BW Idle speed in park v idle speed in drive

[markmark2]

Hi all, is there any way that you can reduce the idle speed in park without reducing the idle speed in drive? Also should the carbs be balanced in drive or in park? Would the difference between the idle speeds affect the balance? and would the fuel mixture affect the balance?

Cheers Mark

[Lingen]

Mark.
Me again. Q1. No.
Q2. In park. Always have it in Park while the engine is running for everyone's safety.
Q3. The throttles openings first need to be balanced to be equally open, and then the mixture can be properly adjusted/balanced..
Mike.

[markmark2]

Thanks Mike for the reply, the reason for the question was that I met another stag owner with a BW65 and the park idle was almost the same as the drive idle. Cheers Mark

[sujitroy]

I have a bw35. when shifting into drive there is some load on the engine and the Revs drop by about 100 rpm.

[Rob Heath]

Hi Mark, I have a BW65, the idle speed is 1000rpm and the drive (but not moving) speed is about 600rpm, this is something I have been thinking of adjusting but haven’t got a round tuit yet. A member of the SOC very kindly gave me a set of Stromberg tools together with a manual and some spare parts so there’s no excuse really.

perhaps today’s the day.

Rob

[Lingen]

Mark.
Something you could try carefully.. Have the (warm) engine running in "Drive" with someone in the driver's seat with their foot on the brake pedal. Then adjust the idling speed down equally on each carburettor to around 600 rpm. When you then put it in Park, it will speed up, but that will probably be as slow as you can get it so it doesn't stall when you put it back in Drive.
Mike.

[marshman]

In my experience with my MK1 (before I sold it) with its BW35 box, the higher the idle rpm in Park the bigger the drop when you engaged Drive - and the bigger the clonk/thump! I adjusted the idle to around 550 rpm - mainly to reduce the "clonk" as you shifted into drive. When properly tuned (valve clearances, ignition timing, carb balance and mixture etc.) it idled smoothly at 550 rpm and there was only a very slight drop in rpm when you engaged drive, but not much. The higher the idle speed the bigger the drop in revs when drive was engaged. If the tick over was at 1000 rpm then there would be a very noticeable thump as drive was engaged and the revs would drop significantly.

[DJT]

In my experience with my MK1 (before I sold it) with its BW35 box, the higher the idle rpm in Park the bigger the drop when you engaged Drive - and the bigger the clonk/thump! I adjusted the idle to around 550 rpm - mainly to reduce the "clonk" as you shifted into drive. When properly tuned (valve clearances, ignition timing, carb balance and mixture etc.) it idled smoothly at 550 rpm and there was only a very slight drop in rpm when you engaged drive, but not much. The higher the idle speed the bigger the drop in revs when drive was engaged. If the tick over was at 1000 rpm then there would be a very noticeable thump as drive was engaged and the revs would drop significantly.

Pretty much the same as mine, but with a ZF. Ticks over smoothly at around 550rpm with only a small change when put into D.

[richardthestag]

all depends on the engine, worked on some that are as lumpy as anything at 600rpm and others smooth as you like.

Decent ignition and overall mechanical condition of the engine impacts greatly. brand new rebuilt engine will run tighter and may need a slightly higher idle speed. but you should be able to achieve less than 750rpm.

by the way do not necessarily rely on that dashboard rev counter, it is just indicating that the engine is running and not a lot more, accuracy of them can be pretty rubbish.

carbs in a **** state of tune and needing an overhaul etc will be almost impossible to set at a decent idle speed. with engine off open the throttle slightly and see if you can feel any play on the throttle shaft. if you can there is a good chance that the throttle shaft seals identify now as fine bone china. Plenty of posts from me about temp compensators and setting a decent baseline so I shouldn't need to do it again

A pair of service kits from burlen and a few hours of your time will have them behaving again.