Topic: Black Engine

[Dusthawk]

I was down at Denny's last night talking to a couple guys about a ride tomorrow and about my bike, when he saw my black wrinkle engine he said uh-oh, you'll have probs with that engine because it is a Black Engine.  Something to do with the cam siezing or something? Has anyone heard of this?

Jeff

[upperlake04]

Jeff - the 78 750Fs had black engines. They had problems but not because of their color.

[Gordon]

Not quite sure I understand.   Is he saying there's a certain engine model that has cam problems and just happens to be black, or that painting the engine black would cause some kind of problem? 

P.S.  Just saw upperlake's post, so that makes a little more sense.  I didn't realize the 78 F's had that problem. 

[scondon]

I was down at Denny's last night talking to a couple guys about a ride tomorrow and about my bike, when he saw my black wrinkle engine he said uh-oh, you'll have probs with that engine because it is a Black Engine. Something to do with the cam siezing or something? Has anyone heard of this?

Jeff

77-78 750F engines(black) have a redisigned head that is not like the other 750's. The valves and guides wear out much faster.

[Dusthawk]

Sorry about that, I could have been more precise. He said that the early 750's had an oil problem up near the cam and the ones that had a problem were the ones that were painted black from the factory. I didn't really understand as well but the way I understood it was the engines slated for black paint somehow had different oil passages or something. Thats why I'm posting the query, I'm baffled. He did say that he had an early 750 with a painted black engine and his cam froze up and that he heard through whatever grapevine that he had heard of others with the problem.

I wish I could be more precise but thats all I have.

My engine number confirms it is a '71 and it is wrinkle black, so I think it came stock like that.

This is me scratching my head

Jeff

[scondon]

To my knowledge only the 77-78 SOHC came with stock black paint.

[TwoTired]

Perhaps the issue is not the color, but the thickness of the paint.  If it is thick, it acts as an insulator preventing the heat from the metal fins to be transferred to the passing air.

The color black radiates and absorbs heat readily, but paint itself is an insulator.  Multiple layers or high buildup thickness can restrict heat transfer.

Wrinkle finishes can be thick depending on how it was applied.  Are you headed for the high desert?  Are you using synthetic oil that breaks down at higher temps?  

No 71 750s came from the factory with black engine paint.  Only the 77-78 750F had that and it wasn't wrinkle finish.  Their valve geometry caused excessive wear.   Top cam oiling problems usually stem from excessive gasket sealant breaking away and clogging the oil restrictors going to the cam.

Cheers,

[MRieck]

I was down at Denny's last night talking to a couple guys about a ride tomorrow and about my bike, when he saw my black wrinkle engine he said uh-oh, you'll have probs with that engine because it is a Black Engine.  Something to do with the cam siezing or something? Has anyone heard of this?

Jeff

For Christsakes that is an absolutely retarded statement on the part of that individual. I have (had) a comparison between sand blast, bead blast and flat black surfaces heat shedding abilities published in RoadRacing World from a million years ago. The thin, flat black surface shed heat the best. Look at Harley's with wrinkle cases, cylinders  and heads. While they might not perform they don't seize.

[scondon]

For Christsakes that is an absolutely retarded statement on the part of that individual.

   Say it like ya mean it Mike

He said that the early 750's had an oil problem up near the cam and the ones that had a problem were the ones that were painted black from the factory. I didn't really understand as well but the way I understood it was the engines slated for black paint somehow had different oil passages or something.

   I also heard this from someone when I first started biking again. Something about small passages restricting flow. I've taken apart '78 750F(black motor), '78 750K, and '76 750F top ends and can see no difference in the oil feed to the cam. They all had one feed,with a oil restrictor, to each cam tower  . Did earlier engines have two feeds to each tower? Were the oil restrictors under the towers not on earlier engines?

   I've just come to the conclusion that people were guessing as to why these "black motors" were burning up and the "oil problem" thing is a myth that got passed around too much. I agree with TT that care must be taken not to block the oil restrictors when rebuilding(fried cam taught me that one). I haven't heard of it being a problem on an unmolested stock motor though.

