Help me fix my Motard.

[JettaJayGLS]

Okay folks. This year has sucked. I've made 2 race weekends. My bike has ran like shit through them all. I crashed out of two races, finished one race in last place after my bike dying on the grid, and pulled out of two races. Last season my bike ran absolutely mint, every weekend. During the winter tear down, I noticed the play in my crank (giggity) was out of spec, so I rebuilt the motor. The bike is an 02 CRF450. This is what I have done since then:

Hot rods crank, bearings, and seals.
12.5:1 wiseco piston and rings for stock bore (exact same as what was in there)
New valves seats and guides along with OEM valves, springs, retainers done my millenium technologies (pretty much a brand new head)

Now, the bike starts and runs beautifully. When riding, it ABSOLUTELY RIPS. Noticeably more powerful than last year, the motor was tired then.

The problem is that it WON'T IDLE! If I turn the idle up a bit it stays running forever, but that is not a good fix.

This may not seem like a big deal, but, once warm these things don't like to start. Meaning yeah, I could go shut it off on the grid and feather the throttle to start it, but that means I gotta hope it restarts when I want it to.

The other option, which is what I tried the two race weekends I actually made it there, is turn the idle up so it does not die. The problem here is that my bike is overheating by the time the race starts and then makes no power throughout the race.

I'm led to believe this is a carb issue, I just can't diagnose it. By memory, I'm at a 162 main, 42 slow, 3rd clip on the needle, 1.25 turns out of fuel screw. I will confirm this later on...regardless, I'm looking for a direction suggestion like "larger main" or "lower clip position" so the specific jets I'm running should not be a HUGE concern.

Plugs indicate that everything is normal. I have taken the carb off and checked the jets/needle many times. They are not clogged and the needle does not show signs of wear. I've played with the fuel screw and the clip position on the needle and can not find a working combination.

What else am I missing, what else could be contributing to this? I'm fairly certain I won't be racing in October but you never know. Regardless, I want this fixed so I can either sell, continue racing, or run this thing in the dirt.

Thoughts?

[JettaJayGLS]

Other mods on the bike include stage 2 hotcam and some brand foam air filter in a stock airbox. I run 93 octane pump gas.

[Kurlon]

Main and needle really shouldn't be involved in your idle, unless you've got the slide jacked way up. Given this is an 02 I'm assuming it's got an FCR carb, have you replaced the slide vacuum diaphragm?

#22 in this diagram: http://www.sudco.com/CatalogJPG/017.jpg
#16 in this diagram with the plate: http://www.servicehonda.com/parts/lo...EB2MEB4E1800HJ

This is a wear item, approx 2 year lifespan according to Sudco.

[Pigman]

Start with Ultrasonic carb cleaning.....pilot is semi clogged poss even if it sat for a few days

[JettaJayGLS]

Main and needle really shouldn't be involved in your idle, unless you've got the slide jacked way up. Given this is an 02 I'm assuming it's got an FCR carb, have you replaced the slide vacuum diaphragm?

#22 in this diagram: http://www.sudco.com/CatalogJPG/017.jpg
#16 in this diagram with the plate: http://www.servicehonda.com/parts/lo...EB2MEB4E1800HJ

This is a wear item, approx 2 year lifespan according to Sudco.

Correct, FCR carb.

I have not replaced the slide vacuum diaphragm. To be honest, I am pretty carb illiterate when you start getting into anything but the jets/needle. What exactly does this do and how does it contribute to my problem?

[Jim]

i talked to Marco about this over the weekend.
step 1 - get a gixxah
step 2 - ride such gixxah
step 3 - thank jim for helping you make an awesome decision

[JettaJayGLS]

i talked to Marco about this over the weekend.
step 1 - get an r6
step 2 - ride such r6
step 3 - thank jim for helping you make an awesome decision

That isn't a terrible idea, except this needs to be fixed in order to be sold to get said gixxer, er, I mean r6.

[CBR929RE]

That isn't a terrible idea, except this needs to be fixed in order to be sold to get said gixxer, er, I mean r6.

R6 over gixxa any day and twice on race weekends

[Kurlon]

Correct, FCR carb.

I have not replaced the slide vacuum diaphragm. To be honest, I am pretty carb illiterate when you start getting into anything but the jets/needle. What exactly does this do and how does it contribute to my problem?

Normally the slide in a carb is a tight fit in the bore which makes for a decent air seal. FCRs have the slide rattling around on rollers which would make for whopping big air leaks all around the slide. Air leaks around the slide pull signal away from the metering orifices of the carb which makes for crap operation at closed and low slide openings. The vacuum plate and seal take up the slop and allow the slide to function properly. When the seal gets tired it looses it's elasticity and either jams the seal making the slide stick or doesn't let the plate move causing leaks. I'm thinking you're suffering the latter, which is why the carb won't function until you raise the slide for a high idle.

This is also why you never ever spray brake and parts cleaner, contact cleaner, carb cleaner, etc into an FCR as you'll damage the seal. If you're going to spray a solvent in for whatever reason, use gas.

[JettaJayGLS]

Normally the slide in a carb is a tight fit in the bore which makes for a decent air seal. FCRs have the slide rattling around on rollers which would make for whopping big air leaks all around the slide. Air leaks around the slide pull signal away from the metering orifices of the carb which makes for crap operation at closed and low slide openings. The vacuum plate and seal take up the slop and allow the slide to function properly. When the seal gets tired it looses it's elasticity and either jams the seal making the slide stick or doesn't let the plate move causing leaks. I'm thinking you're suffering the latter, which is why the carb won't function until you raise the slide for a high idle.

This is also why you never ever spray brake and parts cleaner, contact cleaner, carb cleaner, etc into an FCR as you'll damage the seal. If you're going to spray a solvent in for whatever reason, use gas.

Excellent info! I have definitely doused the thing in carb cleaner...I'll pull the carb apart again and take a look. If it is the same material as your typical o-rings it should show any signs of degradation pretty well. I honestly will just replace it regardless.

This carb is what, almost 12 years old now. Would it be worth replacing the entire thing?

[Kurlon]

I wouldn't toss the whole carb yet unless you like throwing large wads of money into it? Check the plate and seal and replace if necessary, sounds like everything else is working ok just gotta fix the low speed stuff.

[SVRACER01]

its a light bike. why not just push it out to pre grid and then start it out there when the warm up lap starts. then the only idling its doing is on the grid waiting for the green flag

[KB]

What kurlon said. The rubber on the slide is junk. I had the same issue on my crf. Buy a complete new set of jets and all the seals and you will be all set. Buy all brandy new jets.

[lrrs428]

PM'd