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Discussion Starter #1
I bought a 1996 GSX-R1100 about two month ago, and the power is absolutely incredible when I get into the 8K + rpm range. However, this bike does not like riding slow in traffic or in stop and go traffic like city riding. The combustion chamber seems to get flooded with too much fuel being pumped with the 41mm carbs. She starts to sputter when riding at low "stop and go" traffic, or whenever I have to stop at a red-light. I don't know much about flat slide Keihin carbs, but I do know by now that the 41mm are designed for more power in the upper speeds, and the 39mm carbs are designed to pull more power from the bottom end. I talked to Sudco, and they told me that the flooding issue can be taken care off with the proper jetting and carb setup. Other people tell my the the 41mm carb is just way to big for the type of riding (city and back-roads with lots of low speed riding) that I do.

The 41mm FCR carbs that I have now are about 14 month old, and they have seen very little ride-time. I don't know anything about their setup, since I purchased this bike from out of State, and I have lost contact with the last owner. I'm now thinking about buying me new 39mm Keihin FCR's, which will give me more power at the bottom, and less at the top, which is what I really need for my riding style. The 41mm I have now are used without a filter, which I don't like, so I just ordered me K&N filters and the filters to carbs attachment components needed from Sudco, which will fit either carb size. This change already needs for the carbs to be re-jetted.

So, I have actually two questions:

1) Are the 39mm or the 41mm FCR Flat Slide carbs simply to large for my street bike, or if not, what jetting specifications should I use if I were to keep my current 41mm carbs, or what jet sizes should I use if I were to buy me the 39MM FCR's? Sudco told me that I should not have any flooding issues with either carb if the carbs are setup correctly.

2) What could I realistically sell my 41mm FCR's for if I were to buy me the 39mm FCR's?

Thanks for any advice in advance!

Andy
 

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The 41s are fine on your 1100,they just need to be jetted properly. Which nowadays not too many shops want to,or are capable of tuning correctly since FI bikes have taken over.
They're are plenty of knowledgeable folks here who can get you sorted out if you are capable of using tools;)
 

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I have a set of 39 FCRs on my 94, and the bike runs great. My engine has been bored to 1146, and it would benefit from the 41s. I will trade you like as long as your set doesnt have any underlying issues (like cracked slides or anything like that) :cheers
 

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Discussion Starter #4
Thanks for the replies! My biggest concern was that the 41mm carbs are just to large for my bikes engine, but it sounds like that they can be tuned to work with my setup. I'm going to give my local shop a try with cleaning (since they never had filters on them), re-jetting and synchronizing the 41mm carbs, plus installing the new K&N filters. Maybe the 41mm setup will grow on me if they are properly setup for my bike and eliminate the low rpm issues that I have now. I would stay away from any type of trading and just purchase me new 39 FCR carbs from Sudco, since they are "only" $1,250.00 new, and then I would know what I have.

Thanks,

Andy
 

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I hear ya, I was kind of regretting trading my self. Took me a while to tune the set I have on the dyno, and I dont feel like going thru that again. If you have yours tuned, do it with filters on it. If you tune it with the stacks, and then put filters on it later, it will be different. Personally, I would not ride on the street with just stacks on it. Have you ever seen how dirty those filters get? Now just imagine shaking those filters out and putting all that dirt right into your engine. Good Luck :cheers
 

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Discussion Starter #7
Do you have any clearance problems at the alternator/starter location using the Keihin's ?
No issues with the fit, as you can see in some of my carb pics. I am having the carbs cleaned, K&N filters installed, and re-jetted right now, so I may need to keep the left and right side panels off (which are next to the outside carbs), if the filters are to large. I will know soon. I sure hope that the carb cleaning and re-jetting, plus the $450.00 for the new K&N filters will take care of the issues I had. I will know soon!
 

