Carb needles

[Spamy]

I thought Id post this so others can avoid the mistakes I had made.

Ive been fighting with my GT550 carb tuning for a few months now. I originally bought rebuild kits for the carbs. Installed them and they never worked quite right. As I got farther into the troubleshooting I started to replace all the jets, adjust the floats, just about everything. Nothing helped greatly. Lastly I just never double checked the needles provided by the kit, mostly because its such a pain to get to them.

Pulled them out and searched the internet for a while for part number Y48. Nothing really comes up. Anyways I decided to check some old stashes and stumbled upon my old needles that I thought I had lost or discarded. Compared them against the kit needles and the kit ones were not even close.

I put the stock ones back in, and now it runs like a champ.

In the pic the gold one came in the kit, the silver one is stock.

[tz375]

Y48 is an aftermarket number and a pretty good indication that it is wrong. I have measured a few sets of replacement (kit) needles and they are all off, but none quite as far wrong as those.

[pearljam724]

Your finding, Spamy. Is the exact reason, there isn't a rebuild kit out there worth a damn. This is a very common issue. Parts, don't match in regard to size of needles, jets, etc. Knowing that and they're all very over priced. Makes me avoid them at all cost. Also, the parts are much cheaper if bought directly from a Mikuni retailer. You save money that way, get the correct parts and don't pay for 75% of parts not needed in rebuild kits. Jets will last forever, as long as the screw end is not butchered in regards to removing them. Valve needles usually last forever. Only thing that are sometimes subject are the gaskets and o-rings. The gaskets are usually junk in rebuild kits. I once bought aftermarket valve needles that were advertised for my bike and the needle stem was about 3 mm too short, lol ! I reset my float height 95 times, thinking that was the problem.

[Vintageman]

What you are finding, possibly, is the fact the GT550 has two sets of carbs 72-73 and 74-77. The needle is different and you may have bought the wrong kit (They typically only made one of these years and not the other)

Same true for T350, and T500 for example

This is a very common mistake and gives Keyster a bad reputation.

If you need a jet needle and its obsolete I would run a keyster any day given you get the right one

If Mikuni is available of course use this. Machine finish is better

That original needle is not too bad. Just a tad bit of oxidation. Usually, they are not worn unless many miles on bike. And so would the needle jet be worn egg shaped.

Now if they have oxidation unfortunately most likely so does the inside of the Needle Jet where it meters has a moon crater textured surface where it should be oh so smooth and shiny. I find needle jets are more an issue than jet needle on old stuff due to oxidation. If obsolete one wishes there was an aftermarket option

These dang flat slide carbs like you find on 2002 and up carb’d ski doo or polaris snowmobiles have jet needle pressed in … can't change (well, cant get replacements that I know of)... that sucks. Talk about a vehicle that can suffer oxidation from moisture, poor storage practice... or is it ethanol doing this too?

I diverge... yet again