Bike Carbs on S4
Posted: Thu Mar 19, 2020 9:48 pm
Purchased a set of Keihin CVK type C - year 99 carbs with centre pull throttle and TPS.
From Ebay for £125. Nice condition. Stripped, cleaned and fitted new float valve assembly's. Also changed "O" rings on the fuel input Tee's.
Bought adjustable needles to replace fixed needles for rolling road session. I believe that small washers can be fitted under the head of the standard ones if richness is required. The adjustable set is only £16.00. The float valves and brass part about £40.
Removed coolant circuit pipes (prevents icing on bikes), like the issues with Strombergs also being CD. Apparently no issues when used on car duty.
Bought Danst Engineering alloy manifold bespoke for the engine. Really nice job. About £220.00 This includes fuel resistant hoses and stainless clips.
New gasket £15.
I cut about 8mm off the inlet manifold stubs and about the same off the hoses to move the carbs closer to the head and give more clearance for the Pipercross cold airbox.
Initially the side of the airbox was fouling on the U part of the bonnet receiver.
In the end I cut into the side of the airbox, opened it and kicked it in. See photo of cut and alloy brackets and rivets.
Bought cold airbox kit from Danst with their spun alloy velocity stacks, back plate and alloy spacer to mount stacks on. About £330. Also has intergral filter and large input hose to route into the nose.
These stacks replace the bike plastic ones and move the back plate nearer to the head.
Bike carbs have a circular cable pull with two cables nipples spaces and slots. One to open the butterflies and one to pull shut. Very safe and positive.
I tried one pull cable first but on the first test run the engine was not shutting down quickly enough when changing gears.
Dan who owns Danst is really helpful and easy to talk to. It was his confidence and friendly supply of information that encouraged me to do this.
The car started straight away and settled into a tickover. This was with throttle plates set on the bench by rack of the eye. Idle screws set at 2.5. Unchanged main jets and idle jets. Start point only. 40 mm carb size with 155 main jets.
I had Danst fit a vac port at the rear of the manifold plus 4 bottom ports for the Carbtune. Since the air box limits some clearance underneath, I have added 4 rubber pipes and made a little brass fitting with 4 input hose tails and 4 blanks. Sits near the cam cover. The blanks are removed and the normal Carbtune hose tails are screwed in to allow easy connection and balance.
I had a problem with a bug when writing this and lost a lot. Even with copy and paste. Seems you can't write too much at once. So bit at a time.
The bike carbs have butterfly adjustment between 1 and 2 and also 3 and 4. Then middle adjustment between (1 & 2) and (3 & 4). Therefore with the adaptor ports the Carbtune dialed in within seconds.
Nodiz
I changed out an obsolete (unsupported) ECU from Dunnell as nobody could get into program or record any settings, if it failed. An updated unit was very expensive when you consider it is only doing spark advance. Hence the Nodiz at £299.
I had no problems with this apart from voltage drop on the car. Will discuss later.
The Nodiz comes bespoke for the Zetec with coil pack lead and plug, speed pick up lead and plug. The TPS wiring is there but a plug is required for your particular carbs.
Dan gave me a second hand one.
I bought more pins and populated the plug with a few more features.
I picked up the coolant temperature and also gave outputs to run the tacho and the cooling fan.
I normally have a separate earth conductor run out on previous cars, but had not done it on this one as it has always spun over well even with a 2 litre motor. On this one I have good engine straps and also well earthed chassis in the boot. However, the Nodiz would only spark with the plugs out. The loading under compression was the straw that broke the camels back in terms of voltage drop. To crush a walnut with a sledge hammer I ran out two power conductors. A neg direct to the engine and a pos to the front starter terminal. Pre egngaged ! About 35mm conductors as I recall.
I also ran out two 4 mm conductor direct from the battery to the Nodiz with a relay fired by the ignition supply. After this it never failed and the engine spins even faster.
The Nodiz has two flashing LED's that show the coil pack signals. This is helpful as these went out under cranking with the volt drop problems.
Anyway, besides this problem i have not even plugged into the Nodiz yet to program the fan output parameters. It runs on the base map. Saying that, I have been more busy sorting out the choke and throttle cables.
A bike only has limited throttle movement. Also the mech is feather light under the foot. To correct this I have moved the clevis pick up towards the pivot to magnify the pedal travel. This worked fine but upon test driving the return was slugish causing the revs to linger and give poor gear changes. With bikes having two cables, one to pull throttle on and one to pull it off, i decided to add a return cable with an adjustable spring anchor. I made up a mechanism and cable. This works well on the test drives.
So now I need to get the bonnet on and do some runs taking into account that the mixture is not set correctly.
It does however run very nicely and revs through.
Will report back when i have checked the plug colours and ran further.