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IamTheCowboy

05-450x Nightmare to start cold (hot is perfect)

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I bought an 05 450x from a buddy because he never rode it, I can see why, it was in terrible shape. After cleaning, replacing just about everything, I still have extreme difficulty starting the bike. Once the bike is started, it idles perfectly and once warm, it never misses a beat and has tons of power. The E-start turns the engine over slowly. I have tried adjusting the decomp screw until it turns over easier by the E-start, but then my gap isn't to spec. Approx 120 Hours total time on engine, Zero on rebuild.

Here is what I have done.

Cylinder head just done by ASRacing with new Stainless valves installed and valve clearance adjusted to spec.

New Honda Piston/Rings (stock size)

Hot Cams Stage 2 cam (came with the bike)

New Honda Cam Chain

FMF Ti 4 header into stock muffler with baffle removed (the TI4 muffler was just too loud for me)

Jetting  170 Main, 45 Pilot, 50 Leak jet, Fuel Screw at 2 turns out.

New Spark plug, and Ignition coil

2 stage air filter

O-ring mod on the carb.

Like I said, once it fires, it idles perfectly and never misses a beat. It doesn't cough or sputter ever. It just does not want to fire up initially.

The carb is clean, Compression is great, gas is new. I just don't understand why it doesn't want to start.

I have tried to find any info on this issue, but many people suggest dirty carb or wrong jets, or bad valves/adjustments. 

Please help.

 

 

 

Edited by IamTheCowboy
Didn't mention how many hours on the bike.

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Turn on the gas. Pull the choke. Open the throttle quickly all the way to the stop two or three times. Try starting it with the throttles closed. These bikes are cold blooded, and the winter weather exacerbates the problem. Right around 45 degrees F is where my bike gets finicky. 

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Since this time last year, with a 2008 CRF 450X and its duty as a snowbike.  Here was the list of the issues, these all happened at one time or another during last season/winter;

 

1.  The hot start plastic nut had lost all its threads and was allowing air to lean out the mix causing lots of backfiring-you never mentioned any backfiring so not sure if your nut is on and on there good. I had replaced the nut with an aluminum one from CRF's only. 

2.  The aluminum aftermarket fuel screw had backed out at one point and was lost and the replacement did not want to stay in place.  I have replaced it with the R&D Flex Fuel Screw making sure to have the washer, o-ring and spring in and in the proper order.  

3.  Since the 450X is a snowbike, I got a JD Jetting kit and installed the blue needle in the 4th or middle position with the clip.  The pilot jet is a 45 and the main jet is a 165.  All day yesterday, the bike started and ran flawlessly.  

 

It was in the low 20's in the morning and I had tried twice to start the bike on the e-starter with the choke on and had then put the jump pack on the battery and on the 3rd try-as the engine kept on starting but then stopping as it was so cold, by the 3rd try the bike fired and stayed fired up and once at full choke for about 30 seconds I could push the choke in and the bike would idle happily.  We never give the carb any fuel or touch the throttle when starting it, either cold, warm or hot.  

Hopefully you'll get it sorted.  

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I recently replaced the plastic hot start screw with a tokyo mods aluminum unit. I am quite certain that it is seated well. The bike does backfire on occasion. I have an aftermarket fuel screw, and I am positive it has the o-ring and and spring, I am pretty sure I looked up the proper order, but if you know the proper order, please tell me. I will check this. Where are you at on the fuel screw? Mine is at 2 turns out. I love this bike when it starts, otherwise, it isn't my friend. That main jet shouldn't really affect starting, and my other jets are quite close to yours. I should mention I am at 700 ft above sea level.

 

And I do twist the throttle 3 times quickly before kicking with the throttle closed. My 250 always starts with that procedure. This one, just doesn't. #sadface

 

 

Edited by IamTheCowboy

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My fuel screw is 1 1/8 turns out.  I have not had to fiddle with it at all and I have not even tried to test to see if the engine will run better using the test procedure.  

 

Here is one more thing I had learned; if the idle screw is set too high, the bike will NOT want to start.  The last time, after I had installed the JD Jetting kit and the R&D flex fuel screw, I had made sure that when I already had the carb out and in my hands, to adjust the idle knob so that the bolt threads that push the carb slide up, that the bolt was flush so that if I needed to turn the idle up at all, I would just turn the knob right/counterclockwise to raise the idle .  I had learned when the carb was all knackered/dirty/incorrect jets/air leaks from the hot start nut and fuel screw, that if the idle was raised too high, the bike would not want to start but, once the idle was lowered, the bike would fire.  

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Air screw at 1 1/4 turns out. Idle turned down, it pops, but doesn't light. Sometimes backfires. UGH!!! I am wondering if it is the cam? I double checked the cam timing and it's perfect. Brand new spark plug. New gas. Just doesn't make sense. :(

 

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Are you sure you are getting fuel?  

I had to take the carb on and off no less than 8 times to make sure that the pilot jet was clean.  

I had to take the fuel tank off this past summer and had sprayed some degreaser into it and hosed it out and let it dry in the nice, hot sun followed by a new fuel tank strainer as the old one had disintegrated, sending all its plastic sand-like crystals throughout the carburetor.  

