Needle Jet for GT550

[Vintageman]

Hello,

I have a 1973 (K) GT550 it has the O-8 jet needle. I find the midrange too lean and will ping if you hold throttle abuot 1/3 and let the engine pic up RPMs ( I have expansion chambers too). I move the needle clip downto 4 and then final 5th position to richen things up. This helped, but not all. I see the later model GT550 (M, A, and B) ran the next large P-0 Needle jet and 4th clip on jet needle.

Does any one now the proceeding number for the needle jet (182)? Does only one know where I can buy new Needle jets for this? Not sure if still made.

I was thinkng of adding a small nylon washer under needle to create a virtual 6th slot, but would need to fit in slide well and around needle tight so it wount move and be centered. Wonder if need will be too short at WOT. Well a P0 or P1 Needle Jet should do the the trick if I can find one?

Thanks

[tz375]

Good idea to fit larger needle jets. that will increase fueling at all throttle positions and proportionately more at the mid- bottom.

[Vintageman]

TZ375,

Any idea where I can buy one that is a P-0. I don't know the seria of these Needle Jets... Does anyone. For example, they are not 159-P0 for example.

Help!!. Does anyone know the series that is in the GT550. Does anyone have one out and can see if printed on it. If we know the series I wonder if one can still buy them new somewhere. I think the later GT550 with P0 instead of O8 factory knew it was better after much history. Well with chambers I need at least this.

So does anyone know the series of the needle jet for GT550 and who may sell them.


Thanks

[tz375]

I don't know what series they are, but they must be marked on the existing jets.

Have you tried removing one and checking it or is that not an option? We can list many that they are not. They are probably 169, but could be 172, or 182 or 192 or some non standard size made just for those bikes - Yamaha did that a few times.

[Vintageman]

Tz375,

They are on the bike. Recently again took them off to increase main jets (too lean on top would cut out) and adjust need clip. Then I had to re-synce them since seperate carbs; I Just didn't feel like taking them off again unless I get new needle jets, but may have to just to get the series. I looked at babbittsonline.com for example and see not available, so this concerns me.

I wonder if a GT380 is the same series, I have some of those carbs setting around.

Curious if anyone ever had to change them and found some new ones for sale?

Good news though, I turned in the pilot jet air screws (now about 5/8-3/4 turn out versus 1 1/4) to richen things up. This cured the lean issue I was having (maybe I was only around 1/4 throttle not 1/3). This surprised me. Maybe a bit too rich at idle now, but the extra fuel covered a bit for the needle jet early on. I am so pleased. You know when you just lightly open the throttle, riding easy, and let the engine slowly climb in rpms . Now she climbs smooth and with no knocking as rpms get high (yes I should shift earlier, but too fun to here those pipes zing!). Also clue was when I let off I would here a ping for bit as the thing leaned out

Funny I had an issue with my Yamaha R5 bucking when let off gas and again the Pilot jet too small was the issue. Someone on the aircool-rd.com site has for a signataure "Need a bigger Pilot Jet". That quote has helped me for sure.


This bike good really use the P-0 Needle jet. If anyone knows where they can be purchased let me know. They came on the later model M, A, B GT550 and I can see only used there by Suz. If SUz changed to P0 from 08s I see why

[Vintageman]

The GT380 are a 164 series Needle Jet. I don't think the 164 series are made anymore.

[Coyote]

If Mikuni ever made it, these guys have it. Download the catalog pdf.
http://www.sudco.com" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

[Vintageman]

Sudco does not have it. The 164 is a OEM series only (per sudco).

[Vintageman]

I want to correct myself. I opened up a 1976 GT550 set of carbs. The needle jet was stamped 172-P-0 so a 172 series not 164 as I said earlier.

Thinking they were not available I bought these late model carbs used off eBay. They that did have the P-0 instead of the O-8 size. But the insides of the needle jet under a microscope looked pitted due to corrosion . I have found that even this level of corrosion can compromise behavior/ ( I had two 1982 Ski Doo single carb Everest. One crused so perfect and the other not quite so smooth. If I did not have two I would not have known it could be better. Long story short it was the needle jet for one had such pitting and the sole issuey)

Searching it looks like the 169 series is the same as the 172 (Jets-R-Us for example show 169/172). I am stoked ! I will buy three soon.

Not much difference is size between O-8 and P-0 (.001 mm). Should I get P-2s ?

As mentioned my GT 550 has this bit of ping when you back off throttle somewhere between 1/8 open maybe more/maybe less… hard to know for sure.

