I need to sort out the jetting on my FCRs. I've a ram air box with velocity stacks, stock motor with race pipe. The power comes on suddenly and strong about 7 K all the way to redline, but there is very little power under 7 K.
The other problem is erratic idle speed. It will idle fast (3K), then blib the throttle and slow down to about 1100, but then gradually build up again.
I also want to swap the velocity stacks for K&N pod filters.
The bike is rideable at the track and a real rush on the straights, but the sudden power at 7K makes it difficult to roll on the throttle through and out of the turns. The rush of power upsets the bike's suspension.
The erratic idle also makes it difficult to count on reliable compression braking, plus is a hassle in the pits.
I'm not looking to extract the highest HP out of it, but have some good all around settings that will smooth out the power curve and serve me spring through fall at different tracks.
Current settings are 125 mains, pilot out 1-1/2 turns, 100 on the slow air jet, 200 on the main air jet. I don't know the needle numbers or settings.
The carbs were thoroughly cleaned before installation. About 2-300 miles ago the bike got new plugs, valves adjustment and carbs sync'd. I next thing I need to do are order adjustable slow air jets from Sudco.
Then, find the source of the erratic idle. I was told it might be an air leak or the pilot jet setting. I'm wondering if there are other theories for the cause of the erratic idle or ways of diagnosing.
From there my plan was to work through Pat Burn's guide at the track to get some good baseline settings.
http://www.ansusa.com/carbkei.htm
I have a nice selection of main jets, but no selection of main air jets or slow fuel jets. Will that be a problem?
Once I get a good all around base my plan is to put it on a dyno and have some pros do the fine tuning. As mentioned, I'm looking for good all around settings. I don't see myself tuning the bike for each track and weather report.
Suggestions?
Kontoboy
FCR Tuning, YZF750
FCR's
Konto,
Do you race the YZF? If not you need to get into racing with WERA in the Vintage 7 Heavy Weight Class (V7). When I get back this fall I will be prepping the YZF750 and racing at the local rounds. The V7 guys are great, and it's more about sportsmanship, and having fun than the must win attitude of the modern classes. The heavy weight class includes all the bumpups from the middleweight class, so alot of F3's, ZX6-R's, FZR1000's & GSXR1100...etc....
Plus it would be good to see a fellow YZF750 at a few rounds.
Cheers
Do you race the YZF? If not you need to get into racing with WERA in the Vintage 7 Heavy Weight Class (V7). When I get back this fall I will be prepping the YZF750 and racing at the local rounds. The V7 guys are great, and it's more about sportsmanship, and having fun than the must win attitude of the modern classes. The heavy weight class includes all the bumpups from the middleweight class, so alot of F3's, ZX6-R's, FZR1000's & GSXR1100...etc....
Plus it would be good to see a fellow YZF750 at a few rounds.
Cheers
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WickedFZR1K
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I would suspect your high idle is due to either an air leak (lean condition) or your settings on the pilot screws (1 1/2 is pretty lean as well). Spray some carb cleaner around the boots and see if there is a leak, if not, open your pilot screws upto 3 turns and see if that fixes it....
If you want to live life by your own terms, you gotta be willing to crash and burn...
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KontoBoy
- Help!!! I need a LIFE!!!
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I'll try that starting fluid and see if it works. I notice the carbs are a bit hard to get over that last boot (cylinders 1 or 3) so there could be a leak.
If that doesn't work, 3 turns out on pilots.
I ordered the slow air jets. Shoud l have them soon. One turn out on them equates to the 100 jet I have in now (there's a table in Sudco's catalog that has equivalents, but its a big download. I'll see if I can cut and paste it.
Any suggestions on going from velocity stack with 125 mains to air filters. Leaner, but by how much?
I also talked to a shop not too far--Speekwerkes, and was quoted $150 for Dyno tuning. I asked twice! Seems like a great deal but I still want to get a better baseline before I take it in.
As far as racing--you just don't know how slow I am! I'm having lots of fun with the track days and still on a steep learning curve. Maybe some day when I won't embarass myself.
