Double Trouble

If in doubt, or it doesn't seem to fit elsewhere - put it here.

Re: Double Trouble

Postby Lotus54 » Thu Oct 07, 2021 9:48 am

Glad to do the valve covers too- if needed

Looking great!
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: Double Trouble

Postby John H » Sun Oct 10, 2021 7:49 pm

Thanks Mark, the rocker boxes have already been painted.
The oversize rings arrived but were not as advertised. A .044 end gap doesn't cut it. So on to the heads. The seats have been replaced at some point. They are not the powdered metal type that is common but they did a good job. Valves are pocketed pretty deep so will be very gentle with the cutters and lapping. This will be the 3 angle job, 30-45-60.The darker black ring 45º is the seat area that will be lapped.

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Re: Double Trouble

Postby John H » Thu Oct 28, 2021 9:21 pm

As I was getting ready to install the front engine cylinder I noticed the tappet blocks would not line up when tightening the register bolt. Not good. This is why the tappets were damaged. The register hole had to be filled and re-drilled. The error was made when the cylinder was built.
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I picked up a neat old Black and Decker valve grinder that needed spindle bearings. After a day of disassembling, cleaning and installing the new bearings it works great.
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Re: Double Trouble

Postby Lotus54 » Fri Oct 29, 2021 8:03 am

Nice old machine.
They are quite handy to have around. I used to fine tune the closer valve shims on my Ducatis with one- getting closer clearance to zero was pretty easy then (used the stem grinding side).
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Re: Double Trouble

Postby John H » Fri Oct 29, 2021 6:59 pm

I didn't get the rocker radius tool but it looks simple to build. Also need to make the wheel dressing attachment.. While at it, I need to make or modify the stem grinding attachment to hold the 'too small'
Triumph valves. The height of the valve stem must be correct so the adjustable tappets stay centered on the stem. This all changes every time the valve or seat is ground. Eventually the valve gets too short to use. I ordered two new intake valves today.
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Re: Double Trouble

Postby John H » Sat Oct 30, 2021 10:34 pm

The rings for the front cylinder arrived (+.080). They were gapped at .015" and fitted to the pistons. Wrist pins were a bit tight so they were enlarged with a bearing scraper just enough to slide in with a bit of effort. There isn't a taper at the bottom of the cylinders so I chose to insert the pistons and rings while on the bench. It's easier than jockeying the cylinders above the pistons.
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I forgot the engine cases had been bore out to fit the special cylinders. So with a surgical blade I opened up the base gasket about 1/16". One cylinder done, one to go.
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Re: Double Trouble

Postby John H » Wed Nov 17, 2021 11:57 pm

Got some time in on engine two today. Had the cylinder re-honed to straighten the bore on one hole that had a bit of a taper.
Even with diamond hones it took several minutes to get the job done. A lot different than honing cast iron for sure.
With tappets in place and cylinder bolted down the crank would get tight at one spot. Turns out one of the tappets, a new one, was sticking due to a large radius on the stem. Problem solved with a bit of grinding..
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The 3 pc oil rings was tricky installing and then getting them to stay in the bore while adding the wrist pin. The bottom oil ring is only .030" above the pin. It's bolted down for the last time, I hope.
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Re: Double Trouble

Postby John H » Thu Nov 18, 2021 8:30 pm

Both engines are buttoned up. I'm pleased how they turned out. Next will be fabricating the two head torque stays.
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Re: Double Trouble

Postby Lotus54 » Thu Nov 18, 2021 8:42 pm

Wow- moving along.

Should be just in time for some ice drag racing…
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: Double Trouble

Postby ClineDesign » Fri Nov 19, 2021 10:46 am

We all want to be there when you fire it up!
Always wear protective gear. Usually SPF 30 will do.
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