Bimota SB6

[ArcanumOne]

What is the best jetting and carburetor setting for the SB6 with stock cans and air box?  I have mixture screws 2 turns out, stick idle jet #40  120 mains across all 4 carbs, needle height set in the middle 3rd level.  The bike has a bit of stumble and hesitation when warm from about 4k rpm then launches like mad…..

Edited April 17, 2022 by ArcanumOne

[Gammaboy]

On 4/6/2022 at 6:50 PM, Captain Chaos said:

I would have thought there is a breather in the tank cap.

There's a breather sat just Infront of the filler cap, with an overflow hose coming off of it. Dare say it's not working if the tank bloats. If it's building pressure, it's going to fuck with the effective float height and the fueling.

On 4/18/2022 at 12:10 AM, ArcanumOne said:

What is the best jetting and carburetor setting for the SB6 with stock cans and air box?  I have mixture screws 2 turns out, stick idle jet #40  120 mains across all 4 carbs, needle height set in the middle 3rd level.  The bike has a bit of stumble and hesitation when warm from about 4k rpm then launches like mad…..

Don't know honestly. I've set mine up to the Bimota workshop manual. Of course, I haven't even been in the same hemisphere, let alone put fuel in it for the last 2 1/2 years. Hoping to change that this year.

[Gammaboy]

Here's what the manual says. Of course, one of these settings is for the Mk1 bikes, the other for the MK2 - I guess driven by the difference in cam profiles

Edited May 3, 2022 by Gammaboy

[Gammaboy]

Oh, and here's the breather/vent

 

[BimotaMartyn]

As an ardent sb6 owner impressed at your knowledge and persistance I have 3 of these bikes all in various stages of dissasembly. Martyn.

[ArcanumOne]

Thank you for the information on carb jetting from the manual.  I have the "official" Bimota manual, but it does not have any of the info you provided.  

I have it apart again, as I discovered the Signal Generator is bad.  I bought a used one on Eblag and am waiting for it to arrive so I can install and test.

[Gammaboy]

On 5/3/2022 at 8:39 PM, Gammaboy said:

Here's what the manual says. Of course, one of these settings is for the Mk1 bikes, the other for the MK2 - I guess driven by the difference in cam profiles

I'm wrong on the difference in carb settings being Mk1/MK2 - E-04 is French market, which got neutered cams (as opposed to the inlet restrictions that some markets got).

Edited May 18, 2022 by Gammaboy

[Gammaboy]

So, almost 4 years after dropping it off to be stored at my mate's place, I picked it up yesterday and dragged it home.

Good/funny to see it again after 4 years.

Guess I better get cracking!

[Captain Chaos]

15 hours ago, Gammaboy said:

Guess I better get cracking!

Damn right

[Gammaboy]

So last night I was digging through my boxes of stuff I picked up while I was in Euwrop, and realised there was an ignition advancer there... so had a quick look at the cover and realised the factory gasket was not there, which struck me as odd for the low mileage this thing has... what's the bet that when I whip the cover off, there will be a Yosh ignition rotor in there?

 

Ordered a gasket, will pull the cover to have a look tonight.

 

Stay tuned for tomorrow's episode!

[Gammaboy]

Aaaaaand the answer is the gasket was there, everything was untouched... the bit of black sealant was from the Suzuki casebond goo that had extruded out and then been squished during installation of the cover. Anyway, 4 degree advanced rotor fitted, new gasket arrives Thursday.

[Gammaboy]

Haha, so didn't actually fit the gasket untill a couple of days before Christmas. Had planned on getting a fair bit done over the Christmas/New Years break, but between the shitty, stinking hot weather, and all the other (non Bike related) shit I wound up doing, I didn't actually touch it... However, holy shit, I did work on it today. 

Pulled the seat unit and tank, dropped the top of the radiator and swapped out the coolant pipe that had the buggered chrome that I rattle canned with black Killrust with a new old stock unit I'd picked up. Thankfully, past me had made a point of lining up all the hose clamps so I could actually get at them.

Of course, this particular pipe never sees daylight, but I know it's there....

Also swapped the mounting bracket and heatshield across from the stock cans to the factory "race" cans - tips certainly fill the hole a bit better, but I forgot to take a pic.

[Captain Chaos]

Any updates?

[Gammaboy]

Well, it's been a while, not sure why, but I just kinda stopped visiting OSS, sadly. @KATANAMANGLERmentioning his articles on borkface actually made me think "I need to come back"

So, I finally got round to the fiberglass repair work last year (Feb 2025), smashed a couple of extra layers of carbon on the self supporting part of the seat unit too (if anyone remembers there were big chunks of chopped strand glass that had been added that delaminated), applied new insulation, machined up a new (longer) mount for a Guzzi fuel sender (and found out the original is from a Simpson moped after I'd bought the shorted Guzzi unit). Bike then went off in late Feb 2025 to have it's import compliance worked out - eventually got it back in August.

Actually, fuel sensor may have been after I got it back...