Kontoboy
If that doesn't work, 3 turns out on pilots.
I ordered the slow air jets. Shoud l have them soon. One turn out on them equates to the 100 jet I have in now (there's a table in Sudco's catalog that has equivalents, but its a big download. I'll see if I can cut and paste it.
Any suggestions on going from velocity stack with 125 mains to air filters. Leaner, but by how much?
I also talked to a shop not too far--Speekwerkes, and was quoted $150 for Dyno tuning. I asked twice! Seems like a great deal but I still want to get a better baseline before I take it in.
As far as racing--you just don't know how slow I am! I'm having lots of fun with the track days and still on a steep learning curve. Maybe some day when I won't embarass myself.
Kontoboy
It really sounds a bit lean on the bottom end to me KB.
I've found the baseline jetting set-up for OEM carb sets on the Sudco (or Kiehin) web site at one point.........I really had to look, but they are there.
It's a good place to start if you can find it.
The 125 mains sound really small to me, but if it's strong on the top end, I cant question it. Don't fix it if it ain't broke I guess.
One thing that will affect the idle quality a lot is float height.
If that was the case with yours (low float and fuel level), I would also expect it to lean out on the top end after extended WOT, but if it isn't doing that, the troubles are in the low speed jetting somewhere................
The idle mixture screws have teeny O-rings and flat washers under the tension springs to hold them in position once they're set, check the O-rings, that's one place that could be hiding a air leak.
I can't recommend anything on jetting with/without the velocity stacks, I don't think I fully understand question on that.
I would check and raise fuel level if need be (the Patrick Burns article will be very helpfull for that), and maybe install and test the low speed air bleeds at 3/4 or 7/8 turns out.
I've found that changing low speed fuel jets is good way to get way off base in a big hurry.................so if it's even remotely close, try to get the low speed jetting in range with air bleeds if you can.
Good luck
~B~
I've found the baseline jetting set-up for OEM carb sets on the Sudco (or Kiehin) web site at one point.........I really had to look, but they are there.
It's a good place to start if you can find it.
The 125 mains sound really small to me, but if it's strong on the top end, I cant question it. Don't fix it if it ain't broke I guess.
One thing that will affect the idle quality a lot is float height.
If that was the case with yours (low float and fuel level), I would also expect it to lean out on the top end after extended WOT, but if it isn't doing that, the troubles are in the low speed jetting somewhere................
The idle mixture screws have teeny O-rings and flat washers under the tension springs to hold them in position once they're set, check the O-rings, that's one place that could be hiding a air leak.
I can't recommend anything on jetting with/without the velocity stacks, I don't think I fully understand question on that.
I would check and raise fuel level if need be (the Patrick Burns article will be very helpfull for that), and maybe install and test the low speed air bleeds at 3/4 or 7/8 turns out.
I've found that changing low speed fuel jets is good way to get way off base in a big hurry.................so if it's even remotely close, try to get the low speed jetting in range with air bleeds if you can.
Good luck
~B~
Last edited by ExupElvis on Thu Jun 15, 2006 10:48 am, edited 1 time in total.
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KontoBoy
- Help!!! I need a LIFE!!!
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Thanks for all the tips and adice.
I started to work trying to correct my erratic idle. Got a pcakage from SUDCO and put the adjustable slow air jets in and set them to 1 turn out, equivalent to the 100 jets that were previously there.
Then took off the airbox to make it easier to check for air leaks around the boots that secure to the manifold. Also took off the velocity stacks, and put on the air cleaner adaptors and K&N Pod filters.
Started it up and had the same idle problem as before. Idle hangs high, about 3K, blib throttle and it and it drops to normal (11-1200).
After it warmed up I hit it with carb cleaner around the boots. There was no change. I don't think there is any air leaks there.
I did notice that after it was warm and I would blip the throttle there was a greater tendency for it to die. That would argue mixture is too rich.
