Benelli 750 sei

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Re: Benelli 750 sei

Postby Lotus54 » Mon May 24, 2021 10:15 am

Parts got here a bit ago and I’m working on the valves now.
I’ll do a bit of port matching, but nothing else. I did that on my original sei and it worked out really well.
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 » Wed May 26, 2021 10:23 am

I have a Neway small engine seat cutter set for 30º and 45º available if it will help you out.
The range is from .625 to 1.00" The smallest pilot is .214".
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Re: Benelli 750 sei

Postby Lotus54 » Wed May 26, 2021 7:13 pm

Thanks John!
I just got a set of those (plus the intake is too large for that).

Frame ready to sandblast.
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Last edited by Lotus54 on Thu May 27, 2021 6:54 pm, edited 1 time 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 750 sei

Postby John H » Thu May 27, 2021 6:11 am

I guy can never have too many tools, right? If you ever get into any 'big valves' I have the large Neway set that goes up to 2.25". It includes the valve facing tool.
Will you sandblast your frame or send it out? I sent my Bonneville frame out for blasting and it was so coarse it had to be sanded down so as not to show in the finish. Won't do that again.
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Re: Benelli 750 sei

Postby Lotus54 » Thu May 27, 2021 6:37 am

Thanks on the larger valve tools- really, really appreciate the offers.

I’ll just sandblast it myself. Really only rusty around the battery box, but of course paint chips etc. I’m not looking for concours bike at all, but I am trying for very good looking but more importantly- great running/riding bike.

I was considering powercoat, but that is way too hard to repair when chips do happen, plus I can paint it myself. I’ve painted a number of frames, bikes and cars and think it will look good.
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 » Sun May 30, 2021 3:27 pm

I got all the valves done. The Neway setup worked a treat.
Next to match intake/exhaust manifolds up to head well. I’m not going to fool around with port work or any of that. I’m not looking for max performance. Just clean/match.
I’m not sure how long that will take (with other stuff I’m doing)- but after that is done and I do a really good clean on the head, then I can pop it on the engine, then cam, covers etc.
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 May 31, 2021 9:15 pm

That's real progress. I've noticed that some sei's have painted cylinders. Which way are you going?
I'm guessing you have all the porting tools you need to match your ports. If not, I have a good assortment you are welcome to if needed.
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Re: Benelli 750 sei

Postby Lotus54 » Mon May 31, 2021 9:29 pm

I think the cylinder is black, with the outside ‘fins’ bare.

Yes, I have a bunch of stuff that works well for porting. I have a couple of Foredome dental motor/drill setups (foot control) and a load a burrs.
I was a Dental tech, learned if from my Dad who had a Lab here in town from ‘52, and I still have a fair amount of gear from that.
Thanks! I much appreciate the offer.

After ports are matched (getting close already, they are not bad at all) I will do a ‘super clean’ to get rid of shavings, valve paste etc. then install all the valves and pop on the head. That will be pretty cool.

Of course, while I was waiting on parts I should have done the carbs- and I didn’t. Oh well, I have a couple of ultrasonic cleaners (one is tube driven it is so old) and a vapor honer. Plus rebuild kits (that will be missing stuff of course). A ‘master kit’ would sure be nice. But I’ve never seen one for these (with all the passage plugs etc). I should be able to do a good job anyway.
I thought about sandblasting the frame today- but went riding on the 1973 Benelli 250 supersport instead. Ha
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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 » Tue Jun 01, 2021 5:13 pm

I take that back.
The HEAD is black, with right and left ends bare of paint.
The cylinder has no paint.

The one I had new was like that also.
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 » Tue Jun 08, 2021 6:53 am

Head together. Mounting soon
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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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