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Author Topic: modest performance upgrade  (Read 1251 times)

webnash

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modest performance upgrade
« on: August 20, 2008, 01:22:35 AM »
I have a deluxe bullet avl with about 700 miles on it. I just installed a classic pipe and silencer and K&N cone shaped air filter. I decided to try jetting the stock CV carb. After trying every combination of jets that I had, and needle settings I finally found one that seems like a good compromise.

The factory needle setting (middle notch) was hands down winner. For main jet I ended up with the biggest one that I had, which was a 125 (factory is 110). With the main at 125 and the pilot at factory (15), idle was great, acceleration was OK, full throttle was great, but plug was white with ash and new pipe was turning blue. I stepped up to 17.5 pilot and idle is OK with adjustment screw turned as lean as possible, initial acceleration has a tiny hesitation at first then very quickly smooths out, wide open is as much power as I'd want and it seems to want to get up to 70 and stay there. There is gurgling and popping on rapid deceleration - which I like the sound of as long as I'm not doing any damage to engine.  Plug is chocolate brown color, relatively dry.

It seems like it's a little too rich at the bottom, good in the middle, and outstanding at the top. Since there are no changable slides for this carb, I'm guessing that this is as good as I'll get it ?? I love the sound now - it really has a resonant, thumpy, growl with some nice deceleration crackling, gurgling, and popping thrown in. I guess I'll stick with this combo for a while, unless anybody has some good tuning ideas, and maybe consider a trad brit carb down the road. I'm assuming that the gurgling and popping in the pipe is gas that didn't burn in the engine? Am I throwing out an unacceptable carbon footprint or doing the engine any harm

Does changing intake and exhaust effect ignition timing? If so, how would you adjust timing on solid state ignition? Thanks for all the tips and enthusiasm, I'm a very happy RE owner/rider at the moment!!

Mike;D?

PhilJ

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Re: modest performance upgrade
« Reply #1 on: August 20, 2008, 12:01:27 PM »
Later today the carb guys will chime in, but just for grins, I would have thought that the pilot would have been fine for idling. The slight hesitation on start off sound rich to me.

I put an old BSA muffler on my Classic AVL got much better sound more torque and didn't have to change any jetting and the same gas milage, mid 80s. Of course it's not near as loud and free flowing as you pipe.

Thumper

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Re: modest performance upgrade
« Reply #2 on: August 20, 2008, 12:19:28 PM »
webnash,

Sounds like you've got everything covered.

The gurgling and popping on decel was recently discussed:

http://www.enfieldmotorcycles.com/forum/index.php/topic,2054.msg20334.html#msg20334

No, it isn't harmful. Minimize by enrichening the idle mixture and sealing any exhaust leaks.

As for the just-off-idle hesitation, I just read a piece by Kevin Cameron (I think) that describes why this occurs - and in my case is pronounced in my Amal. As the slide raises and opens the throat, the air pressure drops rapidly and excessively. Historically this was addressed by making an egg-shaped throat in the carb so that as the slide first raises only the narrower bottom half of the 'egg' is opened. (In auto carbs they used a pump to squirt in fuel). Curiously, CV carbs are supposed to help minimize the problem (because they are, duh, constant velocity). So I'm not sure why you'd have this effect. As Phil indicates, it might be because of richness in the idle circuit or as you mention the slide cutaway might not be a perfect match for the current configuration.

None of these changes affect your ignition timing. I know of know way to alter the timing other than replacing the unit with a different one.

The Amal Mk1 concentric (32mm) has worked great for me - but it sounds like you've managed to get the stock carb pretty well dialed in.

Matt

webnash

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Re: modest performance upgrade
« Reply #3 on: August 21, 2008, 07:31:00 PM »
Matt,

Did you get a manifold with your amal, or did you have to make one? Did it come with some jets? I sure like the look of the amal.

thanks, Mike

Thumper

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Re: modest performance upgrade
« Reply #4 on: August 21, 2008, 08:35:17 PM »
Matt,

Did you get a manifold with your amal, or did you have to make one? Did it come with some jets? I sure like the look of the amal.

thanks, Mike

Their kit comes with the manifold and is jetted for the application - in my case a 2006 Electra X with a freer flowing exhaust (also one of theirs). I did replace the valve slide with one that was a cutaway richer.

Matt