garrett's tuning/dyno thread

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I think you jumped the gun by removing the 165's too early. You should have played with needle shims first. I would have put everything back to stock, no shims, stock springs, stock PAJ2 and tried it from there. JMO.

All circuits of the carb have an effect everywhere, slightly. It is a broad generalization that mains are 7K and up only. Or A/F screws are idle to 5K and needles in between. Each setting affects other areas, SLIGHTLY. Not only does rpm have an effect but I belive throttle position and vacuum as well so, yes the A/F screws can have an effect on cruise IF you are crusing at a very small throttle angle.

As far as your issue at 7K its hard to say without being there. If the bike just seems like it's falling flat on its face, its rich. If it feels like it wants to go but it is "stuttering" this is a lean surge. Sounds lean to me from what you described.

Clear tubing is the way to go for checking the floats. Make sure its large enuf to fit over the existing drain hoses. A nice set of calipers makes the job of setting floats pretty easy. I used a dial caliper to set the distance on on a pair of inside calipers so I only had to measure once. Yes, I did find it time consuming as those little tabs are VERY sensitive to each touch.

I'm sure you will get it running fine in the end. It will take patience, you just need to think of it as being a fun hobby not an annoying job. Late nights in the garage sometimes make things worse. Sometimes you gotta know when to stop for a night.

I'm no tuning master by any means so, these are more opinions than suggestions. Good Luck

 

[gamorg02]

I'm sure I'll get my hand smacked if I'm wrong, but from what I can tell, the mixture screws only address off-idle throttle response. I'm guessing anything over 1800-2000.

Your float levels are within spec now, so I think you can safely cross them off your list.

As for the question of, does it sound as though I'm consistently lean now... If that's the case your plugs will show it. Pull 'em off and take a peek-see, then let us know what you find.

-

will keep plug test in the back of my mind.. pretty sure i'm lean anywho.

I think you jumped the gun by removing the 165's too early. You should have played with needle shims first. I would have put everything back to stock, no shims, stock springs, stock PAJ2 and tried it from there. JMO.

very well could have, esp since i 'leaned' out the float levels.

All circuits of the carb have an effect everywhere, slightly. It is a broad generalization that mains are 7K and up only. Or A/F screws are idle to 5K and needles in between. Each setting affects other areas, SLIGHTLY. Not only does rpm have an effect but I belive throttle position and vacuum as well so, yes the A/F screws can have an effect on cruise IF you are crusing at a very small throttle angle.

def agreed. just trying to find the biggest contributors at certain spots.

As far as your issue at 7K its hard to say without being there. If the bike just seems like it's falling flat on its face, its rich. If it feels like it wants to go but it is "stuttering" this is a lean surge. Sounds lean to me from what you described.

i think lean still too then. sounds like i'm lean mid and high end. can you describe the "falling flat on its face" feeling better?

Clear tubing is the way to go for checking the floats. Make sure its large enuf to fit over the existing drain hoses. A nice set of calipers makes the job of setting floats pretty easy. I used a dial caliper to set the distance on on a pair of inside calipers so I only had to measure once. Yes, I did find it time consuming as those little tabs are VERY sensitive to each touch.

I'm sure you will get it running fine in the end. It will take patience, you just need to think of it as being a fun hobby not an annoying job. Late nights in the garage sometimes make things worse. Sometimes you gotta know when to stop for a night.

i follow man. gotta take a day or two off i think, at least from pulling the carbs. the needles shoudl shed more light. doing mains are too bad, but float levels just take forever. i think my #'s are good (def not perfect)

I'm no tuning master by any means so, these are more opinions than suggestions. Good Luck

even so, i appreciate the advice and help. always man!

 

[gamorg02]

more main tests via mukini:

http://www.mikuni.com/fs-tuning_guide.html

ROLL-OFF:

The Roll-Off technique is the quickest and is almost as accurate as the Roll-On method. First, one gets the engine warm on the way to a safe roadway. If there is room, use fourth gear as this allows more time to assess the result.

