RVF 400 Low RPM issue

[Neosophist]

well ive replaced plugs anyway ill keep the old set as spares, No i dont have an air line but i do at work so maybe i should take them in a give them a blast as for float heights they are pretty much to spec give or take 0.5mm, mixture screws are set but i marked the old setting out and ive set them to spec of manual but its slightly richer only by 1/8 of a turn, that could also cause my low rpm issue...correct? I might do a plug chop to check this theory.
Airbox is standard but its got an aftermarket filter in ive just recieve my genuine one so need to put that in at some stage doubt it would fix the issue.

Depending on the air filter it could cause all sorts of problems... ususally at higher revs though.

how are you starting the bike? always full choke and no throttle.

[Cammo]

I agree with Neo, aftermarket air filters can cause all sorts of running issues. Stick the standard one in and start from there.

[peter62]

Skinnydog0_0 The Voltages are good and its charging so thats not an issue

think it was 12.8 volts and it was at 14.2 - 14.5 with engine running at 5,00Rpm

Neo I start the bike with little choke and no throttle and i know aftermarkets give all sorts of issues but ive got a standard (covered a few miles and also a brand new standard to try in it) Then ill be ultrasonic cleaning them if that all fails

Thanks for your replys guys :D

[Cammo]

Do you know which cylinder/s are misfiring?

Find out by removing 1 plug lead at a time (they should be ground against the frame with a screwdriver etc while firing to prevent damage). Once you've found the problem cylinder/s swap some plugs around to see if it makes a difference to how the cylinder runs by removing plug leads once again.

The small plugs are fragile, temperamental and responsible for dozens of running problem posts on this forum. I wouldn't rule them out as being the culprit until you try some brand new plugs.

What did you set the pilot screws to? If they're too rich the plugs can be fouled when idling causing slow running problems.

Ultrasonic cleaning will probably clear the issue up if it's a problem with the slow running circuit but I would pursue this as a last option. Most baths will only fit individual carbs in. It's a fairly major job separating them and putting them back together, and they'll need a proper balance after pulling them apart. If you can find a bath that fits the 4 carbs in go for that.

[peter62]

Well weve got brand new plugs in it and it was still doing the same im gonna try the new air filter and see how it goes as for the problem cylinders its the front 2 but saying that i didnt ground the rear plug caps but it only recently started doing that as i tried it and it ran fine on front and rubbish of rear cyclinders,

Set the pilot screws to 1 and 5/8 i think thats what it states in the manual lol,

Yeah thats just it i dont wanna split them and balance etc etc just more work specially if it doesnt need it then i will be pissed, how would i go about cleaning the slow running part of the carbs or by that do you mean the pilot jets aka slow jets?

Thanks Cammo :)

[Cammo]

Well it sounds like you've tried all the logical stuff.

The slow running circuit which Neo referred to in his post can only really be cleaned effectively by ultrasonics. These tiny passages can easily get blocked up by leaving fuel sitting in the carbs and it forming a gum. It might be worth trying to spray carb cleaner through the circuit but I wouldn't be too optimistic that it will help.

Did the problem only start to happen when you put the carbs back on? I'm doubtful as to whether it's a blocked slow circuit if the problem just appeared when you put the carbs back on, usually this is caused over a period of time sitting when fuel evaporates leaving a gummy residue.

If you wind the idle adjuster in so it idles at 3000 or so revs does it run cleaner? If it does run better it would point to a carb balance being needed (i.e. one of your throttle butterflys isn't open enough at normal idle speed for proper combustion). Something else to look at.

[peter62]

Okay quick update of things ive done today :

Took carb tops off to check needles for wear, one or 2 have a slight wear mark nothing major, found where the pre filter has ended up......under the diaphrams so i cleaned it up and re assembled the tops.

Checked the emulsion tubes were in the correct carbs, although it doesnt mention anything about it in the manual however i found there are 2 pairs each pair has slighty different distances betweek the holes on the sides
Pair 1 is there holes space equally apart then pair 2 had two holes space equally apart and the end one further away (end i mean furthest away from the main jet. Ive forgot which i put where but does it matter?

Set pilots to run a little leaner (1/8 of a turn in), Re-checked float heights - were all fine, checked that the jets were all clear - which they were, checked needle valves for wear or perishing cause my stale fuel - all were fine, Re-assembled also put the genuine air filter in and then test rode. Now then....The bike seems miles better past 1,500 - 2,000 RPM but at them specific revs it seems abit hesitant and spluttery like it wants to stall usually only when setting off otherwise the bike is running near spot on also if u keep the throttle steady on 5k it tends to hesitate a little and pop, Sorry for the essay but seem to have managed something out of today.

I was thinking maybe balance carbs and see if that cures the problem i am also aware that the RVF's are known for their flat spot at 5k but would that make it pop if heald at 5k steadily on the road?

Thanks again

[Cammo]

The bike seems miles better past 1,500 - 2,000 RPM but at them specific revs it seems abit hesitant and spluttery like it wants to stall usually only when setting off otherwise the bike is running near spot on also if u keep the throttle steady on 5k it tends to hesitate a little and pop

I was thinking maybe balance carbs and see if that cures the problem i am also aware that the RVF's are known for their flat spot at 5k but would that make it pop if heald at 5k steadily on the road?

The stalling feeling at low revs could be due to incorrect pilot screw setting, unfortunately this is something you'll need to experiment with.

It shouldn't be popping at an constant revs, it's usually due to air leaks or plugs misfiring.

[peter62]

Yeah maybe but its running better maybe i need it alittle leaner that could also be my poppin issue but i dont want it too lean because when youre up in the hills it will run even leaner. I have no way of measuring exactly whats coming out so i dont know for sure how clean a burn im getting.

I dont think plugs are to blame because they are litterally brand new out the box as i said maybe needs to be a touch leaner, any pointers on setting pilot screws it says to turn in untill lightly seated now it that just touching or a little nip so that its tight and seated all the way in but not overly tight? Im under the impression its when you feel it just about seating at the end point but can still nip it another 1/4 or 1/8 of a turn.