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Yamaha TT500 XT500 SR500 FCR carb


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23 replies to this topic
  • BruceD_500

    TT MVP Platinum Member extraordinaire : )

1,341 posts
Location: Ontario
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Posted January 30, 2009 - 09:35 AM


Has anyone installed a Keihin FCR carb on a Yamaha 500 ? Care to share jetting specs?

  • treehopper

    TT Silver Member

925 posts
Location: Other

Posted January 30, 2009 - 02:12 PM


How would you make it fit?

  • Baja trail Rider

    TT Titanium Member

2,391 posts
Location: Mexico

Posted January 30, 2009 - 08:30 PM


Best carb for that bike is from sudco 38mm round slide

  • BruceD_500

    TT MVP Platinum Member extraordinaire : )

1,341 posts
Location: Ontario
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Posted January 30, 2009 - 09:50 PM


Best carb for that bike is from sudco 38mm round slide


just because that's what everyone is using including me doesn't mean that's the best carb for the bike . If it was still 1980 I would agree but it's 2009 and I think carbs have progressed beyond the 38VM round slide or at least I hope they have? but then again things have progressed beyond the 500 Yamaha but that's another thread.

So anyone tried the FCR on these bikes ? I'm thinking a 37mm should do the trick? I'm just not sure jetting wise how far off a 37mm carb from a liquid cooled 250 would be from an air cooled 500 ?


How would you make it fit?


I'm sure it will bolt up maybe with a K&N filter but where there is a will there is a way.

  • plugeye

    TT Gold Member

1,427 posts
Location: Texas
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Posted January 31, 2009 - 07:01 AM


you are correct. mark says this 36mm flat slide pumper mikuni will fit:

http://www.thumperst...RXTTT.html#carb

there is no comparison between a vm & this type carb.
good luck

  • treehopper

    TT Silver Member

925 posts
Location: Other

Posted January 31, 2009 - 07:26 AM


If your motor is stock i would go with the 250 FCR, and if it is a fully built high performance 500, I would go with a 450 FCR. The jetting should be very close, you might have to lean out the smaller carb or richen the larger one.
I was considering this switch for the same reasons, but it really looks big to fit on a TT500. The top of the carb has a lot going on with all of the throttle actuation gizmos. I will be jealous if you make it fit.
I ended up with a Dellorto 38 pumper, a common mod for flattrackers when they raced these bikes.

  • TT500motocross

    TT Newbie

5 posts
Location: Arizona

Posted March 13, 2009 - 11:40 AM


Howdy All
I have had my TT on the Dyno many times trying different things. For a stock motor except for carb and exhaust a 34mm produces the best bottom through midrange power. At Yahoo Group TT500MOTOCROSS I have posted the Dyno sheets and jetting.
Jim

  • treehopper

    TT Silver Member

925 posts
Location: Other

Posted March 13, 2009 - 07:29 PM


Hi, Jim. THIS is the place to post your info, not Yahoo. Since you have joined us, and we are all here together, why not post it here instead of making us join Yahoo Groups? This is, after all, THE place.
I hope you don't take this as being disrespectful, but you have it backwards by putting it on Yahoo first.
Mike

  • TT500motocross

    TT Newbie

5 posts
Location: Arizona

Posted March 16, 2009 - 04:44 AM


Treehopper
No disrespect taken but there was no divine intervention that told me that there was a group already supporting Thumpers so I started my group. I will not be closing my group, it is just for TT/XT500s. This site covers a lot of different thumpers and I have only been with all of you just a short time I am still having trouble sorting through all of the information. I hope to get better at it.
Respectfully
Jim

  • Smacaroni

    Get Help Now

8,485 posts
Location: Pennsylvania

Posted March 16, 2009 - 08:11 AM


I think what he's saying is he's running a membership drive.

I hate having to register for everything.

Might I recommend http://bugmenot.com. This is a site that keeps a database of bogus user names and passwords so you don't have to register for everything to view one little item of interest.

