Rather than call this a tech page,
this a useful "tid-bits" page.
We do not see any reason to talk about Hondas timelines and changes they made unless its useful.
We do not see any reason to copy and paste a bunch of tech articles about theories that do not pertain to the Honda cb750 engine.
Read before purchasing our MLS gaskets or any gasket set.
When purchasing Honda CB750 head gaskets, a couple of questions should be to be asked. Early or late? Big drain holes or small?
The above left photo shows an early Honda CB750 cylinder and the arrows show the drain holes from the top end. We call them small for obvious reasons.
The above right photo shows a later Honda CB750 and the arrows show the drain holes from the top end. We are calling them large for obvious reasons. The later cylinder and head gaskets have larger holes because Honda installed 8 dowel pins and 8 tall "O" rings to try to correct head gasket weepage issues.
When using MLS gaskets, our testing showed the 8 dowels and 8 tall "O" rings are not needed because the MLS gaskets work so well. On the other hand, many people were telling us "Well, if Honda did it, it must be right". So, we offer the later head gaskets so people can sleep better at night.
When installing big bore sleeves, early cylinders are always used
because the larger sleeves leave little to no room for the 8 tall "O"
With that said, you will not see a "big hole" later model MLS head gasket in 890cc and above cylinders.
Head gasket issues solved.
Why do most Honda CB750's leak or weep from the
head gasket area?
Why did Honda install 8 dowel pins and 8 tall rubbers where the oil drains down from the head on later years?
What sealer should be used when changing the head gasket?
Annoyed by leaking head gaskets, here's what we did...
We ordered the following head gaskets:
Cometic head gasket.
Vesrah head gasket.
Athena head gasket.
Honda OEM head gasket.
All of these gaskets measured about the same, .048 thick. and conventional gasket materials.
One by one we installed these gaskets into our Honda CB750 test bike.
We ran the bike for X amount of miles with each gasket and disassembled the top end to inspect and measure the thickness of the gaskets.
Some of the gaskets (forgot which ones) compressed up to .016 and the head nuts only had approx 5 to 7 foot pounds of torque left.
This discover kinda freaked us out and it made us feel the need to mention to people to re-torque their Honda heads.
Only trouble is, to re-torque a Honda CB750 head is a pain.
The other trouble is, like a river, once water finds a path to travel, it's pretty hard to stop. (Same for oil)
So now what?
Well, for years and years MLS (multi layered steel gasket) were used on automobiles, Harley's, Kawasaki's, Suzuki's, and such.
We decided to inquire about having MLS gaskets made for the Honda CB750 world.
About $10,000 later we had a batch of MLS gaskets for Hondas.
We took a pretty big chance, spending this amount of money before we could test them. But we were convinced they would work.
So, right about this time we were building our Honda CB750 (915cc) vintage road racer for the heavy weight superbike class.
We installed these gaskets along with heavy-duty cylinder studs and ran this bike for the whole season, not a drop of oil came out of this bike and you will never abuse your bike as bad as we abused our race bike.
By the way, check out the cylinder stud tech page for our installing procedures.
Also, when prepping the gasket surface for the MLS gaskets, no gasket scraper marks, no left over gasket material, head should be flat or milled, the surfaces should have a bit of texture, not a mirror finish.
If you have a stock Honda frame without removable rails to gain access to your top end, our no leak valve cover gasket might be good idea also.
So, you might be wondering...
"How did they try to control head gasket leaks in the 70's Era?"
Heavy duty cylinder studs, various materials of gaskets, sealers and copper head gaskets were a racers choice.
As far as copper head gaskets for sealing oil leaks, it was momentary.
When installing a copper head gasket, the gasket needs to be annealed (red hot and quench in cold water) this process combined with gasket sealer worked fine for a bit.
Trouble is, after many heat cycles the copper head gasket would reverse anneal it self and become hard again (oil leaks)
On the other hand, copper gaskets can be re-used over and over again making them economical.
The other advantage of copper head gaskets is to keep your valve to piston and piston to head clearances in check after doing all the math. (They do not compress like conventional gasket materials)
How did they try to control valve to piston and piston to head clearances in the 70's era with conventional head gaskets compressing and saw-cut alloy connecting rods stretching and expanding who knows how much?
Some people ran .060 or more piston to head clearances, just in case of a unforeseen problem we suspect.
In closing, we cannot even count how much money and time was spent developing our MLS gaskets and Heavy-duty cylinder studs to upgrade the Honda CB750 head gasket dilemma.
Under heavy construction.
More to come
A 3.99% customer service charge is applied to all phone orders.
If ordering via phone, please also provide the part # of any products you are interested in for faster and more accurate service.
If you encounter a (rare) broken button as you're trying to add parts to your cart (going to PayPal summary instead of your cart or not opening PayPal at all) or anything else of concern, please call us to report it. We'll try to have it fixed for your convenience within the next 5-10 minutes. Afterwards, refresh the page and try again.NOTE: As of July 1st, 2018, an extended goods and services tax (GST) has been applied to all Australian consumers buying overseas, charging an extra 10% in taxes to us with each purchase. To ensure that you can continue to purchase from us in Australia and we can provide our parts at our usual lower cost, please contact us at the email below if interested in any particular parts so that we can make a special shipping arrangement for you.
It is the sole and
exclusive responsibility of the purchaser to determine the suitability of any
part, product or work for his or her use.
The purchaser shall assume all legal, personal injury risk and liability and all other obligations, duties and risks therewith. There is no warranty on High Performance products.
Click to go back to our home page
Cycle X Global Headquarters
6246 US Hwy 51 South
Hazelhurst, WI 54531