Topic: Maduncle's brat style CB750F - now called "The carb eater"

[maduncle]

Thanks for the bike ID and the advice, the fact that the bike has been lying on its side in the open does not work all that well for me. I will inspect it once it arrives here and see if it is a project for a good price.

So - to fill in time I picked up an old steel mobile workbench off eBay and spent a bit of time today cleaning it up. I chose this workbench as the ideal engine rebuild platform. I ground the rust off the bench top, gave the top (and the vice) a fresh coat of paint and fitted a rubber mat to the bench top. I also fitted my bench grinder to the plate welded on one side of the bench where another vice once sat.

So now I have a heavy portable sturdy workbench with vice and grinder fitted. I can work in my shed or if the sun is out, wheel it outside and work in the open.



Now I need to make a bit more space in my shed, where on this forum is the best place to advertise unwanted stock CB750F2 parts?

[maduncle]

Yeah, well... you know that old bike on its side in the US of A that I was trying to identify?

Well now the seller has sent me a photo with some numbers on it.



Going by these numbers - this is a mid 60's CB450 'Black Bomber'

So it is a good project bike?

[Syscrush]

So it is a good project bike?

It's just sooooooooo rough - it seems to me that you'd save money overall by starting with something in better condition.

[Bakeoff]

I wouldn't pay more than $100 for that bike.  As is, it would take a ton of time and money to get it into shape if you want something with all the creature comforts.  If you want to do a stripped down bobber with no dummy lights and some simple hand controls, #$%* yeah!  Go for it!  But again, I wouldn't touch it with a ten foot pool if the seller is asking more than $100.

Wait, how tough will that be to title over there?  I know we have enough problems in the US with that stuff.

[Flying J]

Im with you on that price, 100 bucks IF the motor turns over. Even a 100 is pushing it.

[maduncle]

Minor repair challenge this weekend.

The piston inside the front brake master cylinder is not returning once the lever is depressed. The whole unit has been stripped back and I have all parts out on the bench. The two rubber seals are okay, the one on the piston has a small nick in one edge, but the boot rubber is in perfect condition.

The return spring is fine too, so I think that there may be some corrosion on the inside of the 'barrel' in the master cylinder. I am going to try some 1200 grade wet and dry sandpaper and give the barrel a sand to remove any burs that may be catching on the piston.

So - am I on the right track when restoring an original front brake master cylinder for a CB750F, or are there other things I need to look out for?

[Raef]

make sure the master cylinder is completely releasing, I would give it a good once over and check the rubber brake line to make sure fluid flows freely Both directions.

mark

[Syscrush]

1200 isn't likely to remove any burrs, but the good news is that it probably won't make your bore out of round either.

What you want is a brake cylinder hone. 

[maduncle]

Well, I stripped the front master cylinder down, cleaned all the parts inside and out (the 1200 grade sandpaper and a bit of lubricant cleaned the hardened grime of the inside of the cylinder), reassembled it and tested it using the 'IKEA furniture stress test' method - I squeezed the brake lever 100 times and it returned 100 times without sticking.

So it is going back on the bike.

There is a distinct possibility that this bike will be on the road by the end of the week!

Quick question though - bolt up rear sets for a CB750F? Anyone got any recommendations?

[hapakev]

Raask makes some, but they look cheap and I've heard some complaints about them breaking.  I read omewhere that tarozzi makes some adapter plates, but i haven't seen them.  They probably bolt over the monsterous stock rearset/peg mounts.  I think I will end up making some for my 78F.

[Flying J]

I never found a rearset that I liked so I used a set off an r6 and mounted them to my 750f

[maduncle]

I never found a rearset that I liked so I used a set off an r6 and mounted them to my 750f

Yeah, I was looking at your pictures  - how hard were they to mount?

[maduncle]

Meanwhile,

Tuning the carbies discovered a bent actuator rod in the accelerator pump, now fixed.

Front brake master cylinder wasn't behaving, so it needed a new piston and seals to get it up and running.

Missing head bolt, should be an M6 x 90 but there is no M6 thread in the hole so we have to find an M7 bolt to fit. This might then fix the low compression in #2 and stop the oil coming out.

So hopefully all will be fixed and I will be riding the bike to the registration office next Friday.

[Flying J]

Mounting them was not hard if you have a welder.

[maduncle]

Excellent!

The bike passed the road worthy inspection and got the certificate.

I then took it down to the registration office, got the inspection done, paid the registration and now I am on the road!

I will take it out tomorrow and take some photos to put up here.

[maduncle]

The High Tea Racer is on the road!






Only problem now is...

Whilst riding home in heavy traffic, I took off with too little throttle and stalled the bike, then it would not start on the button, just kinda tried to turn over but there was no juice. Thank god for the kick start, it started on that now worries. But then it got dark so I threw on the headlamp, which worked okay for about three minutes and then slowly went out, along with the speedo and tacho gauge lights, then the indicators would not work...

Getting the picture?

I think I have either a battery that will not hold a charge, or an electrical system that is not providing a charge. So I will kick start the bike tomorrow, ride back down to Modern Motorcycle HQ, get Christian to test the system and maybe go and buy a new battery.

I refuse to be down on this - hey, I have my bike now and this is only a minor setback!

[maduncle]

More photos...

[Retro Rocket]

I don't think there's anything wrong with your battery, it was probably only running off the battery. Sounds like you system isn't charging.....Bike looks great....

[maduncle]

I don't think there's anything wrong with your battery, it was probably only running off the battery. Sounds like you system isn't charging.....Bike looks great....

Thanks for the tip. So if I have a multiple meter and I put the battery back in and start the bike - how and where would I measure voltage to see if the charging system is operating?

[jaguar]

almost the only thing left on that 450 that is the rare "black bomber" is the vin.....
Its far gone but if thats what you want to build from go for it.
But always remember that few things that say honda on them are rare.
You will always be able to fine a honda...lol

BUT that front drum fetches good money with the race guys
looks like an alloy front rim too

[maduncle]

Funny how you learn more about your bike the more you ride it.

Quick question - does anyone know if the kick start lever is cast or forged?

I only ask as I now want to heat it up and bend it so it is a closer fit to the bike.

Or do they cold bend without snapping?

(I think I might buy a second one before I try bending one).

[Syscrush]

Quick question - does anyone know if the kick start lever is cast or forged?

I only ask as I now want to heat it up and bend it so it is a closer fit to the bike.

I don't know, but I do know that at least one guy on here has heated & bent the one on his 550 to clear his rearsets and has been using it with success.  YMMV.

Or do they cold bend without snapping?

I really wouldn't try a cold bend.  I'd heat & bend then heat-treat it, I think.

(I think I might buy a second one before I try bending one).

I think that's an excellent idea.

[kap384@telus.net]

Looks great!!!

[maduncle]

I found my 'lack of spark' problem - it is the old mechanical regulator rectifier.

The mechanic is having a go at adjusting it, but I should probably find a new one somewhere.

[Retro Rocket]

I found my 'lack of spark' problem - it is the old mechanical regulator rectifier.

The mechanic is having a go at adjusting it, but I should probably find a new one somewhere.

Check your PM's mate....