any.

So we bought longer ones the correct dia by the lb (about $20 IIRC). Then sent them to an aviation machining company who cut them to length, rolled new threads etc. then they were to the plating company where they were plated, baked, tested, than back to the machining company for certification etc.
18 bolts for $20 became $250+ each bolts

 

[bugnut]

Yesterday a quick google of m8 x 125mm showed up with this bolt, it is a mm longer, but it is a flange head and surely can meet your torque requirements at less than 5$ each. If the threads are long enough someone can rework to provide the undercut area.

Flange Bolt M8 X 125mm FB108251 RNQ667 | Rovers North - Land Rover Parts and Accessories Since 1979

www.roversnorth.com

 

[yaidunno]

If the purchased alternatives don't meet your needs, i can help you out. I specialize in this sort of stuff, and am quite familiar with Honda's dimple head fasteners.

 

[joe_padavano]

Hi Joe -

this is bolt number 15. It holds the motor to the frame.
As far as material, hopefully someone more experienced in this area can chime in.
Michael

OK, all you need is a relatively tight tolerance shear bolt. The necked down sections are really immaterial. The two thick sections are the important parts for carrying the load in shear. The thinner part just helps on the assembly line to minimize insertion force. A longer bolt is also fine. Again, the only critical part of this is the sections that are in shear supporting the motor. You want a Class 10.9 bolt (metric equivalent to a grade 8 SAE bolt). Don't overthink this. Unless the optics of the bolt matter to you for a totally correct restoration, any Class 10.9 shear bolt of the correct length will be fine.

 

[neitzel]

Maybe worth a trip up to Bent Bike in Washington or Bills motorcycle salvage down in Medford.

 

[rd65]

Maybe worth a trip up to Bent Bike in Washington or Bills motorcycle salvage down in Medford.

Bent Bike is long gone.

 

[rd65]

Being a CR, bolt was necked down likely for weight savings. What is the torque spec for the bolt. You should be able to find a used, take-off bolt from a vintage bike type forum if you are wanting to restore completely to stock.

 

[bsaint]

It's def an engineered bolt as it has two od features probably for going through a boss for precise alignment. I can't see it being a shear bolt. To do it right you gotta find it from Honda or make one. Also it being a 7mm hex it seems like it's JIS flange spec.

 

[joe_padavano]

It's def an engineered bolt as it has two od features probably for going through a boss for precise alignment. I can't see it being a shear bolt. To do it right you gotta find it from Honda or make one. Also it being a 7mm hex it seems like it's JIS flange spec.

The engine mounts in shear, not tension. Any appreciable tension would draw the two frame rails in. Don't overthink this.

 

[bsaint]

The engine mounts in shear, not tension. Any appreciable tension would draw the two frame rails in. Don't overthink this.

Lol maybe you don't understand the difference between a shear bolt and shear force. Maybe you're not thinking enough. I'm talking about a shear bolt. It's not. Google shear bolt.

 

[matt_i]

A pack of 10pcs M8 x 1.25 x 130mm 10.9 HHCs are ~14 at McMaster Carr. Partially threaded, the shoulder is also going to be 8mm nominal. The extra material in the center won't hurt you.

If the unthreaded portion is critical, I've gotten various fasteners before (with the luxury of a binned assortment), some which are too-long overall but the unthreaded shank is proper and then its just a matter of cutting the threaded end shorter and putting the Higby on the lead thread with a file.

A washer will substitute nicely for the flange head, in function.