Topic: Pods Thread

[edbikerii]

OK, so I get the better thermometer, and took some temps today on my 77 CB550K.

Used MT-PROEXP Handheld Digital Infrared thermometer.  Also no calibration data, other than a quick check that human bodies read about 95F on the skin's surface.

I've got PD46A carbs, with 90 mains, completely bone stock.  I've gone through these carbs, including pulling the pilots and clearing all the holes including those on the emulsion tubes.  Idle mixture screws are 1.5 turns out per spec. [Edit:  actually were 2.0 turns out, I forgot that I had set them at 2.0].

I've got the stock airbox, but missing the drain hose from the front half, and missing the pinch hose from the filter box drain.  I'm using that UNI foam air filter, oiled with UNI filter oil.  Might be a little dirty, if anything, as I haven't cleaned it in a while.

26,413 Miles on the odometer.  Currently running Castrol GTX 20/50, about 1200 miles on it.  No windscreens, luggage racks, backrests or anything on the bike.  Valves were adjusted to spec around 100 miles ago.

Running Dyna-S ignition, statically timed to align the advance mark when advancer is turned fully clockwise, per Dyna-S instructions.

Ambient temp today was about 85F.  I rode about 10 miles, including about 2 runs through a busy shopping district with lots of stop lights and soccer moms pulling out of head-on parking spaces in Escalades.  Then scooted home on highway at some 85mph speeds, followed by 1 mile of stop-light traffic back to the garage.  Bike was parked with the sun facing the right side (cylinder 4).

I left the bike idling, but only for about 1 minute while I retrieved the thermometer from the garage.  There was very little, if any wind.

Right side bank cylinder 4 - Peak reading 355F right at head gasket junction, 298F at base gasket.
Left side bank cylinder 1 - Peak reading 324F right at head gasket junction, 266F at base gasket.

Pointing at head between exhaust header flanges 1&2 - 349F
Pointing at head between exhaust header flanges 2&3 - 368F
Pointing at head between exhaust header flanges 3&4 - 351F

Yes, the bike seemed pretty darned hot to me.  In fact, I saw a couple of wisps of smoke coming off the engine while taking measurements.

Obviously, I'm very unhappy with these temps, especially compared to yours, TT.  I'm not really surprised, though, as I've been complaining about the excessive heat all along.

Next steps are to plug the drain lines (both of them) from the airbox, richen up the pilots by 1/2 turn, put some duct tape over the airbox snorkel (maybe 25%).

I got a little too aggravated, so I just had to walk away for now.

[Bob Wessner]

Also no calibration data, other than a quick check that human bodies read about 95F on the skin's surface.

Point it at your home thermostat and see if it matches the temp.

[ChevelleSSLS6]

Would an oil cooler help the temps?  A lot of the heat leaves through the exhaust and is absorbed by oil.  And the rest is radiated from the fins.

Knowing that Honda does not recommend additives to the oil, would synthetic oil be bad (for the clutches) or not?

thanks,
Matt

[edbikerii]

OK, I needed to make two corrections to my above post:

First, I thought I had returned the Idle Mixture Screws to 1.5 turns out, but I had not.  In the last run they were set to 2.0 turns out.  I discovered this because I accidentally turned one of the screws in instead of out (they are upside down, and I had to use my left hand, so give me a break), so I then re-checked all of them.

Second, I am using the Micro Temp MT-EXP, (not the MT-PRO) Digital Infrared Thermometer with laser sight.

I have now "calibrated" the thermometer by aiming it at all four thermostats in my house.  In every case it read 1F LOWER than the thermostat reading.  So, either my thermostats are consistently wrong by 1F, or the thermometer is off by 1F lower (probably 2F lower at the higher temps).

I reset all idle mixture screws to 2.5 turns out for this test.  Ambient temps 80F.  I plugged both airbox drain hoses with lengths of heater hose with large bolts in the ends.

Did a similar run as earlier today, but with better results:

Right side bank cylinder 4 - Peak reading 299F right at head gasket junction, 268F at base gasket.
Left side bank cylinder 1 - Peak reading 298F right at head gasket junction, 261F at base gasket.

Pointing at head between exhaust header flanges 1&2 - 337F
Pointing at head between exhaust header flanges 2&3 - 306F
Pointing at head between exhaust header flanges 3&4 - 320F

I'm getting closer now!  No smoke coming off engine.  I'll try 3 turns out on the IMS and do this run again.  It was a little harder to start when hot, so I wonder how that will be at 3 turns out.  Yes, the ambient temps were 5F lower for the second run, but I don't think that could possibly account for 40F differences in engine temps.

