Atlas Questions

I was having a think last night, very dangerous from experience. The airbox is pretty clever, there is a huge still air section between the filter and the carb BUT it breathes through a rubber snorkel that comes out of the top of the airbox and does a 90 deg bend and points rearward to stop deep water getting in. But it looks very restrictive to airflow for a 4-valve 600cc engine with a very big carby, it's a tiny hole compared to the usual 600cc single I have seen. Back in the day, it was a common mod to add speed holes to Husky and just about every other bike's airbox to aid breathing. It looks like you could drill another hole and add another snorkel pretty easily. I wonder what effect that would have on the often talked about flat spot and jetting issues these bikes apparently have with that huge dual-throat Delordo. Might try it after riding the bike for a while and see how it goes. I think Malcome's mark 3 style new exhaust might breathe better as well. What do you reckon Piet?
 
An easy test is to try riding without the airbox door and see how it goes. But first I need to refit the exhaust and put it back together and maybe even start it.
 
Got another question. I just measured the dia of the fork tubes at 41.58mm. The parts manual called them Forceella Marzocchi 41mm forks, I have also seen some forks described as 42mm forks on various European bikes over the years. I am looking at buying a set of SKF seals, they have a kit for 41mm forks but nothing for 42mm forks. Does anyone have any thoughts about these very close sizes and if there in reality the same fork? These seal kits are expensive and I don't want to get it wrong.
 
The pic above is about those 2 holes at each end of the tool bag on both sides of the bike, I think there should be either lifting handles or soft pannier hold-out bars that bolt on there. Don't know and cannot tell from the parts book..
 
I found the pic on the Atlas register that shows those missing bars, Not quite the same position though. I tried joining the Registery tonight, been a lurker for years, zero activity there but I expect the Admin will know some stuff, but I expect I need the nod from Admin to post.
 
Did a pleasant 3-hour round trip up The Old Road To Gosford to get made a Foam air filter from Unifuilter and Pies for lunch from Pie in the Sky, their Lamb honey and Rosemary Pies are VERY good.
 
I just got the exhaust off, what a wrestle. It has a muffler bracket and mounts to the engine mount bolt plus its pretty snake like BUT the biggest pain in the arse is the header pipes go into the head maybe 30 or 40mm, I didn't measure it but it's by far the deepest exhaust pipe insertion I have ever seen. And to top it off the finned clamps are as tight as a fish's arsehole on the studs, they just don't go on without crazy extreme wiggling. No wonder you struggled Andy, that desperately needs drilling out to get at least a millimetre of clearance on the studs. I tried chasing one of the studs with a brass nut, it went on easily but getting it off pulls the stud as well, there is enough unthreaded stud behind the nut to get some needle nose vice grips on the stud so I need to buy a set tomorrow. Yes, I know butchery but what are you gonna do. So as Andy suggested it needs the correct sequence of assembly to get a good fit so first it needs the headers as deep as possible but still loose and I will go from there.
 
Vince,

The deep insertion of the headers is an attempt to lower the head temperatur by removing combustion gases as quickly as possible with the least possible amount of contact to the head casting.

The OR cylinder head is just as susceptible to warping as the 500 before and the 650/668 after it... a problem befalling all air-cooled 4-valvers.

piet
 
I wasn't going to mention it but there is a section of the left exhaust port missing, it's right at the outside end and is about half the size of your little fingernail and at the bottom of the port. Well outside the sealing area so I am not that fussed. The new exhaust is pretty stout but it's well on the heavy side of the scale. But at least it exists so thanks to that supplier.
 
Vince said:
I wasn't going to mention it but there is a section of the left exhaust port missing, it's right at the outside end and is about half the size of your little fingernail and at the bottom of the port. Well outside the sealing area so I am not that fussed. The new exhaust is pretty stout but it's well on the heavy side of the scale. But at least it exists so thanks to that supplier.
Click to expand...
That's habitual. Castings not very uniform around there.
Paul
 
Vince said:
I wasn't going to mention it but there is a section of the left exhaust port missing, it's right at the outside end and is about half the size of your little fingernail and at the bottom of the port. Well outside the sealing area so I am not that fussed. The new exhaust is pretty stout but it's well on the heavy side of the scale. But at least it exists so thanks to that supplier.
Click to expand...
NOS headers available, off the shelf... ;)

piet
 
I'll have to check Andy.

If I'm not completely mistaken, they are the same for both, they both exit left right. The cross-over is deleted on the later bikes, just a straight collector to the silencer.

piet
 
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Thanks Piet. I did try offering up my old headers on my 'old' Atlas to see if they would work down the opposite side and it looked to me that one of the pipes, I forget which one, would need bending/straightening a bit to get to fit a collector.
 
Hallo Vince,
Diese Soziushalter gehören dorthin.
Grüße
Markus
 

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Thanks for posting the pics, just the bits I am missing. I did a translation and it appears their hand holds for pillions.
 
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