Author Topic: Benelli 750 SEI  (Read 5800 times)

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Offline BenelliSEI

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Benelli 750 SEI
« on: August 16, 2022, 06:38:31 AM »
Pulled it out from the back of the shop yesterday. The Cobble Beach Concours is back on this year, after a three year “Covid Break”. The last time I went, I took my K0 and won the “Best Motorcycle” award, so invited back this year. Fortunately, the category for motorcycles this year is “Italian”. The only non Honda I have is the Benelli!

We’re out of country for a few weeks soon, so I have to get this started. Got it up on the work table. It’s been a while since I ran it, but it was stored nicely. More news to follow......
« Last Edit: September 13, 2022, 07:31:30 PM by BenelliSEI »

Offline rocket johnny

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Re: Benelli 750 SEI
« Reply #1 on: August 16, 2022, 07:05:14 AM »
great looking bike !     good luck & am sure you will hit a home run  ! !

Offline PeWe

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Re: Benelli 750 SEI
« Reply #2 on: August 16, 2022, 07:25:43 AM »
It look like a new bike!
It must be a collectors $$$$$ item in Italy?
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline MauiK3

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Re: Benelli 750 SEI
« Reply #3 on: August 16, 2022, 08:09:06 AM »
We are following
1973 CB 750 K3
10/72 build Z1 Kawasaki

Online Kevin D

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Re: Benelli 750 SEI
« Reply #4 on: August 16, 2022, 08:47:27 AM »
That is a beauty for sure.

Engine castings look surprising like Honda castings, and Wikipedia says CB500 derived.
Did the Italians pay Honda for the any of this?

Enjoy your travels John!
71 CB750 K1
104,000 miles
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
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Whether you think you can or think you can’t, you’re right
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Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #5 on: August 16, 2022, 01:59:46 PM »
The engine is definitely a Honda look-a-like! Nothing is interchangeable, but surely cb550 inspired. Interestingly, a common modification (which I did) is a Honda cb650 sump. It bolts right on and adds almost a full litre of oil to the sump. It does not hang below the frame or pipes and the only modification was an alloy nipple I machined up to extend the oil pump pickup. Will post pictures of my progress.

Offline grcamna2

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Re: Benelli 750 SEI
« Reply #6 on: August 16, 2022, 02:11:29 PM »
Beautiful  8) I love that six cylinder John.
When's the last time you rode it for a long ride ?
That engine must hum along very nicely.
« Last Edit: August 16, 2022, 02:13:05 PM by grcamna2 »
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #7 on: August 16, 2022, 02:45:26 PM »
It had about 8,000 miles on it and I’ve added +1200 miles. Nothing in the past 18 months, but plan to take it out in the next few days. Fantastic brakes and handling, it’s actually smaller than a cb750 and the mass of it seems to be lower. It’s exactly the same bike as their earlier 500 Quattro (that engine really is a 100% knock off of a cb500). So much so, that a cb550 unit is a complete bolt in conversion, that I have seen done! Only difference is the twin front Brembo discs and a few extra pipes! Hiding the alternator above the transmission (RHS) and the triple Dellorto carbs keep it extremely narrow and centred.

P.S. the engine absolutely howls. The pipes are made by Busso, and pretty much empty. Sound like a Ferrari Dino V6 being beaten to death.
« Last Edit: August 16, 2022, 02:51:53 PM by BenelliSEI »

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #8 on: August 17, 2022, 10:54:10 AM »
Started it up this morning. First I pulled the plugs, squirted in some SeaFoam and spun up oil pressure. Cleaned the plugs and used my remote bottle to supply fuel. When I stored it away, I removed the float bowls, dried and cleaned everything, and blew out the Jets.... loaded up with fuel (no drips), and hit the button. Fired instantly, ran perfectly! I totally attribute this to the fantastic electronic ignition system I installed a while back. The triple points set up (in the same space a cb550 has two sets) were a royal pain, and never stayed were I set them. This system is brilliant.

