Carb query

Post by **frank308d** » Thu Jun 19, 2003 9:54 pm

Here is the problem. The choke cable on my 1098 seemed a bit stiff to operate. Checked it and and that all the right bits were moving when operated and all seems to be working ok. While the bonnet was up, I had a root round to see all was well in other areas as the car had been standing for some time. Usual checks and had a peek inside the carb float chamber to check if it had gummed up at all. I know what you're thinking, if it works-leave it alone. Little bit of muck but not much. All back together and seemed fine. Over the last day or two, it seems to be running lumpy on light throttle but clears on wider throttle opening. Had a look at the exhaust and it looks to be running rich. Would that cause missing at low revs or have I dislodged silt etc when I took the float out? It idles just fine and starts on the button. The carb wasn't due for a clean out and tune up for a week or two but I think it should be done sooner rather than later? Oh, plugs, points, rotor arm and condenser are all new. Could it be HT leads breaking down?

Post by **grainger** » Thu Jun 19, 2003 10:59 pm

hi

are you sure when you push the choke back in that its pushing the jet back fully ? mine isnt and its running similar to how you describe. but if its lumpy when slow and clear when fast isnt it just as likely to be running lean ? check the colour of yr plugs mine are light brown so ill leave it as it is until ive rebuilt this spare carb ive got and then swap the whole thing.

cheers
grainger

Post by **frank308d** » Thu Jun 19, 2003 11:24 pm

Hi Grainger,
Thanks for the reply. I think a day off and a carb clean up are due. I'll check the plugs, do you reckon I should I put on another set of HT leads and a new distributor cap as a precaution? Belt and braces and all that?
Thanks
Frank.

Post by **Willie** » Thu Jun 19, 2003 11:46 pm

Don't know your level of competence re the carb? Have you
tried lifting the pin on tickover to check the mixture? Also
is there oil in the piston damper on top of the carb? A blockage
on an SU to the jet is pretty rare but I have experienced it. You
would have to remove the tube from the float bowl to the
jet to check for foreign bodies. Alternatively you could try
revving up and then whacking your hand straight across the
carb inlet!!

Post by **grainger** » Thu Jun 19, 2003 11:49 pm

i dont know, i would have thought that unless it is misfiring it wont have anything to do with the electrics. just check yr gaps are all right, i would check the colour of your plugs like i said it can tell you a lot about the problem.

like willie says, check the mixture by lifting the piston - i couldnt get it right the other week, its very fiddly, i spent at least an hour going back and forth and it still didnt do any good. its very difficult to tell if youre lifting the piston too far or wether youre interfering with the air flow. im thinking of buying one of those gunson colourtune plugs to see if i can get it right.

anyway a new jet, needle and spring, new gaskets etc will only cost about £20. then at least you can be sure the carb isnt causing any problems.

is it burning oil ?

all the best
grainger

Post by **frank308d** » Fri Jun 20, 2003 12:25 am

I lifed the pin tonight. No reaction until about a 1/4" from the the top. Pressed the pin home then the engine would have stalled so I released the pin, then the engine returned to a settled idle. It isn't burning any oil. It was nigh on perfect until a day or two ago. I'll check plug colour in the morning. I'm happy with my abilities to do the carb clean and tune. Go through the tests to see what the problem may be then decide whether to take it apart?