 

 

Together at last:

 

Picked up from Compliancing:

 

Got the bike running back in September and noticed an issue with the tacho - Face was vibrating and missing a screw. So I pulled the tacho out to have a look and discovered that the front had been cut off and gled back on at some point... Curious, it had always had some non factory wiring going on into the back of it, so opened it up. Looked like GSXR tacho gubbins had been installed (badly) into the CEV gauge. Scorch marks and melting of the housing suggested the CEV gauge had suffered something terminal.

Gauge shenanigans:

No problem thought I, I have a spare tacho and gauge loom that I picked up while living in Germany. Turns out it had suffered the standard CEV tacho issue where the solder on the 3 connector pins fails and they push through the board, preventing connection. So I cut the spare open in the area hidden by the isolator rubber ring, and soldered it back together with good lead containing solder, applying plenty of hot snot to support everything while I was there. Bought some styrene card from a hobby shop to use as a backing splice for putting the housing back together, tested the gauge worked, and then it just sat. Travel for work, holidays and Christmas etc all got in the way and I fell down the hole of over analysing and obsessing about how to glue the thing back together without getting solvent crazing of the lens. Eventually I had a moment of clarity and used styrene cement to glue the backing to the back half, and then epoxied it all together. Put it back into the bike, fired it up and it didn't. Pulled it apart, cut the front back off, fresh solder on the screw contact pads on the PCB, tested it, working, glued it back together, put it back in bike, not working. Fuck. Wiggled the wiring a bit, blip of life... Wiggled some more and it came good... got a broken wire in there I guess.

Threw some fresh tires on it at some point, got a road worthy on it and finally rode it. Just to the servo and back to fill the tank (it was stinking hot, to hot to do a proper shakedown ride). First time on a bike in nearly 7 years. Then a week and a bit later rode it to work, and on the way home had what I thought was the bike spin up new tires on a dusty white line, thought nothing more of it. Took it for a Sunday shakedown run, and just as I got to the base of the hills, the clutch started slipping worse than a CVT.... Fuck. Limped home - I guess that's what the "spin up" actually was. A bit of thinking and investigating, and realised the clutch fluid was 6 years old, and probably over-filled, preventing the fluid from expanding into the reservoir when hot. Pulled the fairing, fresh fluid and bleed, and then the weather fucked any chance of test riding it to check... And here we are....

 

At some point I need to modify a mounting bracket so the bigger "race" pipe tips don't foul, and then they will go on. Yes @Evilchicken0they don't make any more power.

[SiBag]

Looks beautiful.

Just a shame the Antera wheels are so farkin heavy.

[Gammaboy]

50 minutes ago, SiBag said:

Looks beautiful.

Just a shame the Antera wheels are so farkin heavy.

Whats interesting is they're not significantly heavier than the 3 spoke Marchesinis that some Mk2s got - someone was selling a bare set a few years back and kindly weighed them for me. 

[Gammaboy]

Forgot to mention, I got given an excellent Australian made digital carb balancing setup for Christmas, got the carbs balanced absolutely perfectly. With the settings from the workshop manual it seems spot on.

[Jaydee]

3 hours ago, Gammaboy said:

got given an excellent Australian made digital carb balancing setup

Raytech by any chance? His stuff looks good.

[Captain Chaos]

@Gammaboyyou still have that E55?

Awesome thing.

[Gammaboy]

9 hours ago, Jaydee said:

Raytech by any chance? His stuff looks good.

Yep!

3 hours ago, Captain Chaos said:

@Gammaboyyou still have that E55?

Awesome thing.

Well, I had it untill about November. I couldn't afford a new Chinese car, so I bought a Maserati.

[Captain Chaos]

22 hours ago, Gammaboy said:

I couldn't afford a new Chinese car, so I bought a Maserati.

you should have kept the 20 year old Benz to ensure a quick, painfull bankruptcy.

Anyway the Bimota looks awesome. I assume it rides just as well as it looks?

Edited February 20 by Captain Chaos

[Gammaboy]

3 hours ago, Captain Chaos said:

you should have kept the 20 year old Benz to ensure a quick, painfull bankruptcy.

Anyway the Bimota looks awesome. I assume it rides just as well as it looks?

It does. Weirdly, with all the suspension and carb settings as per the manuals, it all works really nicely. Good starting point to go and fuck it up completely. I spent lunch time yesterday looking at flatslide carbs... Lol.

General opinion seems to be that the Maserati will bankrupt me sooner, but that's from people who pay mechanics. It's certainly a wonderful thing to drive, and a whole lot of car for the money

[BURNOUT64]

17 hours ago, Gammaboy said:

It does. Weirdly, with all the suspension and carb settings as per the manuals, it all works really nicely. Good starting point to go and fuck it up completely. I spent lunch time yesterday looking at flatslide carbs... Lol.

General opinion seems to be that the Maserati will bankrupt me sooner, but that's from people who pay mechanics. It's certainly a wonderful thing to drive, and a whole lot of car for the money

Many moons ago while doing some work for a Bimota dealer I was lucky enough to ride quite a few and always loved the SB6... defo my favourite

[Gammaboy]

Managed to find the motivation to drag it out and ride to work this morning, and now I have an answer on Schrodinger's clutch. The cat is dead.

Hopefully it's just a set of frictions. But it's a drop the engine job to get at the clutch.

[Gammaboy]

Fuck a tree. It's a 4 week lead time on the plates, back ordered from Japan.