None-the-less, I pulled the carbs off and set pilot jets to 2-1/2 turns out (it was as at 1-1/2) to richen the mixture. No change in idle speed or characteristics.
I started opening the slow air jets, turning in or out one cylinder at a time. I finished two cyclinders and noticed no change in idle when turning air jet in or out. I reset them back to one turn out.
I then noticed the bike was getting awfully hot and shut it off. It's in the 90's here today, no wind and no fans on radiator.
I'm letting the bike cool now. Later I'll try the other two slow speed air jets--see if they make a difference. If not go back to the original 1-1/2 out on pilots and try the the slow air jets again.
It's a real pain. To adjust pilot I have to pull the carbs off the bike. To adjust air jet the air fliters have to come off. To idle more than a minute or so I have to put the gas tank back on. So it's been tank, carb and filters on and off all day.
Now why am I going through this--Oh yeah, the bike pulls like a m-fracker at upper revs. Other riders have already commented on the contrails the bike leaves as I rocket down the straights.
Thanks again for the help. I'll keep you posted.
Kontoboy
I started to work trying to correct my erratic idle. Got a pcakage from SUDCO and put the adjustable slow air jets in and set them to 1 turn out, equivalent to the 100 jets that were previously there.
Then took off the airbox to make it easier to check for air leaks around the boots that secure to the manifold. Also took off the velocity stacks, and put on the air cleaner adaptors and K&N Pod filters.
Started it up and had the same idle problem as before. Idle hangs high, about 3K, blib throttle and it and it drops to normal (11-1200).
After it warmed up I hit it with carb cleaner around the boots. There was no change. I don't think there is any air leaks there.
I did notice that after it was warm and I would blip the throttle there was a greater tendency for it to die. That would argue mixture is too rich.
None-the-less, I pulled the carbs off and set pilot jets to 2-1/2 turns out (it was as at 1-1/2) to richen the mixture. No change in idle speed or characteristics.
I started opening the slow air jets, turning in or out one cylinder at a time. I finished two cyclinders and noticed no change in idle when turning air jet in or out. I reset them back to one turn out.
I then noticed the bike was getting awfully hot and shut it off. It's in the 90's here today, no wind and no fans on radiator.
I'm letting the bike cool now. Later I'll try the other two slow speed air jets--see if they make a difference. If not go back to the original 1-1/2 out on pilots and try the the slow air jets again.
It's a real pain. To adjust pilot I have to pull the carbs off the bike. To adjust air jet the air fliters have to come off. To idle more than a minute or so I have to put the gas tank back on. So it's been tank, carb and filters on and off all day.
Now why am I going through this--Oh yeah, the bike pulls like a m-fracker at upper revs. Other riders have already commented on the contrails the bike leaves as I rocket down the straights.
Thanks again for the help. I'll keep you posted.
Kontoboy
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FZRDude
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Konto,
My buddy Bob (ExupElvis) has a #10 coffe can with a small hole in the bottom. Theres a fitting there (don't know how it attached, but be creative) and off that is a short length of hose and a filter the size of a tennis ball. Another hose, of greater length that will suit you application, comes off the other side of the filter. This hose attaches to the pump or carbs depending on you application. A nice small make-shift fuel tank. He hangs it off the side of a 5 foot step ladder. Works a treat.
My buddy Bob (ExupElvis) has a #10 coffe can with a small hole in the bottom. Theres a fitting there (don't know how it attached, but be creative) and off that is a short length of hose and a filter the size of a tennis ball. Another hose, of greater length that will suit you application, comes off the other side of the filter. This hose attaches to the pump or carbs depending on you application. A nice small make-shift fuel tank. He hangs it off the side of a 5 foot step ladder. Works a treat.
There are some who call me........Tim?
In Memory Of John "Silver" Douglas (Dec. 08, 2008) R.I.P. My Friend.
In Memory Of John "Silver" Douglas (Dec. 08, 2008) R.I.P. My Friend.
