Topic: Headline: Hondaman rebuilds his old friend - FOUND GOOD OIL!

[MOONDOGNYC]

I was not directly working on the 750 (in shops) during the reign of the F2/3 and K7/8, as I had just moved to Colorado. It was about 5 years later (mid-1980s) before I got into those models. The larger F2/3 valves (compared to the K7/8) seemed strange to me, and they wear out fast for their guides and stems, but while they last they do breathe better than the earlier engines. The F2/3 also got some extra cam lift (about .3-.4mm on average, as measured - not as advertised), with steep opening ramps to sort of increase the duration without getting the valves too close to the pistons. This led to "snap" marks on the closing sides of many F2/3 cams, which is how their valve trains take such a beating. If the F0/1 cam is used instead, the top end lasts much longer for the trade, while losing a fraction of a HP at 8500 RPM. I have junked more F2/3 cams than all others combined, over these years, because they have a 'snap', or 'crease' where the rocker slaps against the closing side ramp on the intake valves. This is real hard on the rocker foot.

The F2/3 was said to develop (in advertising) as much as 78 HP. In real life, I think they make about 72-74 real HP on the final drive. The bikes, as delivered, came with overly-heavy 630 chains and even O-ring chains, and a very heavy 4.50x17 rear tire, all of which ate a good portion of that power back up in losses. IMO, this probably cost the bikes the street cred they could have had at the time. Lightening up the drive train by using modern chains in 530 size and either 18" rear wheels or tires like the lighter Metzlers can bring back that 'lost' HP.

FANTASTIC INSIGHT !!  Thanks for the info !

[Tews19]

Subscribed!

[HondaMan]

Well, today I gave up on the idea of letting my cylinders run naked through the streets. 
The newly-created fins are almost white in color, won't even come close to matching the rest of it, so it doesn't look so good. I guess it's the welding rod used? There are also little pinholes in many places on them, which I'll fill in with JB Weld Aluminum (works great in this area) and then I guess I gotta paint 'em.

They have been hidden behind my Vetter fairing (and lowers) for many years, so most folks didn't notice they were cracked and bent (and one missing). It was that fateful July 14 day when the incredible hailstorm packed ice into the fins and finished breaking them off: as luck would have it, I had just removed the lowers on Friday before that. Although, I'm glad anyway: they may not have survived that storm!

Pictures at 11...

[kghost]

Hi Mark,

Glad I'm not the only one who hates casting flash.

Sorry about your pin holes. It sure is tough sometimes to TIG weld stuff up without them.

It has to be so absolutely clean as the pinholes are not from the rod but contaminates in the weld puddle.

It's possible with an acid etch they might all be a similar color, and it's not going to hurt to etch them before paint anyways.

Just a thought.

[HondaMan]

Hi Mark,

Glad I'm not the only one who hates casting flash.

Sorry about your pin holes. It sure is tough sometimes to TIG weld stuff up without them.

It has to be so absolutely clean as the pinholes are not from the rod but contaminates in the weld puddle.

It's possible with an acid etch they might all be a similar color, and it's not going to hurt to etch them before paint anyways.

Just a thought.

What kind of acid? Would it hurt the already-bored steel cylinders?

[Kickstart]

Wow... Late to this party, but very interested in following your build!

Subscribed.

[kghost]

Well there's several schools of thought......

Hydrocloric (muratic),phosphoric, or chromic

Chromic as you probably know has sulfuric acid and a dichromate salt.

It's the recommended thing for aluminium being prepped for paint (organic). In the aircraft industry we usually refer to it by the trade name "Alodine". Such as Alodine 1201. (Gives the aluminium a yellow color btw)

What I have done is used hydrocloric acid (muratic), which is available at most home improvements ( for etching and cleaning concrete) or pool supply (to lower ph levels. I have used it to clean and return the color to carb bodies etc.

Now it's used to pickle steel....but I doubt applying it to the outside of the aluminium fins via brush would adversely affect the bores......

Something to think about......I know you like that sort of stuff

[HondaMan]

Well there's several schools of thought......

Hydrocloric (muratic),phosphoric, or chromic

Chromic as you probably know has sulfuric acid and a dichromate salt.

It's the recommended thing for aluminium being prepped for paint (organic). In the aircraft industry we usually refer to it by the trade name "Alodine". Such as Alodine 1201. (Gives the aluminium a yellow color btw)

What I have done is used hydrocloric acid (muratic), which is available at most home improvements ( for etching and cleaning concrete) or pool supply (to lower ph levels. I have used it to clean and return the color to carb bodies etc.

Now it's used to pickle steel....but I doubt applying it to the outside of the aluminium fins via brush would adversely affect the bores......

Something to think about......I know you like that sort of stuff

I will try this on some scrap carb bodies I have. I have some leftover muratic from a concrete project 5 years ago, been sitting in the garage for years!

[kghost]

You can play with the concentration and timing.

More concentration or time = a darker grey.

[Skonnie Boy]

Sub. Scribed.

Glad to see your finger healed up.

I'm only about a third of the way to your mileage total, but unfortunately I've beaten you in your rebuild count! I'm at four, long story.

Great thread, thanks for posting.

[buckett]

Will be watching this for immense education purposes!

Hondaman, I have some broken fins I need repaired on my cb500, any tips? Do i need to look for a specific kind of welder?

Cheers!

[kghost]

Will be watching this for immense education purposes!

Hondaman, I have some broken fins I need repaired on my cb500, any tips? Do i need to look for a specific kind of welder?

Cheers!

