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Keihin fcr 41

Old 08-04-2011, 04:22 AM
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Keihin fcr 41

Hi there guys.Newby here although a old owner.
After many mod"s in the past , 3 or 4 years ago i installed fcr kit on the vtr.With the filter box in the begining and without it later.
I was totally screwed up with the existing carbs with factory pro race kit.
Anyway bike gained everywhere from top to bottom with the fcr"s.
When i say gained , i mean race type reving up like 2stroke race bikes.
Less fuel consumption all around, top performance.
Recently i rrebuild the engine, fitted new je pistons , new metals on rods, balance the the crankshaft, ........ .
I have fcr"s running free , as i said before with only their red velocity stacks.
After rrebuilfing the engine and brake in period , i reved it up and it seemed funny. The clutch was slipping, at around 7000 rpm, and the bike would not rev up easily.
Anyhow we deciced to richen the air fuel mix since the spark plugs where coming out white.
Still nothing. We use 220 main jets and the bike won"t pass 8000 rpm"s , it coughs and act"s like ignition limiter is acting on. Btw how do we call that? i mean the rev limiter?
Anyway , 230 is the biggest main jet keihin has for fcr"s.
The needle has been lowered one notch, notch 3 of 7 from the top.
Exausts are remus , slip on"s carbon.
We have also installed race ignition coils, green ones don"t remember the brand right now.Ohh and barnet clutch springs, along with new clutch all the way , apart from other things.
My problem is the white plugs , and not revving up.
Has anyone else done this mod , and how coped with it?
Fcr"s are really strange carbs.
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Old 08-04-2011, 05:46 AM
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I recall a thread here with the idea of installing FCRs but the cost of importing them and setting them up proved prohibitive

Try contacting Roger Ditchfield of Revolution Racing in the UK

www.revolutionuk.co.uk

PS Any pics and specs to your VTR?

edit

Superhawk forum FCR threads

https://www.superhawkforum.com/forum...mod-kit-10536/

https://www.superhawkforum.com/forum...tslides-24087/

https://www.superhawkforum.com/forum...unna-do-11455/

https://www.superhawkforum.com/forum...r-whats-15747/

Last edited by Wicky; 08-04-2011 at 05:58 AM.
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Old 08-07-2011, 10:21 AM
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Hi, I had a similar problem, albeit with original carburetors. The solution was a powerful fuel pump because it was not enough petrol in the float chamber at high engine speeds.
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Old 08-07-2011, 10:32 AM
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Vacuum leak?
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Old 08-07-2011, 04:36 PM
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did you figure this out? I would wonder if the vacuum line to the cylinder is crimped or if the petcock isn't functioning correctly. You can measure the vacuum and test the petcock - it just sounds like its starving for fuel and the mods you made really shouldn't have changed the carb jettings that significantly. Would be sure fuel is flowing with the draw from the vacuum line bypass it altogether.
let me know what you find.
by the way wiht the FCR carbs, did they come with TPS or without - and if without did you notice any ill effects running without it?
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Old 08-07-2011, 08:28 PM
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My guess is something other than carbs only because if it worked before all the major engine work. So much was done it could be a whole host of issues, but I would start with lack of fuel issues first so the petcock vacuum line being in the right place and that the tank is venting. Then if enough fuel is present I would check the cam timing is on the money. Check that both cylinders are getting spark too.
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Old 08-09-2011, 09:52 AM
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Hi guys, thanks for the heads up .
The carbs came along with tps.The vacuum line from the petcok is bypassed , so that fuel runs directly to the bowls.
Cam timing is ok.
It"s the rebuild engine with the increased 11,4/1 compression that lead us to the increased jetiting. The fuel flow is , looks adequite.As i said before the vacuum feed is being bypassed , before we even rebuild the engine.
Both cylinders have a spark , from dyna coils .
No we encountered something different.
The bike spurs coughs in the low rpm area from 2500 to 4000 with enough throttle open and then when reaching 8000 stops reving up no matter what i do with the throttle like the kill switch is turned to off.It"s freaking me out this thing.
It looks like electrical but i"m not so sure.
I think i will roll back to smaller jets to see how it does , and if it overcomes the problem that means that float chamber is left with some fuel in it, then i"ll have to play with different needles and needle jets.
Scary thoughts, really if tou think that keihin offers more than 20 different needles with different profiles.

Last edited by jomark911; 08-09-2011 at 03:40 PM.
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Old 08-09-2011, 09:56 AM
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Check your kickstand switch.... sometimes different rpms cause it to cut out, leading to weird behavior that resembles fuel starvation. Try to bypass it and see if you still have the problem...
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Old 08-09-2011, 09:58 AM
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You're not running with an airbox?
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Old 08-09-2011, 03:23 PM
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Thanks for the kick side stand switch but it"s the first thing i checked.
Since it has done this before it"s the first thing i checked.

