PDA

View Full Version : FCR 41 overflow problem


steveoms
08-08-10, 11:42
Hi All

New to forum.

I have an OMS2000M with a ZZR 1052 engine. It has the FCR 41 carb set on which has just started to overflow from the overflow pipes when I switch on the pump. I have taken the carbs off and looked at the float valve and seat and cannot see any obvious wear or damage. Please can anyone give me some advice? I am entered in the Lydden spint this coming weekend and am now panicking a little to get this sorted out. Many thanks for any help.

Regards

Steve

steveoms
08-08-10, 20:04
Quick update. I tracked the problem to the o-rings on the float valve seats. They are removeable on these carbs and the old ones had gone ard and perished. Put on some new o-rings and suprise suprise no leaks. I hope that someone else will find this useful knowledge one day. Thanks.

Craig Powers
08-08-10, 20:16
Quick update. I tracked the problem to the o-rings on the float valve seats. They are removeable on these carbs and the old ones had gone ard and perished. Put on some new o-rings and suprise suprise no leaks. I hope that someone else will find this useful knowledge one day. Thanks.

Useful information because I occasionally suffer the same symptom on my FCR39s (also on a ZZR1100).

I can tell as soon as I have a problem because the reciprocating pump will not shut off ; it keeps clicking slowly as it overflows the float bowl.

sevaun
09-08-10, 08:41
By coincedence I had the same problem with my GSXR 1100 on Saturday at Harewood. Started the engine 5 mins before 1st practice and fuel was spewing from one carb. I guessed it was a float level issue so took off the the float bowl and gave the floats a good "waggle" up and down. This seemed to fix the problem and both Saturday and Sunday meetings the car ran faultlessly.
However bearing in mind what's been said here I guess I'd better take a closer look - as they say there's no smoke without fire!

Richard

AndyBougourd
09-08-10, 08:46
By coincedence I had the same problem with my GSXR 1100 on Saturday at Harewood. Started the engine 5 mins before 1st practice and fuel was spewing from one carb. I guessed it was a float level issue so took off the the float bowl and gave the floats a good "waggle" up and down. This seemed to fix the problem and both Saturday and Sunday meetings the car ran faultlessly.
However bearing in mind what's been said here I guess I'd better take a closer look - as they say there's no smoke without fire!

Richard
Hi Same thing happened to me at Gurston turn off fuel pump ran engine till carbs empty turn on pump all OK
Bugs

sevaun
20-04-12, 14:54
Quick update. I tracked the problem to the o-rings on the float valve seats. They are removeable on these carbs and the old ones had gone ard and perished. Put on some new o-rings and suprise suprise no leaks. I hope that someone else will find this useful knowledge one day. Thanks.

My recently fitted second hand FCRs are flooding badly and I suspect similar is happening with them. Steve, if you read this can you tell me how the seats come out, I've unfastened the small crosspoint retaining screw, but the seats won't come out and I don't want to damage them. Do they just pull out or screw out?

Thanks

Richard

steveoms
20-04-12, 22:34
Hi Richard

I presume they are brass? If so they should just pull out, mine came out pretty easily because the o-rings were perished. Hope this helps.

Steve

Clive Austin
20-04-12, 22:43
The other candidate that can cause the overflowing is a knackered regulator. I was about to strip my carbs until SO recommended changing the reg first. Problem solved.

C

sevaun
21-04-12, 08:14
Thanks Steve I'll try a little more elbow grease then.
Clive I've already changed regs so I've covered that one thanks


Richard

sevaun
07-05-12, 14:39
After a bit of investigation I discovered that my FCRs had 3.2 mm float jets which are for gravity feed systems only. 3 psi from the pump was enough to lift the needle valves off their seats and flood the carbs.
Allens supplied me with the right size of valves and the flooding is cured!! :D
I've adjusted the idle mixture and leaned off the needles by a couple of notches and the engine is running as sweet as a nut......however one problem hasn't gone away.
Having warmed up the engine I use an infra red thermometer to check header temps. All are ok apart from number one header which only reaches 125 degrees when all the others are up in the 3-5 hundreds. This indicates an issue with combustion in number 1.
I've tried the following diagnostics:
1. Swapped plugs and plug leads/ coils between cylinders - no change. However the problem cylinder is wetting its plug and smoke is eminating from the plug hole when I take the plug out. Other plugs ok and no smoke.
2. Checked compressions all ok within 5 psi
3. This one's strange - If I close off the carb trumpet with my hand there is more vacuum on the problem carb and yet the revs don't drop when I do this. If I cover any of the other carbs there is much less vacuum but covering them cause revs to drop and ultimately stall the engine.
I've checked float levels and all seem ok.