Now, get the engine rpm high enough that it is on the cam and in its power band. This may need to be as high as 4000 rpm with some cam choices. Apply full throttle. Let the engine accelerate for a couple of seconds until it has settled in and is pulling hard. Quickly roll the throttle off to about the 7/8ths position. When you do this, the mixture richens slightly for a second or so.
If the engine gains power as you roll the throttle off, then the main jet is too small and you need to fit a larger one.
If the engine staggers slightly or has a hard hesitation, then the main jet is too large and you need to fit a smaller one.

 

[gamorg02]

ok so that was for HD bikes, and altho i thought similar tests might be applicable. i did the roll off test. no difference normal vs full choke. it takes until about 2/3 - 3/4 throttle to begin feeling any decel. can anyone confirm?

top end actually feels pretty damn good. did some tests, 1/2 choke, full choke, ran best at no choke. still doesn't mean i might be able to drop one main sized down, esp with the stage 7 needles tomorrow.

putting choke on for low end decel popping issue, completely clears it and putting it on slightly for 1/3 - 2/3 accel thru midrange clears those issues up as well.

also thru all those tests today got 32 mpg with shell 89.

funny feeling my decel/slight accel popping might be gotten rid of with my a/f screws, but going to take care of midrange first, as i think on decel around even 3k the needles are slight players. and the needles should richen that up a bit.

 

[1967vmax]

Hi i also have Seans kit, I had to send my carbs to him becuse the local yamaha shop fuckd up the floats and the jet blocks, Currently im running 162.5 mains cured the 7k stumble,Pauls shim kit ,dynojet needles and springs, 3rd clip pos with 3/4 washer. I started out with 155 mains and went up, had the stumble with 157,160s @7k. Getting 38mpg I live in Schellsburg Pa, hope this helps, JIM

 

[gamorg02]

hey 1967, thanks for the info. did u get yours dyno'd?

how'd they **** up the jet blocks and floats?

also was yours stumbling at WOT or only like 1/3 - 2/3 throttle?

 

[1967vmax]

No the only dyno is a local Harley shop and i dont expect them to give me honest #s , so i think im go out to Seans for the dyno drags next year. As for the local yamaha shop the left side floats were lean and the right side was so rich that , guys behind me smell raw fuel. Sean said that the jet blocks looked to be casted bad and the somebody really torked the **** out of the jets.Mine stumbled just barly cracking the throtle right at 7k and went away at 8.5k. Im no expert but if your float levels are off , i dont care what you try to do , it will never run right. Also i noticed that the richer i went on the mains the further up on RPMS the stumble went.(155 to 157.5 7k stumble) 160mains stumble started in the red10k. Just to mention before i sent my carbs to sean i was getting 62 mph to a tank just crusing, thats how fuckd up the Yamaha shop had my floats set. Paul Czernics sales the shims for $40 bucks. JIM vmoa#3933

 

[gamorg02]

oh wow Jim, yea thats quite the **** up! man thats nuts....



anyways wicked update!!!!

stage 7 needles came in, started and ended with 3rd clip down. ALL MIDRANGE ISSUES ARE GONE! pluls like a ****** too. had a buddy go try it out as my butt o meter was all off calibrated. he came back and giggled for about 10 minutes. i think we're good to go minus one thing...


the exhaust still pops under light light cruise and engine decel. putting the choke on lightly allivieates all these issues.

tried messing with my a/f screws, but that was really tough to do! i forgot to get my pre-readings that the shop set on th eleft side so i couldn't put them back but that side is richer now as i can smell gas out of it, more so than the right side (which i just left at the setting the shop put it at). the shop used a/f meters....

anyone know if like autozone rents a/f meters or anything. might try to stop by that shop today to see if i can throw it on the dyno quick and/or get the screws set using their meter...


does anyone have a good way to set a/f screws? i tried high idle, low idle and i just couldn't seem to ge ***. i know the front screws need to be like 5 out or something, but on almost every screw i tried, i could make the engine stumble by putting the screw all tehw ay in, bu tnever heard it stumble again once it recovers by bringing the screw back out.

putting the choke on slightly makes my midrange pull slightly worse, so i'm not sure if i want to shim up a half of a clip, but if ya'll think it'd help i'd be willing to try..

