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#414762 - 01/23/12 6:16 am Drat! See what crawled into my cases!  
Joined: Jan 2004
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DMadigan Online content
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ca, us
Keep those cases in a safe place. I left a set on the floor amongst some foreign stuff and look what I found:

There definitely is a problem here:

This is what is underneath the pistons:

Looks like I will be needing one of those offset cams to keep the valves from hitting the pistons. The cylinder is not going to work either, the pistons are too big:

What a mess! Let this be a lesson, keep your parts separated!

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#414764 - 01/23/12 6:36 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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Two Alpha Offline
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North Coast, BC, Canada
I'll bet even Mark hasn't tried that combo yet, course I wouldn't want to bet much though.

Looks like the cylinder has got more problems than just the pistons being too big.

XSA650?


BSA
Matchless
Triumph
#414902 - 01/23/12 10:01 pm Re: Drat! See what crawled into my cases! [Re: ]  
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lemans Offline
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bugger, the wife cleaned the workshop. piled all the parts on one heap. lucky bast....

could you describe you mods as I'm trying likewise myself

http://s1233.photobucket.com/albums/ff390/lemans41/krukas2.jpg

http://i1233.photobucket.com/albums/ff390/lemans41/krukas1.jpg

regards Anne

#414939 - 01/24/12 1:17 am Re: Drat! See what crawled into my cases! [Re: lemans]  
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gREgg-K Offline
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Ottawa, Canada
Certainly got my attention on this one.

Aside from what looks like a center main added, it looks like roller bearing big ends (2 stroke rods?) and a ring gear for a starter.

Tell us more, please.

... Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
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#414955 - 01/24/12 2:35 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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Mr Mike Offline
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HMMMM. Tell us more. Which half is that center main in?? Someone has got some machining in that one

Mr Mike

#414983 - 01/24/12 3:59 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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DMadigan Online content
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DMadigan  Online Content
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ca, us
Well, I guess A74XS would be closer. I was looking at ways to make a 90 degree crank. Carving one from solid takes a whole lot of metal and most ends up on the floor. I rejected the idea of bolting anything together and welding takes a lot of straightening afterward. In addition, the fundamental problem with the British twins is the two bearing crank letting the centre flex all over at high RPM.
The XS650 has the same bore/stroke as the A65. There have been a few XS650s converted to 76 and 90 degrees. The former by just rotating the flywheel on the centre spline, the latter by making a new splined shaft and using two female flywheels.

Great except the XS crank is too wide with the cam drive and two bearings in the middle. Making a few measurements it was clear that it would fit if there were only one centre bearing. Parts are not too hard to come by, a good crank can be had for about $50, though of course you need two. Rods, pins and bearings are relatively cheap and Wiseco makes 80mm pistons to make it a 750cc and cheaper than BSA pistons.
I needed a shaft splined 90 degrees off on each end. I talked to a gear company and they were willing to cut the spines. I made blank shafts, they cut the splines and I ground the bearing surface. The spuds on the female flywheels had to be narrowed so they would meet in the middle of the bearing.


The timing side flywheel had to be recut to take the A65 gear and pump worm drive. These cranks are hardened so most of the roughing was done with a body grinder in the lathe.

The intermediate plate was a chore, cut on a mill and rotary table. Next time I would have the CNC shop do it. The bearing cap had to be rotated backward to give the most support on the front bolts. The left case was relieved to make room for the plate.

I decided to make the centre bearing a ball bearing to locate the crank. The XS has the drive side a ball with the others rollers. A roller on the drive side would be better for load plus there is no way to retain the drive bearing toward the crank. The ball bearing has a circlip to locate it in the plate. The plate is bolted around the crank, inserted into the right case then the left case is added.

The XS crank has odd size bearings with 32mm I.D. Fortunately I found a roller bearing for the drive side and needle bearing for the timing side that are only about 0.040" larger than the A65 bearings.
The XS crank is oiled by a spray bar. I drilled through the OPRV cavity and put a matching hole in the intermediate plate to hold a spray bar.
The 80mm pistons will not work with the stock cylinder. I plan to make a new cylinder and head that will work with both A65 case cylinder bolt patterns.
There is no simple way to use the XS crank starter gear. I have another way to add a starter.

#415038 - 01/24/12 2:05 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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wbabojo Offline
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Knock me out with a feather, clever Trevor, thanks for sharing this on the forum, it just might make a few "Engineers" take notice of what can be done!


Gavin
You can't make a silk purse from a sow's ear.
#415041 - 01/24/12 2:34 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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Alex Offline
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Seattle
That's awesome...you now have a Matchless twin! grin

All kidding aside, that is very nice work. Finally you don't have to worry about the oil pump or OPRV valve working...


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
#415760 - 01/28/12 5:38 am Re: Drat! See what crawled into my cases! [Re: Alex]  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Way cool.

