90 zx400r-H carb help - running VERY rich

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fstarocka
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Joined: Wed May 04, 2016 6:33 am

90 zx400r-H carb help - running VERY rich

Post by fstarocka »

Hi everybody.. go my project bike going weeks ago - struggling my butt off to get it to run well.. i made some rubbers for the intake manifolds (what a terrible design imo)..

Anyway - bike is running VERY rich no matter what I do.. im having a hard time getting the float height correct (using the clear tube method).. manual says 8mm from mark - but my image quality is so poor i cant really make out where, it looks like the split of the carb - regular measurement is 11mm - however, one or two of me needles seem to have a tiny bit more spring to them - so im trying to get it right via the drain / tube method..

Manual main jet calls for 98 standard, mine has 102 jets in (got it like this).. when I had head off there wasnt too much show of carbon build up - valves had a laer on their faces, thats about it..

pulled carbs a few times now - tried between 1 1/2 - 2 1/2 turns out - is it possible i have some air jet blocked or something? I have cleaned these things out a few times now - when i spray on of the front holes, the 3 at the other end of the carb spray solid carb cleaner.. ive cleaned the pilots, mains and completely removed needles etc.. emulsion tubes still look good (perfectly round)..

I cleaned exhaust and did a 100 mile run at 8-10k rpms.. it was powdery black again when i stopped, meaning this seems more ofa mid-upper rpm issue, that would be the mains yes?

going to drill out some brass m5 bolts to 1mm and see if it improves while i order some 98s from china (if it doesnt!)..

fyi - at sea level..would 2 jet sizes make such a difference? even plugs are dry and sooty - and choke def not stuck.. (i checked)
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CaNsA
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Re: 90 zx400r-H carb help - running VERY rich

Post by CaNsA »

What air filter do you have in there?
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fstarocka
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Joined: Wed May 04, 2016 6:33 am

Re: 90 zx400r-H carb help - running VERY rich

Post by fstarocka »

Air filter is missing, only a spandex sock over the plastic.. Got it like this.. I'll remove that and try but doubt it's the issue, stuff is very unrestricted..

Might recheck float height, could not get fuel at 8mm.. Seems carbs at end of adjustment to get there..

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fstarocka
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Re: 90 zx400r-H carb help - running VERY rich

Post by fstarocka »

So this is my float tang at 11mm.. I seems high?

Image

Image



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