Atlas based Domiracer.

We all know that racing has completely different needs than riding bikes on the road, unless of course your local track includes clueless dimwits driving around the race circuit, grannies crossing at the chicane, loose deer on the banking, and a few blind driveways scattered around. Big brakes and slightly bigger tires for me and my road bike, thanks.
 
Yep, on my road '68 Commando I got fed up with the poor front brake and it now has Marzocchi forks, and Brembo/Grimeca twindisc brakes & wheel from the Rotary Classic. Also a Kokusan 220W alternator from the aircooled rotaries. (Benefits of working at Norton)
 
When your bike is neutral handling, you are more limited in how fast you can corner, because you are usually up on the high line with more lean, and feeling your way around. With more trail, you do not understeer. So you do not need to counter steer to get the bike to lean in the direction you want to go. With my Seeley, I just flick it into a corner and as soon as I am in, gas it hard. Which ever way it is leaning when it is gassed, that is the direction in which it will steer itself. The whole operation is mindless, as long as I brake before entering the corner. In right hand corners, I ride up the right hand side of the track while others a high on the left at greater angles of lean.
If you rode my bike, you would not suspect it could handle like that. I used to ride in the same way as a neutral handing bike. But I began to suspect it self steered in the correct direction, when I gassed it early in corners.
With most bikes, when the rear squats they self-steer. we just do not ride them that way.
The last time I raced was the first time I used the bike properly. The difference was ridiculous. I blasted past the three leaders in a corner, as though they had stopped.
 
A quick update on the Atlas Domiracer.
Went out for a short test ride this afternoon & first impressions are very favourable. The bike goes really well up to the 4,000 rpm I was using, seems very smooth, & has more torque low down than I expected. I decided to use the stage 1 Maney head, but machined up a pair of port reducing sleeves to take it from 34mm to 30mm. This is combined with 30mm Mk 2 Concentrics. I may in the future open this set up out to 32mm, but I'm happy for now.
Watch this space as they say, who ever they are.
 
Matchless said:
A quick update on the Atlas Domiracer.
Went out for a short test ride this afternoon & first impressions are very favourable. The bike goes really well up to the 4,000 rpm I was using, seems very smooth, & has more torque low down than I expected. I decided to use the stage 1 Maney head, but machined up a pair of port reducing sleeves to take it from 34mm to 30mm. This is combined with 30mm Mk 2 Concentrics. I may in the future open this set up out to 32mm, but I'm happy for now.
Watch this space as they say, who ever they are.
Click to expand...
Sounds good… but what we really wanna know is what’s it like between 4,000 and 6.000 ??
 
I can now report that it goes rather well between 4,000 & 6,000 rpm. It's also smooth enough, so I guess all the talk about Atlas vibes being unbearable must be down to poor factory balancing. It also very loud & sounds wonderful.
In case this helps anyone, after a bit of trial & error the 30mm MK2s are jetted as follows:
230 Main jets
106 Needle jets
2A1 Needles 2nd clip from leanest
3 1/2 Slides
25 Pilot jets
30 Cold start jets
3.5 Air jets.
 
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Matchless said:
I can now report that it goes rather well between 4,000 & 6,000 rpm. It's also smooth enough, so I guess all the talk about Atlas vibes being unbearable must be down to poor factory balancing. /QUOTE]
⁰

I can second that!!
Your jetting and carb configuration is nearly the same as in my Monoblocs, except my mains are 220.

Slick
Click to expand...
 
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Matchless said:
I can now report that it goes rather well between 4,000 & 6,000 rpm. It's also smooth enough, so I guess all the talk about Atlas vibes being unbearable must be down to poor factory balancing. It also very loud & sounds wonderful.
In case this helps anyone, after a bit of trial & error the 30mm MK2s are jetted as follows:
230 Main jets
106 Needle jets
2A1 Needles 2nd clip from leanest
3 1/2 Slides
25 Pilot jets
30 Cold start jets
3.5 Air jets.
Click to expand...
Ride it for 3 hours nonstop on a boring wide smooth Hwy over here in the states and you might get a feel for what the vibration talk is about assuming you can still feel your hands. ha

My solid mount Norton engine vibrates noticeable at idle, and not so much on the throttle. However, there is high frequency vibration at 70mph droning cruise in the bars and grips that makes my fingers go sort of numb toward the end of a day of riding. I can't feel any vibration in the twisties, cuz. I'm too busy enjoying the ride.

When I say noticeable vibration at idle, I'm talking compared to a modern engine. Like you say it is smooth enough.
 