   I would like to know if anyone can shed more light on this "oil problem" that I have heard so often.

[Jonesy]

I thought HondaMan posted something about the changes made to the CB750 valvetrain in the mid-70's and the changes caused the rockers to wear out faster....

For heat radiation, black is the best color.

[Bob Wessner]

I know, I know, everyone says that black paint actually helps cool the engine, who am I to dispute that. However, darned if it doesn't seem counter-intuitive. 

[Terry in Australia]

I dunno guys, could be something in it, did you all know that more people die in red cars than any other color?

[MRieck]

For Christsakes that is an absolutely retarded statement on the part of that individual.

   Say it like ya mean it Mike

He said that the early 750's had an oil problem up near the cam and the ones that had a problem were the ones that were painted black from the factory. I didn't really understand as well but the way I understood it was the engines slated for black paint somehow had different oil passages or something.

   I also heard this from someone when I first started biking again. Something about small passages restricting flow. I've taken apart '78 750F(black motor), '78 750K, and '76 750F top ends and can see no difference in the oil feed to the cam. They all had one feed,with a oil restrictor, to each cam tower  . Did earlier engines have two feeds to each tower? Were the oil restrictors under the towers not on earlier engines?

   I've just come to the conclusion that people were guessing as to why these "black motors" were burning up and the "oil problem" thing is a myth that got passed around too much. I agree with TT that care must be taken not to block the oil restrictors when rebuilding(fried cam taught me that one). I haven't heard of it being a problem on an unmolested stock motor though.

   I would like to know if anyone can shed more light on this "oil problem" that I have heard so often.

Damn right Sean. The later oil feeds were instituded to prevent oil problems secondary to 1, very small feed hole. The oil jet would be much harder to choke than than that silly little hole.

[MRieck]

I dunno guys, could be something in it, did you all know that more people die in red cars than any other color?

Christ I got more tickets in a bright yellow car than any other I've owned.

[scunny]

red cars are faster, same as a company vehicle is faster, and can rev higher in all the gears than your own 

[MRieck]

red cars are faster, same as a company vehicle is faster, and can rev higher in all the gears than your own 

  That USA policy son.....all company cars must have a rev limiter set 1.000RPM above OEM standards. #$%*....things just couldn't get done otherwise.

[Terry in Australia]

No seriously guys, (geez, that sounds strange coming from me.......) more people die in red cars than any other color! 

[MRieck]

No seriously guys, (geez, that sounds strange coming from me.......) more people die in red cars than any other color! 

Because nobody makes minivans in red Terry.

[Terry in Australia]

No Mike, but there is actually a reason! Keep guessing................. 

[Jonesy]

I know, I know, everyone says that black paint actually helps cool the engine, who am I to dispute that. However, darned if it doesn't seem counter-intuitive.

Aw geez, Bob... You gonna make me dig out my old heat transfer textbook and scribble it all out to prove how it works?

[angeldeville]

and some people think Hardley's are the best bike ever made, doesn't make em' right just misinformed.

[Terry in Australia]

Is that a real tat on your leg mate? How about a bigger pic?

[angeldeville]

that's my left arm

[Terry in Australia]

That's a nice tat mate!

[HondaMan]

Sorry about that, I could have been more precise. He said that the early 750's had an oil problem up near the cam and the ones that had a problem were the ones that were painted black from the factory. I didn't really understand as well but the way I understood it was the engines slated for black paint somehow had different oil passages or something. Thats why I'm posting the query, I'm baffled. He did say that he had an early 750 with a painted black engine and his cam froze up and that he heard through whatever grapevine that he had heard of others with the problem.

I wish I could be more precise but thats all I have.

My engine number confirms it is a '71 and it is wrinkle black, so I think it came stock like that.

This is me scratching my head

Jeff

Your friend is out to lunch.
Some "F" engines were anodized black, some guys just painted "K" engines black. The painted ones ran hotter. If you run 10w40 oil AND paint it black, it will wear the cam bearings (and some other top-end parts) faster because of lowered oil viscosity in the head.

That's the whole story.