Yeah, it seems like this particular model (77 cb550K) might benefit greatly from an oil cooler.  I'll try to tune it properly first for coolest running, however.

[TwoTired]

If you decide to install an oil cooler, please do so without other changes.  It will be interesting to see just how much of a difference it will actually make on cylinder head temps.

Personally, I don't see how the physics and design of the SOHC4 support cooling the engine by cooling the oil.  Oil doesn't transfer heat anywhere near the efficiency of the large aluminum cooling fins on the cylinder head.  Simply put, the engine is air cooled not oil cooled.  Having said that, if your engine is running very hot, an oil cooler CAN help save and prolong the useful life of the oil, which in turn can help the engine.

Speaking of which, with the temps of your engine, and the age of the oil, I have to wonder if the trans gears and the high temps have diminished your oil's effectiveness.  I've seen other testing where the oil in a MC engine began losing it's viscosity at about 800 miles.  I have suspicions that your present oil may now be contributing to your high temps.

I suspect if you install an oil cooler, you'll do so with an associated oil change.  And, fresh oil alone can make a difference in your engine run temps.  Why not do the oil change first and record it's effects on cylinder temps?

Were I you, I would change the oil, and likely use a synthetic blend without moly.  The synthetic bit will still lube when the engine is scorched and the non-synthetic portion has lost it's viscosity modifiers.

Don't expect the IMS to make a significant contribution to fuel mixtures above the 1/8 to 1/4 throttle position.

Look at the bright side!  There is unlikely any moisture in your oil!
Perhaps you should install a cup holder on your bike.  It should keep the coffee warm on the way to work!   Don't all cafe racers need such a mod? 

Cheers,

[edbikerii]

If you decide to install an oil cooler, please do so without other changes.  It will be interesting to see just how much of a difference it will actually make on cylinder head temps.

Personally, I don't see how the physics and design of the SOHC4 support cooling the engine by cooling the oil.  Oil doesn't transfer heat anywhere near the efficiency of the large aluminum cooling fins on the cylinder head.  Simply put, the engine is air cooled not oil cooled.  Having said that, if your engine is running very hot, an oil cooler CAN help save and prolong the useful life of the oil, which in turn can help the engine.

As I said, I'd rather get the thing running right, than mask the problem with an oil cooler.  Combustion chamber heat is the real problem, not the oil temp.  I don't want to burn up valves, blow my head gasket, hole a piston, etc.

Speaking of which, with the temps of your engine, and the age of the oil, I have to wonder if the trans gears and the high temps have diminished your oil's effectiveness.  I've seen other testing where the oil in a MC engine began losing it's viscosity at about 800 miles.  I have suspicions that your present oil may now be contributing to your high temps.

I suspect if you install an oil cooler, you'll do so with an associated oil change.  And, fresh oil alone can make a difference in your engine run temps.  Why not do the oil change first and record it's effects on cylinder temps?

Were I you, I would change the oil, and likely use a synthetic blend without moly.  The synthetic bit will still lube when the engine is scorched and the non-synthetic portion has lost it's viscosity modifiers.

Too late for synthetic.  I just bought Rotella T non synth.

Don't expect the IMS to make a significant contribution to fuel mixtures above the 1/8 to 1/4 throttle position.

No, I'm aware of what throttle range is affected MOST by the IMS.  However, that is also the range which is the most likely to benefit from richer mixture.  While the bike is stopped at lights, in traffic, etc. there is very little airflow to cool the engine, so the richer mixture helps keep it cool.  In addition, the IMS does have a small contribution at all throttle positions, even if it is relatively small at larger throttle openings.

Look at the bright side!  There is unlikely any moisture in your oil!

No joke, she was running so hot that the smoke from the breather (before I replaced the stock airbox) would stop when the condensate boiled off, then she would be ok for a few minutes, then start smoking again from excessive blowby (due to the excessive heat).

Perhaps you should install a cup holder on your bike.  It should keep the coffee warm on the way to work!   Don't all cafe racers need such a mod? 

Ha!  My bike ceased to be a "cafe racer" months ago when I removed those torturous clip-ons and put on GP handlebars (my stockers were bent in a drop years ago).

