loss of power

[davidewanprice]

Hi there, new question, I’m just getting used to my Matra Murena and am finding a few problems both when the car is cold and when the car is at higher revs.

When i start ( it virtually always starts first time) the car i always use the choke and allow the car to warm, then I’ll ease the choke off and try to set off, often I experience to total loss of power and a stall accompanied with a few coughs and splutters. Am i being too ambitious and not leaving the car long enough to warm up?

Secondly, if your on the motorway and doing 115kph and decide to speed up and overtake a car when the car hits 145/150kph the car seems to peak, judder, plato, regardless of revs given, anyone else experience this? It’s a Murena 2.2 with Webbers, maybe it just needs a good tune but i read on a page in this forum that a loss of power in the higher rev band could be down to a failing distributor cap/leads.

Any advice would be great

[Anders Dinsen]

I just edited my post... looks like I was tired or confused when I wrote it.

The Weber DCOE's are not standard on the Murena, and have plenty of adjustment capabilities - it could be correct, but it sounds like it's slightly incorrect.

Even though it's expensive, the best thing would be to have a carburettor specialist check them on a rolling road.

On the other hand, if this is only occurring when you are running on the choke, I wouldn't worry too much. The thing is that when the choke is closed and you open the throttle wide with engine running relatively high RPM, you will end up with a very rich mixture - and this may limit performance greatly.

On the other hand, if you feel it is wrong, it may well be, and my own experience with my single Solex 34CIC (on a Holbay cam) is that cold starting has improved significantly after I have renewed gaskets and seals in it.

Do you know who did the Weber conversion?

- Anders

[davidewanprice]

No im not sure who did it, the car was my fathers and its been past on, I remember him having the carbs looked at, i seem to recall him saying some of the parts within it were totally wrong and he had them changed. I think at some point in the near future I’ll take it and have it looked at by a pro, ive no idea where as yet (south Yorkshire area). I think it’s exaggerated by the fact that the throttle cable also feels sticky. All these little things mean I’m struggling to get comfy driving it and just enjoying it.

[Anders Dinsen]

All these little things mean I’m struggling to get comfy driving it and just enjoying it.

I recognise that feeling, David. It takes some time, and even though I've been using my Murena for more than 6 months now, I still feel that my comfort driving it is growing. But then sometimes it surprises me - like the day when we had a lot of snow here, and I finally got it digged out of the driveway to find that it handled much better than I had expected.

The stickyness of the throttle is mostly due to the way the lever is connected to the pedal. While it wont fix the problem entirely, you can try putting some grease between the lever and the pedal. I also found my throttle pedal very sticky and found a lever on the side of my carburettor that was sticking (accelerator pump lever) - I think the DCOE's don't have this kind of thing (and should themselves be very free?), but you may want to check if anything is incorrect back there. The cable could also be worn.

You may already be a member of the english club, but if not I can suggest you become. I'm in Denmark, but I know a few of them and they are nice and helpful people - a meeting with them and their advice may be just what you need.

Cheers,
Anders

[davidewanprice]

Im filling the form out as we speak, money well spent i think. Yes its an odd pedal, i also have 1cm+ of slack cable before any pedal movementt actually moves the carb. I was thinking of replacing all the old inner cable, i work in a bike shop and can get outer cable very cheap, im sure it will be better than what was originally used. has anyone else tried this?

[Anders Dinsen]

Im filling the form out as we speak, money well spent i think. Yes its an odd pedal, i also have 1cm+ of slack cable before any pedal movementt actually moves the carb. I was thinking of replacing all the old inner cable, i work in a bike shop and can get outer cable very cheap, im sure it will be better than what was originally used. has anyone else tried this?

The slack can be removed by tightening the cable on the carburettors, but you may find that it is a good thing to have as it allows you to lean your foot against the pedal without actually affecting the throttle. Further, with the pedal in all vertical position, some feel that its too vertical - adding a bit of slack angles it better.

Replacing the cable certainly won't harm. You may want to do the choke cable at the same time.

- Anders