Shaking down an old dog

Oct 5, 2008
I've been having fun working the bugs out of my old Dominator fitted with nearly everything Commando.
It feels much like the old Commando that the engine comes from with more vibration, I think more than an Atlas would have.
I had front brake problems but that seems sorted now, just frozen adjusters and glazed shoes.
I'm not quite done with the carbs yet as I think new slides are required. I have one here but the other is still in the mail.
It was shifting poorly so I added a mixture to the gearbox of 50% Royal Purple light multigrade tranny oil mixed with 20-60 Mobil 1 that has helped quite a bit. I think it had 80 or 90 wt and was low on that before.
The clutch required proper adjustment and now that is working well also.
I fitted a new tach cable today which cured that problem easily.
The exhaust to head gasket needs replacement and I'm waiting for a center stand spring but she gets better every day.
What a point and shoot old beast it is with very short gearing.
So what are you guys doing to yours?
This one got a new exhaust pipe, a new rocker oiling line, plugs, carb slides, and tomorrow I'll touch up the frame. I sanded it today.
Today I fitted a set of those Kehin type carbs that are available on the internet. A bit of a disappointment in quality, they appear to be a Chinese copy of a good Kehin model usually seen on dirtbikes. Good parts are chrome plated square slide and pretty good hardware but the work to adapt it for a British bike is a bit slap dash. Only one carb was copied so the center carb is going to be hard to adjust.
If I have time I'll plumb it tomorrow as I'd like to see how they do.
Last night I pulled the left carb off that was overflowing. While I was at it I switched the slide idle adjuster to the side I need, it was very easy as Greg said. It was bit cold in the garage so I just went as far as pulling the carb apart. I have interferance between the float and the overflow tube.
I may get a chance to look at this today but if not it will be after the Xmas trip.
I got time before my trip to check the disassembled carb. All I see obviously wrong is the binding on the overflow tube. After reassembly I bench checked it with the fuel tank, and since it does not leak I reinstalled the carb.
Perhaps on Friday if I get out of work early I can finish it up and test it.
I tested the bike today and I've gotten rid of my leak. It ran fine on the enrichment circuit but as it warmed the RPMs shot up after I shut off the cold circuit. This makes me think I have a vacuum leak somewhere.
Back to the drawing board tomorrow.
After making another test tank to replace the one the Norton shook to bits I got it going an idling around 1,ooo RPM on the jets it shipped with. It picks up quite nicely on throttle. After running about five minutes the right hand carb overflowed the bowl. This is the one I did not disassemble and it looks like I'll be taking a look at it tomorrow.
Thus far I'm not all that impressed with the quality on the assembly of these carbs but that may be par for the course these days.
I did confirm the other report that just enriching one carb may be enough to start the bike.
I was easily able to pull the bowl on the bike and this carb was set up better than the other. There was no interference from the overflow tube when pulling the bowl. The bowl drain design is also superior, taking about an 18mm wrench and being sealed with an O ring.
I found small particles in the fuel remaining in the bowl. I'm not surre if this came from my fuel or if it was contamination.
These carbs go to a machine shop and are cut for clearance and the intake and flange are modified. If they are not well handled during these operations or a chip gets in you will have small problems such as I've had. I doubt they are even dissembled when modified.
The bike now has a sweet idle and seems jetted close enough to run on this engine. Further testing is in order but first I think I should clean and seal the fuel tank and look at some kind of filter.
An automotive type filter often allows too little fuel into a gravity feed system, and can in effect change the jetting.
On my Chang I have two hot rod filters and a Harley petcock to move enough fuel for the Mikunis.
Anybody got any filter recommendations?
you seem to have a thread all to yourself !
have you sorted the Keihins yet ? As much as it goes without
saying that the Amal carburettor compared to those of today (or
even only 20 years old!) are not the most efficient fuel/air mixers - one
cant deny that life sure is alot easier when you can just bolt on an amal
using data for jetting available in most manuals.
i've tried mikunis on triumph and BSA twins with reasonable success , not on the triples however . I find that people often replace their amals because they no longer work right due to being worn out - and when replaced with ANYTHING at all - the new carb works SO MUCH better - but a new amal works SO MUCH better than an old one too. you seem to be working on somewhat of a special engine though ?
so you likely have an uphill climb trying to sort them out anyway right ?
i just purchased two new sets of amals for a 1970 triumph Bonny, and also 73 850 commando - the old ones were tired - and normally i would send them out for a resleeve which i find is superior to a new carburettor anyway - except in this case the triumph had none - and the norton's carbs had been rendered -very high maintenance - by the use of WOOD SCREWS in all the assembly points !!! the things people do to these old bikes. I mean - i could see if the bike had been operated for 30 years in Cuba where they have not parts - but in north america ??? it boggles the mind sometimes doesnt it ? keep us posted on those KEihins!!