Watching with interest!! So all roller ball bearings?

Last edited by Semper Gumby; 01/28/12 5:39 am.

Gaggle of BSAs
a Honda
an old BMW
and a Montesa
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#415761 - 01/28/12 6:21 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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DMadigan Online content
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No, needle rollers on the rods (big end only), roller on the drive side, ball bearing in the intermediate plate and needle on the timing side.

#415931 - 01/29/12 1:30 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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Arnstein Offline
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Kristiansund. Norway

Very interesting indeed!
How many hours making parts? I guess you "live" in your workshop?

Regards


Arnstein

BSA Spitfire MK3.800cc
Honda CB450T -71
Laverda RGS 1130cc -85
Ducati 1098 -08
#415986 - 01/29/12 6:13 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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DMadigan Online content
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I wish, unfortunately the day job chews up a lot of my time. The intermediate plate took the longest, a week of evenings carving the reliefs, making the bearing cap and studs then boring for the bearing. I had to borrow a 12" rotary table to do it. Finding the bearings took a while because the I.D. is odd (32mm), the key was finding the timing side bearing. I did not want to grind the crank down to 30mm.

#700636 - 07/03/17 8:56 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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DMadigan Online content
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Well a lot of chips have passed under the mill since I last posted. The engine has become a little more inter-racial. Now have BSA A65 cases, Yamaha XS650 crank, H*nda CR500 rods, Suzuki oil pump gerotors and lastly (?) BMW 325i valves and guides. When will it ever end?

#700642 - 07/03/17 9:58 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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gavin eisler Online content
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argyll. scotland, uk
Stop teasing us, need more pics, if using 80 mm pistons with the stock barrel centre are you staggering the bores? So many questions , cant wait to see the oil pump set up. The flywheels look a good bit smaller than the A65 centre gyro, the motor will feel V different. Losing that Inertia should make it spin up a lot quicker. I wonder if the "on rails " feeling will be lessened?
probably a rural myth, I recall once reading somewhere that XS 650 flat trackers were not competitive untill the fly wheels got added mass, possibly bollocks, internet nonsense. Very interesting work. thanks for putting it up.
G


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
#700705 - 07/04/17 10:45 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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JER.Hill Online content
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Forfar, Scotland
Good stuff David, always enjoy seen the work of a free mind, as Gavin said more photos please. perhaps if you used an intermediate gear and mounted a starter motor on top of the front mounting you might manage to utilise the original starter ring! just a thought.

Keep up the good work

John

#700810 - 07/05/17 5:34 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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DMadigan Online content
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DMadigan  Online Content
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Before making the 750 head and cylinder I am going to use +1mm XS650 pistons (76mm) to test out the crank arrangement. The bore centres are 3.5" with the XS crank but 3.5625" for a stock A65. Not a problem moving bores with the aluminum cylinder as I plan to use sleeves rather than Nikasil. Aluminum sleeves in the cases would have to be very thin.
Yes, the crank looks a bit lonely in there. Plenty of room for a stroked crank. 80 x 80 anyone (804cc)?
I posted the oil pump before, uses Suzuki gerotors with spur gear drive from the crank.
The starter mounts behind the cylinders and engages the clutch. Trying to mesh with the web gear would require cutting a window in the cases. Not something most people want to do even for the attraction of mounting a starter.

#700822 - 07/05/17 7:47 am Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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NickL Offline
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Aus
Having gone to all that trouble i would think you are after a high revving motor (circa 10k+) increasing the stroke may
not be good for piston speed. As you are making a barrel why not mod the cases and try for the biggest bore you can get.
I ran an SRM iron barrel at 80.5 with no bore related problems, a man of your calibre could do much better.
Having gone to a centre main rather than than a new EN40 crank you must want a significant advantage to justify it,
i don't think the benefit of all that work is being exploited unless you are aiming for 90+BHP.

After all, the old mod of using t140 pistons and norton crank gives you 808cc and you can go +40 on that = about 828cc.
Now decent t140 pistons are generally available it would be a good motor. So you have to do better than that.

Just my 2c.



#701034 - 07/07/17 2:21 pm Re: Drat! See what crawled into my cases! [Re: DMadigan]  
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Mark Parker Offline
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Bega NSW Australia
From memory the Bore on this motor is around 82mm the cyl are made with the bolts moved further out, the head modified to suit. The crank is standard but welded on the pins and reground to give 86.5mm stroke giving 914cc. Compression is over 11-1,maybe 11.4? The rocker castings on the head are machined off and a new section bolted on to support roller rockers which have greater offset, so the std cam gives .5" valve lift to the oversize valves. Valve lengths are longer and use beehive springs. Carbs are 36mm Mikunis. It's a lovely looking cyl casting and sounds very crisp.

[Linked Image]


mark

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