TIG

[buckett]

Will be watching this for immense education purposes!

Hondaman, I have some broken fins I need repaired on my cb500, any tips? Do i need to look for a specific kind of welder?

Cheers!

TIG

Thank you!!!

[HondaMan]

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

[kghost]

Love it. Great solution to the missing little rubber bits.

Any luck with the acid?

[HondaMan]

That rubber thing reminded me: I bought new velocity stacks for the airbox last summer. The old ones are like soft styrene, so hard!

If your hose clamps are getting stretched out too much around the screw holes, you can make a flat-sided washer from a thick #4 standard washer with a pair of dykes (and a strong grip!). I've done this with the clamps on the carb hoses, too. Then flatten out the sheet metal cage around the screw hole and snug things shut.

[HondaMan]

Ofreen has over 140k on his bike! Way cool!

Thanks. It'll be over 143K after the two legs of the relay over the next couple of weekends.  I'll be interested to see what you find for elongation of the cam chain and condition of the various plastic and rubber tensioner bits. 

Mr. O:
Here's a shot of the tensioner roller. It looks worse in real life than here, for some reason? It has begun chipping off bits of the rubber, found in the nooks and crannies of the lower crankcase.

[ofreen]

Kind of ugly.

[CBJoe]

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

Do I understand correctly that those rubber bits are for noise dampening from the engine?  I've got a Yammy that has them and I always thought it was some sort of protection for the fins.

Cheers, Joe

[MCRider]

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

Do I understand correctly that those rubber bits are for noise dampening from the engine?  I've got a Yammy that has them and I always thought it was some sort of protection for the fins.

Cheers, Joe

AS a generic explanation I'd heard it was for reducing the high frequency zing noise as well as the potential for cracking due to the same high frequency vibrations. Though in reality I don't know if either problem really exists. Mark?

Don't know if that applies here, but I kinda need to know as well. I was going to leave mine out. Now maybe not.

[754]

Mark next fins you do try cutting off a donor head. Start on lowest fin, then work up.even if the rod is a poor match the outside should look better.  Some actually cut strips of fin to use as rod.. EXACT alloy match.

[MoMo]

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

Do I understand correctly that those rubber bits are for noise dampening from the engine?  I've got a Yammy that has them and I always thought it was some sort of protection for the fins.

Cheers, Joe

AS a generic explanation I'd heard it was for reducing the high frequency zing noise as well as the potential for cracking due to the same high frequency vibrations. Though in reality I don't know if either problem really exists. Mark?

Don't know if that applies here, but I kinda need to know as well. I was going to leave mine out. Now maybe not.

I always heard both reasons for the rubber thingamabobs, info came from the Honda rep...Larry

[HondaMan]

Mark next fins you do try cutting off a donor head. Start on lowest fin, then work up.even if the rod is a poor match the outside should look better.  Some actually cut strips of fin to use as rod.. EXACT alloy match.

Yeah, there is one of them that had the original piece, still. The welder really griped about welding it back in, though. It's the only one that is the same color!

[HondaMan]

Kind of ugly.

The little missing bits have appeared from time to time in the oil filter, so I knew it wouldn't be shiny new!

[HondaMan]

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

Do I understand correctly that those rubber bits are for noise dampening from the engine?  I've got a Yammy that has them and I always thought it was some sort of protection for the fins.

Cheers, Joe

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

Do I understand correctly that those rubber bits are for noise dampening from the engine?  I've got a Yammy that has them and I always thought it was some sort of protection for the fins.

Cheers, Joe

AS a generic explanation I'd heard it was for reducing the high frequency zing noise as well as the potential for cracking due to the same high frequency vibrations. Though in reality I don't know if either problem really exists. Mark?

Don't know if that applies here, but I kinda need to know as well. I was going to leave mine out. Now maybe not.

Got a couple more things done tonight, but have to go build a fuseblock for somebody (play time's over?).

I made some new ring suppressor rubber dampers fro some test tube stoppers I got at Ace Hardware. Much cheaper than Honda's (yeah, I am a cheapskate...)

Do I understand correctly that those rubber bits are for noise dampening from the engine?  I've got a Yammy that has them and I always thought it was some sort of protection for the fins.

Cheers, Joe

AS a generic explanation I'd heard it was for reducing the high frequency zing noise as well as the potential for cracking due to the same high frequency vibrations. Though in reality I don't know if either problem really exists. Mark?

Don't know if that applies here, but I kinda need to know as well. I was going to leave mine out. Now maybe not.

I always heard both reasons for the rubber thingamabobs, info came from the Honda rep...Larry

I heard that same 'guess' from the Honda reps of old...

I only had 5 of them left in the fins, and only 1 of those was/is still springy enough to be wedged in. The rest were loose. The engine had become quite 'ring-y', well-heard behind the Vetter because it reflects much of the noise right up to you. I have long wanted to install new ones, but didn't have any. These rubber 'test tube corks' are much softer than the ones I have usually found, more like the little white plugs were. They go in easily, like the white ones do/did.

I can't imagine the fins cracking from the noise, but I do know from years past that once a fin cracks, it will work itself along until it breaks off. I've seen it on many of these engines, and on mine 3 times (so far!). It's not a terrible thing, even for the cooling: Honda has admitted several times that the engine is over-finned (and WOT racers know it to be over-cooled). Since I have run mine mostly with the Vetter lowers enclosing the engine, summer or winter, even in Phoenix in August, with no troubles. I believe all the above to be true. The only times I remove the lowers is when the carbs start to boil the gas, which happens a lot since ethanol came along!