 

There are two things;

 

1.  All that work and parts replaced, it has to be one of them that is causing the hard starting or;

 

2.  Something is off in the carburetor.  Who had cleaned it?  The FCR carburetor, from what I have learned, is as close to FI as it gets and many say it is better than either a Smartcarb or a Lectron, but it is also somewhat complex with many seals and items that can wear on the inside.  I had sent mine out to Keihin-FCR.com, and he had both cleaned and replaced every single seal that needed to be replaced and he had remarked that there was very little that was worn but that time and old fuel had damaged many of the seals and from the seals he had sent back, I could see how the old fuel had damaged them.  

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Brand new IMS gas tank, great fuel flow, new pilot jet, new leak jet, new main jet. I do all my work on my bikes. I have been wrenching on them for 40 years, this is the first bike I have owned that doesn't fire up in a reasonable amount of kicks. I am wondering if it is too rich? Maybe it doesn't like the FMF head pipe with the stock muffler. The weirdest part is how well it runs once it fires up. If it wasn't such a giant pain in the a$$ to get the carb off, I would be changing jets like mad. Where did you send the carb? Maybe I can just get a rebuild kit?

 

 

Edited by IamTheCowboy

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If you just loosen both of the carburetor clamps, one should be able to rotate the carb to the gearshifter side to get at the float bowl cap and the jets once the big nut is off.  

I had sent the carb to Keihin-FCR.com, here:

 

http://www.keihin-fcr.com/

 

There is a great rebuild thread if you are up to it, here:

 

https://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild

 

 

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I’ve had backfiring that required replacing the 45 pilot jet and running a piece of fishing line thru the rest of the pilot circuit into the carb throat, it’s a tiny oriface that gets contaminated and hinders flow just enough to be a pita. I read boiling the stripped down bare carb body in simple green water mixture is what is suggested. Making sure the fuel and air passages are 100% before reassembly

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I will pull the carb and inspect it with a microscope if needed. The hardest part of this, is how well the bike runs once it has been started. No hesitation anywhere, idles perfectly, and after the engine is warm, fires up instantly. I will review the carb rebuild. (Thanks for the link).  If anyone knows of a good rebuild kit for the 450x carb, please let me know. It looks like there are several out there, but none that have all the seals. I will report back after pulling and inspecting the carb.

 

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All the stuff on this site might have all you need, and it will be the correct, quality-stuff.  

 

I was losing my mind this past fall and even this past end of November, when the snow finally came but the 450X would still NOT start-like yours.  Mine was a relatively simple solution, just the correct jets and needle and a R&D fuel screw set correctly and I was back in business.  

 

I would follow the DirtRider link/how-to and check all the seals and wear parts and be sure that reassembly is correct.  For all I know it might not be in your carb, all those new parts could have something to do with it not wanting to start but once started, it runs perfect.  

https://www.crfsonly.com/catalog/index.php/cPath/355_357_138_147

 

 

Edited by Ben500RR-S

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This may be a stupid question but to start with the basics since its such a weird problem. This is a problem with starting the bike with the E-start? If you kick it does it start right up? I'm sure you've tried that. I've had the battery at just a low enough level before that it doesn't turn the motor over fast enough to start. Makes it seem like something is wrong.

I saw you have the stock pilot jet. I run the same thing. And your fuel/air screw is set to 1 1/4 turns out. I wouldn't think that it too rich. I'd think if anything it might be on the lean side. Maybe try to back that out to 2 turns and retry. Not sure if that will help but good luck.

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check your cam timing again. Use both the observation window on the left side and the right side. Read the cam timing section of the manual at least 5 times. I swore I had everything timed right when using the left view port but it was a bear to start and ended up being off 1 tooth. After i read the manual for a 3rd time it dawned on me to check the right side timing port and sure enough that sides timing marks were not lined up and the left side looked lined up from the angle i was looking at it. 

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On ‎1‎/‎10‎/‎2019 at 8:02 PM, CSAR FE said:

Turn on the gas. Pull the choke. Open the throttle quickly all the way to the stop two or three times. Try starting it with the throttles closed. These bikes are cold blooded, and the winter weather exacerbates the problem. Right around 45 degrees F is where my bike gets finicky. 

As simple as this sounds, it works every time.  I was having issues on cold starting every time, I chased the carb and so forth.  Just fully twist the throttle 2-3 times before you hit the start button and it fires every time now..............

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I will pull the carb and inspect it with a microscope if needed. The hardest part of this, is how well the bike runs once it has been started. No hesitation anywhere, idles perfectly, and after the engine is warm, fires up instantly. I will review the carb rebuild. (Thanks for the link).  If anyone knows of a good rebuild kit for the 450x carb, please let me know. It looks like there are several out there, but none that have all the seals. I will report back after pulling and inspecting the carb.
 

A classic symptom I use to determine if my valves need adjusting on my 450X is the same thing you are experiencing. Difficult to start and idle cold...starts easily and idles well when warm...usually, its one of the intakes.

You said you had new valves from AS Racing...maybe, they were not shimmed correctly when the rebuilt head was installed?

easy to check...

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if you are really pulling the carb again, check to make sure the accelerator pump is actually doing its job and squirting fuel, and that the fuel is not hitting the slide before making it down the throat to the engine intake...need to make sure that the oring you put on did not mess up some function of that circuit of the carb

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