Dynojet stage 3 tuning HELP

[Kara25]

Hello everyone. A month ago I decided to install a Dynojet stage 3 on my 550E with 4-1 exhaust and K&N dual oval filters RC-2382. Stripped soaked and rebuilt the carbs with new o rings drilled the slides and installed the Dynojet needles with the E clip on the third groove as instructed with the air adapter connectors also installed and used the 150 Dynojet mains instead of the 155s after seeing a similar thread from a 550 owner doing the same thing on his bike (pilots are stock as instructed from Dynojet)Also new carb boot o-rings and clamps while I was in there. Bike starts up very easy keeps beautiful idle carbs bench & vacuum synched to perfection and mixture screws 2.5 turns out from seated. So the problem is while the bike idles if I crack the throttle the motor briefly sputters/flutters and then clear revs up to 4500-5000 rpm. All testing is done while idling (don?t want to ride it yet after finding this problem and have to tear everything apart again) If I open the throttle gradually and slowly it doesn?t do that at all. Is it needle position related? Or maybe mixture screws need more tinkering? Weak 40 year old carb diaphragm springs? Please help I think I am very close to finally perfecting the whole system. Sorry for the long message tried to put all the info in!

 

[Carter Turk]

Were the K & N's oiled w/their brand of filter oil?

What kind of 4-1 exhaust?.

Could the petcock not be providing enough fuel to meet the increased airflow of the K & N's?

I would ride it to see where the hesitation actually is, noting throttle position & rpms.

Then decide where the hesitation resides- pilot-needles-mains or the transition points between.

Not sure what HP gains are claimed for a stock 550, with jet kit & pipe, but it might just be louder w/stumble over stock & maybe only some gains @ wide open throttle.

Suppose there's always questions about valve adjustment, float height & if a too restrictive inline fuel filter is starving the carbs or if the vacuum line might not be attached to the petcock.

Seems all 4-1's have a stumble somewhere when dealing with our era of bikes.

 

[Rob S.]

Seems all 4-1's have a stumble somewhere when dealing with our era of bikes.

Mine doesn't. But I had mine jetted by a pro on a dynamometer.

 

[Kara25]

K&Ns oiled with their specific oil valves adjusted over 500kms ago all tests are done with external fuel tank but for years I have canceled the vacuum operation of the petcock by plugging the lines and using an in-line ON/OFF switch. Everything is in order on the bike I was riding it 1,5 month ago. I was using the <<getto>> method of restricting the air around the air filters using all stock components in the carbs. It was working all right up until 6500-6800 rpms where it would run lean and stop accelerating anymore like hitting an invisible rev limiter. So that?s why I decided to buy the kit and get it over with. I am baffled why when I open the throttle gently on neutral it revs strong but when I blip it or crack on it shows this hesitation. To shed more light the symptom reminds me when our of curiosity in the past I installed the K&Ns without restrictions and rode it around the block you can imagine that after the slightest opening of the throttle it was sputtering and wasn?t revving at all. Now it seems to do almost the same while stationary and while blipping or cracking the throttle. On smooth opening it revs very good with no symptoms.

 

[Kara25]

So after digging more in those forums I found out that over the years people with stage 3s found out that the Dynojet instructions on where to place the OEM washer and the DJ washer are actually wrong. DJ says. Spring -oem washer-dj washer-E clip-plastic donut-plastic cone-circlip. In reality some high regarded forum members stated that it actually the order is: spring-oem washer-E clip-DJ washer-plastic donut-plastic cone-circlip. Gonna swap the washers and see what happens!

 

[Kara25]

So installed the DJ washer on top of the E clip and still the same thing. Light feathering of the throttle in neutral produces sputtering. Steady slow opening of the throttle in neutral revs pick up normally. I am baffled. Any help will be appreciated!

 

[Carter Turk]

Mine doesn't

I thought you were still horizontal guy or are you healed up & back in the saddle?