  • BruceD_500

    TT MVP Platinum Member extraordinaire : )

1,341 posts
Location: Ontario
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Posted April 02, 2009 - 06:59 PM


installed but not tuned or running. Fit up went not bad.
This carb is one from a YFZ450 ATV so it only uses the single pull cable. Don't quote me on the intake boot but i think it is from a ZX9 2001ish . Best to go to the local wrecker with your new carb and your old intake in hand. The carb is a bit shorter than the stocker so something will need to be done to pull the air box connecting boot forward or make it longer. Or one of the older carbs with the removable bell on the back might be the way to go and make your own bell if you have the resources for that kind of thing.
To make a little extra clearance at the tank bottom/carb top, I added about 4 washers under the rear tank mount and used a longer bolt . The carb is also mounted on a very slight angle not much at all really. The oil line is the biggest pain , but it's not in the way of anything the way I have it and with some fiddling there might be other ways to run it.
The fuel line is fine as well the choke/hot start would be easy access ?

This bike is unfortunately not one of my runners, so I was just using it as mock up. It might run but this engine is a complete unknown to me so I would hate to spend much time trying to tune the carb on this engine. I'll have a fresh engine in my daily driver in the next few months then I'll swap all this over to that bike. But it looks like this is all possible. This only took me about an hour and a half and I'm using the stock cable.

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  • plugeye

    TT Gold Member

1,427 posts
Location: Texas
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Posted April 03, 2009 - 03:29 AM


wow, looks do-able. i fitted that same carb to my dr650 & it works great.
we made a sleeve on the boot side bell to fit (well-documented on dr forum & you can see in my garage on the dr650 bike)
its a 39mm, a 35-37mm might be best for the xt500.
a flatslide pumper is the poop man. not just for best performance, excellent throttle control & smooth pulling throughout the rpm range, including low-end.

  • BruceD_500

    TT MVP Platinum Member extraordinaire : )

1,341 posts
Location: Ontario
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Posted April 03, 2009 - 05:05 AM


I think you are correct the 37mm should be just the ticket once the exhaust is opened up. The YFZ450 carb was just the closest one at hand. I've got a 37mm from a yz250f also that's probably what I'll use in the end. My new engine has a 10:1 piston also so I'm hoping it will work well. It might even get some reasonable fuel mileage once I get over the inital urge to crank it open all the time :thumbsup:

  • firstplacephoto

    TT Bronze Member

218 posts
Location: Massachusetts

Posted May 13, 2011 - 07:02 PM


i have a tt500 deraked flattracker,90 mm carb,powroll 7 mm stroked engine,ported,vance hines ss2r slipon from an r-6,ard ignition,pipe,megacycle cam,heavy valve springs. i put an fcr from a wr400,i believe a 39 fcr carb. not sure of jetting. had to shorten intake manifold to almost nothing to get it to clear frame,maybe 3/16" thick thick. what a big difference from a 38 round mikuni. i changed carb and now you get a kick in the ass about half way into the rpm's,and revs longer. you might lose just a touch right on the bottom,but it is such a great carb. go figure,all the new mx bikes run them,it is not an accident that they do!

  • scalejockey

    TT Addict

4,646 posts
Location: Idaho

Posted May 13, 2011 - 08:08 PM


i have a tt500 deraked flattracker,90 mm carb,powroll 7 mm stroked engine,ported,vance hines ss2r slipon from an r-6,ard ignition,pipe,megacycle cam,heavy valve springs. i put an fcr from a wr400,i believe a 39 fcr carb. not sure of jetting. had to shorten intake manifold to almost nothing to get it to clear frame,maybe 3/16" thick thick. what a big difference from a 38 round mikuni. i changed carb and now you get a kick in the ass about half way into the rpm's,and revs longer. you might lose just a touch right on the bottom,but it is such a great carb. go figure,all the new mx bikes run them,it is not an accident that they do!


Good to know:thumbsup:


Iv'e also had found that a newer style of 2-st carb replacing the old vm38 on my vintage racer made it run like a new bike.