In fact, I don't even have the cafe seat on it anymore.  I had to replace the stocker when I replaced the stock airbox.

I put a NOS front fender on a few nights ago, too, as I got tired of stuff getting kicked up off the road onto the engine and my legs.  I'll soon be replacing the rear fender (the last remaining cafe-removed part) too, as the bike just doesn't look right with that big ol' chrome front fender and no rear fender.  NOS gauge chromes topped off the stock look.  These NOS chrome parts have been sitting around my home(s) for 12 years.  Finally I decided "what am I saving these for?", and I tossed the old, rusted and bent junk into the trash.

No need for cup-holders now that the engine is running nearly 40F cooler (rough average of the head gasket temp reduction)!!!!  When I get it down the next 30F to your temps, then I'll start wearing warmer clothes, lest I forget that I'm riding an air-cooled SOHC4.  I'll no longer be able to tolerate winter temperatures without the space heater between my legs, though.  The charging system still is too pathetic to drive my electric jacket and gloves.

Cheers,

Thanks again, TT.

[coyotecowboy]

OK, you guys talked me into it, I put my stock airbox back on my K2 750 tonite.  It had Uni-filter-pod-foam whizbangs on it with the needles in the lowest position and the stock 110 mains.  With the pods ,up to 1/3 throttle was a little spluttery at a steady throttle, and snappy under acceleration.  1/3 to 2/3 throttle couldn't have been any better, great throttle response and dead smooth held steady.  2/3 to WOT......well, you might just as well back it off to 2/3 for all the good it did ya, it wouldn't completely fall on its face, but it was damned close.

I yanked the carbs off this evening and put the clips on the needles back to the third position, slipped the airbox on, fired it up and went for a quick buzz around town.  I immediately noticed that the throttle was easier to modulate when letting the clutch out (saving countless "cool points" as my Harley riding buddies call them) and it pulled much better off idle than before.  It quickly ran to redline in any gear but fifth, and that was only because my clutch decided to slip after grabbing fifth at 8000 rpm.  It's more resonsive and much more enjoyable to ride now, but I'm not sure if its making quite the same power in the midrange as before.  It might just be my imagination, it just sounded like things were happening faster with the pods.

So, having never ridden this bike completely stock before tonite, I think the hour spent getting it back to stock was well worth it, if for no other reason than to provide a baseline for future modifications.

[TwoTired]

 It might just be my imagination, it just sounded like things were happening faster with the pods.

Something to note is that part of the engine noise you hear is that of the carburetor intakes.  The stock induction quiets that better than pods do, as well.

When I was hot rodding a 58 olds so many years ago, I loved to take the air cleaner off just to hear the sound it made when it was floored and all the quad barrels gulped underhood air.  The whole car kind of reverberated from the growl.  Cheap thrills.  Don't know if it was actually faster, though.  Never put the stopwatch to it.

Cheers,

[edbikerii]

OK, latest run with IMS @3.0 turns out, ambient @86F

R bank cyl 4 325F head gasket, 295F base gasket.
L bank cyl 1 325F head gasket, 275F base gasket.

Head btwn exhaust header flanges:
1&2 346F
2&3 335F
3&4 344F

Conclusions:  IMS 3.0 turns out made no improvement over 2.5 turns out.  Bike ran about the same, at idle and throughout throttle positions and RPMs.  In fact, there appears to have been an increase in temperatures above those with the IMS 2.5 turns out.  Ambient temperature is approximately 6F warmer than last run with IMS 2.5 turns out, so unable to determine whether the increased ambient temp is the cause of the increased temps.

I then proceeded to tune the IMS setting to the "best idle".  I ended up at 2.5 turns out again.

Unfortunately, the MicroTemp MT-EXP laser infrared thermometer died on me (after only thee uses).  It reads an 'Er5', which is not listed in the trivial instruction guide inside the blister pack.  Removing the batteries did not correct the problem.  Back to Pep Boys it went, exchanged for new.

Next step:  Cover 25% of snorkel, ride and take temps again.

[MRieck]

I have used K&N individual filters for years on many older bikes with excellent results. The real world disadvantages are getting caught in the rain and getting a bit more particle ingestion. Modern airboxes work well because they have 5 or 6 times the volume of early boxes and generally incorporate ram air which allows for good fill. I think there is a definite lack of understanding regarding carb tuning especially in regards to fuel circuit overlap. I also think to many guys over fuel their engines finding the ability to say "I run 135 mains" macho. If you don't have a solid understanding of carb tuning you will have problems.

