Struggling with FCR flatslide set-up on FZR489. Anybody have baseline jetting for one of these things? Hints, tips, things to look for are all welcome. Currently struggling with drive out of corners, the thing is bogging unless the throttle is rolled on super slow and even then it is slow to respond. I have experience tuning Mikuni roundslides and Keihin CRs, but have not tuned flatslides before, any help would be appreciated. Thanks.
You probably need to adjust the accelerator pump. Too much fuel. I've jetted dozens of 400s and variants, main is usually 112-118 depending on fuel, but I've had to use different needles to get the first 1/4 turn of throttle right. Lots of times it turns out to be so lean on the main and mid circuit to get response that it is dangerously lean on the top end. I recommend a good dyno tuner, an old guy familiar with carbs.
Thank you. I wondered about the accelerator pump. I am getting lots of spit back on the bottom of the fuel tank (running stacks only, no airbox), is this common with the FCRs?
Get the adjustable main air's from Sudco, they will solve 90% of it. Beware, they are sensitive, 1/16 of a turn is @ 1 jet size. Otherwise you should be running, ETV or GTV needles, 120's is big and cold out. 116-118 when its hot/humid. Go up 1-2 sizes for O2 Fuels.
FCR's with stacks blowing fuel all over things is pretty normal. What Steve said is pretty spot on for a starting point.
Do the make adjustable main airs? I can't find them on the site, but did find the adjustable slow air jets, which my FCRs already have. Thanks.
only slow air is an option for adjusting. http://www.factorypro.com/tech/tech_tuning_procedures/tuning_FCR_Burns,Pat.html read it all. and find a dyno with a step brake
I have read it, several times :up:. I am not sure if the guy at Sudco was mistaken, but he told me they do have an adjustable main air jet for the FCR. I didn't order any because they are not in the budget right now, but I will check on them soon.
That web site is good info. Here is some of my notes on an FZR428 without airbox but with pod filters. http://29dreamsracing.com/carbnotes.htm The carbs are a bit oversized for our applications here, so any small adjustment is a pretty large difference. I found that just running a main jet one size different was a huge difference, whereas on other bikes a single main jet size difference was a subtle change. Change needle position until it wants to get on the main smoothly. I also found that when the accelerator pump was putting in too much fuel it would bog around 10k coming out of corners. Lean it up with the tab until there is no bog. I also found that with the airflow and such only so much could be done on the dyno and mine would act a bit different at 80 mph on the track vs static on the dyno.
I installed slow air screws and did away with the slow air jets. I had main air jets on mine and wasnt aware of a screw conversion for the main air jets. That being said, I never changed the main air jets on mine, but I changed and played with just about everything else. On your 489 you likely need to use Steve's info as baseline and go from there. Its possible that everything is jetted right but if the accel pump is dumping too much fuel it will fall on its face coming out of the corner. I adjusted mine so they shot gas out 2 or 3 feet instead of like 15' across the garage and it did wonders. It helps to know what bike the flatslides were set up on last. If it was a much different motor or intake than you have some of the stuff may be way way off.
Thanks, this is all very helpful. After racing Summit this past weekend I think I may have a couple of different carburetion issues. I rebuilt the accelerator pump and can confirm I have a big squirt going in when the throttles are opened. This seems to have helped the bogging issues, but the bike simply will not pull off the corners, it just sort of lags when the throttles are opened. After what seems like an eternity the power will start to come on and then it pulls reasonably well (of course by then it's too fucking late). I watched the tach to make sure I wasn't letting the revs drop too low in the corners. These have a needle that no one has recommended or in fact heard of: GTM (yes M) and it is on the leanest setting. On top of that the bike refuses to idle. When warmed up, after blipping the throttle it hangs up at about 2500 RPM for about 3-5 seconds and then just dies. 48 slow fuel jet, fuel screws at 2 turns out, then 2.5.
way too rich on needle and maybe slow speed circuit. and reducing the gap on the pump fork makes it come in sooner and more.
What have you changed since you got it from me? You have to keep them clean and have to run it. Even if it means heating it up and keeping a heat lamp on it and starting it in the winter. Start it once a week. No matter what. I had it down to a science. That includes the starting and jetting. I checked this against the Wide band analyzer. What everyone else runs your bike doesn't run. There is a reason it has the GTM needles in it. Because they are the leanest needles. I studied over Ryan's note and could never use his numbers. I want to say you need to be at 3 turns on the fuel and 1 on the air. I ran the 112's because that is what the bike wanted. That bike also likes revs. It CAN get boggy in the midrange but you gotta keep it tacked up.
I went up one size on the slow fuel jet (to a 48), with the fuel screws at 2 turns out. When I got the bike the fuel screws were out at 3.5 turns with a 45 SFJ and the float levels were off on 3 of the carbs. Starting the bike is not the problem, it starts fine. It will not pull coming out of a 4th gear corner at approximately 10k. Can't do it in third gear because it will be over-revving. In my mind that bogginess is indicative of a jetting issue, the only thing keeping the motor at super high revs does is mask the jetting problem. It should be making some sort of power between 9 and 11k but it is very flat and simply not accelerating. Keep in mind I have been running in ambient temperatures between 65 and 80 degrees. And yes, the carbs are clean, this isn't my first bike.
I could never run a larger slow jet. It would..... bog.. I stopped looking at Ryans excellent notes and Steve's settings because they just wouldn't work for that bike. What made you change them? I tried to change mine per 600 feet and go down a jet size, that only worked for one jet size. That was from 110 and 112 I believe, I could be a jet off. As far as cleaning them, what I mean by that is if you don't run it weekly, then I had to break down the whole things and clean them all over again. That was why, even in the rain I would start it and ride it down the street and back. OR you could run it out of gas every time. I didn't like that idea because it seems to dry the plastic out. You also may want to look at the slide rollers, the ones under the cap with the needles. They tend to get warn and can bind up. This happened on my Hawk and I had to adjust them and lube them and/or replace them. Here at Barber I would be at 8K after downshifting coming out of Charlottes. No bogging. https://www.youtube.com/watch?v=r27wGzR4F08
