Discussion
Anyone good with Keihin FCR's? Just about at the stage of tearing my hair out. These are FCR39's fitted to this same ZZR1100 before rebuilding it and the fueling's good with the exception of idle where it's chucking fuel in. I've got got the idle fuel screw tightened fully home now and although it's better than the original position of 1 turn out it's still over fueling at idle.
The car's idling well but if I start the car and leave it to idle till warm and then a bit more the plugs are black and when I take the carbs off there's puddles of fuel at the intake rubbers and the valves look wet also. They are dry before I started and I've also checked that no fuel is leaking out of them when priming before starting the engine and it seems OK.
The full settings of the carbs are:-
Float Height = 9mm
Main Fuel Jet = 175
Main Air Jet = 200
Needles = OCEMV
Needle clip (from top) = 4th
Pilot / Idle Mixture Screw = Fully leaned out
Slow (Pilot) Fuel Jet = 60
Slow (Air) Jet = 100 (fixed)
Looking at getting a set of standard ZZR1100 carbs and using them instead but seems a bit of a shame because the FCR's have been good through my ownership up till now. The car starts from stone cold at the press of the button and sits idling away at 1100rpm, it's all a bit strange! Only other idea is getting an adjustable slow air jet (and leaning it out) which covers the idle as well but no idea why the fixed one (that was fine before) should need changed in the same engine.
Wanting to get a couple of race weekends in this year but time's fading away fast, annoyingly the rest of the car is spot on!
Hope this post makes sense to someone and open to any suggestions, thanks!
Dunc.
The car's idling well but if I start the car and leave it to idle till warm and then a bit more the plugs are black and when I take the carbs off there's puddles of fuel at the intake rubbers and the valves look wet also. They are dry before I started and I've also checked that no fuel is leaking out of them when priming before starting the engine and it seems OK.
The full settings of the carbs are:-
Float Height = 9mm
Main Fuel Jet = 175
Main Air Jet = 200
Needles = OCEMV
Needle clip (from top) = 4th
Pilot / Idle Mixture Screw = Fully leaned out
Slow (Pilot) Fuel Jet = 60
Slow (Air) Jet = 100 (fixed)
Looking at getting a set of standard ZZR1100 carbs and using them instead but seems a bit of a shame because the FCR's have been good through my ownership up till now. The car starts from stone cold at the press of the button and sits idling away at 1100rpm, it's all a bit strange! Only other idea is getting an adjustable slow air jet (and leaning it out) which covers the idle as well but no idea why the fixed one (that was fine before) should need changed in the same engine.
Wanting to get a couple of race weekends in this year but time's fading away fast, annoyingly the rest of the car is spot on!
Hope this post makes sense to someone and open to any suggestions, thanks!
Dunc.
Edited by dunc_sx on Sunday 26th August 13:38
Hi Dunc
If you haven't already come across it, some real useful stuff here >
http://www.zrxoa.org/forums/showthread.php?181609-...
Nowt wrong with FCR39s; good stuff, just the momentary poor fuelling on the move at lift that all carbs suffer from (that you simply have to drive around) that FI overcomes.
I'd start with the 'Say What You See' approach; if it's just at 'idle', then focus on the idle/slow jets i.e. are they 'gummy'/dirty/worn?
PS How many are 'wet' @ idle i.e. one, two, three or all four; particularly if the latter, check the link to see when the mains should be starting to open ......... I'm wondering (given the extent of 'wettening') whether they are starting to 'open' when they shouldn't be?
If you haven't already come across it, some real useful stuff here >
http://www.zrxoa.org/forums/showthread.php?181609-...
Nowt wrong with FCR39s; good stuff, just the momentary poor fuelling on the move at lift that all carbs suffer from (that you simply have to drive around) that FI overcomes.
I'd start with the 'Say What You See' approach; if it's just at 'idle', then focus on the idle/slow jets i.e. are they 'gummy'/dirty/worn?
PS How many are 'wet' @ idle i.e. one, two, three or all four; particularly if the latter, check the link to see when the mains should be starting to open ......... I'm wondering (given the extent of 'wettening') whether they are starting to 'open' when they shouldn't be?
Edited by splitpin on Sunday 26th August 14:12
Cheers Trev,
I've been on the zxr forum a good few times, they do seem to be the guys for FCR's but their settings aren't matching up with mine. The fueling is consistent across all cylinders with the same amount of excess fuel left in all inlets and plugs similarly black, they are nice light brown after running flat out.
Dunc.
I've been on the zxr forum a good few times, they do seem to be the guys for FCR's but their settings aren't matching up with mine. The fueling is consistent across all cylinders with the same amount of excess fuel left in all inlets and plugs similarly black, they are nice light brown after running flat out.