Placing the clip on the needle to the last position (5th) and turning the pilot air jet about ¼ open pretty much gets rid of the problem. However, I found the needle at 5th caused a large drop in miles per gallon. I was getting high/mid 30s which sucked and not even 30 mpg at 5th. So I put the clip back to fourth, and some of the ping came back, but gas mileage did improve.

So from my understanding in need to richen pilot or needle which cover most of the area I am concerned. Maybe just a larger pilot will due. Well the later model up the Needle Jet size and drop the clip from 3 rd to fourth. … Some specs show the later pilot size drops???

I need to make a decision. I think I’ll get the P-0, and up the pilot jet. I hope this does it. I am getting tired of taking those carbs a part plus the $$$$ Don’t we just love taking carbs a part.

Long reply, but at least wanted to correct myself about needle jets series for the gt550

[Buffalo-guy]

Have you checked the obvious, and made sure that your ignition timing is correct? Too much advance can give you the ping that you describe. Just a thought. Cheers.
Fred

[Vintageman]

Buffalo-guy,

Yes good point. My timing is set to factory via dial gauge method. Event though I use chambers I set to factory advance setting. I know that some state to back off and go a little more retard with chambers, but this is for over rev/top end if I understand. I find that I drive mostly street and cruise/torque. I suppose the other issue is I am running lean (week seal)

Why do you think the factory changed the jetting on the GT550 during the 75, 76, and 77 versus 72, 73 and 74. I don't think anything else changed? I am optimistic they found what I see on the early model (worse with chambers?). The issue is right where the Pilot jet and Needle jet overlaps.

So no else has seen this?

Still don't have new Needle jets, on order, but will let everyone know.

[tz375]

Some pipes create a more effective cylinder filling ie higher effective CR and that needs later timing to avoid ping. Back off teh timing by 1 degree and see how that compares and then try 2 degrees if it doesn't fix it.

To make it richer at small throttle openings up, go for a larger Needle jet. If the issue is 1/2 - 3/4 raise the needles.

I'd try timing first and if that doesn't cure it, go for larger needle jets - say p-2 or even p-4 which will richen it disproportionately at the bottom end.

[H2RICK]

My service bulletins show that the GT550L used a P-0 needle jet.
This would make sense because the unitized carbs were used for the first time on the L models so there were bound to be changes in the internal bits as well.
However.....the listing I have in the crossover book for the L model is part #09494-00116....but it is shown as an O-8 jet instead of the P-0 listed in the service bulletin !!!

The crossover book shows part #09494-00105 as the needle jet for the GT550K....but it does not list the size or the type, of course.....and there's NO listing for the 550J needle jet at all !!!

And, in another twist, the 550M/A/B models used ANOTHER size entirely which is part #09494-00142.....again NO size or type listed !!!

And, at the end of all this, the carb set I have been robbing bits from to help other 550 owners keep their bikes on the road is missing all of its needle jets.....so no help there, either!!!

[Cliff]

Pinging? I'll just throw this in to help confuse things! My bike will "ping" on any fuel with ethanol in it. Doesn't matter what octane rating it is, if it's an ethanol blend, she'll ping and I have to retard the timing. I'm 1.0 mm oversize bore with .05mm milled off the head, stock intake and exhaust, circlips in the fourth groove from the top.
Also, try running with the petcock in "Prime" instead of "Run" or "Reserve". On the older petcocks there were some issues with fuel starvation.
Cliff!

[Vintageman]

I still could use some help one this. First the needle jets I bought were not correct. 169 series were supposed to be same as 172. Maybe true, but I think the Gt550 with separate carbs has a different style needle than the later model 3 ganged unit (where I got the 172 number from think it was the same).

Does anyone have access to a separate gt550 carb to see what is written on the needle jet? I could take mine apart again, but would be nice if someone had one off. If I can't buy any no need to take off

I have tried fuel without ethanol (93 octane) and have back-off timing. Regardless , I can make my bike ping. It only happens in a specific way, need to be between 5000 and 6500 RPM and the throttle about 1/4 open. I know where it is and I keep going there ... drives me nuts. Either side of this throttle position is fine. If put larger Pilots that helps but drowns the low end since the issue is really not idle to say 1/8 throttle, it is just above that.
I need either a different cut slide (2.0 instead of 2.5) or the large diameter needle (P-2 instead of O-8). These items cover that area. It looks like there were two offering for a slide and needle jet, but both are obsolete today and no description as I look online at Suzuki parts data

Well I am not sure if someone knows the number of the on the older style gt550 carb .

As an option, I think if I could buy a a used set of used O-8 needle jets I could have them reamed to a P-2 size.

Thanks