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

[Jones]

Big fan of the work on this bike. I especially like your custom seat, and the softbag. I've been thinking about a seat like that for a while now, but i think I'm settled on it after seeing how good it looks on your bike.

[maduncle]

Thanks,

The seat was fun to make, I think what makes it work so well is the steelwork under it that ties the rear end of the seat to the frame.

If I get bored with it, I might make a cafe single seat with a glass rear painted to match the tank as an option.

[orange550]

How does the Lossa muffler sound? I got one coming for my 550.

[Psychonaut]

I love how you did the seat. It looks like it was a lot of work.

[maduncle]

Orange 550, the Lossa muffler sounds great, got a good deep note but not too 'blatty' under acceleration. I am getting a bit of backfire, but I hope the tuning will fix that.

Psychonaut, the seat was a bit of manual labour, but not too hard. If you look back through this thread there are some pictures of it under construction. I did all the fabrication work using aluminium sheet and angle, not hot metal work - just a power jigsaw, a vice, a drill and a pop rivet gun. The upholstery was my design, but I took it to an expert to do the work.

One thing I would not do on the seat again, and that is use 1.6mm thick aluminium angle as the side rail. The seat vinyl is stretched and glued over this edge, and theedge rests on the bike frame. So when I am riding, I am pressing down on a 1.6mm edge of aluminium, which in time will probably cut through the vinyl.

Next time, thicker angle.

I have also just bent the kick starter in the blacksmiths forge and re-finished it. Photos soon.

[Oakleyguy]

Great build!

I'd love to get more detail on the combination required for the High Tea Color. And MORE details on the alarm!

[maduncle]

Great build!

I'd love to get more detail on the combination required for the High Tea Color. And MORE details on the alarm!

Hmm, I will need to ask Mitch my painter mate what went in to the High Tea colour mix we brewed up from scrap paint he had in stock.

Mitch will probably reply with...

"three drops of essence of terror, five drops of sinister sauce"

And I will pull out the alarm specs and post the brand and model number here in a day or so.

Meanwhile - quick question for the carb specialists - if I want to put a set of Mikuni's on the 750, which model bike can I get them off second hand so they just bolt up with minimal fuss?

[Retro Rocket]

Meanwhile - quick question for the carb specialists - if I want to put a set of Mikuni's on the 750, which model bike can I get them off second hand so they just bolt up with minimal fuss?

Hi Cliff, i don't think any Mikuni's from other makes will be a direct bolt on. CycleX have RS34 Mikuni's that have been made to be a direct fit but may be a bit big for your bike if its stock, i am going to run them on my 1000 whilst running it in then put them on my 970.  Tank came today mate, thank you very much. Man the packaging on that tank was almost human proof....    Needed the misses to help get it out of the box and now there's no way known to man to get it back in......   thanks again.....

[mick7504]

From what I've seen, these RS34's are suited for a GSX1100, GS750, GSX600 Katana, KZ750 & GSX-R-750 and have been reracked for the 750 head.

RS34-D21-K is the Mikuni Part #

They probably would suit the Z900/1000 & the KZ Kwakas as well.

You could rerack them yourself but you'll need some bigger than stock pistons in the engine.

They are a bit of a bugger to fit but will go on with some grunting. 

Mick

[Terry in Australia]

I wouldn't bother with Mikuni's on a stock engine Cliff, bigger carbs (if that's your intent) don't mean better performance, and the stock 28mm pumper carbs, when set up properly, work great on CB750's anyway.

I've got an engineer friend who can re-space just about any carbs to suit a CB750 (he did the 32mm CV's on my K2, below) and he's recently re-spaced a set of Mikuni 33mm smoothbore race carbs that will eventually go on my 1060cc RC Cobra engine. (second pic) Rebuild your stock carbs and install a weaker return spring and it'll feel like you've added nitrous! (which is another possibility........) Cheers, Terry. 



 

[maduncle]

Thanks guys - I was idly speculating on different carbs, if Daryl can get the bike all tuned up and running well on the dyno then I will be happy with it.

Meanwhile, here's what happens to a kick starter when you 'blacksmith' it.



Stripped back lever in the forge getting nice and hot.



Old stock lever next to the newly bent, filed, sanded, polished and clear coated lever - complete with brass dome nut attached by filing and thread cutting the foot peg and with a short length of ribbed off white hot water tube that matches my tank colour.



The new bent lever in place.

To be honest - it is a little too extreme in the two offset bends, as it just rests on the carbs. But it is the rubber water tube part resting on the carbs so it should be okay. I am well pleased with the end result and now I have a spare stock kicker.

[Syscrush]

Old stock lever next to the newly bent, filed, sanded, polished and clear coated lever - complete with brass dome nut attached by filing and thread cutting the foot peg and with a short length of ribbed off white hot water tube that matches my tank colour.

I notice that list doesn't include "heat-treated".  Are you confident that it'll be strong enough?

[maduncle]

Old stock lever next to the newly bent, filed, sanded, polished and clear coated lever - complete with brass dome nut attached by filing and thread cutting the foot peg and with a short length of ribbed off white hot water tube that matches my tank colour.

I notice that list doesn't include "heat-treated".  Are you confident that it'll be strong enough?

Good point. I did in fact heat treat it by allowing it to cool naturally after each bend, otherwise quenching it would have hardened the steel and made it brittle. I could have annealed it by burying it in ash or sand to slowly cool, or by dunking it in quenching oil - but that wasn't required.

[Syscrush]

Good point. I did in fact heat treat it by allowing it to cool naturally after each bend, otherwise quenching it would have hardened the steel and made it brittle. I could have annealed it by burying it in ash or sand to slowly cool, or by dunking it in quenching oil - but that wasn't required.

