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Rough running


Adrian
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Evening chaps, started to sort the accelerator cable play with a solderless nipple (separate thread). Was very disappointed when on startup the engine was not ticking over smoothly at all and seemed to splutter and eventually die. This was with choke and whilst fiddling with the amount of choke at a certain point the engine raced to over 3000 revs. Now other than adjusting the throttle linkage to remove play I haven’t messed with any other settings from last year. My gut is it has something to do with choke but inexperience means it is only a guess? Any advice please?

 

thanks Adrian 

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The choke has a cam which contacts a adjustable contact screw (tappet)  with normal idle setting the screw needs a small gap to the cam when choke is fully home, or it will take over from the  the idle screw.

At full,choke expect around 1500rpm  maybe a bit more 

Most over reving problems start with the outer cable jumping out its abutement and  this holds the throttle open

Pete

 

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Hi Pete, I sorted the over reving on the choke. When I reattached the cable the clamp twisted the end so the tip was catching the choke cam. I’ve attached a short video of how uneven it is running. I’ve colour tuned it an am getting a blueish burn. Not sure how to get it running evenly, as far as I can tell once warm the only adjustment is the fast idle, pictured.

image.jpg

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what have you used /set the timing too ???

when were tappets last checked 

do check manifold clamps are tight , not just seized so they  seem tight but not holding the gasket from air leaks

there  is some thing well off there , doubt the colour tune is telling you the correct story.

Pete

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Tappets very recently done. Manifold all torqued up when put together last year but will check again. Timing set up with a strobe after rebuild. Synchronised carbs last week when I realised the throttle linkage had actually slipped (somehow). Not actually tried the vacuum balancing with the hose to the ear job. Might reset the needles to see if that improves it and ignore the colourtune setting. I’ll set some time tomorrow to have a go.

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How did you synchronise the carbs? (I use the krypton gauge which is by far the best if you can find one, but others work well, I struggle to be as accurate by listening with a tube)

And colortunes are funny things. They will get the same mixture on both carbs, but unless you have 2 so you do both together, I have had to do one, then the other, then recheck the first as settings can affect each other. But then, it seems some cars are too lean when correct on the colourtune. And so driving and adjusting the carbs equally, and then checking the plug colour. Unless you have the luxury of an afr gauge ( which make this mixture stuff a doddle)

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I reckon  without a  flow device   the  idles screws being set to the same is better than trying to rely on tubes and ears

After all, thats how they were supplied  to the assembly line , air flowed carbs didnt happen till late 70s.

Agree you could be chasing your tail using a single colourtune.

I would take then  jet 3 turns down from flush as a base  to  from  adjust each the same 1/4 turn at a time note better or worse

Adjjust  to best , then try a colourtune 

Pete

 

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Thanks as always for the advice. So I ditched the colour tune and reset the needles flush with the piston. What a difference as per the video, taken at full temperature and fast idle set to 850-900 ( difficult as the needle wanders). Even if it runs a little rich it seems so much smoother.

next to continue soundproofing the mini

image.jpg

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