MK 111 engine to cradle bolts .

Torontonian

Torontonian

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Corrosion , mangled the thread tips up punching all 3 out .
What new ones ? Diameter , lengths , thread size that are good replacements or upgrades ? Stainless ?
Thanks in advance . Enjoy .
 
They should be 3/8" UNF high tensile preferably.

Sizes are here.
andover-norton.co.uk

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
The lower mounting bolt on the Mk3 is also 3/8" instead of the previous 5/16".
 
L.A.B. said:
They should be 3/8" UNF high tensile preferably.

Sizes are here.
andover-norton.co.uk

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
The lower mounting bolt on the Mk3 is also 3/8" instead of the previous 5/16".
Click to expand...
Thanks L.A.B. , appreciate that . Enjoy .
 
Take the opportunity to replace the three bolts with 10mm ones 8.8 grade minimum. They might need the holes reaming out slightly but they are a better fit in the holes and help prevent the engine moving in the cradle. Using the std 3/8"UNF bolts the engine can, and does, move about in the cradle (the cradle and engine holes are clearance holes after all) . The factory tuning notes recommend that these three bolts are replaced with centerless ground studs sized to be 'fitted' studs in the holes. I always make sure that the plain unthreaded shank of the bolt/stud is long enough (95mm) to span the cradle, so the bolt thread is not wearing into the cradle as the standard bolt shank is not long enough. 150mm long 10mm bolts should be ok. If your bothered about it looking 'original' you can cut a 3/8 unf thread on the over long bolt/stud. The 10mm head will be on the inside (between the cradle and primary drive), so not seen. Metric bolts are cheaper and more available.
 
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Good standard ones available from Andover.

Excellent quality stainless replacements using 12 point nuts available from cNw.
 
Fast Eddie said:
Good standard ones available from Andover.

Excellent quality stainless replacements using 12 point nuts available from cNw.
Click to expand...
Looking at the CNW kit, it looks like the plain shank of the bolts are still not long enough to span the cradle and they will be 3/8 dia so no better than std ones and at a very high price (almost $100) and because they use 12 point nuts you have to grind a bit out of the front engine case to get a socket or spanner on them.....Not on my engines
 
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dobba99 said:
Take the opportunity to replace the three bolts with 10mm ones 8.8 grade minimum. They might need the holes reaming out slightly but they are a better fit in the holes and help prevent the engine moving in the cradle. Using the std 3/8"UNF bolts the engine can, and does, move about in the cradle (the cradle and engine holes are clearance holes after all) . The factory tuning notes recommend that these three bolts are replaced with centerless ground studs sized to be 'fitted' studs in the holes. I always make sure that the plain unthreaded shank of the bolt/stud is long enough (95mm) to span the cradle, so the bolt thread is not wearing into the cradle as the standard bolt shank is not long enough. 150mm long 10mm bolts should be ok. If your bothered about it looking 'original' you can cut a 3/8 unf thread on the over long bolt/stud. The 10mm head will be on the inside (between the cradle and primary drive), so not seen. Metric bolts are cheaper and more available.
Click to expand...
Well, if we’re talking making the perfect ones then I agree with reaming out for 10mm. And ensuring the threads are long enough for thick washers and nyloc nuts. And in a top grade stainless… And… I’d like to see waisted stems to ensure correct stretch and constant clamping forces.
 
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Fast Eddie said:
Well, if we’re talking making the perfect ones then I agree with reaming out for 10mm. And ensuring the threads are long enough for thick washers and unlocks nuts. And in a top grade stainless… And… I’d like to see waisted stems to ensure correct stretch and constant clamping forces.
Click to expand...
The 'unlocks' nuts? Careful Nigel, you are close to sounding like Knut
 
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With all the hunt for perfection, don't forget: no powder coat on the cradle, anti-seize on stainless, and torque correction when anti-seize is used.

I can and have powder coated cradles in-house. I don't anymore. The required masking and then painting of the masked areas is ridiculous IMHO. I use VHT Roll Bar and Chassis paint on cradles. Easy to apply, strong, looks good, and no issues like are caused by powder coat.

Here's an Old Britts article on the subject. IMHO, most of it is overkill, but the cradle and front iso mount part is not. The masking is important since over time the powder coat will compress and the mounting bolts will loosen. This is especially true of a "professional" powder coat job with primer, then black, then clear. Only ever let the powder coater use the black layer over freshly blasted steel!

 
Fast Eddie said:
Well, if we’re talking making the perfect ones then I agree with reaming out for 10mm. And ensuring the threads are long enough for thick washers and nyloc nuts. And in a top grade stainless… And… I’d like to see waisted stems to ensure correct stretch and constant clamping forces.
Click to expand...
Nigel, I guess you were not too serious about the waisted stem statement. These bolts are loaded in shear (even under torque reactions), not axial tension. The bolt/cradle load transfer can not rely on friction due to the comparatively soft aluminum causing the clamp force to be 50% approx. of the bolt's yield (proof) force, which in turn creates a modest contact pressure between nut and cradle. Tensioning the bolts to normal clamping load levels (75% of proof load, for steel/steel) becomes impossible. Thus, no friction load transfer can be assumed.
That's why the bearing surface of the bolt _and_ the cradle becomes important. Equal clamping forces is irrelevant in this case. The performance of a metric bolt grade 8 or ASTM A325/1 is sufficient.

- Knut
 
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marshg246 said:
With all the hunt for perfection, don't forget: no powder coat on the cradle, anti-seize on stainless, and torque correction when anti-seize is used.

I can and have powder coated cradles in-house. I don't anymore. The required masking and then painting of the masked areas is ridiculous IMHO. I use VHT Roll Bar and Chassis paint on cradles. Easy to apply, strong, looks good, and no issues like are caused by powder coat.

Here's an Old Britts article on the subject. IMHO, most of it is overkill, but the cradle and front iso mount part is not. The masking is important since over time the powder coat will compress and the mounting bolts will loosen. This is especially true of a "professional" powder coat job with primer, then black, then clear. Only ever let the powder coater use the black layer over freshly blasted steel!

Click to expand...
My cradle and frame came powder coated . No clear coat .
 
ludwig said:
+1 for M10 bolts, but go for M10x1. Not the std M10x1.5.
Reaming is usually not necessary.
Click to expand...
Why this finer pitch? Prestressing the bolts in the common way isn't possible anyway, thus fine-tuning the application of torque is pointless.

- Knut
 
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marshg246 said:
Check the fasteners that go through the cradle and front ISO for tightness. It's bad when they work loose :( Much less likely without primer and clearcoat but still can happen.
Click to expand...
In my days before the MK 111 , my 750 developed a loose top cradle bolt , apparently this is the one that slackens off first of the 3 .
 

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