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450 sxf cold start help

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got a '07 450 SX-F. How do you cold start your's?

we pull choke and push starter button. Good, hard cranking from battery (initially). I might get an early burp (almost fires). then cranks more. I leave it choked, no throttle. takes a lot of cranks before it finally fires. Is it flooding, or just taking awhile to get gas? Should I close choke after the first hint of a burp? (that's what I do on small engines, to prevent flooding).

The 4 & 5 batteries seemed a bit weak. we made a new battery box and used the size 7 battery. It worked better and stayed charged longer. But it was a mickey-mouse set up the way we fabbed the battery holder, etc...

So now I went to the Shorai Lithium iron battery, 130 CCA. It has good early cranking, but then seems to get drawn down (opposite of what they claim they do).

Am I doing something wrong on cold start? great compression with new piston, & new sparkplug.

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My 07' was a temperamental cold starter as well. Most importantly was to make sure the battery has a good strong charge. Overall battery strength has a huge impact on these bikes starting right up, I learned that the hard way. I would give it 2 throttle twists, choke on then try and start it. Recommend keeping the choke on even after an initial "burp". If your still having problems you may want to verify your valve clearances.

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thanks, you are correct...tight intake valves are often symptom of hard cold start. mine are at the outer edge of the spec (= looser) than tighter.

I may try a throttle twist before we choke it.

I also read KTM manual said the mixture screw and idle screw will affect the cold start. Maybe I'll play with that once it's warmed up. I believe it recommends 1.5 turns out on mixture screw and fine tune from there.

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I have a 2011 450sxf . I simply changed out the start jet from the stock 85 to a 70. Its just too rich, espically in cold weather. You can get the 70 start jet from any honda dealer. Its what comes stock on the cr450f..

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thanks racerxx276.

another guy told me he choked it AND had the hot start lever on (which gives more air). so maybe that helped compensate for the rich pilot jet?

Interesting, because I've seen guys go to bigger pilot jets to help with cold start (on other bikes), but not smaller. so the Honda jet fits no problem? and you noticed much better cold starting?

the carb sure seems like a royal PITA to get out.

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I still have cold start issues. Upgraded to the 210CCA Shorai Lith Iron battery. After bike is started, the header pipe quickly glows red. I'm thinking too lean on pilot jet. What size pilot do you run?

I think the newer model that racerxx276 refers to must be different carb?? you mentioned your pilot is too rich and you went from a 85 to a 70. I think stock size on mine is 42 (??).

this is a 2007 450 sx-f. what have you found works?

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I have a 2011 450sxf and yea  jetting for cold starting is hard.

 

Today is cold, at 43F/4c  and I'm at 250ft above sea level. I'm using stock header with an after market muffler.

 

In summer I run a #48 pilot, and #70 starter jet, but today I moved down to a #68 starter jet and it worked much better.  Stock is  #42 pilot and #85 starter jet.  What is happening is the the richer pilot is effecting the start jet, so in order to have good warm-running idle, you need that rich pilot, but with that, for good choke starting you need a much leaner starter jet.

 

Cold weather starting:

Pilot jet: 48

Starter jet: 68

Fuel screw:  2 1/4 turns out

 

Stone cold starting method: choke on, one throttle twist, wait 5 seconds, with zero throttle, hit start button.

Edited by speedbump49

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Gets below 35F with a stock lead acid that's a year or two old.... get lucky or jumper cables! Once their warmed up no problem!

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On my 09 45.sxf , it has always been a beotch to start when below 40.

I go out and set a little electric heater on a bike stand and let it blow on engine. After 15 minutes it fires right up. I let it run till hot, throw her on the trailer and she starts easily when I get where I'm riding out. Never rejetted, nothing.

It's easy to over think things.

Sometimes you gotta outsmart them.

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