So I have heard that regardless of carb size, there is a fitment problem with the Yoshi exhaust & the FCR carbs....just more custom mods in the pursuit of hp......I heard that the Sparks' exhaust clears no trouble & so do a few others but how about LRD?

My current setup is a 686 12:1 with head porting & bigger valves & S1 cam. As of today, I plan on keeping the 686 setup another season. From what I hear, the 35mm FCR's would definitely make more power with this setup. If I got the 35's,
I would definitely delay spending any more $$ on motor work. I save $$ by doing my do my own motor work but mom still sees what I spend & our newly built house needs a new deck & shed & lansdcaping & a bedroom set & the kids want to go to Disney World & ..............

Sudco recommends the 39mm FCR's even with a 686 setup since they said the 39's would make even more mid-top end power than the 35's. They said the 39's may make less bottom end than the 35's with a 686 setup, but the 39's will still make more bottom end than the stock carbs. Comments???

I just want to be sure that if I get the 35's now with my 686 setup, will they still make a noticeable difference when I upgrade to a 105mm bore??? Intuition tells me that the 35's would be best for a 686 setup & that the 39's would be best for a 105mm bore. The 105mm bore by itself will make a ton of bottom end but without running either FCR carb its hard to guess what will happen.

So, I am interested in any comments & hearing from anybody who ran the 686 with either the 35's or 39's & also from anybody who ran the same carbs with the 105mm bore. Thanks!

 

you have a 686 and your only making 53hp.....???? i would get rid of the yoshi, and you need to look into teh option of FI. if you are willing to spend the $1000 on getting teh fcrs you mights wants to look into spend $1200 and getting the Fuel Injection kit and not have to worry about it. The fcrs will feed any size motor, but one is easier to tune, everyone seem to be running the 39's no matter waht size bore you got, but then again some people still use the 35's

 

I concur with CT. Dump the yoshi. It's holding you back big time. FCR's are big bucks and a pain to tune I hear. It would be more fun to play with EFI mappings. Then you are set for either a 686 or 727.

 

They are very "user friendly" SAE ponies, I'll have to add my 686 dyno graph to my profile.

The last I heard a FI module was around $2-3k, where can you get it for $1200?

Still looking for FCR user's comments. Thanks again.

 

kelly at KMS performance is the only guy i know of that does it, he is a good friend of mine, cuz he is local to me. i take my bike to him for everything.


www.kmsperformance.com

 

I spoke to Kelly from KMS & he opened a whole new can of worms. He said the FI module is $1500. He didn't recommend it for my setup since its better suited for exotic fuels & nitrous/supercharging/turbo applications.

He did recommend the 39mm FCRs over the 35's & also recommended going with a 4mm/720cc Hotrod stroker kit that uses a 686 Wiseco piston. He said that was a better way to reach 720cc than to just resleeve & bore out to 105mm.
The Hotrod kit rod/crank can handle the power & its already balanced so its just a drop in kit. The stroker kit combined with the FCR carbs sounds like the best bang for the buck......hmmm.......

 

I have the 720 HotRods stroker and 39mm FCRs, and I can recommend it. With your setup I think you would be happy with it.

 

Definetly the 39mm fcr's. [img]i/expressions/face-icon-small-smile.gif[/img]

 

I probably should say though, If you are worried about spending cash, once you commit to the stroker you will be spending a lot for things you may not be thinking about. Stroker kit, pipe, carbs, longer swingarm, clutch to handle it....= $$$$$$

I have seen used 35mm FCRs for sell on several forums for around 500-600. That is alot cheaper than what you'll spend for the whole 720 setup. You could always sell the 35s later.

 

i have a 686 with 11.5:1, megacycle ect ect.... and i run the fcr 35's. they work great with my motor! Ive never tried the 39's so i cant tell you which is better, but in my opinion.....an engine can only use so much fuel and air if its displacement cant use it or pump it. I have gobs of low,mid and top end grunt and think the 35's are perfect for the 686!