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Jetting '78 750 for pods, headers only

  • Thread starter Thread starter verde
  • Start date Start date
Ridability is pretty good. Just barely missing a touch of torque on take off compared to other bikes I've ridden. I assume these are more rev happy engines anyway though, so spooling it up a bit for take off would make sense. Changing the pipes would probably find some of it:o

1 turn, 1.5 turns, 20 pilots, 130 mains, 2nd notch. Audio is terrible, but this little clip of a test ride you can definitely hear the 'shhook' cough sound at 0:19 and 0:25. Got lots of cackle from the wind and pipes too though. It's happening at very little throttle, cruising rpms. Rolling off the throttle invokes it more, of course, but it does it just when it feels like it too.

http://www.youtube.com/watch?v=dqPLBf4LnVA

Next change will have to wait, either tomorrow or the weekend.

Edit: I lied. Couldn't keep my hands off her. Found out my goldfish memory failed me again, was not on 4th notch(read that suggestion the first time and though 'yes, don't have to go in there just yet') Remembered reassembling them on the 4th notch, but that must have been my '79's carbs. Double checked the bench sync while I was at it and #3 was a c-hair tighter. Hopefully that's the last of the straggling details.
 
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Now that the needles are actually in the 4th notch, she's running like a champ. Might bump down to the 17.5 pilots as the needle change seems to have made it a tad too rich down low, but just lovin' it right now.
 
Now that I'm in the right AFR range and have put a few miles on it, the plugs are starting to show some color. Not a chop, just pulled them this morning after riding around yesterday. 1&4 are on the same page, 4 a little fouled though, and 2&3 are on the same page. I'm thinking 2 and 3 are running a little lean since they have a better pool of air to suck from at speed and the airflow around the engine is robbing 1 and 4 of their fair share.

plugs.jpg
 
Hi Verde, 1 looks just about perfect,2&3 are way too lean&4 looks a little rich, have you balanced them with the engine running( fitting a dummy tank from a lawnmower is the easiest) as for your gas prices try where I am, which is Northern Ireland-$8.20 a gallon!!. good luck with your bike.Johnny
 
have you balanced them with the engine running( fitting a dummy tank from a lawnmower is the easiest)

Is this second part a joke? My tank IS from a lawn mower:D Having the bike being nothing but frame and engine makes tinkering a breeze. I put a sig together, click on the pic for the build thread.

Thanks for your input. I was a little annoyed when I realized I was finally getting color but the inner cylinders were showing lean. Haven't gotten a chance to get a manometer on it yet. Unfortunately I don't think that will solve my inner/outer cylinder dynamic. I'm playing with the idea of fabing up dual air boxes to get the inside cylinders and outside cylinders getting an equal share of air. Otherwise I will have to try some weird unequal fine tuning.

Some background on my thought process: On my triumph running pods, I can watch my A/F meter go lean, up into the 16's, if I spool it up at a stand still because it's got steady air to suck from. However, when I'm rolling down the road at the same high RPM it is in the low to mid 12's since it just can't get the same amount of air. Doesn't matter there since it's a twin and both cylinders are affected the same.
 
as for your gas prices try where I am, which is Northern Ireland-$8.20 a gallon!!.

:eek: Holy Smokes, damn, and I thought we had it bad, paying $5 a gallon here.
Although with all this nonsense in Egypt and the Rand going to sh*t against the dollar again, we will probably be at $8 in a month or two as well.
 
are u guys seriously talking about US Dollars?

Yeah they are, the dollar is toast over seas compare to what it used to be(on top of some other infrastructure considerations I cant begin to pretend to understand). I'm actually sorta greatful paying "just" $3.40 a (us)gallon.
 
Verde, no it's not a joke that is what I use to feed my bike when I balance the carbs! it is small enough to hold a litre of fuel which lets the bike run for a good while,and to everyone else who commented on the gas prices it comes to ?5.89 per gallon in sterling so you need to check the exchange rate but I bought parts from Z1 not so long ago and they came to $50 US which was ?35 sterling so going by that it works out at $8.36 a gallon but it goes up here every 3-5 weeks. Diesel is worse costing $8.63 US a gallon as of today and to make it worse again the pumps here are callibrated in litres, enjoy the cheap gas guys!!.Johnny
 
Imperial gallon is 20% more in volume than the US gallon. If that isn't taken into account, then the $8.20 becomes around $6.50.
 
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