Benelli 750 sei

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Benelli 750 sei

Postby Lotus54 » Mon Jan 06, 2020 8:55 pm

I’ve been mucking about with the sei a bit.
Engine turns over well- after some wire cleanup, it has great spark. Low compression in #6, oil brings it right up. Could be stuck rings, broken rings or just worn out. Or maybe a bit of all.

I’m trying to ascertain what sorts of things I’ll need- if engine needs overhaul or what (likely). I believe it has sat since the 90’s.
Last edited by Lotus54 on Mon Jan 13, 2020 7:57 pm, edited 2 times in total.
1974 OSSA Explorer- 78 Benelli 750 sei, 73 Benelli 250 SuperSport, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, 2020 Electric-Motion Escape ‘R’
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Re: Benelli 50 sei

Postby John H » Wed Jan 08, 2020 12:09 am

Sounds like an interesting project. Probably not many sources for parts or info out there.
I would just take the gentle approach. As for low compression, there are many thoughts starting with soaks of a mixture of atf / acetone. I personally like Kroil either for soaking or aerosol for places you can't soak.
Last edited by John H on Wed Jun 02, 2021 5:15 am, edited 1 time in total.
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Re: Benelli 750 sei

Postby Lotus54 » Wed Jan 08, 2020 1:22 am

Yes, I’ve been giving it the Kroil treatment.
Almost certainly I’ll tear it apart.
Parts are not bad for a lot of things. Cosmopolitan Motors here in the States had a huge supply, but so,d to an outfit in Germany a number of years ago. Makes it more another layer and cost...

I have new 6-6 pipes, those were not cheap.
1974 OSSA Explorer- 78 Benelli 750 sei, 73 Benelli 250 SuperSport, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, 2020 Electric-Motion Escape ‘R’
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Re: Benelli 750 sei

Postby John H » Thu Jan 09, 2020 7:52 am

I'd sure enjoy a show & tell if you would care to do one. I know it's a PIA resizing images to 257 or less. It's not to difficult with Macs but a couple of guys with MS said they had trouble getting it done.
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Re: Benelli 750 sei

Postby Lotus54 » Fri Jan 10, 2020 6:08 pm

As you can see- it is rough. But I think it won’t be too bad to bring back to a good rider.
I already have proper 6-6 pipes, seat cover, fenders, tyres, handlebars and many others.
I have a 900 sei small fairing I plan on using (the one in the pics is up for grabs if anyone wants it).
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Re: Benelli 750 sei

Postby John H » Sat Jan 11, 2020 8:54 pm

The bike has lots of potential. Like to see it when it's done.
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Re: Benelli 750 sei

Postby Lotus54 » Sun Jan 12, 2020 3:00 pm

Popped the engine out today. The cherry picker/balancer made it pretty easy. I couldn’t fit the legs of the cherry picker under the lift- so had to move it back on the ground.
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1974 OSSA Explorer- 78 Benelli 750 sei, 73 Benelli 250 SuperSport, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, 2020 Electric-Motion Escape ‘R’
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Re: Benelli 750 sei

Postby Lotus54 » Mon Jan 13, 2020 6:17 pm

popped off the head and cylinder today.
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1974 OSSA Explorer- 78 Benelli 750 sei, 73 Benelli 250 SuperSport, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, 2020 Electric-Motion Escape ‘R’
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Re: Benelli 750 sei

Postby John H » Mon Jan 13, 2020 7:44 pm

Did you find any stuck rings?
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Re: Benelli 750 sei

Postby Lotus54 » Mon Jan 13, 2020 7:56 pm

Yes, #6 (the one with low compression) had the top two rings stuck.
1974 OSSA Explorer- 78 Benelli 750 sei, 73 Benelli 250 SuperSport, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, 2020 Electric-Motion Escape ‘R’
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