Tuning and Jetting My 1982 450

[gs11ezrydr]

I looked at the Dynojet web site and they show 2 different jet kits for the 1983 gs450 which has the same carbs you have been working with. The U.S. part# is 3113 and they have a euro model part# E3113.002 they both are stage 1+3 and come with special profile needles,shims,slide lift hole drill bit,clips,and 4 sets of jets. They use there own jet numbering system so the sizes won't match the mikuni ones.What I have seen in the past what I'm really paying for is the needles as often I have had to use some of my own jets with doing other mods not described in the jet kit. But it may be a source for some unique profile needles for you to play with.

[PPPPPP42]

That is something to look into but the cheapest I can find the US kit is $70 with free shipping off ebay. I'm guessing they use a different numbering system so people don't just go buy the equivalent Mikuni parts for 1/3 the price.
I would still like to find a widely available mikuni needle and jet that would fit both US and euro spec carbs with intake and exhaust mods.

You did however tip me off to an interesting fact, 83-* GS450's used a 5CDT60 needle and O-6 needle jet, 45 pilot jet and 115 main. They have different floats and needle and seat and a few other bits.
The drastic difference in pilot jet is because they changed around the design and added the rubber plug over the pilot jet so its getting fuel in a different way. I'm not sure if that needle and jet would work in earlier carbs but I am curious to see the specs on them if I can find them.

EDIT: if this is accurate

http://www.ebay.com/itm/GS450-GS-450-MIKUNI-CARBURETOR-JET-NOZZLE-414-0-6-/300577967764

the 83 stuff looks totally incompatible. That jet is a totally different series and not just size.

[pete]

Hmmm ok, sounds like I need to get one of my needles out again for some more measurements... not sure when I can do that just yet but will try soon.

That's weird how the US carbs are done, as mine have all those same components and when assembled with the needle in the richest position, I can still feel the needle has some movement and is not binding on the retaining stem at all...

So, with the needle assembled as per stock, can you pull it down and have it spring back in place? If you add shims under the E clip can you still do that? If you can, then it's not binding...

Here's a crappy photo of my needle with a shim installed:



And another crappy photo of the needle assembly from my factory manual:



Note that there is a washer under the E clip to stop the E clip binding in the spring... this is not a shim. The shims go under that washer...

If one of you have your needle out, can you take those measurements?

I need to work out where the taper starts on mine as well.

With the Dynojet kits, be very careful with the 450 kits... the one to fit these carbs in only a Euro one as is the E3305 stage 3 kit, listed as "External main jet". The '83 ones are different carbs and won't work.

The '80 - '82 carbs have the brass floats and main jet in the float bowl, the '83 and onwards have the plastic floats, different pilot, etc.

[PPPPPP42]

The problem is that 3, 4, 5 & 7 in that diagram are all smashed together on ours, so unless you remove 5 and replace it with something thinner there is no more up for the needle to go.
On yours with the extra notches moving the needle up (clip lower down) actually makes it go farther inside 4 and 5 which can't happen on ours with only one clip notch to use. Near as I can figure 5 has to be replaced with shims of less than its 2.2mm thickness. Extra shims anywhere else just compress the spring more because the needle clip is already maxed out for upwards travel.
If you get a needle out again double check the spacing on the grooves, I am curious to see how many shims equals one clip position adjustment.

[MOC]

Pete, think about the layout of the diagram above. the spring is pushing up on the clip from below. eventually the clip hits something. adding spacers beneath the clip isn't going to raise it higher because it runs into the spacer.

it's kind of like if you were to put stilts on and try to walk around in your office. you'd bump into the ceiling. putting on bigger stilts wouldn't allow you to stand taller. the only way to stand up straight is to move the ceiling.

same principle here. The distance between the bottom of the Jet Needle stem (4), and the hole in the bottom of the slide is fixed, (ceiling to floor). moving the clip allows the needle to shimmy up higher into the recess in the bottom of the jet needle stem, but adding shims beneath it has no impact on the mix. and the poor sad sacks over here in the US don't have the option to move the clip

adding shims ABOVE it will lean out the mix because you're effectively lowering the ceiling. the only way to enrich is to remove the nylon spacer (5) to raise the ceiling.

that's the problem i have. i've totally removed the spacer and have run out of room to raise the needle. and my needles aren't grooved, so i can't adjust that way. I'm going to try tearing my carbs down again this week and put a video up on the tube of what i'm talking about.

once again, sorry for derailing. and sorry for the poor typing. i'm doing this on tablet and it's kind of fidgety

[pete]

I get what you mean guys, it's just weird given how much movement I have in mine. There's definitely something different there!

