MOTOR OIL: Are you using the right kind??? It's very important!

[Dr Zoom]

I have other obsessions besides CB 750's. I have a few old cars. Over the years, I've seen heated debates (esp on Corvette Forum) about which modern oil to use in our old cars. One thing they (the Vette guys) all DO agree upon is that vintage flat tappet cam/lifter engines REQUIRE about 1,200ppm concentration of zinc (zddp) in the motor oil for proper lubrication and reduced wear. The second thing they all agree on is that the oils for the modern roller cam engines of today are so much better at lubrication, that oil companies now deem zinc as almost unnecessary. AND therefore, they have greatly reduced the zinc content in today's modern oils... Other than that, the small block chevy gurus agree on little else especially concerning which oil to dump into their Stingray's crankcase...

Sooooo the point of my rambling today is to inform you if you're using the same type oil in your old flat tappet Honda 750, as you're using in your new(er) Honda Civic, Accord, etc, your camshaft and lifters are likely wearing much faster than you'd want.

I will spare you the the gist of the multitudes of childlike spats these grown corvette men vehemently support, but I'll relate to you what I've done, and strongly suggest if you're pouring modern oils in your precious four cylinder scooter, it may not end well. The simplest solution I've seen for my cars is to use valvoline Vr-1. Many others use Diesel engines oil like Shell Rotella T-4. (Both oils have the necessary zinc). In my old (1970's) tractor I use the same Penzoil or similar SAE 30 wt oil I've always used, but I add enough ZDDP additive to give me the 1200ppm zinc to keep the old girl in the field.

With no further ado, I will leave you dear friends with this: To say it better, here's what Google's AI Q&A app had to say when I asked the questions about flat tappets, vintage CB 750's, and zinc. Here ya go:

From Google AI:
Yes, your 1972 Honda CB750 Four with a flat tappet camshaft likely needs extra zinc (in the form of ZDDP - Zinc Dialkyldithiophosphate) in its engine oil.
Here's why

• Flat-Tappet Design: The cam and lifters in older engines like your Honda CB750 have a flat-tappet design. This design creates higher pressure and friction between the camshaft lobes and lifters compared to modern engines with roller cams.
• Reduced ZDDP in Modern Oils: Modern engine oils (especially those rated API SN and ILSAC GF-5) have reduced levels of ZDDP. This is because ZDDP can degrade the efficiency of catalytic converters found in newer vehicles. Since your classic motorcycle likely doesn't have a catalytic converter, this isn't a concern.
• ZDDP's Role: ZDDP acts as an anti-wear additive, forming a protective film over metal surfaces under high pressure and heat, preventing metal-to-metal contact and excessive wear in flat tappet engines. Without sufficient ZDDP, flat tappet cams can suffer premature wear and potentially fail.

Recommendations

• Look for a high-zinc oil: Consider using oils specifically formulated for classic cars or motorcycles that explicitly state a higher ZDDP content. These oils are designed to meet the needs of older engines.
• Check ZDDP levels: Ideally, look for oils with a ZDDP content between 1200 and 2400 ppm (parts per million), according to Speedway Motors.
• Consider ZDDP additives: If you're using a modern oil, you may want to add a ZDDP supplement to ensure adequate protection for your engine. However, be careful not to add too much, as excessive zinc can cause issues like spark plug fouling.
• Consult with experts: If you're unsure, consult with a mechanic specializing in classic motorcycles or contact the camshaft manufacturer for specific recommendations.

In conclusion, ensuring adequate zinc content in your oil is crucial for the longevity of your 1972 Honda CB750 Four's flat tappet camshaft.

 

[pmcnulty]

Excellent info and as an old VW / Porsche aircooled guy, this topic is very familiar. Your post is spot on in my opinion and your suggestions should be followed. Check out Jake Rabe’s and others thoughts at L&N Engineering for more:

https://lnengineering.com/oil.html

 

[Loki]

Whilst I agree with most of the previous comments, and by the way I use VR-1 in both of my Chevys, the info all refers to CAR applications which don't have WET CLUTCHES or if they do they have a serious problem!
So I will continue to use good quality MOTORCYCLE oil in my bike.

Loki

 

[Dr Zoom]

Excellent info and as an old VW / Porsche aircooled guy, this topic is very familiar. Your post is spot on in my opinion and your suggestions should be followed. Check out Jake Rabe’s and others thoughts at L&N Engineering for more:

https://lnengineering.com/oil.html

Man.... I didn't know what I was getting into when I clicked on that ^^^^ link! WHEW!

That's a LOT of info to digest, but it's all critical, so I read the whole enchilada! I wish I could find a similar article applicable to my old corvettes, as the oils for air-cooled engines must meet differing demands than water-cooled SBC's.

Never the less, the part about detergents was interesting and important, and the fact they state to NOT use ZDDP additives got my attention.