I did put over 1200 miles on this bike, so although it looks great, definitely not “Concourse ready”.....
Clean up starts next.
« Last Edit: August 17, 2022, 10:57:55 AM by BenelliSEI »

Offline RAFster122s

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Re: Benelli 750 SEI
« Reply #9 on: August 17, 2022, 11:06:37 AM »
Good luck with the clean up and weekend on the concourse field... Hope it comes together like you want and you bring home a trophy.
David
David- back in the desert SW!

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #10 on: August 17, 2022, 02:06:13 PM »
Good luck with the clean up and weekend on the concourse field... Hope it comes together like you want and you bring home a trophy.
David

Thanks! I’m sure there will be some pretty spectacular machines for the “Italian Motorcycle” class. Last time, the timing was perfect. I had just finished the K0 and it was “as new”. This bike will get points as an original survivor, but I doubt there will be any trophies! Looking forward to the spectacular cars, in a really picturesque place. The event is held on the 18th fairway, over looking a lighthouse, the club house and Georgian Bay! Check out their website.

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #11 on: August 18, 2022, 12:46:26 PM »
Got into it today. The Boranni rims and stainless spokes are lovely, but what a pain to clean and polish! I also had to spend some time rerouting the wire and harness to the electronic ignition control box. Managed to hide it under the battery box. Most judges deduct points for non- standard modifications. If nobody asks, I won’t be pointing at it! Pulled the inner and rear fenders too. Only way to really get them tidy and they come away easily. This “prep” may take a few days, but it’s been a while since I worked on a non-cb750. Pleasant.

Offline grcamna2

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Re: Benelli 750 SEI
« Reply #12 on: August 18, 2022, 02:16:39 PM »
Got into it today. The Boranni rims and stainless spokes are lovely, but what a pain to clean and polish! I also had to spend some time rerouting the wire and harness to the electronic ignition control box. Managed to hide it under the battery box. Most judges deduct points for non- standard modifications. If nobody asks, I won’t be pointing at it! Pulled the inner and rear fenders too. Only way to really get them tidy and they come away easily. This “prep” may take a few days, but it’s been a while since I worked on a non-cb750. Pleasant.

A labor of love  8).
John,did you notice a much more smooth running engine with the EI control box compared to points/condenser;how about more performance ?
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline MRieck

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Re: Benelli 750 SEI
« Reply #13 on: August 18, 2022, 03:21:06 PM »
Started it up this morning. First I pulled the plugs, squirted in some SeaFoam and spun up oil pressure. Cleaned the plugs and used my remote bottle to supply fuel. When I stored it away, I removed the float bowls, dried and cleaned everything, and blew out the Jets.... loaded up with fuel (no drips), and hit the button. Fired instantly, ran perfectly! I totally attribute this to the fantastic electronic ignition system I installed a while back. The triple points set up (in the same space a cb550 has two sets) were a royal pain, and never stayed were I set them. This system is brilliant.

I did put over 1200 miles on this bike, so although it looks great, definitely not “Concourse ready”.....
Clean up starts next.
Nice to hear about the ignition system as I bought one for my CBX rebuild.
Owner of the "Million Dollar CB"

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #14 on: August 19, 2022, 05:38:28 AM »
Got into it today. The Boranni rims and stainless spokes are lovely, but what a pain to clean and polish! I also had to spend some time rerouting the wire and harness to the electronic ignition control box. Managed to hide it under the battery box. Most judges deduct points for non- standard modifications. If nobody asks, I won’t be pointing at it! Pulled the inner and rear fenders too. Only way to really get them tidy and they come away easily. This “prep” may take a few days, but it’s been a while since I worked on a non-cb750. Pleasant.

A labor of love  8).
John,did you notice a much more smooth running engine with the EI control box compared to points/condenser;how about more performance ?

