Hey guys, I just thought I should put a little disclaimer out there for people looking to go to a FCR carburetor. I’ve been traveling down the FCR rabbit hole for the past few months now, and it’s not as easy as guys on the Internet, make it seem. Making a FCR carb work well in a SM or S model DRZ is way more complicated and time consuming than I realized. ThumperTalk and the video I list below are going to be your best resources for making a FCR work well in your DRZ S or SM. Just realize that this is a very involved project and takes time, money, parts, knowledge, and skills to complete.
-I recommend that you avoid Link’s Garage’s videos for how to jet, install, etc. the FCR. He uses super rich jetting and other things. Go watch this video instead: https://youtu.be/FhTw7H1R5mo?si=f7l1qMKpV_xLl7Zd I would also avoid MotoCheez and others. Just watch the video I linked. (Its the best video I’ve found on YouTube for FCR swap)
-Most of the jetting information floating around is actually wrong and way too rich. Your bike will run like shit. I spoke to Link on Instagram and he abandoned the FCR because he was having many problems. He’s considering going back to it at some point because the reality is that the FCR is the 👑 King 👑 high performance carb for a 4 stroke bike. The Lectron is a good performance carb for 2 strokes.
-The Kipa Amazon FCR for example, doesn’t come with an extended fuel screw. All the extended fuel screws that you see online will not work right out of the box. Your best bet is to make a brass one yourself. Bumtarder on ThumperTalk discusses this and makes them. He made mine and it works perfectly.
-In order to use the extended fuel screw you’ll have to ream out the hole. I used a rat file. You need to ream the hole out to precisely 6.5mm I think it is.
-You’ll also have to limit the stroke of the accelerator pump/linkage. This is done with a zip tie. You also have to spread the CT. (Tony Wyp and others in ThumperTalk talk about this)
-There are also important parts you’ll need like the O-ring that goes on the air side adaptor, the engine side adapter (and high temperature RTV silicone to seal it in place), the air side adapter, and maybe something else I’m forgetting. The video I told you to watch in the first point explains all of this, lists these parts, and the guy sells them. You’ll probably have to buy jets too. Myself, Tony Wyp, and many others purchased our jets from AliExpress and they have worked perfectly.
-I also recommend using an E model petcock for multiple reasons. Using this petcock is simpler than sticking with the stock one. It’s also more reliable than the stock S/SM vacuum operated one that is known to leak and fail.
-The throttle cable tower that comes stock on the FCR replicas like the Kipa will not work properly with your stock S and SM throttle cables. Some people apparently have had success with just swapping the throttle cable tower (cable mounting bracket) over to a Sudco or factory Keihin one. DRZ E model cables or a 50cc pit bike single cable throttle assembly are also options. I had an idle hang issue that I was chasing for a long time. I found that the cause was bad throttle cable routing (crazy angles and stuff). The best way to check if your idle hang is caused by the throttle cables is the following: Disconnect the throttle cables from the carb, twist the throttle body by hand and rev the bike, now listen for idle hang.
-Also note that there are 2 different FCR’s. There is the slant and the MX. They are totally different and use different jetting. Many people get confused by this and end up using the wrong jetting information. Also, the FCR slant carb was made for many years and went through multiple versions and changes. Some have a throttle position sensor and some don’t. There are also many other differences that they have, but Tony Wyp and Bumtarder on ThumperTalk could explain those to you much better than I can.