GT550 main jet mystery

[tz375]

Anyone here got a GT550 J or K by any chance?

I stripped a set of J (72) carbs last night to clean them and noticed that it has Large ROund main jets which are 5 x .8mm threads but the 192 series needle jets are tapped for Hex jets 5x1.0mm. There are small brass adapters in there that I have never seen before.

It also had two O-2 needle jets and one O-5 needle jet but the parts list shows no adapters and all 3 O-5 needle jets. Anyone been inside a set of early carbs care to comment?

[Alan H]

I've got a J and two Ks under rebuild, so exactly what info do you need and I'll have a look this w/end when I get home. (Currently in a hotel near Cambridge!!)
What carbs are they? High top or low top? Can you see any numbers on the carb bodies near the top?

[tz375]

J model with high tops and long slides.

Carb numbers
340
11M and R and L

Question: are all three needle jets the same or are they O2 on outers and O-5 center?
Q2: Do they have Large Round main jets and if so do they screw into teh needle jets or into an adapter with different threads each side (male and female)

Thx.

[Alan H]

I'm currently away from home, but someone is asking similar questions HERE (clicky) so it might be worthwhile to have a look if you need details sooner rather than later.

[Suzukidave]

Its something .. just when you think you have seen all the changes Suzuki did you run across something new .

[tz375]

You are right Dave.

My High tops have 192 series needle jets with O-2 outers and an O-5 center. The book suggests that US had O-5 and Europe had O-2 with different needles and much smaller main jets.

I have seen a couple of pdf files now with different suggestions so now I am totally confused.

[Rustygt550]

Try looking at this thread here too, http://www.kettleclinick.com/viewtopic. ... 9&start=10 I posted a few GT550 carb pics & what i thought should be in them.

That was untill i looked at a few other Suzuki sources & I am now totaly confused.

Hopfully Alan H can take a look at his carbs this weekend & maybe confirm a few things

Fom what i have seen the J model carbs are pretty straight forward they have 192 0-5 fitted with a main jet extender & jet needle should be a 5DH21

[Alan H]

After cleaning loads of spider crap out of the carbs, I have the following;
They are Hitop carbs numbered 340 13 L,M & R.
Needles are 5DH21 - same as my Low top carb needles.
Slides 2.5, same as my Lotop slides, but longer slides (natch!)
Mains are 95 L & R, 92.5 M (same as my Lotops)
Pilots all 25 (same as my Lotops.)

Now The K that I am rebuilding is a US model, dated August 1972 so I would have thought the jets would be different.
According to my service data manual 'other market than europe' carbs should be as above but with 27.5 pilot jets and the Lotop carbs are from an original UK J model (also 1972) with different needles and jets.
I do have another set of carbs, but I couldn't find the damn things today. I'll get the other boxes down either tomorrow or Tuesday and have a look at them as a comparison. I can't remember if they are Lo or Hi top type.

If anyone would like a copy of my original service data manual, PM me your email and I'll send a copy.
It's nearly 4 megs worth of 27 Jpeg files and covers ALL 1972 models.

[tz375]

Alan, that's great info. What series and size are the needle jets in those carbs and are they large round jets or something else?

[Alan H]

I'll have them out in the next couple of days and get some pics.
Just realised I didn't put main jet info on. They are 0-5s.

Check the other link I posted earlier, I've added to that post too.

[tz375]

Hmm. Mine has 2 O-2s and one O-5. I wonder if a PO replaced a couple with the wrong parts or if some markets and a mix that they never got around to documenting.

It also has large round main jets - are your round or hex?

And were those needle jets 172 series or 172 series?

[Knut]

You are right Dave.

My High tops have 192 series needle jets with O-2 outers and an O-5 center. The book suggests that US had O-5 and Europe had O-2 with different needles and much smaller main jets.

I have seen a couple of pdf files now with different suggestions so now I am totally confused.

Which book and pdf's? I've tried to research if there are differences in jetting in different markets. After taking apart three different carb sets (low top) from 550 K models, all of them had main jets in the 80's range (regular round type). All came from bikes that were sold new in Norway in 1973. I can not find anything in any source printed or online suggesting that some Euro models had leaner main jets, all sources specify main jets in the 90's range regardless of model year and market.
First time I saw this I just thought a previous owner had jetted it down, but when it was the same setup on two other sets from bikes that had been more or less untouched I figured it had to be a factory setup. I don't remember the needle jet size or the stamping on the needle.

[Alan H]

Yes there are different carbs for different markets. PM me your email addy and I'll forward a copy of my original service data manual from 1972 that covers ALL models.

[Rustygt550]

After taking apart three different carb sets (low top) from 550 K models, all of them had main jets in the 80's range (regular round type). All came from bikes that were sold new in Norway in 1973. I can not find anything in any source printed or online suggesting that some Euro models had leaner main jets, all sources specify main jets in the 90's range regardless of model year and market.
First time I saw this I just thought a previous owner had jetted it down, but when it was the same setup on two other sets from bikes that had been more or less untouched I figured it had to be a factory setup. I don't remember the needle jet size or the stamping on the needle.

photo.JPG

Take a look at this photo I took of the parts book showing differences for the Swedish, German & French market item number 7 shows a long snorkel type fitting on the intake of the air box, the USA & UK models never had this, just a simpler free flowing fitting.

My guess is that this snorkel would cause more restriction hence creating more vacuum pulling more fuel through the main jet. Suzuki listed for these markets 87.5 & 85 main jets whilst USA & UK markets 97.5 & 95 main jets

[Knut]

There might be a snorkel like that on one of the bikes I know of but its not something I've seen often. Guess it perhaps was the same with these as the air snorkels on the H1 and H2, most were thrown in the bin.

Alan, I'll pm my email addy. Curious about all elements of intake/carbs differences here, as two of the bikes running the carbs I mentioned has been rejetted for chambers (only mains), and there are some tuning issues with one of them running the most extreme chambers. That one probably has an ebay air box from the US too, which mean no snorkel to restrict air flow.

Thx!