Just fitted twin 40s..... now it misfires

[Gaz1300SR]

I have fitted some sport carbs to my 1.3 SR and now cylinder number 1 is not running. It was fine before I fitted the new inlet and carbs.

There is a spark from lead but I haven't check the plugs as yet. I will look at it again tomorrow.

I'm not too familiar with twin 40s so I am asking those with more experience to point out other causes of this?

It fired up (eventually) first time and idled at about 1800 rpm without choke connected. How do I adjust this?

Thanks

[paul james]

Theres a throttle screw you can adjust to change what RPM the car idles at. Theres an installation instructions PDF on this site:
http://www.rogerfletcher.pwp.blueyonder.co.uk/novasport/index.html

With the throttle stop screw shown on this page: http://www.rogerfletcher.pwp.blueyonder.co.uk/novasport/images/install5.pdf

[Gaz1300SR]

Thanks for that link, i started to mess with the balance screw but thought it didn't seem the right.

[paul james]

I've used that screw to get me through an MOT before, turn the idle RPM up a bit and then it passes its emissions :)

[Novasport]

Probably just the carbs that need balancing or an air leak, I had the same problem with my Sport when getting back on the road after winter....

http://www.pngclub.com/forum/showthread.php?144276-The-new-Sport-has-arrived!/page24

[Gaz1300SR]

Probably just the carbs that need balancing or an air leak, I had the same problem with my Sport when getting back on the road after winter....

http://www.pngclub.com/forum/showthread.php?144276-The-new-Sport-has-arrived!/page24

Cheers, I did replace the inlet gasket and tighten everything up. Could be one of the gasket things that go inbetween the carbs and inlet?

Also had a thought it could be a blocked jet? The jets are under the round thing on top that can be accessed through the holes in the airbox right? The 4 things with a flat head screw on top? (if that makes sense?)

[C612DNM]

There are many factors which may cause the misfire.

You should have first turned all of the idle screws in fully home, then back 1/2 turn.. It may be too weak, but it should start when you try .... later....

Using a mirror and a light, you should be able to set the balance screw fairly close - if you're good.

If not, don't worry too much, get it pretty close.

Fire it up. You may have to adjust the idle speed screw (normally on the right-hand carb - as you look from the front) until it's idling at a reasonable speed.

Get a bit of hose - long enough to go from the carb inlet, to your earhole as you lean over the engine.
Assuming you have a musical ear - you should be able to notice the difference between the sounds of each carb. When they sound the same, they are in balance. If not, don't bother - get someone who can in to do it. People that are tone deaf often have problems balancing carbs in this manner.

With it balanced, you can adjust the idle mixtures - turn the screw equally one at a time to the point where it runs sweet. The revs will pick up as you get it to the sweet spot, then fall off as it gets too rich. At that point, turn them back a bit to just before the point where revs reach their peak. Again, this is a "by ear" thing - many people just can't do it.

If you have an air leak in the thackery washers, it won't run right.
If you have the carbs bolted up uneven, it'll be difficult to get it running right.

Check the jets, take off the float chambers, make sure there's no water in there. Water droplets can "hover" over the jets and screw up the mixture.
Crud in the float chambers can cause catastrophic misfires on one cylinder only - because it's like having one carb per cylinder, and one half of a DCOE can be "broken" with the other half working perfect.

Can I recommend you buy a copy of the Haynes Weber DCOE manual. It's well worth it.

When/if you get it running fairly well, get it on a rolling road - you're in Manchester - call Ric Wood in Stockport - Telephone : 0161 483 4810, he's not the cheapest around, but the man is the business.

[Stuart]

also, before you actually use the car, set the throttle pedal to fully decked and adjust the carb linkage so that its just OFF full throttle.... this will prevent you from bending the sodding spindle and causing the usual 'they always go out of tune' bullsheets.

[Gaz1300SR]

Thanks for the advice guys! I am going to spend sometime trying what you have said c612dnm, possible that the misab gasket thing is leaking as I am not sure the are on square (so to speak!) Couple of the studs are a bit short.

Stuart, thanks for the advice, I have got a mk1 astra 1.3 throttle cable which fits the carbs end but is too long the other end on the peddle, do you know if there is a direct fit I can get? I assume the sport ones are not available these days? If not I will try and adapt the one I have.