So the search continues.... I know Amsoil has formulated an oil for vintage engines (but it's synthetic) and the Valvoline VR-1 I use was likewise created. But I'm now interested to check the detergents (type and amount) used, as well as the actual levels of calcium, molybdenum, phosphate, and ZDDP in the oils I'm using, and what LN Engineering deems suitable for my old chevy 327 engines, as well as the 750 Honda.
Thanks for the comments and the article.... at least I now know about the "4 R's" and what a tribologist is .... and sadly, I also now know how ignorant I am (and have always been) about motor oils.... LOL

OBTW, Welcome to the forum.... I think you're gonna be a needed contributor!
Thanks again, brother!!!

 

[Dr Zoom]

Whilst I agree with most of the previous comments, and by the way I use VR-1 in both of my Chevys, the info all refers to CAR applications which don't have WET CLUTCHES or if they do they have a serious problem!
So I will continue to use good quality MOTORCYCLE oil in my bike.

Loki

Interesting thought about wet clutches.... Like I said, the search continues.... hmmmmm

 

[hinksy]

We have this downunda , will always use zinc for a flat tappet cam

 

[MarcinMMz]

What do you think about such oil for our machines? I consider to try it next time... https://www.silkolene.com/en/products/silkolube-20w-50/

 

[grewth]

Anyone care to name a zinc additive which is commonly available in the UK ?
I seem to find that as soon as I ask for something unusual, it's either not available or it's an extortionate price.
Someone is apparently selling Penrite oil on ebay for £1000 a litre.
Maybe that's just because they're out of stock ?

 

[Loki]

There's a few out there Frosts have an Eastwood product which should be enough for 2 oil changes and not that expensive but before going off half cocked there must be classic bike oils around which are formulated with zddp already in them? Millers is one that springs to mind also Morris.
At the same time there are still "modern" bikes with ohc engines with similar valve gears to ours and they run fine on modern motorcycle oils, I'd say stick to established manufacturers and you can't go wrong.

Loki

 

[hinksy]

Grewth , it would cost less for me to transport some penrite for you from the antipodes . 1000 pound ! ole mate is nuts

 

[grewth]

I think that maybe ebay charge for suspending a listing, but not for altering the price.
So when stocks run out, seller just adds £1000 to the price

 

[grewth]

There's a few out there Frosts have an Eastwood product which should be enough for 2 oil changes and not that expensive but before going off half cocked there must be classic bike oils around which are formulated with zddp already in them? Millers is one that springs to mind also Morris.
At the same time there are still "modern" bikes with ohc engines with similar valve gears to ours and they run fine on modern motorcycle oils, I'd say stick to established manufacturers and you can't go wrong.

Loki

Morris Oils are only a few miles away from me at Shrewsbury, although obviously they don't do retail sales.
But my local agricultural supplies store has a whole isle full of Morris products, all at very competitive prices.
If they don't actually stock the classic oil, I'm sure they will order it in for me.

 

[UK K6]

You can go round in circles on oil.

I just stick to some simple rules:
- JASO MA2 standard allows the clutch to work and not glue the plates up.
- 10W40 or 20W50 (I use the latter, as it doesn't generally get as hot in the UK).
- Change the oil and filter regularly. We have gearboxes chewing the polymers up, as well as engine heat and clutch shear. I do as Honda say, 1500 miles for oil, but as they're cheap, I also do the filter each time.
- I regularly sniff the dipstick for fuel contamination! The carb overflow pipes are pretty useless, one sticky float chamber can ruin the oil.

I use ZDDP oils in my Norton and older triumph car (both have pre-unit construction: gearboxes and clutches don't sit in the engine oil). But I don't know what ZDDP does to the Honda's clutch, so I stick with MA2 20W50 motorcycle oil.

 

[grewth]

You can go round in circles on oil.

I just stick to some simple rules:
- JASO MA2 standard allows the clutch to work and not glue the plates up.
- 10W40 or 20W50 (I use the latter, as it doesn't generally get as hot in the UK).
- Change the oil and filter regularly. We have gearboxes chewing the polymers up, as well as engine heat and clutch shear. I do as Honda say, 1500 miles for oil, but as they're cheap, I also do the filter each time.
- I regularly sniff the dipstick for fuel contamination! The carb overflow pipes are pretty useless, one sticky float chamber can ruin the oil.

I use ZDDP oils in my Norton and older triumph car (both have pre-unit construction: gearboxes and clutches don't sit in the engine oil). But I don't know what ZDDP does to the Honda's clutch, so I stick with MA2 20W50 motorcycle oil.

Interesting!
I never thought about the gear teeth chopping up the long chain polymers which make the oil multi grade.
I knew a long time ago that the bits of hardened steel which come off the gears over time will eventually kill the oil pump if various magnets don't catch them.
Apparently the Austin "A" series engines only had half the lifespan when fitted in a Mini with it's in unit gearbox, compared to a traditional set up.

