- Thread starter swannieg
- Start date
paulandpat
Enthusiast
- Messages
- 320
- Location
- Percy, Normandie
We had an 850 for a short while, and to me it seemed happiest at around 90 kph, any faster and it all got a bit frantic, whereas the 1108 will cruise happily at 100 - 110.
Quite prepared to be corrected of course!
Quite prepared to be corrected of course!
Cruising speed of an 845cc R4 depends on when it was built : the older ones with Zenith 281 carbs will cruise happily at 55mph (85 kph) but not much more, pressing the throttle further simply uses more fuel and cokes the plugs. This was my experience when driving 1970s R4s. The later 845cc R4s have a more sophisticated carb (Solex) and my current machine (1984) will, once warmed up, do a steady 60 (95 kph) with occasional bursts up to 65 - 70 (115 kph).
I wouldn't advise trying to get an R4 to do 70 for sustained periods. The 845cc cooling system isn't great and this could lead to overheating/head gasket problems. Having said that, my personal speed records are . . . 80 (125 kph) (off the clock) downhill in a 70s R4, 87 (138 kph) (same location) in a 1982 R4 GTL 1108cc, 845cc 1976 R4 long trip average 58 mph (95 kph) (as I pelted 75 miles to the intensive care unit after my father had suffered a cardiac arrest).
I wouldn't advise trying to get an R4 to do 70 for sustained periods. The 845cc cooling system isn't great and this could lead to overheating/head gasket problems. Having said that, my personal speed records are . . . 80 (125 kph) (off the clock) downhill in a 70s R4, 87 (138 kph) (same location) in a 1982 R4 GTL 1108cc, 845cc 1976 R4 long trip average 58 mph (95 kph) (as I pelted 75 miles to the intensive care unit after my father had suffered a cardiac arrest).
cruising
With an R4 I find that your ears are the best judge. Sustained high speeds can be quite painful! Despite the frivolity, you can tell by the engine sound/performance/economy*.
Easy way, wind it out to what your car will do flat out, then lighten the throttle until the car feels "sweet". This will probably be 1/2 inch (12mm) off the floor. Possibly twice as much as there are a few variables at play.
* assuming that all is well-ie timed/tuned
David
PS - I would not have thought that cooling would be an issue. Constant fan, small heat output from a small engine. I think an investigation of the cooling system could be in order.
With an R4 I find that your ears are the best judge. Sustained high speeds can be quite painful! Despite the frivolity, you can tell by the engine sound/performance/economy*.
Easy way, wind it out to what your car will do flat out, then lighten the throttle until the car feels "sweet". This will probably be 1/2 inch (12mm) off the floor. Possibly twice as much as there are a few variables at play.
* assuming that all is well-ie timed/tuned
David
PS - I would not have thought that cooling would be an issue. Constant fan, small heat output from a small engine. I think an investigation of the cooling system could be in order.
Last edited:
Richard Williams
Enthusiast
- Messages
- 113
I would add weight to the opinions already voiced. Comfortable cruising speed is 55mph.
60/65 achievable depending on road conditions. Laden will be unable to maintain 55, and will drop to 50mph on motorways with long inclines.
60/65 achievable depending on road conditions. Laden will be unable to maintain 55, and will drop to 50mph on motorways with long inclines.