From another thread...... Tuning FCR's...idle fuel circuit, adjustable idle air circuit, main air jet, main jet, needle taper etc. Like I said....if you don't understand learn. It really becomes satisfying when you have a GOOD idea what to do. And....it'd not that hard.....just think about during your day to day stuff and it will dawn on you. You have to be the persistant type and really want to solve problems/find solutions. I have lost sleep over trying to figure out a solution to a problem.

[mmtsquid]

OK, so the pods came in yesterday, and here are the initial results.......
77 cb550K, stock carbs, 4-2 exhaust.......
With pods, idle is a bit rougher...
0-1/4 throttle - seems fine
1/4 - 1/2 - splutters and runs like a$$
1/2 - 3/4 - great, no problems
3/4 - WOT - feels like someone strapped a rocket to my back!

I know plug chops are needed to see whats going on - will do tonight.
I will try moving the needle up a notch on all carbs and see if that helps the 1/4 - 1/2 throttle issues.

Have I missed anything?
Please, let me know if I'm screwing up!

[edbikerii]

Do you have the stock #90 mains and the needle clip on the 2nd groove from the top?  What about the Idle Mixture Screw setting?  I found that my 77 CB550K with PD46A carbs would completely bog out at any more than 1/2 throttle with pods and the #90 mains.   The only difference is that I have a MAC 4-1 rather than 4-2.  At WOT on the open highway in 5th gear, the bike wouldn't get past 6K RPMs.

For comparison's sake, when was the last time you went for a ride with the stock airbox on it?
Have you checked/set your timing?  Are you running points or Dyna?

OK, so the pods came in yesterday, and here are the initial results.......
77 cb550K, stock carbs, 4-2 exhaust.......
With pods, idle is a bit rougher...
0-1/4 throttle - seems fine
1/4 - 1/2 - splutters and runs like a$$
1/2 - 3/4 - great, no problems
3/4 - WOT - feels like someone strapped a rocket to my back!

I know plug chops are needed to see whats going on - will do tonight.
I will try moving the needle up a notch on all carbs and see if that helps the 1/4 - 1/2 throttle issues.

Have I missed anything?
Please, let me know if I'm screwing up!

[mmtsquid]

Stock 90 mains, needle in 2nd position.
Timing is perfect, running stock points (Dyna will come at christmas!)
I've ridden the bike 70 miles a day 5 days a week for the past month with the stock airbox.
I'm picking up 100 jets tonight, but I won't put them in until  AFTER I play with the needles and record some results.

My gut feeling is that it is lean overall, but moving the needles should get rid of the sputtering at 1/4 to 1/2 throttle.

[edbikerii]

Emgo pods, 106 mains, needles in stock position (2nd leanest), IMS 2.5 turns out.  Works pretty well, but still blubbers a little (rich?) at WOT in 5th gear at 7K rpm.

Temps will follow when I've had a chance to ride her more reasonably.  I rode her hard today, and she was very hot (325F at head gasket, 297F at base gasket #4 bank, from side).

[mmtsquid]

So, I was all set to play with the needles, and discovered that I couldn't get them out!
I got some additional info this morning, so I'll try again tonight......

But last night, since I had the carbs off, I replaced the #90 mains with #100s.....
And it ran like crap - sputtered all the way until nearly WOT.  Hmmmm......guess those needles really ARE important.

[edbikerii]

Hey mmtsquid,

Everything I've read has indicated that you should tune the main jet first.  First pick the main jet, then start fine-tuning with the needle position, and finally worry about the pilot last.  I've heard that you should start out too rich, then gradually reduce the jet sizes until it is slightly too lean, then go up to the next richer jet size (for engine longevity).

Yes, you can get the needles out without removing the carb banks.  You need to remove the screw that holds the lever on the throttle shaft, and then lift the lever and slide up as high as possible in the carb, then slide the lever off the pin on the slide.  #2 is easiest as there is no adjuster in the way.  The others require a little "manipulation" to get them off.  Then, with the slide removed (one at a time, please), use a narrow phillips to take out the two screws down in the bottom of the slide.  The clip is under there.  Don't forget how to put that stuff all together in the right orientation.  It will go back incorrectly if you're not careful, and then you'll have a real mystery on your hands.

Good luck

So, I was all set to play with the needles, and discovered that I couldn't get them out!
I got some additional info this morning, so I'll try again tonight......

