Topic: CB 750 Project 1 - Rides Well but a few tweaks needed

[timbo750]

Terry, that's pretty much what I had in mind, I will check everything I can for size and clearance. There is some slight rust on one the cam lobes, I think the engine has no been run since it was last assembled.

Otherwise I am still slowly working on the mounting for the right hand calliper.

[Terry in Australia]

No worries Tim, and it's not unusual to have a bit of rust on a cam lobe that's been sitting for awhile, as long as it doesn't have any major pitting just clean it off with some steel wool and hit it with some WD40 and it'll be fine. Cheers, Terry.

[timbo750]

I have been working on finally getting the forks ready to assemble, I was cleaning the inside of the tubes and noticed one of them looked almost new and cleaned up very nice. The other seems to almost have a build up on it, I have cleaned it and rubbed only with a rag so far.

I have been trying to search for info on weather I can hone the inside of the tubes, I was only think of some 300 or 600 sandpaper on a split rod and using the drill. Just not sure how much can come out without affecting the workings of the forks.

[Terry in Australia]

Are you talking about the alloy lowers, or the steel tubes Tim? Obviously alloy is a lot softer than steel, so you'll remove a lot more material, and you don't want any slop between the alloy sliders and the steel tubes. Cheers, Terry.

[timbo750]

Finally got the forks assembled, and fitted. Just need to get some oil and install the springs and caps.

I have how ever stuffed up with the dual disc mounting. I was reading one the threads about to do the various bits and read that there are two bolt holes not used that can cut off and used as spacers. Without fully looking into it I cut off one of the higher tabs of each arm mount bracket and now can't mount the front guard. So now I have another part I need to source. I did always say this was going to be a bike that would teach me a thing a two about the CB750.

[SOHC4 Cafe Racer Fan]

If you ever change your mind and want dual discs, you may look into swapping the front to a 75-77 GL1000.  It's a direct swap and the 37mm forks are more rigid than the CB750 35mm, and the brakes are much better.  Just some food for future thought, since you already just rebuilt your stock forks.

[timbo750]

Made some progress over the last week or two. Got the forks assembled fitted and the springs in. The twin disc setup is a real PITA for first timers, and if you are anything like me and tend to skip read things unless there diagrams and pictures you will miss something and have to redo it more than twice, but I have been doing more reading on the subject and now I have a plan to get me back on track.

I have two questions for anyone that is reading this stuff. Firstly when I installed the progressive springs they sat a lot lower than I expected and after reading the paperwork that came with it I used the washer and cut down plastic tubes to get the right preload on them, approx. 1".

The second question is about the twin discs and the spacing between the forks. The two forks are spaced quite differently away from the fork tubes, but I do not think this is as critical as the alignment of the caliper mounting arm.

I also started inspecting my second engine. Took the head off and all looks good, pistons 0.50 over, there is nothing in the oil pump screen but it appears that the cases have been assembled with silicone between them and I cant tell if this engine has been run since it was last assembled. So I will split the cases as there was excess silicone inside and around the sump.

[SOHC4 Cafe Racer Fan]

It sounds like the PO used too much RVT on the mating surfaces of the cylinder, head and valve cover.  That stuff should be used sparingly or it will get into your oil passageways and screw up your motor big time.

[Terry in Australia]

G'Day Tim, you're right about the disc to fork leg clearance, on the bike I'm building for a customer, the clearance is approx 5mm on the left (shifter) side, and 10mm on the right (points cover) side.

You need to make some spacers between the caliper bracket and the right fork leg so that the hinged caliper arm runs parallel to the disc, or else the pad won't sit flush, and will wear at an angle.

You can do it with washers, mine came from Rex Wolfendon (TRex Racing) many years ago, and he'd made up some little alloy spacers and welded them to the bracket. Good idea about stripping that engine if there's a lot of silicone present, and it won't hurt to freshen up the engine with new gaskets etc, while you're at it. Cheers, Terry.    

[timbo750]

I found out from some more searching an easier way to get the alignment right.
Start by bolting the caliper to the arm and putting the C bracket onto the arm and put the caliper over the disc and then work out the spacing. 

I haven't started on this yet as I am waiting on another C bracket to arrive, but will let you know how I go.

I have also been shortening the guards. Have cut and welded the front and will cut the rear today and weld it tomorrow.  Just not sure weather to panit them black or the same color as the tank.

[HondaMan]

I found out from some more searching an easier way to get the alignment right.
Start by bolting the caliper to the arm and putting the C bracket onto the arm and put the caliper over the disc and then work out the spacing. 

I haven't started on this yet as I am waiting on another C bracket to arrive, but will let you know how I go.

I have also been shortening the guards. Have cut and welded the front and will cut the rear today and weld it tomorrow.  Just not sure weather to panit them black or the same color as the tank.