I think to see the difference clearly, I'll need to take more measurements of my needle, and you guys will need to do the same.

Once that's done accurately, then we should have an idea for different needles etc. too.

The only issue for me is that my digital verniers are cheapies, so I'm not going to be 100% accurate. Not sure when I'll get time at the moment either but hopefully soon.

[furu14]

I have now done some testing to see the effect of floatheight on these carbs(44100)- do not go lower than 26.6mm or problems w idlecircuit may occur-bad idle transitions and no good function on mixturescrew.
good pods/airbox (no lid) and "open exhaust"-3,5rounds out(17,5 jet)-needle raised 1,5-2 clip position and main jets reamed out to 1,30mm.
now my bike runs real clean and strong in 20degrees C.

[pete]

Thanks for the info, and yes float height definitely has to be right on these!

Glad to hear she's running well

Yesterday I got out with the Katana guys for our Dyno Day and I've got 32hp at the rear wheel (although some of the guys were saying the dyno was reading low) but the big thing for me was seeing how rich I've made the carbs... off the scale at 5K RPM!



I must say though it was nice hearing my bike without sitting on it too, sounds real nice once she gets up past 5K RPM

So now I have the required motivation to pull the needles and measure them.

I'm going back to the 145 mains and dropping the needle one notch.

[pete]

Ok, 145 mains in and needles down one notch, mixture screws remain the same for the moment until I see how she runs tomorrow.

I also took a bunch of measurements of one of my needles and also measured the recess in the retaining stem as well.



So referencing this one again and remembering my digital verniers aren't top notch:



a = 48.30mm (needle length)
b = 12.69mm (taper point)
A = 2.98mm
B = 2.62mm (tip diameter)
10 = 2.98mm
20 = 2.93mm
30 = 2.86mm
40 = 2.72mm

And the recess in the retaining stem as best I could measure is about 5mm.

I also measured the notches for adjustment, and best I could tell by measuring the E clip is the notches are 0.40mm and are also 0.40mm apart.

The bottom of the lowest notch is 6.60mm from the top of the needle, and from the top of the top notch to the bottom of the bottom notch is 4.80mm.

Hopefully that helps you guys somehow...

[PPPPPP42]

That should help, thanks.

If the plastic spacer in our carbs is 2.2mm then we should be able to remove it and replace it with three of the .5mm washers as a starting point (or file it down). That would give somewhere in the neighborhood of 1.5 to 2 notches richer adjustment on the needle.

If I ever got another bike it will be an 83 T model since it seems to already have the handlebars, seat, wheels and carbs that I want (they have kits for the later carb). But my 81 L was only $200 so I will make do.

[pete]

Cool... but bugger! I knew I forgot to measure something... that spacer!

[jeffasaurus2]

I measured my spacer to be 2.5mm exactly...

[MOC]

I have some larger main jets on order at this point. I'm hoping that a richer main and a leaner needle setting with sort out most of the problem. Thanks for those measurements!

[pete]

No worries, hopefully they help somehow!

You can also try a leaner mixture screw setting as a bit of a compromise, but not sure how much that will really help.

As for me, the leaner settings have messed up the idle and mixture settings as expected, but to make it worse I also had the idle bumped up to help prevent the bike stalling while I had my starter issues last week.

Now that she starts instantly when I press the button, I've wound the idle back down and I've leaned out the mixture screws about 3/4 of a turn too.

I'll keep fiddling but it does seem a little better at that 1/4 to 1/2 throttle mark I think so far...

[MOC]

im tempted to buy an Air/fuel gauge and sensor just to see what's going on... it may come in handy with other projects as well, like an eventual exhaust upgrade... let us know how things turn out.

cheers