Did you check that the floats are air tight and actually float , if they are perforated they will take in fuel and not lift up to shut the needle valve off . You said about the vaccum petock failing and allowing fuel to overfill the carbs and fill sump , why did the float needles not shut off and stop the carbs from over filling . In the very first post you say about the mods , jetting and so on ....has the bike ever run correctly with these jet sizes , how much bigger are they from standard size jets
The vacuum line goes to the inlet runner on the vertical cylinder. The diaphragm failed allowing fuel straight into the runner. I'll be replacing the float bowls due to a marred thread so the carbs are coming off anyway. I might as well put everything back to factory while I'm there, I guess. The jets are the 'middle' option that FactoryPro supply in their stage 1 kit. Pilot is only one size bigger than standard, main in two.
I can't advise on Factory Pro Stage 1 kit, but if it was a Dynojet Stage 1 kit, the only things that change are the main needles, the main jets and the long springs..........the pilot jets don't change, but with the carbed SS the screw setting is increased by say, 1 extra turn out. If it is a Factory Pro Stage 1 kit, I assume your airbox has not been cut about and your exhaust cans aren't straight through.
Correct. Just a K&N filter, no airbox mods & the exhaust has not been cored. Jets were sourced locally after a shipping issue with a US vendor. Jet sizes were chosen based on them being "middle of the road" for the kit. Perhaps 140 is too big for the main? There is a thread over at UKMonster where another used used 42.5 mains and it cured the small hesitation issues I had prior to pulling the carbs apart on a very similar setup. I'm just surprised that something like that can cause such a big running issue. That said, it was clearly the case for @higgy748 so Maybe I'll put it all back to stock and see what happens...
I'm going to try a bit of logic here.......But it might just be a load of b*llox...... As mentioned, I know bugger all about Factory Pro kits......But I do know Dynojet ones. Firstly bear in mind that Dynojet main jets are measured differently to the OEM Mikuni ones. The main jet size in a Dynojet Stage 1 kit for a 600SS is between 124 and 128.....IIRC the OEM Mikuni is 132.5, which I think is the same as the 600 Monster. The main jet size for a Dynojet Stage 2 kit for a 750SS is between 144 and 148............The OEM Mikuni jet is 140...... ......on that basis, any Dynojet kit (and I assume Factory Pro kit) will probably have a numbered main jet about 2 - 4 up or down from the OEM number....... ..........Note 'numbered', not actual size because of the measuring differences........I can't recall which way round the difference is but one is measured by actual dimension, the other by flow rate. Therefore I would expect if yours had a Dynojet Stage 1 kit in it, the jet size would be between 124 - 128 (they are the same size for the 750 SS Stage 1 kit as well)....... If Factory Pro sizes are anything like OEM or Dynojet, then 140 seems rather too big.
It might be worth taking a look at Ducatisuite. The guy who created the site had a monster and fitted a factory pro kit. Iirc, he used the smallest main jet and got great results. It improved smoothness, economy and performance. Imho, it would be a mistake to revert to standard settings, which as I have said, are aimed mainly at emissions regs.
Yeah agree. I had a look on there. He used the biggest main jet supplied (142.5) and the same pilot jet (42.5) that I used, which is why I'm confused that his results were great and mine were less so...
I'm interested in how the jet sizes relate to the OEM and Dynojet Stage 1 kit ones............Why fit a main jets to a 600 Monster (or 600SS) that are nearly as large as those for a 750SS Stage 2 Dynojet kit?
FAQ Mikuni vs keihin vs dynojet Not sure how accurate that is, but the sizes listed in the pdf files on Dynojet's website seem all out of whack. I.e. a YJ128 converts to a Mikuni 120, which is a fair bit smaller than factory... Unless I'm missing something about part numbers vs sizes for Dynojet.
If you have filter or pump in tank check hoses are good. A leak in those causes similar problems to yours on injected bikes.
Ok so their stage 2 kit seems to almost marry up with what I'm running. Interesting that the stage one has a much smaller jet than standard...
FYI chaps. The Mikuni and Factory Pro jets are numbered according to the size of the orifice. So a 140 main jet has a 0.140mm dia hole in it. Dynojet use their own numbering system, so can't be directly compared.
Thanks Derek. Confirms my thoughts around the sizing that I have. Could still be too big for the set-up, I guess... It still seems mad to me that jumping 0.0075mm could be causing such a poor running condition.
I doubt if the poor running is related to the main jets. The bike will reach 4000 rpm with no load or a light load long before the carbs are far enough open for the main jets to come into play,
I should hire you to articulate what my brain says... This is exactly why I've been spinning my wheels (so to speak) over the issue. Assuming the ignition system is fine (I have replaced everything but the ignition boxes, but these test within spec and the issue doesn't change cylinders when I swap them over), what am I missing? Can I run tests on the ignition circuit under load? Is there a 'must check' relay related to the ignition circuit that likes to die?
had someone in work saying their son's bike (ZXR 400) wouldn't rev past 5k after having a jet kit. Turns out it was the float needle assy was put back wrongly. Something to do with washer/shims.
I thought it was about 3000+....... ......the OP says his slides are lifting which means the main jets are in use to a degree........but it won't run over 4000rpm.
I'm still wondering about the air cut-off diaphragms............they can cause all manner of problems if they are split or have hardened......and the spring can rust / break. The OP said he didn't split the carbs to clean them and as one aircut diaphragm is between the two carbs, did it get checked over? You can actually remove it without splitting the carbs but it needs some nifty work with a driver bit and a small open end spanner.