Anybody got any ideas please?:)

Craig Powers
07-05-12, 15:03
3. This one's strange - If I close off the carb trumpet with my hand there is more vacuum on the problem carb and yet the revs don't drop when I do this. If I cover any of the other carbs there is much less vacuum but covering them cause revs to drop and ultimately stall the engine.

I wouldn't get hung up about point #3. The problem cylinder is not firing and is just working as an air pump.

image
07-05-12, 16:13
I agree with Craig --- blanking one cylinder shouldn't stall your motor --- the fact it does when you do it to one of the 'good' cylinders means that the 'bad' one's already not firing leaving you trying to run on two.

K

sevaun
07-05-12, 19:24
I wouldn't get hung up about point #3. The problem cylinder is not firing and is just working as an air pump.

Yes I see your point Craig, but it must be firing as I don't have any misfire, the engine sounds sweet and there is some heat in the header, just not as much as there should be. I's almost like it's overfueling and "damping" the cylinder. When I take out the plug it's wet but not drenched. Could it be that there's some jet drilling blocked in the carb that's causing overfuelling?

Richard

image
07-05-12, 20:05
not that familiar with these carbs but presumably the choke is via an extra 'Jet' rather than a butterfly --- could this be faulty leading to that cylinder hardly firing as it's on full choke?

K

asklepios
07-05-12, 20:17
Float heights ?

sevaun
08-05-12, 22:48
Even though I have fitted corrected float valves, the pressure reg was still not reducing the pressure sufficiently and number 1 carb was still flooding the combustion chamber.
Following advice I got on here some while back (from wombat 58 if I'm not mistaken) I fitted a tee off the fuel line with a 1.8 mm orifice(old weber air jet)and piped this back to the tank. This works a treat! No more flooding, all headers now up to temperature and no plug fouling. This tweek is also a safe guard against the carbs ever flooding the combustion chambers.
On this last point I drained the oil tonight to be on the safe side and it definitely had petrol content in it from the flooding past the rings, I only hope it hasn't done any permanent damage to bearings etc. I measured the volume of oil from the sump and it only seemed to be little over capacity so maybe I've got away with it!
Thanks for all your suggestions and help especially wombat58:):)

Richard

Craig Powers
09-05-12, 18:26
The alternative approach is to use one of the standard reciprocating diaphragm pumps that most of the bike manufacturers use on carbs. They produce just enough pressure and cut off when there is a small amount of back-pressure. i.e. the float bowl is full.

Diagnosis is a breeze. If the pump keeps pulsing slowly then it is continuing to feed the carb, suggesting a stuck float. If it pulses really quickly then you are either out of fuel or the diaphragm has failed (rare).

Cheap and readily available from bike breakers. 15~20. Cheap enough to carry a spare. They seem to be more or less universal across the Japanese big four manufacturers. No need for a regulator. No need for a spill-back line from the (non existent) reg. Low pressure, so easy plumbing. Simple. Reliable.

wombat58
10-05-12, 09:32
Good to see that I was of some help. BTW, next time you have those FCR41's off the engine check the throttle plates from the engine side for cracks. Mine had cracked around the moon-shaped cutouts, and were 1mm from being digested by the engine! Apparently this is a common problem. I replaced them with some HD items I found on fleabay, and they were cheaper than original.

sevaun
10-05-12, 22:57
Good to see that I was of some help. BTW, next time you have those FCR41's off the engine check the throttle plates from the engine side for cracks. Mine had cracked around the moon-shaped cutouts, and were 1mm from being digested by the engine! Apparently this is a common problem. I replaced them with some HD items I found on fleabay, and they were cheaper than original.

Yes a big thanks for your help Steven . I've also checked the slides and they seem to be OK. The acid test will be at Harewood on Saturday. Brand new slicks, carbs sorted, looking for a good result. Only one other thing stands in my way of a brilliant result - 17 other entrants in the Class!!!:(

Cheers

Richard