Wanted - Tuning Advicefor Touring Use

Hello All,

I would like to try and pool your collective knowledge for some work I want to carry out on my Commando.
I know that many of you out there will have tried things that are either brilliant or don't work well, so I thought I would ask for some tips before I start work.

My bike is used mainly for touring work and I am looking at ways of possibly increasing its 'grunt', it usually carries two people and masses of camping gear and I do find it struggles at times on long motorway journeys or on long climbs either in Britain or away in the Alps, etc.

I have a 1974 Mk2a Interstate :

Fitted with

Single 34 mm Amal Mk2 Carb
K & N Air Filter
Peashooter Silencers
RGM Belt Drive
+ 20 overbore cylinder
Crack tested and shot peened con rods

Everything else in the motor is stock, i am considering a rebuild sometime over the next year and wonder if people could suggest the way to go with it ? Should I stay with a standard cam ? stay at standard capacity ?, big valves ?, etc, etc.
Which way to go with carbs ?, for long distance use and ease of riding.

The main thing is that it MUST remain reliable and must be usable power for real road use. Out and out speed is not an issue, but I would like a bit more go when fully loaded.

What are peoples views ?, should I just stay standard or are there modifications that I would really benefit from ?

Hope you can advise

Keihin 35mm FCR flatslide carbs are great for power, easy starting, and stone reliable.

They're also bloody expensive.

When I did long distance stuff on my old Commando I added more oil with the frame as a bag, a large custom oil tank, and lowered the compression.
For cross country use in the US Commandos chew up oil and the small fin area means the only way to get more cooling and longer oil life is to add more. I also ran the biggest battery I could fit and Ford coils, but that stuff has been far surpassed by modern ignitions and plastic batteries.

You didn't mention what speed you like to cruise at or what gearing you are currently using. But if 2 up and loaded with camping gear you may not want to go larger than a 20T sprocket on the front. If you are running a gear larger than that, going down to a 20 would give you some more grunt and still let you cruise comfortably around 70mph.

Shaggy,
Usually the standard set up is more than adequate for touring and should allow 70 to 80mph cruising. The RGM belt will gear the bike up perhaps a little too much. As trinorman says anything above a 20 tooth sprocket could turn 4th into an overdrive and 1st into 2nd.

Cash

trinorman said:

You didn't mention what speed you like to cruise at or what gearing you are currently using. But if 2 up and loaded with camping gear you may not want to go larger than a 20T sprocket on the front. If you are running a gear larger than that, going down to a 20 would give you some more grunt and still let you cruise comfortably around 70mph.

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Hi,

I like to cruise around 70 -75mph, with 90mph on hand to pass big trucks etc, currently running a 21 T sprocket on the front.
The RGM belt conversion is around 15 years old and even Roger ( RGM )says he made so many different ones in the early days that he is not sure how it effects the gearing on mine !

At the moment, the feeling I get is to stay with the standard motor set up and possibly look at going back to twin carbs ???,

if you have a chance to look in the primary note the tooth count on both pulley's and let us know what you have. from that info it will be easy to find you a good finial drive ratio. it you indeed intend to tour the single carb works better in low and mid range. I would stay with it.

I'd be another vote for the Mikuni. My most simple and reliable bikes have had Mikunis. Once they are dialed in I've been able to forget them. I don't know what everybody else's experience with Amals has been, but as they wear I've had to keep adjusting them. This gets annoying in the middle of a 3,000 mile trip.
I also used to switch my front sprocket as the other guys mentioned. For two up and around town I used my short one. On the highway I was one up and only carrying a bag and sleeping bag, so the higher ratio carried me to California.

If you're taking the engine down, it might be worth trying a PW3 cam.....LOADS of torque, but still a flexible motor.....a lot more friendly than 4S etc. Give Mick Hemmings a call!

Not to change the power subject but what is the seat that you use. It looks interesting. Could you post a photo that better shows the seat?

Sweet looking bike. Neat front brake.

Jean

Yellow_Cad said:

Not to change the power subject but what is the seat that you use. It looks interesting. Could you post a photo that better shows the seat?

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It was a standard Interstate Seat that I had cut down at a small motorcycle seat company Nr Bradford U.K.. He just cut it down, as I asked, and covered it with a fabric I chose from his selection ( £50 ).

Seeley920 said:

If you're taking the engine down, it might be worth trying a PW3 cam.....LOADS of torque, but still a flexible motor.....a lot more friendly than 4S etc. Give Mick Hemmings a call!

Click to expand...

Thanks for that, I will be taking the motor down, so if a PW3 is worth a look I will follow it up. I was just a bit concerned that fitting a decent cam with a single 34mm carb may be a waste.
I'm trying to come up with an overall build plan now, so that I can start buying bits in over the next few months.