New frame/engine bolts. What type?

[alexdecker]

Hey

I am buying this kit soon for my CB550F 1977. For the long bolts, I can choose between dome, full hex, nyloc or toothed flange. Which version would you guys recommend I go with? Which would be the most "correct" version?

https://www.zed-parts.com/product-page/honda-cb500-four-engine-mount-kit

- Alex

[Oddjob]

I personally wouldn't buy that kit at all Alex. The long top bolt is not supposed to be threaded at both ends, it's a normal bolt with a head at one end and a nut at the other.

Socket bolts as engine hangers is also a poor idea, cheaper and easier to just buy normal stainless bolts if that's what you like.

[alexdecker]

Thanks! It’s the only set I have been able to find that mounts the engine to frame. My own bolts is rather beat up, rusted and half of them not original. Is there any others sets you know of that could be an option?

[davidcumbria]

Don’t know about the long bolts but I have used a combination of bolts from Kay fast and Middletons. Take care to get matching bolt and nut thread pitch sizes. The markings can be filed or ground off if required and polish up very well

[Seabeowner]

If it's the only way of sourcing the long mounting studs/bolts the your bike your choice. There are a couple of sets on UK ebay. I'd choose the hex head to look slightly standard.

[Oddjob]

You can get all the bolts and nuts from Middletons, and with the correct size heads as well.

I got Middleton to make me the top and bottom long ones back in the 80s but they don't do that anymore unfortunately.

Shame Max isn't a member anymore as those 2 long bolts would have been something he should have been able to make, bottom one especially as it's just a rod threaded both ends, nothing special there.

[alexdecker]

Could I perhaps do this set then? Then I would only need to figure out a solution for the long bolts to make it a complete set, right?

https://www.ebay.de/itm/266394764819?hash=item3e065d8613:g:adsAAOSwBRVh3sTX&amdata=enc%3AAQAIAAAA0By6bS01FdHCVno0vdg0BcJB9TxUcImfxSwXHyG167zlwZEXi0C6haCGxIDhtuNZP5quonAszdAbRPysYRXAxCoBPvhC5b2eqHgx1e8aNaW82Q1FEhTVQ49%2Bd8OPHZIYkNNTNaFxh2asjNwIr7G5Cgpd6bSB8psYKpGScl4hQWJ3n8gDmwuc3tYFg4Z1XjSKI6HmBkPOtH2IeAQ0Na1BOoeS1dSJevGt87Ex9MfhyjkYhZkHyxvn89s5byMFGOROaq8yL2Cl8N%2BgnaA8RvX3iUA%3D%7Ctkp%3ABk9SR66j3qr_Yg

[Skoti]

Stainless stuff has not the same strength as normal zinc plated high tensile steel fasteners.
Not ideal for engine, shockers, forks or brakes etc.
But probably ok for other light duty cycle parts.

Anyhow for a show pony it probably won't matter.

Stay safe

Skoti

[Nashfly]

Stainless stuff has not the same strength as normal zinc plated high tensile steel fasteners.
Not ideal for engine, shockers, forks or brakes etc.
But probably ok for other light duty cycle parts.

Anyhow for a show pony it probably won't matter.

Stay safe

Skoti

Yep, the scrutineers at the Isle of Man TT & Manx Grand Prix/Classic TT check (with a magnet) that engine mounting bolts are not stainless as they have been known to fracture

Doubt it would happen on a road machine though

[Oddjob]

Stainless stuff has not the same strength as normal zinc plated high tensile steel fasteners.
Not ideal for engine, shockers, forks or brakes etc.
But probably ok for other light duty cycle parts.

Anyhow for a show pony it probably won't matter.

Stay safe

Skoti

That would be sort of true Skoti IF the SOHC engines used tensile steel bolts, which to my knowledge they don't (and if they do why aren't they marked as tensile bolts, like 8.. The engine bolts are AFAIK mild steel, seen more than a few with stripped threads, fractured etc which you wouldn't see in tensile steel. Saying that, the various grades of tensile bolts means that some are actually the same tensile strength as good stainless. BSB and MotoGP bikes for instance use a lot of titanium bolts for lightness, it's also stronger generally than stainless and significantly stronger than most steels except for high grade carbon steel, which would be unsuitable for engine bolts due to the water these bolts are exposed too. AFAIK Titanium doesn't stick to a magnet either so why scrutineers would frown on a material that strong is beyond me, it could be more to do with the bike being or using original parts than strength.

