Roadster/Interstate/Thruxton R tank (2020)

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I'm using the RGM supplied flat tops, same weight as stock 850 pistons. Nothing fancy.
The supplied circlips are loose so I'm stalled in the water on assembly.
Getting the good McMaster Carr SS clips that Comnoz uses is proving difficult this side of the border.
I'm not putting it together with loose circlips.
The stock pistons from this engine appear to be originals.
The engine has not done many miles from the look of things, but those circlips are quite worn on the outer edges from movement.
I can see where this problem has ruined lots of engines.

Glen
 
Glen , I have tried to use McMaster-Carr for Duc o-rings , couple yrs ago now , was a no go then .... maybe you got trusty buddy south of border ....
 
worntorn said:
I'm using the RGM supplied flat tops, same weight as stock 850 pistons. Nothing fancy.
The supplied circlips are loose so I'm stalled in the water on assembly.
Getting the good McMaster Carr SS clips that Comnoz uses is proving difficult this side of the border.
I'm not putting it together with loose circlips.
The stock pistons from this engine appear to be originals.
The engine has not done many miles from the look of things, but those circlips are quite worn on the outer edges from movement.
I can see where this problem has ruined lots of engines.

Glen
Click to expand...
You’ve got the abilities Glen... how about turning up some PTFE plugs ?
 
That's a good idea Nigel. Will see if my farm supply company can bring in the McMaster Carr item.
If not, PTFE seems a good way to go.

Glen
 
I wish I had noticed the circlip issue earlier. They are now ordered from McMaster Carr. Deliveries from US to Canada are very slow right now. I knew there would be some tiny detail that would de-rail engine assembly.

Glen
 
worntorn said:
I also made up a sprocket mount/ spacer/cush drive similar to the type Ken Canaga detailed.
The rear wheel is a GSXR front so the bolt pattern is for a rotor, a bit smaller than any standard sprocket I could find. That actually worked out ok as it left room to get the cush in. The natural offset was also helpful, this required a 9/16" spacer for alignment. This is a good space for the cush pieces.



Click to expand...

Glen, what material did you use for the cush drive bits?
I'm thinking of doing this sort of thing on a YZR rear wheel to get rid of all that weight on the rear end.
 
The cush material is polyurethane rubber , shore 80. The plate is 1/2" 6061 Aluminium. Bolts and washers are stainless for now. I'm trying to find some titanium bolts at a reasonable cost, no luck so far.
The replaceable sleeve inside of the polyurethane cush is also made from 6061 Al, machined to fit.

Glen
 
That's about it for the 920 assembly. I'm waiting for the 304ss head bolts which are 10mmx75mm with a very long threaded connection going into the alloy cylinder.
The engine weighs just 85 pounds with the steel stand.
The stand weighs about the same as carbs, manifolds and airfilter, so 85 should be it.
That is with MK3 cases and crank. The MK3 cases are 2 lbs heavier than the Combat cases I have here. That is 2 lbs well spent.
The rolling chassis weighs 158. The rest of the parts bring the bike with engine in weight up to 286 lbs.
This seems too light and it is. There is still the fairing and it's mounts, wiring, throttle and cables etc.
It looks like finished weight will come in at about 305 lbs ready for fuel.
I was happy to get it down to 320, so this is a bonus.

 
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Motor in.
The weight number is good, 263lbs at this point, according to the hanging scale.
I'll have to resist the temptation to start chucking heavy ready made items on just to finish up.
There's already a list of items to replace with lighter stuff next winter. Most of that is fasteners that can be switched to Titanium or shop made in Aluminium 7075 for low stress items.

 
I fired the bike up yesterday. It went well, rolled it over with plugs out until the oil return started to flow, then put the plugs in. It came to life with a crackle and sounds really good, not overly loud.
A puff of smoke on startup , just burning off assembly lube, and then the exhaust ran clean.
The engine runs much smoother than my 850 below 3000. Both are smooth above 3000 but the 920 seems smooth right from idle.
This could be due to the dynamic balance. It's not due to lightweight pistons, these are the RGM provided 920 pistons( steel strut!) and are very close to standard 850 piston weight.

It's not quite roadable yet , no lights, speedo or charging system.
I might put it aside until next winter for the final bits, although I'm itching to see what it will do on dyno hill.
Of course it needs a full break in before doing that.

Glen
 
I've been putting a lot of shop hours in and neglecting the rest of life. Who knew that one could spend a whole day just making an Al. battery tray?
So I might put it aside for just a little while then sneak back to it.
The whole bike has to come apart at some point for frame painting. I resisted the temptation to do
that beforehand. Good thing, I welded some tabs on yesterday.

Glen
 
worntorn said:
I decided to paint the crankcases with VHT 900f caliper paint in cast grey.
The crankcases on the right are a 750 Combat set I'm working on for a friend. They have been blasted with walnut shells and look nice.
I think the painted cases are a close match in appearance and might be a bit easier to keep clean. The VHT requires baking at 200f for one hour in order to achieve full hardness and chemical resistance. This can be done anytime after the paint is fully dry.
The baking will happen... eventually.
Click to expand...


Nice shop. That kind of room is something I can only dream about. ;)
 
I'm fortunate to have this shop on the property. We converted an existing 1200 sq ft Implement shed to a woodworking shop, then added about 4200 ft to that as new equipment was added.
If we ever move to city lot I know that space will be much less and most of the equipment will be sold.
So not rushing into that change!
Glen
 
I set the timing with a strobe today. One of the pilot jets must be plugged as it's mostly on one cylinder until the revs climb. When it hits on two it runs clean on up, although I didn't take it above 5500 today. This is a guesstimate, there's no tach mounted at the moment.
It sounded so nice that I had to sneak it out on the pavement for a short blast. Of course much is Mickey Mouse at this point, no Speedo, wrong gear lever, no rear brake, temporary pegs in the wrong place, no idle and so on.
Perfect for a tryout!

Also I forgot about the plastic Wassell timing disc that was still clamped to the alternator nut. I somehow hit that with my toe when my foot came off the temporary peg on acceleration. The disc disintegrated, but no worries, timing is already set.
The acceleration was more than I was expecting- a lot more. It's going to be fun.

Glen
 
worntorn said:
The acceleration was more than I was expecting- a lot more. It's going to be fun.

Glen
Click to expand...
That is exactly how I felt after my Muttster rebuild. It spun up so much more quickly than before the rebuild, I had to be REALLY careful.

Here's to ear to ear time! :D
 
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