GT550J pinging

[crazyeights]

My gt550 pings from roughly 3800-5000 rpms when the bike gets up to full temperature. I checked my timing with a strobe timing light and all three were spot-on. The carbs all run stock jetting and all three plugs are brown-tan. It has 93 octane gas in the tank. I don't think it has an air leak because it always quickly returns to idle and it also idles consistently at any temp. I did notice that the ram air gets relatively hot after a ride, is that normal? Should I retard the timing a bit? Is it something with jetting? Any ideas appreciated. Thanks!

[Vintageman]

3800-5000 rpms

.

Maybe it's not so much the rpm range as it's the throttle positions at the time you are in this range. Let me try here first with you.

Does your bike ping say between 1/16 - 3/8 throttle when in this rpm band?

Does it ping 5/8 to full throttle?

[crazyeights]

Maybe it's not so much the rpm range as it's the throttle positions at the time you are in this range. Let me try here first with you.

Does your bike ping say between 1/16 - 3/8 throttle when in this rpm band?

Does it ping 5/8 to full throttle?

It mostly pings from 1/4 to 1/2 only in the rpm band. It doesn't ping in other rpm ranges with the same throttle positions.

[GTandcbr]

I too have a 550j that was doing the same as yours. I solved mine by going up a size on the pilot jet from 27.5 to 30. Problem disappeared for me.

[Vintageman]

I suspect you needle jets are corroded inside. Up a size on needle jet was on option bake in the day too. Te exact size part is Obsolete. Find part #and call Paul Miller maybe he has some.

I found new 0-6 (was O-5) needle jets with chambers, back to stock pilot and stock clip position fixed this ping issue and good low speed and mpg again.

Raising needle a clip or increasing size of needle jet is a work around each with possible side affects (rough low speed - poor mpg respectively)


He is what available O-2 then jumps to P0 -http://www.jetsrus.com/a_jets_by_carbur ... mikuni.htm.

I think there is a hand reamer that will make the O-2 and O-5.5 if I recall

There is a post here -> viewtopic.php?f=2&t=12024" onclick="window.open(this.href);return false;

[tz375]

Maybe it's not so much the rpm range as it's the throttle positions at the time you are in this range. Let me try here first with you.

Does your bike ping say between 1/16 - 3/8 throttle when in this rpm band?

Does it ping 5/8 to full throttle?

It mostly pings from 1/4 to 1/2 only in the rpm band. It doesn't ping in other rpm ranges with the same throttle positions.

In that range it's a combination of Pilot jet which is less involved as throttle is opened, Slide cutaway which is most important at that points and needle jet (or needle root diameter).

Richare pilot jet may be enough to make a difference but a larger needle jet or smaller cutaway is the best solution. I'd suggest raising teh needle first as it's an easy and cheap option.

[Alan H]

If it's slightly weak at low throttle and you can't get new oem jets, lift the fuel level a couple of millimetres in the floatbowls.
Or easier, just put 95 octane in.
Your plugs should be NGK B7ES, you could go up to B8ES which are cooler.
Pinging or pinking is usually caused by either slightly weak mixture, poor quality fuel, plugs too hot a grade, or ignition timing advanced.

[Vintageman]

If your needle jet is worn inside you can tweak anything and everything else you want to attempt a solution.

If me I would simply do a look see at the inside of needle jets. If it is pitted or eroded in the barrel its the root of the issue.

good luck

[Clifford]

Could be the ethanol in the fuel! Find some ethanol free fuel or use an additive such as SeaFoam. My bike will "ping" on the interstate at cruising speed with no load at about 4500-5000 rpm. Open or close the throttle and it goes away! I use SeaFoam, about two ounces every second or third fill up and even with regular gas I don't have a pinging problem anymore! Could be carbs, could be jets, could be etc, etc but I didn't have a problem until ethanol was introduced and I have over 150000 miles on the original carbs! Check your float height first, mine are set at one inch, and try a few tanks of ethanol free or find some SeaFoam. Not saying it's not a jetting or carb faulty but keep it simple and do the simple things first! What has changed in the 40 years since the bike was made? You need fuel, spark and compression. I assume compression is good, timing is spot on, but today's fuel is not what it used to be!!