Mini-tank
I found a plastic bottle with a lid with a narrow spout (think shampoo, dishwashing liquid, whatever) which plugged into a length of fuel hose. Plugged the other end of the hose into the carbs, and hung the bottle upside-down, full of fuel, on the mirror, in a cradle made of a coat-hanger. Didn't need to run it for long but thinking about it, I might have had to vent it if I had. Oh yeah, and I had a cheap inline fuel filter (as for a car) in the fuel line too.
(1994 YZF750R)
Sounds like your having the same kind of fun I do when the urge to adjust carbs bites me KB.
The idle mixture screws are heinous.
For what it's worth, I ran my 1070 with pod filters originally, and other than the monstrous intake noise - I didn't feel any benefit powerwise.
The carbs were running pretty well with 160 mains and mid clip on the needles.
That's dead-on baseline jetting average for those carbs on my bike with the pod filters.
I didn't like listening to the vaccum release plates rattling, and I did want to see if the stock airbox would add any ram effect. (It does).
Search for some back posts by flyingcircus68, he threw some quite sage advice my way at one point.
I had to modify the throttle linkage to work with the stock air box (cut/weld the bellcrank guide to relocate the cable angle),
But I can say that my 160 main jets are no longer big enough.
It moves that much more air, and it's way quieter now too.
Anyway, all that ^ is really just an aside, our scoots are different animals when compared............What I can say about the idle hanging is that I noticed the importance of the throttle return cable, and how well it's adjusted.
I needs to be able to return the slides all the way to idle, or at least very close to it.
The vaccum release plates will tend to hold position in the slide bodies once opened, and even though your throttle hand may not feel much, the return cable does need to pull them shut - or they will not return to idle position untill engine vibration makes it convenient for them to do so.
That can take up to 10 seconds I've noticed.
10 seconds is a long time to wait for the power to go away if your at the end of a straight, and a corner is coming up.......(you know this, right?):lol:
So, um.......make sure that return cable is doing it's thing.........it may not be a mixture issue after all.
There still may be some mixture stuff to go after, especially running a full exhaust - but I know how much fun it is to pull those lumps.
Did you have a chance to check the float level, and if so what height are they at now.
Just curious of course...
If you get those sorted out before I have a chance to get back into my set, I'm gonna be soooooo jealous.
Good luck
~B~
The idle mixture screws are heinous.
For what it's worth, I ran my 1070 with pod filters originally, and other than the monstrous intake noise - I didn't feel any benefit powerwise.
The carbs were running pretty well with 160 mains and mid clip on the needles.
That's dead-on baseline jetting average for those carbs on my bike with the pod filters.
I didn't like listening to the vaccum release plates rattling, and I did want to see if the stock airbox would add any ram effect. (It does).
Search for some back posts by flyingcircus68, he threw some quite sage advice my way at one point.
I had to modify the throttle linkage to work with the stock air box (cut/weld the bellcrank guide to relocate the cable angle),
But I can say that my 160 main jets are no longer big enough.
It moves that much more air, and it's way quieter now too.
Anyway, all that ^ is really just an aside, our scoots are different animals when compared............What I can say about the idle hanging is that I noticed the importance of the throttle return cable, and how well it's adjusted.
I needs to be able to return the slides all the way to idle, or at least very close to it.
The vaccum release plates will tend to hold position in the slide bodies once opened, and even though your throttle hand may not feel much, the return cable does need to pull them shut - or they will not return to idle position untill engine vibration makes it convenient for them to do so.
That can take up to 10 seconds I've noticed.
10 seconds is a long time to wait for the power to go away if your at the end of a straight, and a corner is coming up.......(you know this, right?):lol:
So, um.......make sure that return cable is doing it's thing.........it may not be a mixture issue after all.
There still may be some mixture stuff to go after, especially running a full exhaust - but I know how much fun it is to pull those lumps.
Did you have a chance to check the float level, and if so what height are they at now.
Just curious of course...
If you get those sorted out before I have a chance to get back into my set, I'm gonna be soooooo jealous.
Good luck
~B~
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KontoBoy
- Help!!! I need a LIFE!!!
