Atlas Manifold gaskets.

Hi James, I’m not 100% sure what part you are after. The original manifolds AFAIK didn’t have any gaskets between the carb and manifold, well there was no sign of any when I removed mine this week. The newer after market CNC version does have rubber o rings between the head and manifold and between the spacer and carb and manifold.
 
I know that Andys Atlas has the twin choike car type Dellorrto (was I correct in that the rubbers are perished Andy?)
but James (longshanks) White Coopers bike may have the bike type Dellortto's
The car tyoe is an odd shpaed rubber inlet which adapts head to carb and allows for missalignement as well, the bike type is pretty much conventional

Tell us more about the aftermarket bits then Andy, and show a picture or two, many have this problem, including Per Erik in Norway
CLEM
 
I was reading on that specific Atlas site someone makes a CNC replacement manifold for the Twin Choke Delordo carb that came standard on all those bikes. I didn't think bike type Delordos fit because there too long for the space as the exhaust runs there. Good to learn from that site as one day I would love to own one. I also found where dearly departed Grant found some upgraded jetting specs after fetaling a couple of these.
 
CLEMTOG said:
I know that Andys Atlas has the twin choike car type Dellorrto (was I correct in that the rubbers are perished Andy?)
but James (longshanks) White Coopers bike may have the bike type Dellortto's
The car tyoe is an odd shpaed rubber inlet which adapts head to carb and allows for missalignement as well, the bike type is pretty much conventional

Tell us more about the aftermarket bits then Andy, and show a picture or two, many have this problem, including Per Erik in Norway
CLEM
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Yes Clem I think you may have been correct about sucking in air as when I started it up it wouldn’t idle below 3000 rpm. However, when I started to dismantle the old manifolds I did discover one Allen bolt missing from the right hand side which can’t of helped with sealing it to the head and there is signs of cracking on the inside of at least one manifold.
But annoyingly, having now fitted the replacement manifolds https://or600.webspace.rocks/index_e.html the bloody thing won’t start at all and I haven’t touched anything else. 🙁 And yes I do have spark.
 
Thank you for responses to date. I think I will be making the gaskets that I need, none too complex!

I removed the carb as part of a diagnosis fault finding process...
Shortly after I walked away from taking the past it's MoT photo, posing beside my MG Magnette, my neighbour advised me: "a bike has fallen over in front of you house, your's?"

Yes, doh. And I had not turned the petrol taps off. I picked the bike up, nice and light :0 Snapped brake lever, poo. Ride round to the garage and put to bed? Ah, non. Fluid locked???

Yes, fluid locked. Spun up on the starter no probs 24 hrs later, did run before changing the oil. Fired up no worries afterwards, tickler steady off choke straight away, clean running until a wall at about 5,200. I best guess was that being on it's side with a flooding carbs may have disturbed some shit in the carb. The bike has been basically unused since 2018.

Vince: This bike is ex Grant Duguid, he isn't quite "dearly departed" just yet! :)

Clem: Apparently the red Mk3 bikes (all 50 of them!" had twin Dell 'Orto carbs with the exhaust exiting to the RHS. Graham Rose has modified his Mk2 to the twin carb/RHS exhaust spec. He reports a big improvement in feeling. He plans to use it to explore South America a bit further.
 

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Departed sadly from here, not other sites. I hope the bloke doing South America does a blog, the prep and trip would be great. I hope we get more posts on these models.
 
BTW dirt bikes obviously fall over a lot, there was a mod available to my 350 Husky 4 stroke that came standard with a Delordo carb. The standard carb came with a float bowl that didn't have any overflow system. You could swop that bowl with one that did have an overflow so in that case any overflow drained out of the engine and not inside at a minimum flooding it and making starting HARD or Hydrolocking it. It worked much better, that's on bike type Delordoes, not Twin throat car Dels. I know nothing about them
 
Update:-

Following the advice of Andy J and consultation of the factory parts book it transpires that there should not be a gasket between the carb body flanges and the rubber inlet manifolds. I therefore carefully cleaned all traces of gaskets and silicone from the flange faces. Obviously I also completely stripped and cleaned the carb before re-installing, using a thin bead of flange sealant.

Atlas fired up straight away, nice steady tick-over AND revving cleanly all the way to the redline. Short test ride to check on the road. Yeah, problem fixed. Added bonus is noticeably cleaner running through the entire rev range, not entirely surprising considering the amount of shit that was found inside the carb. Happy bunny.

Now time for a beer :p
 
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Yes, it's posted here as well, I PMed JLO right away but under the proviso on crank repair in OZ and then I made some inquiries about crank work and sadly it's in the 2 hard basket for me. Seems crank parts are a rare commodity for the 500s. If the crank could be repaired it's a great opportunity to buy one at that price and ship it to OZ with plenty left to upgrade the suspension and add some protection, eg Barkbusters and soft pannier bracing. Not to mention that billet inlet. Did I see you and yours at a bike meet pic here the other day? How's it going now.
 
Owning one of these is a bit of a fantasy for me. I have only ridden one of these once, Yogi kindly let me ride his back at the last National Oz rally on Bruce's farm and I never got past 1st and 2nd gear. I didn't want to cross that river and risk drowning someone else's bike so I tootled around his front paddock. Now I couldn't help myself and thought that nice steep grassy hill heading up to the BBQ and house would be a fun test. So halfway up I start to think ripping up Bruce's nice lawn would not be a good idea so I turned hard right and headed to the vehicle track at 90 degrees. That's when I noticed IT. Along that track was a deeply grassed and disguised spoon drain approx a mitre across and who knows how deep. By more luck than good management, I somehow managed to Bunny Hope it unscathed. I put the bike back after that but I did enjoy the quick ride and it seemed very capable, who bunny hops bikes that big. I think I heard someone did lots of knee damage hitting that drain on an Electric bike a few years later. I was very lucky.
 
Vince said:
Yes, it's posted here as well, I PMed JLO right away but under the proviso on crank repair in OZ and then I made some inquiries about crank work and sadly it's in the 2 hard basket for me. Seems crank parts are a rare commodity for the 500s. If the crank could be repaired it's a great opportunity to buy one at that price and ship it to OZ with plenty left to upgrade the suspension and add some protection, eg Barkbusters and soft pannier bracing. Not to mention that billet inlet. Did I see you and yours at a bike meet pic here the other day? How's it going now.
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Parts availability better in Europe, could Piet at OCT or Van Dyck do the work on the crank?
 
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