Thanks.  I really wasn't clear on what's the best approach for a part like this.  Wouldn't annealing make it too pliable?

[maduncle]

Good point. I did in fact heat treat it by allowing it to cool naturally after each bend, otherwise quenching it would have hardened the steel and made it brittle. I could have annealed it by burying it in ash or sand to slowly cool, or by dunking it in quenching oil - but that wasn't required.

Thanks.  I really wasn't clear on what's the best approach for a part like this.  Wouldn't annealing make it too pliable?

Yes it could. Which is why I took the old smithies advice and just let the hot metal cool naturally.

Today I found time in Sydney to visit Deus HQ - what an amazing bike shop, full of great custom bikes, parts, clothing, books...

[maduncle]

Okay, first decent ride on the High Tea Racer today since the project began.

I picked up the bike from Collingwood, freshly fitted with new regulator, rectifier and float valve needle in carb number two.

I rode it down to Oakleigh for a meeting and then home to Thornbury after, so I got plenty of Monash Freeway, Warrigal Road and even some Eastern Freeway action. That was about two hours riding in traffic all up at various speeds.

What I learnt...

On the freeway, 100km per hour is achieved at 5,000rpm in top gear. That seems a little high and I put it down to the bigger rear sprocket that came on the bike when I bought it, so I may change it at a later date if I plan to do long runs at high speeds.

Travelling at 100kph seems okay, a bit rough in the suspension area, but then last time I was doing that speed on a bike was on my 2001 VFR800 which was built to do that. So I reckon it is just me on an older bike and I need to get used to it.

I have an exhaust leak, there was smoke coming up between the engine and gearbox, adjacent to the exhaust 4 into 1 trap, right where the cracks were in the trap that I puttied up with exhaust putty before I wrapped it. So my bad, not a good fix and something that will need a right proper fix soon, as I reckon there is a performance loss resulting from the leak.

All four cylinders are now running fine, no leaky carbs and no backfiring. But the revs at idle are a little high (over 2,000 rpm) and I will need to adjust that back a bit.

Finally - I had a 'moment' in town on the way home when I lost all revs, no amount of throttle would keep me going and I 'putt putt putted' to a stop, and then the bike would not start.

This was after a good 2 hours riding so I started to fear the worst, I was thinking...

'buggerbuggerbuggersomethinghasshatitselfintheenginenowIhavetogetatrailerorabandonthebikehereandgoforhelpwhatamIgoingtodonow'...

...

...

... then I popped the fuel filler cap and looked inside to see a dry tank. So I rolled 30m back to the BP petrol station I had just passed, 'fixed the problem' and rode home.

So there endeth the lesson.

[hapakev]

Lost in the moment.. No one can blame you for that. 

[Terry in Australia]

Looks like you had a good ride Cliff, if the weather improves this weekend I'm gonna have to drag my K2 out and take it for a ride, poor old thing has been sitting for the last couple of months and I feel guilty not letting it have a run. Cheers, Terry.

[maduncle]

Looks like you had a good ride Cliff, if the weather improves this weekend I'm gonna have to drag my K2 out and take it for a ride, poor old thing has been sitting for the last couple of months and I feel guilty not letting it have a run. Cheers, Terry.

Good idea Terry - get out there, and maybe consider a ride up to Wallan on the 25th September for the classic car and bike swap meet...

[Terry in Australia]

Sounds good Cliff, thanks for the swapmeet info, I ride thru Wallan quite regularly (SteveK0 lives in Wallan) so I'll be up for that, are you going? Cheers, Terry.

[maduncle]

I am planning on getting some good rides in each weekend now - sort of test riding the bike and checking for any weak points in the build.

Next step - fit the Raask rear sets that have turned up for me this week with a supplier who I forgot I asked.

EDIT: quick question - what shocks should I get to replace the old worn stock ones?

I got a quote on IKON 7610-1296 shocks here in Australia at $465 delivered, but I don't know if these are the best shocks to get.  Any other ideas?

[maduncle]

Okay, so I learnt something new today.

Now I know what happended to KONI and who the hell IKON is.

And I have found a good pair of KONI's on eBay for my bike, strange how the KONI part number magically matches the IKON part number.

So, when to we start to see OINK shocks on the market?

[Retro Rocket]

Now I know what happended to KONI and who the hell IKON is.

You only had to ask......

[Terry in Australia]

Yep, Koni stopped manufacturing motorcycle shockers around 10 years ago, and the official Aussie Koni distributor bought the rights to manufacture Koni-esque shoks under the Ikon brand. Good quality and rebuildable, probably one of the better quality shokers around. I bought Progressive 440's for my Triumph (1200 bucks from the Aussie distributor, or 600 from any bike shop in the US.........) and they're OK, but I wish I'd bought the Ikons instead. Cheers, Terry.

[Terry in Australia]

Are these the one's Cliff?

http://www.ebay.com.au/itm/Honda-Goldwing-GL1000-CB-750-Koni-shocks-/260850323293?pt=AU_Motorcycle_Parts_Accessories&hash=item3cbbe40f5d

I don't think that parts are still available for the old alloy bodied shocks from Ikon, so be careful mate. Also, after so many years they'll need a rebuild, if the damping oil is still present it'll be like vinegar and the common problem with the alloy bodied shocks is that they weld themselves together with electrolysis.

I've got a pair here that another member sent me to rebuild for him, but I could never get them apart. I ended up sending him a NOS pair of Boge shockers, so if you want his old ones (no springs or collets, he took them off before he sent them to save weight, they're yours, for free. Cheers, Terry.