Seems there's always a flat line or dip in the graphs for HP & Torque at a certain throttle opening, that I was referring to as a stumble.

This was a pull done at the trackday mobile semi-truck awhile back, where dyno operator-Nels said my ignitor was breaking up a 7500 rpms, hence the broken

lines on a tired/beaten engine.

Jetting was done in unheated garage by this hack/me after many on/off sessions with carbs & fouled plugs, before discovering worn carb internals, such as oval

emulsion tubes & broken air/fuel mixture needles.

20210517_150607 by Carter Turk, on Flickr

 

[Rob S.]

I thought you were still horizontal guy or are you healed up & back in the saddle?

Was horizontal, now vertical/diagonal. Trouble is, big red is in my brother's storage unit, and possession is nine tenths...

"How about we come down this weekend and buy you a nice new shiny bicycle?"

"I want my motorcycle!"

Is that 115 rear wheel HP I see from a 550?!?

 

[Carter Turk]

Is that 115 rear wheel HP I see from a 550?!?

No, a 1229-1150, w/stock cams-valves-gixxer carbs-old yosh-k & n's, w/a lot of miles.

Not wanting to hijack thread, just trying to show that sometimes there are different lines compared to a stock graph & maybe that's what being felt (flat, dip in graph) when the throttle is wacked.

The lack of velocity stacks inside the air filter confuse the air flow entering the carbs. A random thought of course.

 

[Kara25]

I understand what you are hypothesizing carter and I know CVs are not know for their mind breaking response to sudden throttle changes but still seems weird I can?t imagine if it does that stationary how it?s gonna behave while starting from a standstill on the road. Guess today is the day that I test drive it

 

[Guest]

So installed the DJ washer on top of the E clip and still the same thing. Light feathering of the throttle in neutral produces sputtering. Steady slow opening of the throttle in neutral revs pick up normally. I am baffled. Any help will be appreciated!

Try the same test with the choke pulled a bit. If it improves you are likely lean right at that point, if it gets worse you are rich. At least this gives you some idea of which direction to look. Also, testing at idle in neutral is not really a good test because it will respond differently under load. I would do the choke test and then try a short ride to see how it goes with some load on the engine.

Note that you need to be over 1/8 throttle or so before you start getting the needles involved. Below that is all pilot circuit, so don't go adjusting the needles until you have test rode it some.


Mark

 

[Kara25]

Mark speak of the devil. I am just outside my garage I took it for a short ride (the most it could carry me in that condition) up until 4000- 4.500 revs in first second or third things seem ok after that opening the throttle makes it sputter fall on its face horribly I pulled the choke and it got EVEN worse if you can believe that it almost killed the motor entirely.so I believe the needle must be raised meaning I have to move the E clip from the third groove from the top which DJ says is base setting on the second one from the top which will lean things out. Garage smells like gas galore so it must be pig rich. Tomorrow when it has cooled I will also take out the plugs to verify but I think they will be pitch black

 

[Buffalo Bill]

You got so much to learn about building power, none of the engine tuners here wanna write anything.
It starts on the inside, not the carburetors. Buy a book about building engine power.

 

[Kara25]

Sorry bill wasn?t trying to build power anyway. Just wanted to jet my carbs

 

[Buffalo Bill]

Ok, you say it idles ok and runs up to 4000 RPM, then floods.
I'm thinking you got too big main jets and the needles are too high.
Put in 1 size smaller jets that OEM to lean out WOT.
Drop the needles as far as adjustable to lean the midrange.
Test ride the bike.