Dunc.
May not feel it your end, but all four is probably good news. Makes it very doubtful in the extreme in my mind that there's actually anything wrong with the carbs as such.
Have you checked the throttle plates when it's idling? Eg broken/detached spring on the throttle linkage.
Other thought is has the ATS/air box link gone AWOL?
Have you checked the throttle plates when it's idling? Eg broken/detached spring on the throttle linkage.
Other thought is has the ATS/air box link gone AWOL?
splitpin said:
Have you checked the throttle plates when it's idling? Eg broken/detached spring on the throttle linkage.
Other thought is has the ATS/air box link gone AWOL?
Throttle's fully closing and the vent hose is correctly connected and into the air box. Keep them coming though, it must be something!Other thought is has the ATS/air box link gone AWOL?
Going to strip them down and and see if I can see any broken seals of anything but there's a surprisingly little amount of seals etc in these (which is a good thing)
Cheers,
Dunc.
Just about to eat, so leave it with me.
Now, it's getting more fuel than it needs, so what's causing it .......... fuel regulator keeping shoving when it should be sending surplus back to the tank? Maybe .......... what else could cause all four carbs to oversupply when they were presumably just fine before ........... yes dearest, I did hear you say FOOD! I heard it the first time, just as clearly as I heard it the sixth time
Now, it's getting more fuel than it needs, so what's causing it .......... fuel regulator keeping shoving when it should be sending surplus back to the tank? Maybe .......... what else could cause all four carbs to oversupply when they were presumably just fine before ........... yes dearest, I did hear you say FOOD! I heard it the first time, just as clearly as I heard it the sixth time
Bike carbs are normally set for gravity feed, as the tank is just a few inches higher than the carbs, the fuel inlet jet size is around 2.5 mm to work with the low pressure form the gravity ( around 30 gramms/cm2). Very often when these carbs are mounted on a car, peoples use an electric pump giving about 10 times the normal fuel pressure. Therefore you must use a fuel pressure regulator set to very low pressure or change the fuel bowl inlet jets for 1.5 mm ones wich are available from Keihin. You can reach me at +41 79 240 2424 if you need more help.
Dan
Dan
Great Stuff Dan
Sooooooooo Dunc ......... to my mind (providing I'm reading it right i.e rebuild of existing engine and re-install of 39s and the problem did not exist before, meaning that it wasn't wet, not simply that you hadn't noticed it - I'm not being clever when I say that, because plugs are often just checked after a hard run and yours sound to be just fine in that scenario), that puts the Fuel Regulator right back in the frame > "fuel regulator keeping shoving when it should be sending surplus back to the tank?"
Obviously you need to check the fuel return to tank is clear, but for sure I'd want to fully check whether its the FR before going to all the time, trouble and balls-ache of swapping carbs, because if it is the FR, you'll do all that and most likely find you still have the problem.
You may think, 'how come, never touched it as part of the work I've done!', to which I'd reply 'That's the magic of the principles of Sod's Law'.
Sooooooooo Dunc ......... to my mind (providing I'm reading it right i.e rebuild of existing engine and re-install of 39s and the problem did not exist before, meaning that it wasn't wet, not simply that you hadn't noticed it - I'm not being clever when I say that, because plugs are often just checked after a hard run and yours sound to be just fine in that scenario), that puts the Fuel Regulator right back in the frame > "fuel regulator keeping shoving when it should be sending surplus back to the tank?"
Obviously you need to check the fuel return to tank is clear, but for sure I'd want to fully check whether its the FR before going to all the time, trouble and balls-ache of swapping carbs, because if it is the FR, you'll do all that and most likely find you still have the problem.
You may think, 'how come, never touched it as part of the work I've done!', to which I'd reply 'That's the magic of the principles of Sod's Law'.
Thanks Dan, I'll give you a call very much appreciated.
Trev, there's no fuel return on these carbs it's just a line in and the float valve stops the flow once the bowls are full enough. I've tested that the fuel pressure isn't simply overpowering the valve by turning the fuel pump on with the carbs off the car and checking that no fuel is leaking through. Too much fuel getting pushed through as it's running as Dan suggests may well be a different matter?
The carbs were checked over when they were off the car to rule out them being the reason for the holed piston, it was later found that the hole in the piston was due to fatigue and the carbs were given a clean bill of health when checked also. I was told that nothing had changed on the carbs when they were checked but running out of other options I'm beginning to wonder. Perhaps this thickens the plot and should have been mentioned earlier, surely the jetting wouldn't have been changed here though.
I'll be stripping them down tonight and comparing with a parts list to make sure everything is accountable for! You are correct though, sods law is definitely at play with this one!
Thanks,
Dunc.