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fcr's are probably the best carbs for these engines. i'm interested if the shop will be able to "dial" them in for street use. running filters on the street is a smart idea, so like someone stated, get them "tuned" with the filters mounted.

good luck and keep us posted.
 

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For the type of riding you do, and what you want from the bike, the stock setup with air box is the way to go. I have the same bike and she starts pulling pretty good around 4000 rpm with a rush near 7000. Power flattens out a bit on top, but for street riding not doing high rpm constantly, it's pretty satisfying.

You will never get the low end response of the stock setup with flat slides and no air box, no matter how you jet. I'm pretty sure you can convert it back for a lot less than the price of new carbs too, though installing the air box might need the engine pulled.

Just my opinion, take it for what it's worth to you.
 

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Discussion Starter #10 (Edited)
I think that we are there! The shop called me today and asked me to take her out for a ride on the highway and into the city to see how she rides now versus before they started to tune the carbs. They also installed the K&N filters, so my bike is being fine-tuned with them in place.

As some of you may remember, I had issues with the bike making "burping or coughing" sounds when I had to stop at stoplights, which was then followed by the carbs flooding out when I started to give gas after the light turned green again. She also did not like riding at low RPM / low speeds like one does inside of a city or busy traffic. She would then also flood out and at times kill the engine. However, she was a rocket out on the open roads, and nothing could hold her back after you got the rpm's above 4k. But also keep in mind the the previous owner had her tuned for the Maryland International Raceway, which was probably just a little more demanding then riding the back roads around my house!

Make a long story short, the shop did a great job so far with tuning the carbs in. They talked to Sudco, and between the both of them came up with a setup that cured the issues of flooding the carbs at low speeds or stops, and the burping / coughing of the carbs is also completely gone now. I rode the bike in the city, with lots (on purpose) stop and go traffic, making sure that the engine would get hot to the point that the fan was running frequently, followed by 30 minutes of highway speeds, and then followed my a couple of warp speed acceleration on some county back roads, and she did perfect. At least, perfect for the way I ride. I did noticed that she tried to flood, just a little, when I was riding in 5th gear at about 50 - 60 mph and I pulled the throttle wide open in one quick twist. She barked down a little, and it took her a couple of maybe 3-5 seconds to respond to the gas being flooded into the carbs, but she eventually burned off the excess gas, and she took off..... She had no issues, or hesitations as I did a couple of fast high rpm, running through the gears, fast acceleration runs, where I switched gears around 6-8k rpm's.

The shop told me that this is also what they noticed during their runs, and that they could adjust the carbs a little more the get rid of the midway fuel overloading at lower rpm's, but I told them that I was absolutely pleased with the way that she is riding now, and that I'm more then capable to downshift to raise the rpm's and thereby bypassing the mid-range flooding potential!

The carbs have also quieted down after the K&N filters were installed. The slides are not as noisy anymore during stop idle rpm's, which I think is a little downer, since I did liked the sound of those slides flapping around! :smile:

I also noticed that the engine rpm's at idle are now elevated to around 1100, when they were before at around 800 rpm's at stop idle. I think that this, besides the jetting and needle work, could also now help in burning off some excess fuel during the engine sitting at idle at stoplights, but that is just a guess.

So, I'm glad that I kept the 41mm FCR's, and I will post the complete setup / tuning of the needle placement and the jetting, and any other changes that the shop made and also Sudco recommended next week after they are completely done and me getting the bike back.

Andy


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Discussion Starter #11
I picked up the GSX-R this afternoon, and the shop kept adjusting the carbs until they got everything tuned perfectly within all three: lower, mid, and upper RPM ranges.

Here is the final carbs configuration:

Was # 165 Main, now a # 158
Was # 55 Pilot, now a # 52
Was 0CEMP needle, now 4 notches from the bottom
Set fuel screws at 1-2 turns out
Air screws now at 1 1/2

It is way to cold in NC now to go riding, so I will give an update on how she is doing now after it warms up a little.