how much popping is expected with this exhaust. i do have a small exhaust leak on the clamp going from the Y to the muffler on each side where the clamp screw is (where the clamp itself isnt' touching the pipe)

 

[gamorg02]

okay...

so shot by the tuners on my lunchbreak, and he helped me set the a/f screws, the left front carb (i think #2) was way outa whack. there was something weird in it, it didnt' want to adjust, finally with some comrpessed air, problemo solved.

ran a few more dyno runs and pulled about the same numbers as before, but its hot and humid as holy **** out today. i'll post teh sheets later, but with tboost on, my a/f curve is flatter than its ever been. makes sense with running stage 7 needles that it'd like tboost eh?

the butt o meter is liking it so far, but it'd still like to be knocking on 120hp/80tq door eventually.

he did all of that (about an hour and a half) i was helping out a bit too, free of charge. I gave him $25, figured it couldn't hurt.

he said if i came back with the stage 1 needles and all the jets n whatnot we could set up a session and get it perfect. that would be a bit more $$ tho.

i'll post the curves up in a bit, but i gotta wonder if thats about all i'll get outa this one. he did some cruise tests at 50mph/70mph and the cruise is back, as my but o meter confirmed, and not lean anymore.

 

[one2dmax]

sounds like you made it.

Sean

 

[gamorg02]

sounds like you made it.

Sean

haha getting there. i'd be interested to see the stage 1 vs 7 needles, since i may not need that much needle, but it just may need to be adjusted more.

when do you want your needles back by? and how much $$ for either set, depending on which way i go?

i am taking the bike to central NY this weekend so i'll probaby do 600-700 miles, and that outghta be a good testament.

 

[gamorg02]

oh and as far as i can tell, no more exhaust popping on decel, looks like it may have been a function of that one carb idling rediculously lean (well over 18:1 a/f ratio)

 

[gamorg02]

dynosheet attached...

the one green line is hard to read, but thats the same run i attached in the beg of the thread (for comparison)

the red/blue are:

stock springs
162.5 mains
stage 7 needles on 3 clip down
177.5 PAJ2's

blue is tboost
red is vboost

i attached it twice and here it is, not sure which is gonna be easiest to read..

 

[1967vmax]

Yeah sounds like you are real close ,I messed with the A/f mix screws and i still have the pop on decel but, i ended back a 2.5 turns out,my bike seems to run the best there. Sean let me knw when you have the dyno drags. JIM

 

[gamorg02]

yea def...

minus that 3k dip on the blue (tboost) line, that a/f looks pretty good eh?

 

[gamorg02]

another interesting tid-bit. the N at 5k RPMs was actually where the bike goes to the main jet. we wathced the carbs to see at what point it goes to mains at WOT. its right about 5k incase anyone was wondering.

 

[gamorg02]

oh also, there was a hyabusa sitting next to us at the shop.

it just broke a land speed record this weekend for 'stock' bikes (non torpedo bikes he called them)
268 mph in a mile i think.

it was the 636 hp one, had to be detuned to high 400's/low 500's

 

[[email protected]]

another interesting tid-bit. the N at 5k RPMs was actually where the bike goes to the main jet. we wathced the carbs to see at what point it goes to mains at WOT. its right about 5k incase anyone was wondering.

How can you see the carbs go to the main? Just curious, never heard anyone say this before

 

[gamorg02]

watched a full WOT run with the airlid off the carbs. watched once the slides were completely open.

its obviously not perfect, but +/- 5-10%.


it actually came about b/c he was saying it was all mains at 3.5krpms and i said i though *** was closer to 5.5k or 6k. he said well lets find out.

now this was a 5th gear WOT run, so it might be slightly different for other gears (maybe?) but just a guide maybe?

 

[[email protected]]

watched a full WOT run with the airlid off the carbs. watched once the slides were completely open.

its obviously not perfect, but +/- 5-10%.


it actually came about b/c he was saying it was all mains at 3.5krpms and i said i though *** was closer to 5.5k or 6k. he said well lets find out.

now this was a 5th gear WOT run, so it might be slightly different for other gears (maybe?) but just a guide maybe?

Gothcha, thanks.
I would think throttle position, rpm, and vacuum all have an effect??