I’ve commented on the Elektronic Sachse system in the past. Just can’t say enough about it. Simple installation, with one critical point. When first energized, the process includes identifying top dead centre (TDC) to the control box. In the Benelli, this was complicated as the advancer (and associated crank position markings) is removed. I installed a degree wheel at the other end of the crank to ensure precise set up. Once the trigger and sensor are set, the “box” takes over. At cranking speeds it fires at TDC, immediately switching over to the standard ignition curve at revs over 800. There are six different advance curves built in. I just use the base (stock). The engine runs as smooth as silk on this system. Astoundingly consistent and “balanced”. According to the literature, it will work at very low voltages, an added bonus as the Benelli’s alternator is known to be “fragile”. The tool kit includes a punch to knock out the drive pin, should it seize up, with instruction!
« Last Edit: August 19, 2022, 01:55:25 PM by BenelliSEI »

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #15 on: August 19, 2022, 05:41:26 AM »
Started it up this morning. First I pulled the plugs, squirted in some SeaFoam and spun up oil pressure. Cleaned the plugs and used my remote bottle to supply fuel. When I stored it away, I removed the float bowls, dried and cleaned everything, and blew out the Jets.... loaded up with fuel (no drips), and hit the button. Fired instantly, ran perfectly! I totally attribute this to the fantastic electronic ignition system I installed a while back. The triple points set up (in the same space a cb550 has two sets) were a royal pain, and never stayed were I set them. This system is brilliant.

I did put over 1200 miles on this bike, so although it looks great, definitely not “Concourse ready”.....
Clean up starts next.
Nice to hear about the ignition system as I bought one for my CBX rebuild.

I’ll be interested to hear what you think of it. They aren’t cheap, but I’m really tempted to try one on my K1.

Offline MauiK3

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Re: Benelli 750 SEI
« Reply #16 on: August 19, 2022, 07:14:49 PM »
Best of luck, we’ll worth the effort
1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #17 on: August 21, 2022, 07:31:11 AM »
Best of luck, we’ll worth the effort

Thanks! Back at it today.....

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #18 on: August 22, 2022, 02:35:14 PM »
Slowly working, end to end. Despite regular washing and polishing, 1200 miles has packed a bit of grime into the corners. When first fitted (2018), I spent a few afternoons getting the 6-6 Busso pipes to hang fairly symmetrically. Today I discovered the bottom two pipes, left side, were grinding on each other, for about a six inch strip. Pulled them off, polished out the damage (only visible to me!) and reset. A few shim washers and I may have got it right this time…..

« Last Edit: August 22, 2022, 02:38:07 PM by BenelliSEI »

Offline Gurp

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Re: Benelli 750 SEI
« Reply #19 on: August 22, 2022, 05:13:51 PM »
Do you have a link to a video where we can hear this thing? Man I bet it sounds as beautiful as it looks❤️❤️❤️
slow Progress 74 cb550.

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Future project 77 Cb750 Amen Savior

Offline BenelliSEI

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Re: Benelli 750 SEI
« Reply #20 on: August 22, 2022, 06:35:42 PM »
Will do that next time I run it. Check out UTube, there are a few there.

Offline MauiK3

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Re: Benelli 750 SEI
« Reply #21 on: August 22, 2022, 07:30:21 PM »
VIDEO or it doesn’t run!!!!!
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Offline grcamna2

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Re: Benelli 750 SEI
« Reply #22 on: August 22, 2022, 07:50:20 PM »
VIDEO or it doesn’t run!!!!!

Yeah,let's hear that sweet sound of 6 cylinders through those mufflers !
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline PeWe

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Re: Benelli 750 SEI
« Reply #23 on: August 22, 2022, 10:38:14 PM »
One ride can cause lots of cleaning.
Insects, my bikes are full of them, my K6 that frequently get a +200km ride has lots of dried kamikaze insects.

I need to lay wet cloths on bike to make the dried glued insects softer a d easier to remove.
They fill all areas..... My helmet too.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline RAFster122s

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Re: Benelli 750 SEI
« Reply #24 on: August 22, 2022, 11:38:26 PM »
A wet towel is how most helmet makes tell you to soften the bugs for cleaning...
Might take a while longer that way but you don't scratch up the face shield or helmet cleaning it that way.

I bought some shield anti-fog and cleaner made by RainX but haven't used it yet.

PinLock face shields help a lot with fogging but can do only so much...
David- back in the desert SW!