Andy
 

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Andy I took some 750 cabs and did the factory Pro kit designed to run on the 1100's I got plenty of power and was able to keep my choke. It's pretty cold over here in the Pacific northwest and the choke was definitely needed. If I was to go FCR's I'd go 39's unless you had mods done to your motor.
Bobbychet
 

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Discussion Starter #13
Hi Bobby,

I fully agree that 39mm FCR's, or even the original stock setup would have been a much better choice in carbs for the type of riding that I do. However, the 41mm carbs came with the bike, so I spend the money for tuning and adding the filters to them, which was not cheap at a total cost of $850.00! I talked to Sudco, and they recommended me keeping the 41's, since they were already paid for, and I'm not using my bike to race on a track, were I need lots of bottom, low rpm power. The issues were that my carbs were setup for the drag strip, for high rpm's, high top-end power, giving you high mph. I ride much lower speeds and much lower rpm's. The only difference between the carbs, as I'm sure you know, is that the 39mm give you more power at the 0-100 mph / lower rpm's getup and go, and the 41mm kick in at about 50mph to + 200mph, at higher rpm's.

My carbs are setup now to let me enjoy my bike for my riding style, so I am more than good with the way the carbs perform today. I doubt that I will ever sell this bike, but the next owner, if I do one day sell her, may not like this setup. But this will be something that he or she needs to address when the time gets there.

Andy
 

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However, the 41mm carbs came with the bike, so I spend the money for tuning and adding the filters to them, which was not cheap at a total cost of $850.00! I talked to Sudco, and they recommended me keeping the 41's, since they were already paid for, and I'm not using my bike to race on a track, were I need lots of bottom, low rpm power.
Ok,now that is insane :blink
 

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Discussion Starter #18
Ok,now that is insane :blink
:) Right on, it was, but then again, I know what I wanted, which was the sound and performance of the FCR's! And paying $850.00 for something that I'm going to like for years to come is a small cost to pay in my book. And what would have been my alternative? Pay close to $2k for a new set of 39mm FCR's? Buy a used set for $1k without filters which probably had issues? Spend $1.2k for a smaller "non FCR" carbs and setup?

At the end of the day, I spend $850.00 to have the setup I like. I don't think that there is anything insane about this, at least not in my world.
 

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:) Right on, it was, but then again, I know what I wanted, which was the sound and performance of the FCR's! And paying $850.00 for something that I'm going to like for years to come is a small cost to pay in my book. And what would have been my alternative? Pay close to $2k for a new set of 39mm FCR's? Buy a used set for $1k without filters which probably had issues? Spend $1.2k for a smaller "non FCR" carbs and setup?

At the end of the day, I spend $850.00 to have the setup I like. I don't think that there is anything insane about this, at least not in my world.
Uh,no justification needed,asked for,or warranted. It's your money.
Alternative? I would have rejetted and set them up myself instead of paying a shop. :thumbup
 

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I do not know how much you spent on the bike itself so I dont know how much money you have totally invested into it. As for comparison, I bought a near mint 02 gsxr 1000 and am into it for a total of about 3000 dollars and it puts out around 200 rwhp ( had a 1070 kit in it that I did not know at purchase, but thats another story ). I just find it hard to dump money into an old bike on labor. Like OG said, you could have jetted it yourself. I do all my own work on my bikes so I just cant see paying someone almost a grand just to get it running right. I would have rather just bought a modern bike. For the sake of argument, lets say you paid 2200 for you bike, and paid 800 to tune it. With that much money (3000 total) you could have bought the bike I did, and have a reliable, great running in town and on the highway, low maintenance, modern bike. Dont get me wrong, your bike looks awesome and looks to be in excellent shape. I love the old bikes, I have a few, but I would not dump money into them on labor. That is one of the few generations of GSXRs that look good with the dual pipes. On the other hand, if you have the money and dont mind other people working on your stuff, and if it runs good, and your happy, thats all that matters :cheers
 
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