Fact or Fiction:



Hondaman via SOHC forums: "I just finished rebuilding an F2 head (twice) that has the "high performance" CycleX valves with a coating of some kind on them. After the engine was run a couple of hundred miles, this [thick] coating wore off the stems and left the valves very loose in their guides. The clearance had started at .0010" intake and .0020" exhaust: by the time the head came back to me they were nearly .0060" intake and even more on the exhaust side. I had to remove the valve guides, which had just been resized using bronze liners, and replace them with oversized CycleX guides because after I finished polishing off the REST of this coating, the valve stems were slightly below Honda's new-spec size. Once all the rest of the coating was removed from the valves, they look like nice stainless-steel ones. I polished their stems and faces smooth, sized the new valve guides to fit appropriately, and will be sending the head back into service. I don't know what the coating is/was, but it doesn't last long in the guides and it REALLY holds carbon tightly to the valve faces. It is about .0005" to .0008" thick on the surface, so when it wears off in the guides it adds about .0016" extra clearance, quick."



Quote: "Coating of some kind on the valve stems."

Response: These coatings improve wear properties, reduces friction, and provides resistance to corrosion and wear that is superior to chrome and nickel electrolysis plating.
Most modern valves incorporate these coatings and have decades of proven performance.

Quote: "The coating is about .0005 to .0008 thick on the surface, so when it wears off in the guides it adds about .0016 extra clearance."

Response: Wrong. The coating is .0001 or less. (One tenth or less)

Quote: "Just resized with bronze liners."

Response: What?

Bronze liners are from the automobile world and are known as a poor man's repair on vintage cars with loose clearances.
Trouble is, they need to be installed by experts and improper installation will have catastrophic results.


Quote: "Holds carbon tightly to the valve faces."

Response: What?

Quote: "The clearance had started at .0010" intake and .0020" exhaust"

Response: Those clearances sound kinda loose.


Find a new machinist.
Purchase some measuring devices.
Find a new method of cleaning the inside of the guide after machining.
Tune your bike or install a oil cooler if in a hot climate.
Do not use bronze valve guides or bronze liners.
You screwed up!



Hello all at Cycle X,

After using your products for three seasons of racing, I feel that I must contact you to thank you for your service and help over the last three seasons. We race in the Camathius Cup, which is a European wide championship for sidecars with engines manufactured up until 1972. In the last three seasons, we have finished in the top five in the championship. (2017 - 4th, 2018 - 4th, 2019 - 5th) Our 970cc engine using all Cycle X parts has performed perfectly at all meetings attended and has been competitive against the fastest classic sidecars in Europe. The only breakdowns we have had have been due to outside influences, ie. Punture and taking a stone into the inlet valve. The quality of all the Cycle X parts we have used have been exceptional with no problems whatsoever. We are in the process of building another engine, so we will be contacting you soon with an order for various parts.

Best regards,

Keith Walters

Thanks Keith and many others that read these comments and offered their success stories using our valves and other products.
Keep in mind that Keith Walters has a side car with limited air flow for cooling, over 220lbs of spring pressure at the nose of the .430 lift camshaft.
His valves and guides are perfect after 3 race seasons.





There seems to be a debate or discussion about head gasket oil leaks, head gasket and oil ring thickness between the head and cylinder.
Here is our opinion or rebuttal because we make our own kits.

(Our response is written in white.)


Opposition: "Don't get new springs, but DO get CycleX's special valve retainers for this engine: that is REAL important."

Opposition: "A step-bore should be enough to clean it all up: I'd suggest the piston kits from CruisinImage. I just got [another] one from him for the F2/3 engine. You must use that piston, as they have a domed crown. Contact me for more details if needed."



Quote: "Don't get new springs."

Response: Don't you mean check your springs on a good spring tester because they are 40+ years old and they lead a hard life?


Quote: "I'd suggest the piston kits from Cruisinimage."

Response: Don't you mean you like and get their pistons because they are dirt cheap? Facts are, the pistons do not measure correctly and the piston rings are brittle and have very little sealing pressure against the cylinder walls. It's kinda like measuring pistons from the 70's area.



Opposition: "Before you bolt the head back down, contact me for some special O-rings for those oil journals at the back of the cylinders. Otherwise it WILL leak oil after all your work is done...!"


Response: Special "O" rings? WILL leak oil? There was a racer in Europe that must have used those "special oversize" "O" rings and they compressed inward. Blocked the oil from getting passed the heavy duty studs to the top end and ruined everything.



Opposition: "There's another thing that causes your leak....the O-rings that fit into the head gasket around the 2 oil passages at the back of the cylinders, between cylinders 2-3, are too thin. They came to you that way in the gasket kits, because the gasket kit vendors will neither listen, nor care, that their head gaskets are 0.2mm thicker than the OEM version. So, these 2 O-rings MUST be 0.2mm thicker, or else the cylinder deck must be milled 0.020", to make it seal again. I send these out for donations to these forums, unless you are in UK: if so, then find a Parker O-ring dealer and get #01-111 O-rings, 2.62 x 10.77 metric size."

Opposition: "Oh - and you will need a new head gasket, sorry to say..."


We disagree.
You will need to check your measurements or buy some measuring devices.
We checked the thickness of 5 different head gaskets (including OEM Honda's)

Here's what we did years ago...

We ordered the following head gaskets:
Cometic head gasket
Vesrah head gasket
Athena head gasket
Honda OEM head gasket
Several eBay gaskets

All of these gaskets measured about the same, .048 thick with 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)
With the compressed head gaskets (after running) measuring a average thickness of .035, we decided to describe standard size and make our MLS head gaskets .040.
Yes, we are the company that financed and tested MLS head gaskets for Honda SOHC 750's.



Opposition: "No, these are the 2 O-rings that seal the main oil passages between the cylinders and head. They are the 2 in the center back of the cylinders, by the cam chain tensioner. The issue is: the OEM Honda head gasket was thinner than today's head gaskets by about 0.2mm (0.030"-0.032"): today all head gaskets are 0.040" (1mm) thick. The difference can be made up in 2 ways: you can either deck the cylinders by 0.020" (0.05mm) or increase the thickness of these 2 O-rings: I often deck the cylinders by 0.010" anyway, and still use these O-rings."

Opposition: "In UK you can find these O-rings from a Parker O-ring dealer: they are Parker #01-111 all over the world."

The third photo below might help.




These 2 photos are the area of discussion.





Look close at this photo of cylinder head "O" ring sandwiched between some Plexiglas and notice the width of the sealing area.
With a stock cylinder that has been surfaced approx .005. and a .040 MLS thick head gasket, the sealing area is approx .048 wide. (perfect).
By the way, these are standard size "O" rings found in our gasket kits and many aftermarket kits.






Intake Rubber Boots

Cruzinimage and other distributors have said there is nothing wrong with their 77-78 K model intake rubber insulators.

Since then, they have purchased new glasses and agreed there is a length difference.





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