  • Se nisei

    TT Newbie

1 posts
Location: New Zealand

Posted August 13, 2013 - 09:22 PM


Yes have one on one of my 3 Yamaha's 5undys ..... Works mint

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  • BruceD_500

    TT MVP Platinum Member extraordinaire : )

1,341 posts
Location: Ontario
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Posted September 29, 2013 - 03:59 PM


I've just posted one of the FCR carbs in the classifieds if anyone wants to give this a go on their 500 yamaha.

 

http://www.thumperta...hin-crf250-125/



  • BruceD_500

    TT MVP Platinum Member extraordinaire : )

1,341 posts
Location: Ontario
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Posted May 24, 2015 - 09:57 AM


Ok so this is a pretty old post but I spent some time today and finally got one of these things mounted and running.  It works pretty well. I went with a carb from a YFZ450 ATV as opposed to one from any of the modern MX bikes.

reason being there is a bit of a difference in the castings on the air filter side that makes it pretty much impossible to fit the carbs from the MX bikes on.  After I had it all mounted up it started first kick warmed up and idled right down. a quick trip around my back yard showed very crisp throttle response and what felt like lots of power.   I can't do much beyond this now until I find some place to test the bike on some wide open areas . My back yard is a bit too small and the bike is a bit too noisy  

 

The carb on the left fits.  The one on the right does not. Note the difference in the TPS mounting on the left side of the carbs is different. The carb that fits has the idle adjustment in a very awkward spot.  

IMG_2660_zpse6vucbfv.jpg

 

 

 

 

 I'm going to have to see if I can move that idle cable to the same place as the MX bikes. This will require drilling and tapping a hole.    

 

 IMG_2663_zpsats1yulv.jpg

 

 

 

 

 

IMG_2665_zpsfqcywlvf.jpg

 

Has anyone else on here mounted one of these successfully and feel like sharing jetting #'s ?  So far it seems pretty close but that may change once I get it out for a real ride. 


Edited by BruceD_500, May 24, 2015 - 10:19 AM.


  • firstplacephoto

    TT Bronze Member

218 posts
Location: Massachusetts

Posted May 24, 2015 - 02:17 PM


I got these numbers a fewyears ago,sorry don't recall who sent themto me,but they were very close  !#48 Pilot Jet.
Adjustable Pilot Air Bleed Kit (Begin with 1.0 turn from seated)
#200 main Air Bleed
#155 Main Fuel Jet
Pilot Fuel Screw (Begin with 1.0 turn from seated)

Metering Rod (Needle)
Begin with FHR @ 4th clip slot (from top)

EMS, FMR and FMS should be in your tuning kit.
Also have on hand a #45 Pilot Jet and main Jets ranging
#150 - #175

Note:
Suffix "S" neelde will often require a step up in main jet size
over that of the "R".



  • pcnsd

    TT Bronze Member

102 posts
Location: California

Posted May 25, 2015 - 09:20 AM


I got these numbers a fewyears ago,sorry don't recall who sent themto me,but they were very close  !#48 Pilot Jet.
Adjustable Pilot Air Bleed Kit (Begin with 1.0 turn from seated)
#200 main Air Bleed
#155 Main Fuel Jet
Pilot Fuel Screw (Begin with 1.0 turn from seated)

Metering Rod (Needle)
Begin with FHR @ 4th clip slot (from top)

EMS, FMR and FMS should be in your tuning kit.
Also have on hand a #45 Pilot Jet and main Jets ranging
#150 - #175

Note:
Suffix "S" neelde will often require a step up in main jet size
over that of the "R".

 

I remember that post at the FT forum, it is from a 534 setup by Dale Lineaweaver. I use very similar jetting on my street SR540 but I ended up with a 162 main to eliminate WOT hesitation (7/8 throttle test) and a 42 pilot. Do your jetting with a AP disabled then jet to minimum shot only if needed.

I personally would not recommend the FCR for a stock framed bike. For all it's benefits, it is a huge carb and fitting will require surgery to carb and a custom manifold at minimum.

 

This is what I imagined would work.

 

CarbAdpt1.jpg

 

CarbAdpt2.jpg

 

This is what was left after reality set in. It does not left much to hold on to.

 

carbfit4.JPG

 

carbfit2.jpg

 

Ta Da.

Srdone1.JPG






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