ZXR 400 L2 series

[Daddypellecx]

I have a 1992 zxr 400 with me with very few km 19.000 (who knows if they are true), I have done an infinite series of aesthetic and mechanical works on it, polishing, electrical, adding missing parts and replacing rubber parts that were now gone etc.. I currently have this configuration.
•Fuel supply: starting from the tank, tankerite, tap filters + new gaskets, new fuel pipes, new filter ,new Mitsubishi fuel pump,

•Carburetors: min jet 40 , max 100 , mix screw 1.45 turn from fully closed , float height 11 mm , new conical pins and gaskets + new internal pin filters

•Foam air filter similar to oem without snorkel valve play not perfect but within limits (I add photos) cylinder pressure 156/150/150/156 psi 1/2/3/4 new spark plug cables + NGK caps, cr9ek spark plug

•exhaust manifolds 52 mm 4/2/1 + exhaust terminal with Db killer inserted.

Impressions, the bike runs well, very well after a lot of cleaning and synchronization, the idle and the entire 1500/10,000 rpm range is fantastic but from 10,000 to 14,000 approximately the limiter seems to have a hesitation before opening completely, which I can only do if the bike is perfectly warm otherwise it goes around 10,000 which has improved by removing the snorkel, furthermore I have noticed that now the starter enricher even when very cold floods the bike, in fact it starts simply by touching the accelerator and maintaining the idle at 1,500 rpm for a minute or less and then turns by itself, if I try to insert the starter it turns off the bike.. all things that make me think of a rich carburetion, in fact I would like to ask if you tried as a test to remove the sponge filter and see how it turns, because if I am right about it being rich it should help to lose weight right? I might in that case get some 98 top jets..
I hope my English is understood, I write from Italy, any advice is welcome, thanks

[Daddypellecx]

I'm adding a video of how it idles, and one where I try it by pulling a bit even if it's due to road conditions etc.. I couldn't show the problem of hesitating at 10,000+ rpm

https://youtube.com/shorts/RSsuraUp2XE? ... s9IJDvScVM

https://youtube.com/shorts/rfxaTjnSCmk? ... PDkMaUD5ol

[Daddypellecx]

small updates, going from minimum jet 40 to 35 as per the use and maintenance manual and mix screw at 1 and a half turns from fully screwed. the bike has started working again with manual air (before it drowned) and even if it mumbles a minimum between 5/6 thousand rpm then it opens well up to the limiter, however it was a quick test, today we switch to the vacuum gauge as the minimum now remains accelerated (probably with a smaller jet the carburetion has been refined). I will keep you updated, I hope it does not remain a monologue

[Daddypellecx]

[album][/album]

vacuum gauge test update: the butterflies are perfectly synchronized, but the bike always stalls at 2000 rpm for a few seconds and then goes back to 1,400/1,500 rpm, the strange thing is that when I performed the test with the vacuum gauge instrument none of this happened, it went up and down perfectly, obviously the test was done without the airbox because due to its shape it would be impossible to synchronize the screws, so it had been removed, the only thing that comes to mind is that the OEM sponge filter does not match well with the complete exhaust system 4/2/1 air emptying/refueling ratio, making the idle a mess, also because as an air/fuel mix from what I notice with manual enrichment it seems right, perhaps slightly lean, and I know I read that this defect like double minimum can happen, being lean.. now I don't know whether to try to use a more breathable K&N air filter even if I would lean the whole range and I would prefer not to, since I mount 100 at high or try to increase the screw of the air/fuel mixture by unscrewing it half a turn, bringing the adjustment to 2 turns or 2 and a half, which I will probably try tomorrow, I remind you that I am using the original set up from the use and maintenance manual, any advice is welcome, thank you very much

[Daddypellecx]