I did my 2-disc arrangement way back when only the C-bracket was available. Today you can use the T-bracket on both sides, for lighter weight and less grinding-spacing-diddling efforts. I ran the right-side one for 50k miles with it at a steeper angle to the disc: the pad wear with 2 discs aboard was so slight that in all that time I never used 1/2 of the puck thickness (up to Honda's "Red line" wear indicator).

-When I got married in 1979 and needed some quick $$ for my new bride, I sold the 2nd disc to someone who kept asking me to build one for his K4. He bolted it right on and rode off into the sunset!

[timbo750]

Mark
Where the fork lowers different for the T brackets?  I was led to believe they were.  I actually have a T bracket in the parts box, could I use that on the tight and the C on the left?

[Terry in Australia]

Nope, the T brackets are for K3 on, and the C brackets are for K0-K2 Tim. The T brackets won't fit the earlier forks, nor will the C brackets fit the later ones. Cheers, Terry.

[timbo750]

Terry, I thought that was the case but had to ask anyway.

Got the rear wheel on and rolled it out of the shed so I could at it in the day light.

[Terry in Australia]

Looking good Tim, well done. I posted on another thread that I've got a spare inner fender for you if you need one too. Cheers, Terry.

[timbo750]

Not much progress to report. I have working on the fenders that I have shortened,  I am not experienced with welding the thin steel so it did not come out all that well.  So I first tried to fill some of the low spots with brazing but that didn't work to plan either but did improve things. So now I am just going to use filler to get it right and paint them either gloss black or same as the tank.

[timbo750]

I mentioned earlier that I was going to use the second engine I have and now my mate finally pulls his finger out and gets the first engine nearly finished.  But I am still going to use the stock engine in this bike and put the 836 in another frame I have. I did get the cases water blasted and thay now look to good to paint.  So I asked a guy about clear powder coat but he didn't make me confident about the quality of the taping he would do. But now I am thinking of anodizing,  not sure of the cost yet but have someone who can do it and will ring during the week.

[calj737]

If you're thinking of anodising the cases, that may not turn out the way you hope. Because the cases are cast, they are quite inconsistent in their porosity and "quality". Which means, your anodising will be very inconsistent and irregular in the finish.

Some other options are to spend the time and effort necessary to polish the cases, then anodise them. This is rumored to be the method for greatest likelihood of a consistent finish. Maybe not what you're up for...

Sounds like a power coat finish might be a better option?

[timbo750]

I know what you mean by the inconsistent in the porosity, which can be seen in the surface.  I will ring the anodisor and see what they say.  If there are slight differences in the appearance it may not be highly noticeable as there are not many large flat areas. Never hurts to ask I say unless you are offended by a no answer.

[SOHC4 Cafe Racer Fan]

The inconsistencies in porosity may equate to different shades of color. Might be no bueno.

[Retro Rocket]

From another bike forum..

The problem is that the cases are cast. Cast aluminum is really hit or miss as to how it looks after anodizing. Depending on the alloy of the cast, more often than not it comes out looking blotchy and a different color than expected. I am an engineer at a metal finishing plant and we see this from customers all the time, they send in cast parts for anodize expecting it to look like a billet part, then are not happy with the results.

Cast alloy does not anodize well at all, This subject has been covered on this forum a few times in the past.. ...

[calj737]

When I had my GSXR forks done locally, it was that shop that warmed me about cast pieces. Told me to polish to a mirror then I might get what I was after. Thought of having to polish the entire cases, covers and head to a mirror just for anodising didn't appeal too greatly.

Let us know what you discover, Timbo. Like you, I love the look of anodising!

[MRieck]

From another bike forum..

The problem is that the cases are cast. Cast aluminum is really hit or miss as to how it looks after anodizing. Depending on the alloy of the cast, more often than not it comes out looking blotchy and a different color than expected. I am an engineer at a metal finishing plant and we see this from customers all the time, they send in cast parts for anodize expecting it to look like a billet part, then are not happy with the results.

Cast alloy does not anodize well at all, This subject has been covered on this forum a few times in the past.. ...

I completely agree (based on experience). It looks like absolute crap.

[timbo750]

Not that I ever doubt the knowledge of you guys, but the phone call confirmed that the cast aluminum gives a #$%* finish when anodising,  even with a clear coat. Pity because I was thinking semi transparent look of the black would look good.

So I went to the powder coaters near work who said he could do it in clear, but I think he might have an allergy to masking tape because he was telling me how he will only mask some bits and the others he will remove the dust before baking. Now I am no expert on PC but I would rather pay extra and go to somone who I willing to mask everthing.

[Terry in Australia]

Those cases look great Tim, who blasted them for you? Cheers, Terry.