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Engine Problems


SpencerH

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So here is the current problem. I have jsut thrown everything back on the engine, and it fires up just fine, but the problem right now is that it won't rev any higher then like 900-1000rpms. Even if i pull on the throttle cable it does nothing. There is no gas leaks or anything to speak of. So im not quite sure what the problem is. It idles fine but it wont rev up even if i punch on the gas. I am very confused. Any ideas of what i could do?????

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Okay so i checked all of my connections and they seemed to be fine. Yesterday i let it run for about 15 minutes and it was fine(while it was idling). It ran smoothly other then that fact that pulling on the throttle does nothing. So i thought maybe it just was stale and old gas. So i let it run today and after about 3 minutes it started to idle lower and lower and sounded almost like it was idling lower, then higher again. So it was making a weird noise like it was going fast, then slow, then fast, then slow. And then it started to shake a bit, and then it died and now it wont fire up again.
Any ideas now? if it is the diaphram, would that be an easy fix? Also keep in mind im new to these british cars and im not the most mechanically inclined, because im only 18.

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to replace the diaphram remove/undo the black plastic knob on top of the carb. remove the four crosshead screws, one in each corner of the top of carb and lift away. this should reveal the diaphram, note it should have a small location tab on the outer edge. take diaphram off a check for any splits etc, or if it looks perished. good idea to replace it anyway if not sure how old it is. when putting it back together pour a small amount of thin oil down the centre tube , fill to about 1/4 inch from the top then replace the plastic knob with the damper on it ,a slight resistance will be felt when pushing it in.

anything your not not sure off just ask away :)

regards,    bryan

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And make sure the metal top of the carb goes back the same as it came off (yep, got it right third time :B)
In fact, make sure the piston (visible through the air intake) can move up and down freely before taking apart. That is rather important ;)

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OKay so good news is that problem is solved!! Silly mistake of putting the piston in!

But now there is another problem. This happened near the end of last year. Its along the same lines of the problem i jsut fixed.

We had everything up and running fine last year. No problems. Then when we got the tires changed they did the Spark Plugs. After i got it back it started running weird, and if i let it idle long enough it died. So i asked a local guy here and he said sometimes what happens is over time the whole car performace goes down, but its all running in sync, and then when you tune up one thing (In this case the spark plugs) it can throw everything off. So over the last couple weeks as summer approaches we did the Contact Breaker Point, and the Valve Clearances. But now it still does the same problem as last year, where it dies if it idles too long. So could this be that maybe when the spark plugs were done, that the guy who did them was wrong? and maybe the mixture is too weak or too strong? or maybe does the carb need a solid tune up?

Im not sure where to start to look for this problem so any ideas now??

Thanks

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It could be that the needle valve in the float chamber is not sealing completely, allowing the fuel level to rise.   This would make the mixture richer and after a while cause the engine to stop.  (If this is the case it is unlikely you can restart the engine unless you open the throttle.)

If you increase the idling speed, as you have noted, the rate of fuel consumption keeps up with the leak past the needle and so, the engine keeps running.

Check the condition of the needle valve.  Most likely just dirt but these valves are cheap to replace.   Make sure you check the float position if you do so.

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It could be your throttle mechanism is sticking (try a little WD40 on teh linkage) or the return spring might be weak. This cold result is setting the tickover when the guy thought the throttle was closed, but as the throttle slowly returns to it's fully off position so the revs will drop still further. Either way I wouldn't use that mechanic again, new plugs only improve things, not make them worse!

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