But last night, since I had the carbs off, I replaced the #90 mains with #100s.....
And it ran like crap - sputtered all the way until nearly WOT.  Hmmmm......guess those needles really ARE important.

[TwoTired]

Hello Ed,

Here is some food for thought that may be helpful.
In a previous discussion with Deltarider,  I learned some of the earlier style carbs had a stamping 649A and a corresponding main jet of #78.  These carbs were found on some Dutch model honda 500s (not the K3.)  To go along with this jet, the air filter box was fitted with a snorkel.  I remember seeing a posted picture of the narrowed inlet opening compared to what I have seen on the 500 K2 that I have.  (I could not find the picture in searching).  The 500K2 without that restrictor had #100 mains, of course.

There was never a positive confirmation that any other parts in the carbs were different, and no other settings/adjustment differences were noted.

I also gave some thought about why the PD carbs had #90 Mains, and the earlier ones had #100s despite the same engine displacement and the same carb throat size.  Besides the obvious exhaust flow difference, I speculate the ramp shape for the venturi also effects carb throat pressure depression and thus the draw through the main jet.  The two body castings are certainly different in this regard, with the PD carbs formed in an inverted pear shape and the early style being oval openings.

Well, that's enough rambling,

Cheers,

[Deltarider]

Hello Ed and Twotired,

Here is the pic of that snorkel. I'm still puzzled why the 500Fours for Germany, Holland and some other European countries were equipped with the 649A carbs with #78 jets, being the  countries with no speed limits in place and believe me: 140 kilometers per hour was a normal cruising speed in those days. As I have mentioned before, our K1 and K2's perform very well. Mine is capable of 170 km/h and testriders managed to squeeze 179 km/h out of it. Recently somebody in Germany reacted saying that he still does 180 km/h on his K2. BTW, the difference in handlebars show that ours were marketed for faster riding. So I think there must be some extra difference in those carbs. After reading several posts by Hondaman and Twotired, here is my guess. Could it be, that that little hole in the carbthroat makes the difference. I am not referring to the little hole for the slow jet, but the one on the other side, the one that Hondaman (be it on a 750) advises to clean with a wire. In our 649carbs that little hole is closed with solder. Maybe, just maybe on your 627carbs that little hole is open, feeding air to the needle jets, where ours suck more fuel. It's just a guess and I wonder if somebody can have a look or maybe post a pic of the 627 carb, showing the throat. If that little hole in your carbs is open, I've finally solved a mystery (at last), if yours is closed as wel, I'm mistaken and have to look again.

Happy motoring

[edbikerii]

Thanks Deltarider!

The only thing I can think of is a mandated restriction in the intake tract for graduated licensing.  I would have expected that the effect would be to slow the bike down, however!  Could the solder plug have been installed "aftermarket" to defeat the restriction or something?

On my PD46C carbs there are two open tubes in the carb throat (facing into the intake air flow).  Both of them are open.  I have flushed carb cleaner through both, and seen the carb cleaner come down into the bowls through the jets.  Also, I've covered those holes with a finger and seen the carb cleaner flow up into the carb throat -- although exactly where from I cannot say.

Does that solve the mystery for you?

What kind of fuel consumption do you get?

Also, I took my bike for a more leisurely ride today with those 106 mains.  The head gasket temp was only 285F and 268F at the base gasket.  Granted, I was kind of granny-riding though.

[TwoTired]

Okay, this could be hard to explain in print.  But, here goes.

The PD carbs have dual tubes at the inlets, for the slow system and the main system also with restrictor orifices.  I've not measured, but the Honda Shop Manual states these are #130 and #150 orifices.  The shop manual also shows screw in types there.  (Probably engineering early samples pilfered for the photo op.)

The earlier 627 type carbs have one tube at the mouth of the carb and a hole at the side of the venturi ramp on the inlet side.  The pressed in tube is the air jet that feeds the emulsion tube for the main and throttle valve system.  The 627B carbs (and other early model carbs) for the cb500/cb550s here in the states have a jet restrictor orifice deep in the tube; #150 if I recall correctly.
The small hole in the venturi ramp is the air bleed feed ( #180 hole).