I've used either stainless or titanium bolts for my bikes since the late 70s, the cost then was exorbitant but they were also the only bolts to survive rat piss for 40 years, a quick wipe and they were as good as new. The Honda bolts were scrap, even zinc plating has it's limits. I've yet to suffer a failure except once when I tightened down some nyloc nuts onto the ends of the long end bar running through the footrests, being new to stainless I was unaware of galling. When I attempted to remove the nuts they were as solid as if they'd been welded in place, in the end I used a piece of scaffolding tube 6ft long as a lever on a T bar, the force exerted was so powerful the actual bar sheared just behind the nut, the nut never came off even when heat was used to melt the nylon locking part. Middleton made me a replacement FOC and advised using copper grease in future.

I can safely say I have fewer than 10 of the original Honda bolts left on my bike and possibly even less than that figure on my 1300, only specialised bolts are kept as standard, caliper bolts are either stainless or titanium, pad pins titanium, never a failure in all that time and I've raced the 500 and ride the 1300 very hard.

[DomP]

Hi Alex, I'm ordering all of the m10 and m8 bolts, nuts and spring washers for my engine mountings from Kays (Kayfast) on Ebay, it racks up quite quickly for a few odd sized bolts and you can often get 10 for very little more than you can 5 for example but I done see where I'd ever need the spares.   

[Oddjob]

The trouble with a lot of these sellers Dom is that they tend to be stamped on the head with markings, which tbh I think look awful and they also tend to have the wrong size heads on the bolts, 6mm ones are fine with 10mm heads but 8mm tend to have 13mm and they should be 12mm and worse 10mm tend to have 17mm heads and they should be 14mm on a Honda, sometimes this means they won’t fit properly due to space constraints. You’ve also got the thread pitch being wrong, mostly on 10mm and above. Honda used metric fine for most of these bolts and the ones you normally get are standard metric

[McCabe-Thiele (Ted)]

Ken is right about the head sizes you will only be able to get an open ender on the front bottom engine mount when not using original so an accuratecTorque setting is pretty much impossible.

[DomP]

Good points by Ken and Ted,  I wasn't worried about thread pitch as the engine mounting bolts are all going onto their own nuts but I hadn't considered this with the lower yoke pinch bolts.  Are they standard 1.5mm pitch on the m10 bolts?

I might have to have a rethink on the lower engine mounts.

[Oddjob]

I think metric fine for M10 is 1.25 pitch Dom.

https://www.stainlessmiddleton.co.uk/32908-metric-fine-bolts-setscrews

Middletons sell the correct type, 14mm head.. A hex set is threaded full length, most Honda bolts are not hex set bolts, just the stand hex bolts. Most bolts under 40mm in length tend to be threaded full length so are hex set, same for screws, those are called setscrews.

Middleton bolt are really good quality, the head has no writing on and tends to be highly polished, the end where the thread stops is domed. The only ones I've found that have the writing on the top tend to be ones I think he buys in nowadays and are small M5 bolts which I use for the carbs. I tend to file the markings off and polish the top myself when I get them.

For engine bolts you have a choice, use metric fine but remember to also buy metric fine nuts to match OR buy normal standard bolts and use normal nuts, so long as where it is fitting isn't prethreaded you can choose either.

He also does M8 nuts in 12mm spanner size, M10 in 14mm spanner size.

https://www.stainlessmiddleton.co.uk/32930-metric-nuts-full

The M8 bolts do tend to be 13mm spanner size though but TBH that matches the size that Yamaha and Suzuki used, it was Honda that was the odd one out. He does do some really long ones though, great for crankcase bolts etc that can be seen

https://www.stainlessmiddleton.co.uk/32906-metric-bolts-setscrews?page=3