[album][/album]

vacuum gauge test update: the butterflies are perfectly synchronized, but the bike always stalls at 2000 rpm for a few seconds and then goes back to 1,400/1,500 rpm, the strange thing is that when I performed the test with the vacuum gauge instrument none of this happened, it went up and down perfectly, obviously the test was done without the airbox because due to its shape it would be impossible to synchronize the screws, so it had been removed, the only thing that comes to mind is that the OEM sponge filter does not match well with the complete exhaust system 4/2/1 air emptying/refueling ratio, making the idle a mess, also because as an air/fuel mix from what I notice with manual enrichment it seems right, perhaps slightly lean, and I know I read that this defect like double minimum can happen, being lean.. now I don't know whether to try to use a more breathable K&N air filter even if I would lean the whole range and I would prefer not to, since I mount 100 at high or try to increase the screw of the air/fuel mixture by unscrewing it half a turn, bringing the adjustment to 2 turns or 2 and a half, which I will probably try tomorrow, I remind you that I am using the original set up from the use and maintenance manual, any advice is welcome, thank you very much

[Daddypellecx]

various updates.. installed 35 point minimum jets as originally (I thought the 40 were oem) since they came out in a carburetor rebuild set for the zxr 400, and the manual enrichment system for starting worked again, so yes I had a very rich idle, played for a while with the mix screws and it seems after trying and retrying various configurations to have found the right balance, now after a rev the bike no longer stays at 2000 rpm for a few moments (a symptom of leanness) but the rev needle drops immediately, nor does it drop below the 1,500 rpm threshold (a symptom of richness) (set idle) after a rev, all this with 2 turns of mix, instead of the 1.5 recommended in the use and maintenance manual, now the bike at idle is perfect even if it seems to have a flat point around 6 thousand rpm, then just insist slightly on the accelerator to go up perfectly to limiter, which makes me think of the needles, to have more clues if the needles are lean or rich, I got myself a narrow band lambda probe with its relative screen where I can read the values while I'm running, in fact I'll do some tests by recording the air fuel values via video during the openings with a hot engine and with my weight (so with the engine in traction), at the moment I'm waiting for the connection for the sensor that is arriving that I will take to tig/mig welding... new updates soon

[Daddypellecx]

apparently the forum is no longer frequented, a real shame for the zxr 400 and the lovers of this small great bike, I went ahead with the work, and instead of continuing to disassemble and assemble, I welded a small flanged nut m14x 1.5 mm on the exhaust manifold in the 4/2/1 position (1) where 2/1 join so as to have the reading of how the bike turns, noting a narrow lambda band and its stoichiometric detector, now it will not be a hi tech instrument but it did its job, showing me a very high lean condition at idle even with 3/3.5 turns of the mix screw open, put a larger jet of the minimum 40 instead of 35, and with a 1/6 of a turn therefore almost closed, I found the right amount of fuel at idle by putting it on an arf that goes from 12/13, while at cruising speed with a jet 100 and float height 11 mm from an 11 arf that drops to 14.5 in deceleration, needless to say that the little zxr has completely transformed, no longer having holes in the delivery or hesitations, in the meantime I am looking for a more breathable air filter, to improve the flow of air for when the heat comes, but I have never been so satisfied, it runs like clockwork, I recommend the modification to many especially because I often read, problems with starting hot/cold, probably lean revs.. I want to remind you that it is completely original in terms of engine or other with the exception of the 4/2/1 exhaust I think it is micron, with LeoVince exhaust and db/killer cap for road use.

[Daddypellecx]

Qualche foto del set up per ottimizzare la carburazione

[masterofinsanity]

Great to see people keeping these bikes alive, looks a very clean bike you have!

[Daddypellecx]

yes thank you very much friend, me and a group of friends, we care a lot about this bike, and each of us has made our own dream bike, I personally always make some improvements, soon a new clutch will arrive with a new oil change 3k km

here is a test with the arf instrument mounted, the bike has become another story, increasingly happy to own one

https://youtube.com/shorts/OcqlxS50sTI? ... C_u8x5Ysnq_

https://youtube.com/shorts/gWz88xDqmOg? ... NxYz0Dx8fU

[banner001]

very nice!

[Daddypellecx]

thanks banner I'm very proud of this little zxr 400, today on the big ride it performed really well, even though it was incredibly hot, it worked like clockwork, really really satisfied with it and the emotions it gives.