It's hard to believe the air jet is sealed off in the 649 carbs.  Perhaps the bodies are drilled differently for an alternate source of air for the mains emulsion tube?  I don't know, but, it just seems the emulsion tube function would be seriously f'd up without frothing the fuel before insertion into the carb throat.  I have noticed different emulsion tubes have different hole sizes and placement.  And some carbs may have different air jet sizes.  But, no air to the main emulsion tube?  I'm skeptical. I think I would pressurize the main emulsion tube cavity and see where the carb cleaner went.  That would probably be the air source.  Not likely I'll ever see 649 carbs in person though.

Cheers,

[mmtsquid]

Ok so I got the needles out - they have 5 different possible settings - they were on #2 (1 the top or leanest setting, 5 the bottom or richest setting).
I moved them to #4 and......
It's better - I still have some sputtering between 1//4 and 3/4 throttle, but it is definitely better!
I rode to work this morning, and noticed I havealmost NO torque in 5th gear above 5500 rpm - at WOT, it just creeps up to speed.  it took FOREVER to hit 90!
The plugs are nice and tan at the spark area, but black around the edges.

Any thoughts?

[edbikerii]

Like I said, tune the mains at WOT first.  I think you are still too lean on the main jet.  At 106 I am ever-so-slightly too rich.  If I were you, I'd try 104s and do the same test, WOT in 5th gear all the way through the RPM range.  Then when you're satisfied with that, tune the needles.

Ok so I got the needles out - they have 5 different possible settings - they were on #2 (1 the top or leanest setting, 5 the bottom or richest setting).
I moved them to #4 and......
It's better - I still have some sputtering between 1//4 and 3/4 throttle, but it is definitely better!
I rode to work this morning, and noticed I havealmost NO torque in 5th gear above 5500 rpm - at WOT, it just creeps up to speed.  it took FOREVER to hit 90!
The plugs are nice and tan at the spark area, but black around the edges.

Any thoughts?

[mmtsquid]

You're the man, ed!

I'll go see if the dealer has these jets in stock.........

[peten]

new to posting here, but a seasoned lurker.  am I to assume that you're using dynojets?  where can you get 104 and 106 mains from?  I've just put a MAC 4-1 exhaust with competition baffle onto my 78 550k with emgo pods, and am experiencing an intermittent burble at higher rpm's (will find out what throttle position soon) and only up slight hills with a lighter load (gently rolling on throttle).  I'm running one position richer on the needle, and almost sure I've got 105 mains (K&L supply Keyster jets).  Temps are hot here in upstate NY, altitude varies between 1000-2000 ft mostly.  Going to do more experimenting soon; hope to have some cobbed-up air ducts and filter to run where the air box was (rubbers cracked--airbox is under workbench).   Must get more power!!

[edbikerii]

What's wrong with the Emgo filters?  I quite like them.  People knock them because they are inexpensive.  You know, "it must be better because I paid more"?  Plus, they actually fit on the 77-78 CB550K, whereas I've read that the K&N's are blocked by the frame.

Dynojet supplies jets in sizes above 100 only in 2s.  102, 104, 106, 108, etc.  Part numbers are like DJ100, DJ102, DJ104, etc.

Call them up and they'll ship them to you for $2 each ($8 a set), plus shipping.  UPS ground is $8!  It pays to buy a couple of sets in case you don't want to wait 5 days for the next set to come via UPS.  Personally, I'd rather pay $8 than wait, unless you know exactly what you want.

I would say that you should do a plug chop, but honestly, I've never had any luck with them on my 77 CB550K.  I've read that it is because I'm running Dyna S ignition and Dyna coils (5 Ohm), and my plugs are therefore too hot for the deposits to survive the run.  I don't know why, buy my plugs always look exactly perfect, even when I knew the bike was running way too rich.

Another thing to consider is that the float height spec for your bike is 12mm rather than 14.4mm like on the 77.  Perhaps that richens up the mix a bit?

new to posting here, but a seasoned lurker.  am I to assume that you're using dynojets?  where can you get 104 and 106 mains from?  I've just put a MAC 4-1 exhaust with competition baffle onto my 78 550k with emgo pods, and am experiencing an intermittent burble at higher rpm's (will find out what throttle position soon) and only up slight hills with a lighter load (gently rolling on throttle).  I'm running one position richer on the needle, and almost sure I've got 105 mains (K&L supply Keyster jets).  Temps are hot here in upstate NY, altitude varies between 1000-2000 ft mostly.  Going to do more experimenting soon; hope to have some cobbed-up air ducts and filter to run where the air box was (rubbers cracked--airbox is under workbench).   Must get more power!!