Jetting '78 750 for pods, headers only

[verde]

What are the caps, for lack of a better word, on the ends of your pipe supposed to do? I don't quite understand the idea.

It's an attempt at a non-invasive version of this: http://www.nightrider.com/biketech/exhaust.htm Dunno how effective it is in my case. Might try to make the strips a little flatter to impede the exhaust flow more. Could also do the lollipops but on tabs that are pipe clamped in place at the end of the pipes. It's only for a little while anyway until I have time to rework the exhaust system(spring break probably).

[verde]

Getting Close...

I would start 4 sizes larger on the mains, needles 2nd notch from the bottom/tapered end pointing down, 1 up on the pilots, and adjust the screws using the highest idle method.

Wasn't getting very far with the screws. Finally got some 20's in the mail and she's a lot happier Getting a rare cough back into the carbs at "just puttin' about" speed/rpms. I think #3 most frequently, so maybe a screw setting. Petcock vac hook-up is capped.

First attempt at a plug chop wasn't all that successful and was before the new pilots. Didn't get a long enough run before having to cut it before catching up to too much traffic. Plugs looked right out of the box. As I understand it modern fuel burns a lot cleaner so you can only really tell if it's pretty far one way or the other. My next move might be to bump up on the mains and see when I can start to feel it bog, back off from that and see how my cough is doing. If I'm still getting that putting speed cough then I'll try raising the needles. Sound like a decent plan?

[GabrielGoes]

What are the caps, for lack of a better word, on the ends of your pipe supposed to do? I don't quite understand the idea.

hes trying to create back pressure

[tejasmud]

Wasn't getting very far with the screws. Finally got some 20's in the mail and she's a lot happier Getting a rare cough back into the carbs at "just puttin' about" speed/rpms. I think #3 most frequently, so maybe a screw setting. Petcock vac hook-up is capped.

First attempt at a plug chop wasn't all that successful and was before the new pilots. Didn't get a long enough run before having to cut it before catching up to too much traffic. Plugs looked right out of the box. As I understand it modern fuel burns a lot cleaner so you can only really tell if it's pretty far one way or the other. My next move might be to bump up on the mains and see when I can start to feel it bog, back off from that and see how my cough is doing. If I'm still getting that putting speed cough then I'll try raising the needles. Sound like a decent plan?

When the screws don't seem like they are adjusting anything changing the pilot jet size is what you need to do. The low speed cough could be the valves need adjusting. Didn't see anything posted if the valves were in spec or not.

As to the "fuel burning cleaner" these days, I read that in a
thread where Dynojet replied to someone installing a jet-kit. Don't know the validity of that statement. Could be true in some locations on this big blue planet where fuels are a different blend. Here, I run regular 87 octane unleaded that has 10-15% ethanol, and with an AFR of 12.5:1 the plugs do color. Light brown in color on the base of the insulator like always has been my observation.

Anyways, sounds like you are on the right path.

E

[verde]

Engine was out of spec when I got it. I had the head off, lapped all the valves. First time doing valve work. Exhaust valves took about 3 times the elbow grease that the intake valves did, but they all looked nice and concentric even after their neglect. Mixing and matching 2 engines and an extra set of shims I got all but one exactly where I wanted them. #1 intake is the only one that was borderline tight, and that's not the side I'm getting my cough on most frequently.

If there's anywhere on this big blue planet that will have different fuel blends, I'm right in the middle of it... paying $3.40 a gallon. Might try some plug chops again later, but will continue with seat of the pants erroring on the side of rich for now. Thanks for the help so far.

[verde]

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

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.

[verde]

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.

[verde]

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.

[Johnny Drummond]

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

[verde]

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 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.

[GabrielGoes]

[QUOTE=$8.20 a gallon!![/QUOTE]

8 us dollars for a gallon?

[Flyboy]

as for your gas prices try where I am, which is Northern Ireland-$8.20 a gallon!!.

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.

[GabrielGoes]

are u guys seriously talking about US Dollars?

[verde]

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.

[Johnny Drummond]

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