 

[bbaart]

I have other obsessions besides CB 750's. I have a few old cars. Over the years, I've seen heated debates (esp on Corvette Forum) about which modern oil to use in our old cars. One thing they (the Vette guys) all DO agree upon is that vintage flat tappet cam/lifter engines REQUIRE about 1,200ppm concentration of zinc (zddp) in the motor oil for proper lubrication and reduced wear. The second thing they all agree on is that the oils for the modern roller cam engines of today are so much better at lubrication, that oil companies now deem zinc as almost unnecessary. AND therefore, they have greatly reduced the zinc content in today's modern oils... Other than that, the small block chevy gurus agree on little else especially concerning which oil to dump into their Stingray's crankcase...

Sooooo the point of my rambling today is to inform you if you're using the same type oil in your old flat tappet Honda 750, as you're using in your new(er) Honda Civic, Accord, etc, your camshaft and lifters are likely wearing much faster than you'd want.

I will spare you the the gist of the multitudes of childlike spats these grown corvette men vehemently support, but I'll relate to you what I've done, and strongly suggest if you're pouring modern oils in your precious four cylinder scooter, it may not end well. The simplest solution I've seen for my cars is to use valvoline Vr-1. Many others use Diesel engines oil like Shell Rotella T-4. (Both oils have the necessary zinc). In my old (1970's) tractor I use the same Penzoil or similar SAE 30 wt oil I've always used, but I add enough ZDDP additive to give me the 1200ppm zinc to keep the old girl in the field.

With no further ado, I will leave you dear friends with this: To say it better, here's what Google's AI Q&A app had to say when I asked the questions about flat tappets, vintage CB 750's, and zinc. Here ya go:

From Google AI:
Yes, your 1972 Honda CB750 Four with a flat tappet camshaft likely needs extra zinc (in the form of ZDDP - Zinc Dialkyldithiophosphate) in its engine oil.
Here's why

• Flat-Tappet Design: The cam and lifters in older engines like your Honda CB750 have a flat-tappet design. This design creates higher pressure and friction between the camshaft lobes and lifters compared to modern engines with roller cams.
• Reduced ZDDP in Modern Oils: Modern engine oils (especially those rated API SN and ILSAC GF-5) have reduced levels of ZDDP. This is because ZDDP can degrade the efficiency of catalytic converters found in newer vehicles. Since your classic motorcycle likely doesn't have a catalytic converter, this isn't a concern.
• ZDDP's Role: ZDDP acts as an anti-wear additive, forming a protective film over metal surfaces under high pressure and heat, preventing metal-to-metal contact and excessive wear in flat tappet engines. Without sufficient ZDDP, flat tappet cams can suffer premature wear and potentially fail.

Recommendations

• Look for a high-zinc oil: Consider using oils specifically formulated for classic cars or motorcycles that explicitly state a higher ZDDP content. These oils are designed to meet the needs of older engines.
• Check ZDDP levels: Ideally, look for oils with a ZDDP content between 1200 and 2400 ppm (parts per million), according to Speedway Motors.
• Consider ZDDP additives: If you're using a modern oil, you may want to add a ZDDP supplement to ensure adequate protection for your engine. However, be careful not to add too much, as excessive zinc can cause issues like spark plug fouling.
• Consult with experts: If you're unsure, consult with a mechanic specializing in classic motorcycles or contact the camshaft manufacturer for specific recommendations.

In conclusion, ensuring adequate zinc content in your oil is crucial for the longevity of your 1972 Honda CB750 Four's flat tappet camshaft.

You specifically mention 72 Honda 750 but I assume the 79-82 DOHC 750s also have flat tappet design?

 

[Old_Crow]

You specifically mention 72 Honda 750 but I assume the 79-82 DOHC 750s also have flat tappet design?

They aren't flat tappet, they're what they call shim and bucket design. Not sure how that affects the oil, but I'll be interested to see what others say. Personally, on my '79 I use 20/50 Castrol conventional, just like I did with the '79 I had back in the '90's.

 

[bbaart]

They aren't flat tappet, they're what they call shim and bucket design. Not sure how that affects the oil, but I'll be interested to see what others say. Personally, on my '79 I use 20/50 Castrol conventional, just like I did with the '79 I had back in the '90's.

Thanks. Yes, shim and bucket. I asked cause I thought the flat tappet design had more to do with the shape of the camshaft lobe. But definitely shim and bucket.
Coincidentally, I also use Castrol, in my case 10/40. I've owned the bike since 86 and have used that brand it's whole life.

 

[grewth]

I went into the farm store yesterday.
They stock Morris Oils products in a classic 20W50, and monograde SAE30, 40, and 50.
All in stock, but possibly of limited use to me.
I'd think that the monogrades would be of interest to the owners of clattering old British Iron, but nothing Japanese.
Apparently full spec sheets are on Morris's website