My 850 crank has a steel plug filling the hole in the counterweight, so it is probably similar to an Atlas crank. When the motor idles, the bike moves backwards and forwards. As soon as I start to ride the bike, it smooths out, and at 7000 RPM, it tries to over-rev. It runs dead smooth past 5000 RPM, and that is usually as low as I go. My bike runs absurdly high overall gearing with close ratio. With the Manx type gear cluster, first gear was high, so in tight corners - the bike was really moving. I used to race a bike which as ten times worse, so it is not a problem. The 850 motor gives loads of torque. You always have enough go to get out of a corner, if you go in too hot.
I do not know what it would be like to race with a Commando frame.
 
acotrel said:
I do not know what it would be like to race with a Commando frame.
Click to expand...
Well… rather like a Commando…!

Can you tell us more about your gearing ie is the primary ratio standard? And what gearbox and rear wheel sprocket sizes are you running?
 
Matchless said:
A quick update on the Atlas Domiracer.
Went out for a short test ride this afternoon & first impressions are very favourable. The bike goes really well up to the 4,000 rpm I was using, seems very smooth, & has more torque low down than I expected. I decided to use the stage 1 Maney head, but machined up a pair of port reducing sleeves to take it from 34mm to 30mm. This is combined with 30mm Mk 2 Concentrics. I may in the future open this set up out to 32mm, but I'm happy for now.
Watch this space as they say, who ever they are.
Click to expand...
Late to this party but very sexy! Any chance you snapped pics of inlet sleeves? I'm toying with that idea for the A65 at the moment... did you stamp out the primary cover yourself?

Nice work!
 
Schwany said:
Ride it for 3 hours nonstop on a boring wide smooth Hwy over here in the states and you might get a feel for what the vibration talk is about assuming you can still feel your hands. ha

My solid mount Norton engine vibrates noticeable at idle, and not so much on the throttle. However, there is high frequency vibration at 70mph droning cruise in the bars and grips that makes my fingers go sort of numb toward the end of a day of riding. I can't feel any vibration in the twisties, cuz. I'm too busy enjoying the ride.

When I say noticeable vibration at idle, I'm talking compared to a modern engine. Like you say it is smooth enough.
Click to expand...
What I done to my solid mount 850 in the Featherbed frame balanced my crank but at highway cruise (around 70 and above) the handle bars did have that effect but what I done to stop the tingling in the hands was to replace the handle bars with a set of Renthal alloy bars, steel bars only have 1.6mm wall, the alloy bars have 6.5mm walls, now I can ride all day without any problems to my hands, was a cheap fix to that high frequency vibration in the handle bars.
 
As well the 750 Atlas was noted for higher vibrations compared to the 650 Domie motors, the 650 were a smoother motor.
 
acadian said:
Late to this party but very sexy! Any chance you snapped pics of inlet sleeves? I'm toying with that idea for the A65 at the moment... did you stamp out the primary cover yourself?

Nice work!
Click to expand...
Unfortunately I didn't take any photos of the sleeves, but they are just simple tubes turned from HE30 (6082) into which I milled a vee shaped groove to clear the valve guide boss. It helped that the ports had been CNC milled by Steve, & as such were perfectly round. The sleeves are a light push fit & reach just down to the start of the guides.
As for the primary guard, I made the components & had Nigel at NRP weld it all together at the same time he was making the exhaust system. I've since swopped my DC TIG set for a AC/DC set. Just need to practice my ally welding now.
 
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ashman said:
What I done to my solid mount 850 in the Featherbed frame balanced my crank but at highway cruise (around 70 and above) the handle bars did have that effect but what I done to stop the tingling in the hands was to replace the handle bars with a set of Renthal alloy bars, steel bars only have 1.6mm wall, the alloy bars have 6.5mm walls, now I can ride all day without any problems to my hands, was a cheap fix to that high frequency vibration in the handle bars.
Click to expand...
I have not tried Renthal bars on the Norton. I have thought about it many times though. I'm sure they are better than what I am using. My bars have 2.5mm walls, are one of the Triumph bends cut 2" shorter on both ends and filled with clear silicon sealer. Sort of like a do it yourself Bar Snake if you remember those. I've looked at Renthal bars online a few times, but not seen a bend I like. I did have Renthal bars on all the off road bikes I've owned, but engine vibration wasn't something I was thinking about riding off road. I wasn't thinking about the bar bend either.

When is the last time you rode your Norton all day with that comfortable Thruxton sitting in the garage?

I have not done an all day ride on my Norton in at least a year. Hope to change that next year and get in maybe 2 or 3 good rides.

Good luck with getting the Manx on the road.
 
I have to agree regarding Renthal bars. I have them on three of my bikes, the 758 pattern which I find very comfortable. I never really thought about their vibration damping qualities though.
 
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