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Well I was running out of time before my track day on Sunday (read about it in the YZF750 forum) to do much more fiddling with the carbs.
I did recheck the main jets. My apologies, they are 152, not 125 as I earlier stated. (I think they told me I had early onset alzheimers, but I can't remember.) So EXUP is was right, the 125 would have been way too lean.
Since time was short I reset the carbs back to thier original settings, pilot 1-1/2 turns out, 100 on the slow air (1 turn out on the adjustable air jets), 200 on the main air, and 152 mains. I also loosened the throttle cable some--it already had a bit of free play and carbs seemed to snap back fine--but I had nothing the loose.
Then put the K&N pods on instead of the velocity stacks, then air box, buttoned it up without even starting it up and went to the track yesterday.
I was pleasantly suprised! While it didn't pull as hard up top it did everything else surprisingly well.
While I still noticed some tendency for the revs to hang coming off throttle, it was not as frequent nor as severe as before. It might hang at 2k instead of three and just once in a awhile.
And it ran much much better under 6K than before--I could barely get it off the line unless reving high, and trying to drive out of corner with the revs below 8K was just an embarassment. Yesterday--no problem.
In addition, that surge of power around 7-8K was much less pronounced, probably in part due the the loss of power up top. I was getting a lot smoother exits, able to roll on throttle through the corners.
This backs up what I was hearing here--I was running lean, especialy at lower RPMs. With the filters on it was richening the mixture across the powerband, reaping good benfits at low RPM, but suffering on top.
Being that this is a track and not a race bike I could ride it like this all season. I would like to get some of that power back up top--but that may be a lost cause unless I go back to the velocity stacks. I'd also like to try to get that final bit of "hanging" taken care of. Maybe play with the cables some more, look for other mechanical isses, and open the pilot jet some.
FYI, I don't think Mike Walsh designed that air box for the K&N pods. It's a very tight fit and I was stretching that fiberglass to get it buttoned up. It's not surprise--just the pods alone under the tanks with no airbox barely fit. I think I partially crushed one filter.
Kontoboy
I did recheck the main jets. My apologies, they are 152, not 125 as I earlier stated. (I think they told me I had early onset alzheimers, but I can't remember.) So EXUP is was right, the 125 would have been way too lean.
Since time was short I reset the carbs back to thier original settings, pilot 1-1/2 turns out, 100 on the slow air (1 turn out on the adjustable air jets), 200 on the main air, and 152 mains. I also loosened the throttle cable some--it already had a bit of free play and carbs seemed to snap back fine--but I had nothing the loose.
Then put the K&N pods on instead of the velocity stacks, then air box, buttoned it up without even starting it up and went to the track yesterday.
I was pleasantly suprised! While it didn't pull as hard up top it did everything else surprisingly well.
While I still noticed some tendency for the revs to hang coming off throttle, it was not as frequent nor as severe as before. It might hang at 2k instead of three and just once in a awhile.
And it ran much much better under 6K than before--I could barely get it off the line unless reving high, and trying to drive out of corner with the revs below 8K was just an embarassment. Yesterday--no problem.
In addition, that surge of power around 7-8K was much less pronounced, probably in part due the the loss of power up top. I was getting a lot smoother exits, able to roll on throttle through the corners.
This backs up what I was hearing here--I was running lean, especialy at lower RPMs. With the filters on it was richening the mixture across the powerband, reaping good benfits at low RPM, but suffering on top.
Being that this is a track and not a race bike I could ride it like this all season. I would like to get some of that power back up top--but that may be a lost cause unless I go back to the velocity stacks. I'd also like to try to get that final bit of "hanging" taken care of. Maybe play with the cables some more, look for other mechanical isses, and open the pilot jet some.
FYI, I don't think Mike Walsh designed that air box for the K&N pods. It's a very tight fit and I was stretching that fiberglass to get it buttoned up. It's not surprise--just the pods alone under the tanks with no airbox barely fit. I think I partially crushed one filter.
Kontoboy