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fcr 35 on a 04 klx300r

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After 3 months of toiling, wanting on jets and needles and replacing a bad float valve I finally got it running. I ended up settling the needle on the 3rd clip, went with a 152 55 set up on the jets. It seems to run best with the fuel mixture screw about 1 1/4 turned out.

Luckily it only bogs if I quickly turn the throttle from idle to wide open, then it only bogs for maybe 1/2 a second. Riding normally there is no bog.

The response I get now makes it like a new bike. With the CVK it seemed power had to build up (the vacum setup), now the engine hits right away. In fact while doing a farely steep climb I ended up hitting the throttle too hard in 2nd, did a wheelie and went down. That never happened with the CVK. In fact I can now do most climbs in 3rd which wasn't possible before (I'm 220 lbs)

Anyway my original thread was deleted from back in march, so I just wanted to thank everyone who answered my questions and helped trouble shoot this project. I now know a lot more about carb's then I did when I started. Considering I got the FCR used on Ebay and am $270 in including the hot start, awesome bang for the buck!.thumbsup:🙂👍:banana:

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  • 2 months later...

ok my carb has been great since I got it jetted correctly or so I thought. It runs great and always starts at home which is about 1000 ft. Also no issues at Rohwer flats which I think is between 2000 and 3000 feet.

Friday night I started the bike at home no issue. Then Saturday went up to Lake Arrowhead to ride with some buddies. It's between 5000 and 6000 feet and was about 85 degrees. My bike made no effort to start. Hot start didn't matter, even starter fluid wouldn't work. The only thing that would work was rolling it down hill and starting it by poping it into gear with the clutch. Then it ran fine, no bog, no hesitation & idled fine.

However even warm once off it would not start with the kick.

Once I got home (1000ft) it starts again no problem on the first kick.

ANy ideas? I'm guessing the fuel screw is adjusted too far out making it run too rich? Is the Carb that tempermental about a few thousand feet?

any input would be great.

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Check your valves ASAP When the intakes start to close they go quickly and I would suspect that you need to re-shim the intakes.

It is a place to start and it might sound odd but my bike did the same thing to me. If they are fine then you have eliminated a possible problem.


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pumpers are more sensitive to elevation changes

I agree. I run a 147 on my 300 with a 37mm fcr/mx. as far as the WFO whac bog that is the nature of the beast the engine at that low a vacume signal cant take the fuel squirt like an engine thats spooled up alittle or under load.

I notice a little less r's at @ 5000 feet. havent had a starting issue as I have the magic button.

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