Project The Dying FZ

Don't know about you guys I have a different taste in sausage...



Ummm... so back on topic. I think the attention here needs to be the carbies... don't know why it's flat spotting at high revs (may be too lean) or why it's so damn sensitive with the throttle. I can tap it or turn the handlebars the revs drop and it cuts out.

 

Could be... It didnt do that before i put the exhaust on and the coolant in though.

 

Soooooo... after much tinkering I decided to pull the carbies off and see what we got again.. make some records and all that crap. The erratic behaviour of this bike is definitely carby related in my opinion. Starting at the top (be prepared for lotsa images after the waffle!)

According to the manual these should be Mikuni BDS26 carbies. I'm hoping they're not a dogs breakfast of things because for all I know they could be. Interesting that the needle jet setup is similar to the 3LN5+, as this bike actually predated the 3LN3 and even the 2KR being from 1986. It has the holding needle setup we all love, hence the needles seem to be worn evenly. Why did they change it to change it back I wonder? And yes it's real and not some sort of retrofit - I checked the manual. I also know the washer/o ring is missing from the pilot screw photo and also the retaining clip from the needle photo, I just left them out when I happened to take it. The O-rings for the pilot screws are toast though, but the carby bowl seals look pretty good. The setup at the float needle is quite different to what is on the FZR though. The other thing I noticed is that (have a look tell me I'm not imagining things) the main jet seems to be 72.5. The manual calls for 77.5 so they might be too small. The pilot jet is "15", the emulsion tube (called the main "nozzle" in japanese) is marked N-8 (and has a 496 marking on it) and the Jet needle is 4DV1. So apart from the main jet, everything else corresponds to the manual.






This one's for @maelstrom... I don't know if litetek have something that could replace these seals. I reckon pilot ones have got to be the same size as the FZR so I might pinch those O-rings from the rebuild kits I have.



Definitely 72.5 right? Might need to find some 77.5 ones...?



The other thing confusing me is how the idle screw impacts the pulley that the throttle cable is attached to. It doesn't look right to me.... The manual isn't overly clear on it either which doesn't help. Something's going on there, I'm sure of it.

 

Ah good to know... could you possibly take a photo/measure your idle speed screw position please mate? I'd like a benchmark for this one if I can.

The manual definitely says 77.5 main jets for this bike. I'm thinking now that these could be recycled 2KR carbies....

 

Perfect thanks. So the carby isn't missing anything then. 9mm of thread is a good start I'll put it at that when I throw them back on the bike. I think I should order some new main jets, there doesn't seem to be anything untoward with these carbies so the erratic behaviour of the bike at idle etc is a bit mysterious. Could need a sync i suppose, should look at that as well although they have been bench synced.

 

Yeh I just pulled out my keyster kits and are using the pilot O rings from there (new ones) and putting them in, they're the same size. I've richened it up a bit, taken the needle down a notch and put the pilots to 3 turns out so we'll see what happens. I'm not sure it will run that well but can only try to see what happens. When I get the new jets they'll go back in and I'll put it all back to stock.

 

Main Jet #3 is 75 too, the rest are 72.5 when all should be 77.5 so there's another issue.

 

Well there she is after doing the idle/pilot screw seals. The carbies with the 72.5 jets are all two notches from bottom and the one with a 75 jet is 3 from bottom (ie at stock). All pilots 3 turns out. I think it's better at least now it can hold idle without cutting out. it's still a bit sensitive so I expect on the test ride it will probably die on me. She's a bit ticky as well, sounds like one or two of the exhaust valves may be out of spec... not sure how as I did them all on the loose side. Could be the old crappy oil I'm running through her as the rings cut in making it top end noisy. Might do an oil/filter change after a brief test ride and see if it quietens down a bit.

Getting a bit excited now too...

 

Yeh I didn't write it lol

Hey @my67xr can you do me a favour... are you able to tell me if in your 2KR carbies the thread is 5mm or 6mm? I don't have the tools to measure (nor the bits to go that small) and the people selling jets have asked me what I want. I would even consider sending you a few bucks if you sent me one of the main jets so I can compare and then send it back to you... it all comes for the US or the UK so I want to be 100% sure before I order them.