Dynojet kit in FZR600R carbs

[plodder]

The 600 carbs I've got fitted on the hybrid are dynojetted but have a very big hole in the midrange and is very lean just off idle, whereas the DJ kit is supposed to improve midrange.

Part of the modification is to blank the main air jet. Does anyone know what this does?

How can I improve the big lean spot off idle and the inability to use full throttle at low revs?

[plodder]

Anyone?

I'm thinking of getting bigger pilot jets. Any idea what size?

[cagiva996]

plodder what are running with your carbs?pod filters,3tj airbox?have you had it running ok before you put the dyno jet kit in as the 600 dyno jet kit is meant to work with the 600 airbox which flows more air.i had lots of fuelling issues when i fitted the fzr600 motor which was mostly down to getting the right amount of air to the motor cuz the 600 airbox is quite alot bigger but nearly the same shape-let me know.

[plodder]

I run a 3TJ airbox with no snorkel. The tank is raised 12mm at the front. Above 4000rpm, torque rises and then at 8000rpm, it is very high and does no choke down like when there's not enough air. There is enough air I can say that for sure.

The DJ kit was fitted to the carbs already, so no chance to take it out and it is as per the DJ manual. DJ#112 mains (equivalent to Keihin #118), Kehin #35 pilot jet.

It's the low RPM fuelling that's the issue before the main jet & needle kicks in.

I'm certain it's a pilot jet issue... it's just how much bigger to go. I'm currently getting prices for replacement Kehin N424-25B jets in #42 and #50 sizes. My concern it that the step changes (7 and 8) are either too high or too low.

[plodder]

All gone quiet . Surely someone on here knows carbs?

[Evilchicken0]

We were waiting for you to say something.

All I can say is to go up one size on the idle jets and see what happens

[plodder]

I ain't being a free development house when it's costing me £20 a set.

[Evilchicken0]

fair point

[cagiva996]

sorry i havnt replied but the old pc has had a virus so i havnt been able to have any internet access since last week,but all fixed now.just a thought-i could not get mine too run properly at all without the snorkel on,all nasty dips and all screaming top end power delivery.i tried main jets 113 to 120s and all needle settings and everything inbetween but as soon as the snorkel went back on it ran ok.i think that keeping the shape of the airbox is critical to how the air is delivered to the carbs.i was talking to another hybrid owner this week who raced a tj/tcat hybrid and his airbox was the standard tj but running no(not ideal for the road) filter and was kicking out 92hp.im sure the airbox intake has to be a certain diameter and length to get the air to move at a certain rate to feed the carbs.i did this with mine and not fancying the motor sucking in road bebris i removed the filter and stretched a stocking between the two airbox halves and another between the snorkel base and the airbox top, and has made a big difference with lots of torque qnd a cracking top end.i understand your frustration as i was pulling my hair out to try and make it fuel properly but was worth the effort.i have a set of fzr600 carbs that ran on my fzr600 foxeye hybrid if you want to borrow them with a factory pro jet kit which ran 118 mains and the needles on their weakest setting and it ran well(a bit rich) enough.they also have a good cv carb set up guide on the factory pro website.

[Stumac]

Hi, I am no expert but have done a fair bit with carbs. Blocking of the main air jet is done quite a lot, if you block this of it means you need to run smaller main jets, apparently this is better as the fuel droplet size is smaller which makes the carb work better.

On the 400 we always set the main jet first then try to sort the midrange, if your midrange is not right I would start changing needle heights first before buying pilot jets.

To be honest I have never changed the pilot jets on any of the bikes I have built, I have always set them up the same way, ie main jet first then needle position for midrange.

As I said I am no expert but everyone I know does the same as this.