Last edited by jomark911; 08-09-2011 at 03:37 PM.
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Old 08-09-2011, 03:36 PM
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Originally Posted by 7moore7 View Post
You're not running with an airbox?
Nope i"m running them completely free as they are supposed to run.
I mean fcr"s.
BTW my mechanic still believes that there are some goblins in my yard.
2 days ago we found pieces of an oring behind the front floating valve in the carb.Quite big , the float valve wouldn" close and the gas would overfill and drain into the cylinder head freely.
Next we found out that the alternator plug coming out from the coils and entering into the cable harness was burned out and the bike was running on one coil.(alternator). The other plug had been fixed and replaced earlier by me. The one that goes into voltage regulator.Same three phases ac current from alternator.
I don"t know but something weird is going on here.
Allbeit all those findings bike still runs funy.
Today i checked ground cables , allmost everywhere, not a sigle fault.
Tomorrow will change back to smaller jets.195 Instead of 230 , and needles back to the midlle position to see how it goes.
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Old 08-09-2011, 03:49 PM
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I was thinking how stupid i"ve been for not letting my mechanic install a fuel injection system complete with the computer -cable harness and all the stuff from a crashed varadero .The one that has same cylinder heads with VTR.
We could install a power commander along with a electtronic ignition box and play along as we liked.He had everything and sold for 300e. We would be kings.Figure of speech.
The only thing that was probably missing would be the larger fuel injection body"s , which could be found .
Stupid me.

Last edited by jomark911; 08-09-2011 at 03:53 PM.
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Old 08-09-2011, 03:58 PM
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Originally Posted by 7moore7 View Post
You're not running with an airbox?
He is running these carbs:Special Applications

pricey, but some have had great luck with them.
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Old 08-09-2011, 04:08 PM
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I would run those for aesthetics alone. Hope you get the tuning to work out jomark!
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Old 08-10-2011, 08:31 AM
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Hello again, I think it really will be a small float chamber. Between 2000 to 4000 rpm. apparently the needle, but above 8000 rpm. I had the same problem. When diffuser reduced from 48 to 41 mm will be very increased intake and the consumption of gasoline. I mounted fuel pump with a flow rate of 2 x 150 l / h. Since then I have full power to 10,300 rpm. Veny - Czech Republic, Europe
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Old 08-10-2011, 10:14 AM
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Originally Posted by veny.biker View Post
Hello again, I think it really will be a small float chamber. Between 2000 to 4000 rpm. apparently the needle, but above 8000 rpm. I had the same problem. When diffuser reduced from 48 to 41 mm will be very increased intake and the consumption of gasoline. I mounted fuel pump with a flow rate of 2 x 150 l / h. Since then I have full power to 10,300 rpm. Veny - Czech Republic, Europe