Trev, there's no fuel return on these carbs it's just a line in and the float valve stops the flow once the bowls are full enough. I've tested that the fuel pressure isn't simply overpowering the valve by turning the fuel pump on with the carbs off the car and checking that no fuel is leaking through. Too much fuel getting pushed through as it's running as Dan suggests may well be a different matter?
The carbs were checked over when they were off the car to rule out them being the reason for the holed piston, it was later found that the hole in the piston was due to fatigue and the carbs were given a clean bill of health when checked also. I was told that nothing had changed on the carbs when they were checked but running out of other options I'm beginning to wonder. Perhaps this thickens the plot and should have been mentioned earlier, surely the jetting wouldn't have been changed here though.
I'll be stripping them down tonight and comparing with a parts list to make sure everything is accountable for! You are correct though, sods law is definitely at play with this one!
Thanks,
Dunc.
Edited by dunc_sx on Monday 27th August 12:15
Still got this problem unfortunately. Had the carbs out and sent to the Keihin main dealer who said they were fine but changed the inlet jets, needles etc just to be sure. He also confirmed that these were the correct settings for ZZR1100's.
I checked the fuel pressure and it's 1.9psi (kawa state 1.6 to 2.3psi as the working range for their fuel pumps).
Put everything back together and it's still the same.
Going to be trying original kawa carbs now (thanks BertBert!) but any other suggestions appreciated!
Thanks,
Duncan.
I checked the fuel pressure and it's 1.9psi (kawa state 1.6 to 2.3psi as the working range for their fuel pumps).
Put everything back together and it's still the same.
Going to be trying original kawa carbs now (thanks BertBert!) but any other suggestions appreciated!
Thanks,
Duncan.
Dunc
Had a horrible feeling you'd finish back at Sq1.
I'm actually prepared to put money on it being your equivalent of this .........
http://secure2.cyberware.co.uk/~rad-shop/acatalog/...
Yep, the fuel pressure may apparently be fine 'static' but I'll bet it isn't when it's running. Over-fuelling/fouled plugs at tickover are really classic signs of a FR misbehaving usually simply through age. A stronger than usual smell of fuel when it's running and/or any sign of dampness (remembering it will of course rapidly evaporate and perhaps leave no sign) on the FR itself would endorse the likelihood of that being the fault.
Had a horrible feeling you'd finish back at Sq1.
I'm actually prepared to put money on it being your equivalent of this .........
http://secure2.cyberware.co.uk/~rad-shop/acatalog/...
Yep, the fuel pressure may apparently be fine 'static' but I'll bet it isn't when it's running. Over-fuelling/fouled plugs at tickover are really classic signs of a FR misbehaving usually simply through age. A stronger than usual smell of fuel when it's running and/or any sign of dampness (remembering it will of course rapidly evaporate and perhaps leave no sign) on the FR itself would endorse the likelihood of that being the fault.
Hi Trev,
Thanks for your continued head scratching, I'll give you the full run-down of how I tested the fuel pressure (I was expecting it to be high as it was my last idea to the fault really).
I plumbed in the gauge as close to the carbs as possible, just before the line splits into two to feed the right and left pairs of carbs. I checked the rubbers between the carbs and the inlet to see if it was dry, I then started the car with no throttle and continued to let it idle until it was up to temp. Avoiding using the throttle so the accelerator pump was not activating.
I then removed the carbs quickly to see the fuel in the rubbers and slightly wet looking valves, the plugs were still very dark although the exhaust gases seem reasonably clean.
The fuel pressure was constant through this time, if you still think it could be to blame then I may replace it as a precaution (probably with an adjustable one if available for carb levels of pressures).
It must be something, it's certainly got me stumped though - I took some pics of the setup in general which I was going to put up on here and hopefully someone can point out an installation error of some type.
Pics to come!
Dunc.
Thanks for your continued head scratching, I'll give you the full run-down of how I tested the fuel pressure (I was expecting it to be high as it was my last idea to the fault really).
I plumbed in the gauge as close to the carbs as possible, just before the line splits into two to feed the right and left pairs of carbs. I checked the rubbers between the carbs and the inlet to see if it was dry, I then started the car with no throttle and continued to let it idle until it was up to temp. Avoiding using the throttle so the accelerator pump was not activating.
I then removed the carbs quickly to see the fuel in the rubbers and slightly wet looking valves, the plugs were still very dark although the exhaust gases seem reasonably clean.
The fuel pressure was constant through this time, if you still think it could be to blame then I may replace it as a precaution (probably with an adjustable one if available for carb levels of pressures).
It must be something, it's certainly got me stumped though - I took some pics of the setup in general which I was going to put up on here and hopefully someone can point out an installation error of some type.
Pics to come!
Dunc.
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