I used Amals for quite a number of years and had little trouble with them, except for at first on the Commando I bought new. It had somehow been fitted with incorrect jets on one side and after the dealer had several tries at getting it to run right it took me several dissasemblies to find that. It had not occured to me that was a possibility.
The Kehins are running quite nicely at the moment but I seem to have rust in the tank and perhaps worse. After draining it last night I think I may see a failed coat of Creme in there.
I have a couple of sets of Amals around, 30 and 32s. I might get the 30s sleeved later on for proper looks.
Generally once I get later carbs sorted they tend to be better everday runners, and that's what I'm looking for at the moment.
Everybody has tried Mikunis so I thought that that trying these little Kehins
might be interesting.
So far this seems fairly easy as I think the jetting may be close enough for this bike. I need the weather to warm up enough for proper tuning and testing though.
I'm not really sure what is in this engine. It is a 72 block but has quite a lot of compression. I'm fairly sure it was not a Combat as the head does not appear shaved and the cam is not as lumpy as I remember.
The only problem with this installation has been that in the featherbed frame the clearance is less than on a Commando.
i had to make a longer and curved intake with my featherbed project in order to make amals work. interference with the top left frame tube.
there's no end to the fun is there ?
Since my engine is on a slant it could be worse. To get a decent flow I'm thinking of making up a special fitting for the petcock.
I have room for Amals or these carbs, I have a couple of 32 mm Mikunis that I think would be a squeeze in there though.
there is room for a pair of amals or mikunis -i'm not certain about the kehins though - in a wideline between the top fram rails - then you need to consider access for tuning etc. is your featherbed a wideline or slim line ?
It's a slimline I think, with a very unusual custom engine mounting set up. Some of the stuff is done so professionally I wonder if they started with a kit, I haven't gotten around to contacting the owner four folks back who may have done the conversion. You never know who may have had a machine shop though.
When I was a kid I used to take pride in making things look factory built, the builder of this bike may have too.
i've found over time that i've spent more in machine shops than equipment would have costed me- so i purchased a mill, a lathe and build alot of my own parts - i still deal with machine shops - but mainly to do things i cant at home - EDM , or more complex machining that requires multiple axis.
i find that the quality of my build has gone up considerably due to the ability to do more 'in house' . no need to drop insane $$ either - there are alot of excellent second hand machines available.
I'm envious. When I was a shop manager I had access to good equipment and I miss. it.
Here in suburbia I am so pressed for space that I have no real room for a good shop unless I cut down on bikes or perhaps sell my Roadster.
In a little while a friend is coming over who is helping me expand my garage.
I may be able to close the door on my bikes and add a drill press when I'm done.
HAHA - well there's not much to be envious about really ! although i dont live in suburbia - i do have a single car garage and i just make it work - sometimes it's a REAL pain in the brain figuring out the logisitics of moving around in there though , i've got one bike on the lift, and 5 on the floor - when i need to do some machining, or welding - anything other than bike assembly - i need to move things around to make it possible - and even then it's alot of side stepping and dancing to reach the benches on each side of the room ! of course prior to the snow i was able to move some out doors - but now the 4' of snow in front of the doors make that impossible. I'm not complaining though , things could be alot worst ! good luck with the garage extension !
cheers, marc
It's all just work after all. I have bikes in both halves of the garage now, together with table saws and construction bits. Today we pulled the entire front sheathing off and replaced uprights with termite damage. I have a bunch of rot in one corner that will need new 2X6s.
I'd like to get an hour or two on the Norton this weekend so I feel like I'm making progress. I have the tank off and I'll run two types of acid through it and seal it.
This was helped by the fact that the train I had planned to work on Saturday did not move to the Port of Redwood City because of a yard incident. This gives me a bit more good weather time for myself.
My new coils came yesterday, I've got a bit of a bug but this afternoon I'd like to get a chance to start the testing and mounting.
Cookie, Regarding your comment about vibration, if you are using a Commando engine it will have a different crankshaft balance factor to a 750 Atlas that came out of a Featherbed frame. The Commandos were balanced at 52% dry whereas the Atlas was at 84%, according to the 'Paul Dunstall Norton tuning' notes. The lower balance factor on the Commando was to accomodate the isolastic mounting and move the vibes to a less noticeable point in the rev range. The Atlas being rigidly mounted did not have this option.