Sunday, June 24, 2007

Another job bites the dust.

Sorted my throttle linkage...Which actually turned into a nightmare!

I had never bothered to look at it, bar fitting the levers to the carbs..

Anyway the spacing of the manifold is for throttle bodies really, with underslung linkage or single cable, so you cannot use a Magard or top linkage kit...Good job cause I sold mine :) Anyway thats £50-60 saved.

As such I came to a better solution, both more simple and lighter!

Carbs are at the "perfect" 5degrees of inclination as recommended by the factory.
I happened to have some DHLA40 N Alfa Romeo cable carrier lever arms...

This enables a cable to be run directly from the spindle via a V groove on the main lever. You can see the spacing is VERY tight, as such, a rod-end linkage arm will foul the balance screw on the left carb in any location at full throttle, bar if the linkage is underneath. After noting this gave up on the standard twin cable top linkage idea and started rooting through piles of carb bits for other parts...Lucky have tonnes of levers and linkage stuff.
Levers need a couple of small shaves when the carbs are removed.

I made a tiny cut washer which slips over the cable to sit between the lever and the lead ball on the end of the cable as the able is not Alfa Romeo so the ball isn't a perfect fit on the lever hole -to spread the load on the lead a bit better. (not shown)

Had to cut the middle brace from the manifold, but I cannot see it doing too much, the manifold walls are a bit thin, but should hold, the manifold is useless really...but its perfect in port and shape after MASSIVE porting and modification.

I also found yet another problem with the manifold...Its JUNK really...I have invested so much time in it! The flange pattern holes for the carbs are not correctly placed or drilled, the one carb is angled up left to right and the one is correct/flat. The maker couldn't even drill the stud holes in the right place! I noticed the central alignment axis of the spindles was not flat, the nuts on the end of the shafts in the centre were not level..The rear carb was up a little, compared to the front one- which is correct...This is VITAL that they are level...

When you link two carbs on a lever system like the images with a tab and pinch screw, the spindle shafts must be PERFECTLY aligned in the centre, or better still level through both carbs and aligned in the middle...With one "off angle" the levers swipe slightly when the throttle is opened, to exactly the ratio of difference in spindle axis's...As bolted on there was a 1.5mm mismatch between the axis of the spindles..This means a 1.5mm swipe.

The balance screw on the front carb swipes across the tab it sits on -on the rear carbs lever. This means every time you press the throttle the end of the balance screw rubs across the tab 1.5mm, so it wears, so the carbs go out balance ALL the time...No good for me!

I was pissed off to see this and after checking the stud pattern with a straight edge and measuring the distances I was seeing it was a physical pattern difference or mismatch - which was probably impossible to sort, bar welding up the manifold and redrilling the stud pattern...

Anyway, lucky I am using wide carb mount plates (o-rings) from a Lotus Esprit, this means I could tweak all the manifold studs up on the one side and down on the other, after about 1hr pissing around with about 10 fitments and removals I managed to get the spindle axis perfect with no swipe...

I see loads of twin carb manifold fitments that are not aligned, but usually when there are two manifolds and people are just too silly to align them correctly, missing the small details that make and break the carbs, they then moan about balance problems, uneven idle as the levers are rubbing and locking/sticking etc.

I have never seen a manifold with such badly drilled holes! Anyway it was lucky the spacers are wide, cause I could tweak the studs and repair the problem as the carbs are not sat right on the manifold face where you could tweak the studs and it would make no difference, the further from the manifold the greater the effect of tweaking studs. Just had enough gap to get enough tweak and get it aligned.

It now runs a single cable, which could break, hense I like twin cables best, but can carry a space -the throttle pedal is perfectly weighted, not light or heavy, super smooth, travel is the same as the Magard linkage, feel is the same and its more simple.

I need to adjust the top bracket, I happened to find this in a heap of junk, its from a linkage for Dellortos on a BMW 2002, it just happened to fit :) I will remake it as it flexes a bit but its a good template!

Could it be anymore simple? :) NO! Nothing sat on top of the carbs, minimal, effective. Happy, yes.
Trick to using a single cable no extra return springs is to use special return springs on the carbs, these are from Harley Davidson conversion kits?! I happened to have a pair, they are stiffer than normal, fatter coils and shorter with more initial pull, the return is every bit as good as the Magard linkage...It feels no different...It did take me all afternoon to do it though!

Carbs are actually Turbo models, hense the epoxy you can see glued over the lead plugs to stop them blowing out at 25psi of boost? :)

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