 

[Guest]

Mark speak of the devil. I am just outside my garage I took it for a short ride (the most it could carry me in that condition) up until 4000- 4.500 revs in first second or third things seem ok after that opening the throttle makes it sputter fall on its face horribly I pulled the choke and it got EVEN worse if you can believe that it almost killed the motor entirely.so I believe the needle must be raised meaning I have to move the E clip from the third groove from the top which DJ says is base setting on the second one from the top which will lean things out. Garage smells like gas galore so it must be pig rich. Tomorrow when it has cooled I will also take out the plugs to verify but I think they will be pitch black

I agree with Buffalo Bill, that sounds very rich. I would leave the main jet alone for now and lower the needle one notch to see if that improves things. Only ever change one thing at a time, never make two changes or you won't know which one did what. Keeping copious notes also helps a lot. Once you get it coming onto the needles OK then you will have to sort the mains as it will bog when it comes onto them. The needles control from ~1/8-1/4 throttle, then the mains take over fully by around 3/8 throttle.

Carbs don't work on engine RPM, they work only on the throttle opening. To really see what is happening take a piece of tape and put it on the throttle housing. Put a mark on your grip or the throttle tube and mark full open and full closed on the tape, then divide the middle into at least 1/4 increments. This lets you look at the throttle while riding and easily see how far open it is. That tells you which circuit you are on when the problems begin. Your description of revs and low road speed does correlate to getting onto the needles when it bogs, but marking the throttle will let you confirm that.

Once you get it sorted well enough to run OK you can use the choke test while riding to fine tune things. I find it works best if you go onto a quiet back road where you can change speeds and tinker with the bike without having to worry about traffic. Get up into 3rd or 4th gear so the bike can pull a load without revving off the tach, let the revs fall to 2000-2500 and open the throttle to whatever circuit you want to test. Once it's pulling steady pull the choke and see if bogs, improves or stays the same. When you have it right you will get a very slight bog on the choke but nothing dramatic.


Mark

 

[Kara25]

Thanks for the replies guys today I will raise the E clip 1 position (second from top) at first to see if the problem is eradicated. I am under the assumption the distance from one notch to the other might seem small but makes HUGE difference so not gonna take it yet to the first position. As for the mains bill they are already the smallest of the two in the kit it?s the 150s DJ numbering. If even those are too big for stock motor with K&Ns and 4-1 then I am into for a big headache bcs I was under the assumption that all I need is in the kit and I will just have to fine tune it via trial and error. All the procedure up until now shows me how well the ghetto way with the restricted filters worked.. the magic of 2 pieces of bandages . I have to add that I am not looking into building a road burner just want the bike to function as properly as possible without using crazy techniques as restricting the filters etc. maybe in the future I will do a small overbore with +1mm pistons to freshen things up but that?s it.

 

[Kara25]

UPDATE. Moved the E-clip on the second groove from third. Smell of gas is gone BUT the symptom remains as before. Gonna try tomorrow moving it to the 1st groove and see what happens. Also noticed today during the short test ride that when the sputtering starts under load if I slowly close the throttle the bike picks up as NORMAL.

 

[pdqford]

UPDATE. Also noticed today during the short test ride that when the sputtering starts under load if I slowly close the throttle the bike picks up as NORMAL.

Do you think that when “under load” it is on the mains, and as you close the throttle it is on the needles?

 

[Buffalo Bill]

I had a very frustrating time trying to tune my GS550T, it just did not like any mods to the carbs. I returned to all stock. It did work fine with MAC 4>1 exhaust.
In my GS1100G I tried shimming the needles up with a tiny washer. That worked well, but I took them out. Last year I installed a Delkevic 4>1 exhaust, K&N air filter, did a head & valve valve job, and exhaust side porting. Carbs are stock. It really takes off above 7000RPM and exceeds red line easy.
I have a Dynojet kit in my 92 GSXR 1100 with a K & N air filter, stock headers, and Dyno main jets same as stock. It ran rich in the midrange and would gag at 4000RPM coming out of corners on the track. I dropped the needles down to the 2nd notch then all the way. It now has killer torque 4000RPM up. I never ride it on public roads anymore, it'll take corners at 70 mph where my other bikes do 50 mph, just way too fast.
It took a few years to understand a little bit more fuel is way too much.
Keep checking the plugs after road testing, burn the soot off with a propane torch then carefully scrape the remaining crust off with a razor knife.