THANKS but it"s not that.
After some unsuccesful swaps of needle position and main jets , we concluded it hasn"t anything to do with the fuel.It"s something else.
I wish i knew what , but beats me. Rembember that fcr"s are mechanically linked slides with acceleration pump.No it doesn"t have to do with fuel flow, since as i said before , the vacuum has been bypassed long ago , and whatever fuel is in the tank flows unlimited to the carb bowls.
I"m afraid the ignition sensor in the rh where the small star is that reads pulses and sends signals to the ignition unit.If it"s that, then it"s quite obvious why the engine does those tricks, like misfiring coughing , etc.
The hard part is to empty new oil , coolant , unscrew the rh cover bla bla bla.
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Old 08-14-2011, 12:49 AM
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OK guys mystery reveiled.
Problem solved.
Yesterday ,all day , teared the bike apart and xheck everything. Some ansuccesful swaps again.
Finally swaped dyna ignition coils with stocks.Voila.Everything fine.
Engine revs up, bike does a whilie while spinning the rear and rushes forward like a rocket.I almost run on to some trafic lights or other vehicles, and my mechanic too.
It is screaming and shots everything on the road.It easily swalloed gsxr 1000r k8 , in a small straght road around 1000m long.Now we are talking.
Probably will have to jet down , even from #210 main , and lower the needles from the middle pos to one, or even two pos down to get it wright.
And will have to figure out a way of stoping the clutch slipping.Barnet clutch springs obviously are not enough.We have in stock spare discs both barnet (not installed yet).
It seems like the bike does easilly 150 bhp.
Wil do more post, along with some photos.
One thing is for sure though. Riding this thing is pretty scary now.
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Old 08-14-2011, 03:24 AM
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Originally Posted by jomark911 View Post
OK guys mystery reveiled.
Problem solved.
Yesterday ,all day , teared the bike apart and xheck everything. Some ansuccesful swaps again.
Finally swaped dyna ignition coils with stocks.Voila.Everything fine.
Engine revs up, bike does a whilie while spinning the rear and rushes forward like a rocket.I almost run on to some trafic lights or other vehicles, and my mechanic too.
It is screaming and shots everything on the road.It easily swalloed gsxr 1000r k8 , in a small straght road around 1000m long.Now we are talking.
Probably will have to jet down , even from #210 main , and lower the needles from the middle pos to one, or even two pos down to get it wright.
And will have to figure out a way of stoping the clutch slipping.Barnet clutch springs obviously are not enough.We have in stock spare discs both barnet (not installed yet).
It seems like the bike does easilly 150 bhp.
Wil do more post, along with some photos.
One thing is for sure though. Riding this thing is pretty scary now.
Would love to see some photos and videos please! Glad you got it sorted!
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Old 08-14-2011, 08:06 AM
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Will try.
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Old 08-15-2011, 11:14 AM
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Old 08-15-2011, 11:15 AM
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Old 08-15-2011, 11:16 AM
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Old 08-15-2011, 11:18 AM
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Old 08-15-2011, 11:28 AM
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Some better photos will folow.
Some hints, front brakes are 6pistons calipers from gsxr 1000 02. Pump is lucas.
Same , lucas pump for the clutch, works very soft.1/10 the pressure on clutch lever compared to stock.
Mufflers are upward tilted like the sp"s. Sp1 are the rear footpegs brackets.
Rear fender is from cb 1300 if i remember correctly.
Headlight fitted with xenon kit, some years ago.
Flash lights are aftermarket , don't remember where from.
Oil cooler is from somewhere in the us, larger than the stock, and placed where it is like moriwaki does.
Oh and undertray is ermax.
After some more tune up nos bottles controler and generally the whole kit will be installed.

Last edited by jomark911; 08-17-2011 at 03:26 PM.
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Old 08-17-2011, 03:21 PM
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Ok the thing is a beast.
Ok we knew that. BUT we have a problem. The all new clutch is slipping.
It can not control the power the engine produces.That's it.
Slips for endless periods of time with 5th and 6th gear.
Actually both theese gears never come to their limit , so that i can have a accurate reading of my top speed. Slipping 6-7000 and on all the way. Today i took it out to the highway. With a stupid smille , on my face.It would rev up from 7000 to 10200 in 4 seconds. But the odometer had a different opinion.It wouldn"t show more than 240 kmh.The gear box has been altered also in such a way that its lengthened by 5 to 10 percent. So odometer should read easily 300 .
Keep in mind the whole clutch is new , discs also , and harder barnet springs are installed.
Any sujestions?

Last edited by jomark911; 08-17-2011 at 03:35 PM.
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Old 08-17-2011, 03:47 PM
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Wow that sounds awesome. Would love to see dyno numbers on that motor.

Perhaps the clutch discs were never able to break in properly with all the slipping going on from the start. Maybe driving gently on a new clutch to give it time to break-in will give it better grip....maybe not.
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Old 08-18-2011, 12:05 AM
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I don"t think so , clutch had a breaking in period of 2000 km. Where the bike was riden gently.It should be enough.
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Old 08-23-2011, 03:01 PM
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Hey guys , hello , i"m in a good mood tonight.
We just finished some dyno runs.
Since i don"t have the paper yet , but only some nunbers , the bike did.:
156 bhp / 9680rpm. best power.
12,67 kgm / 8840rpm best torque.
100,1bhp/6050rpm
9,23kgm/6050rpm .
Theese are some numbers that i wrote down on paper.
After the all gear run we had to wait for about an hour or so to cool down so the clutch would not slip.
I hate this situation. Having a VTR that does 156 hp on the wheel but can not take advantage of it just because the clutch slips.
My luck..#$%^&&&&&%%^^#@!
Any ideas guys?
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Old 08-23-2011, 03:13 PM
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What crank are you running, my understanding is that the stock crank is only good for ~130hp before it tends to break.
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Old 08-23-2011, 03:29 PM
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Originally Posted by lazn View Post
What crank are you running, my understanding is that the stock crank is only good for ~130hp before it tends to break.
Well all dyno's read different and I would think the one he is using is a bit on the optimistic side...... as it sounds like he did a pretty basic Stage 1 build. So I would say somewhere in the 120's true but that is just my opinion and I've only been messing with these bikes for a little while....

The only real thing I would add is, if you are running the bike with just the stacks, your engine isn't going to last very long. You need some kind of filter or the engine will be trashed in no time flat.
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