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Idle confusion

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2008 crf450r, starts first kick, fresh rebuilt everything. Idles fine on stand, ride it hard for 15 minutes, idles higher. Does not hang, snap throttle and it comes right back down to the now higher idle. After it cools down goes to original idle. This would be a) fuel screw lean, B) pilot lean or.... havent messed with it much, am not completely in tune with 4stroke fcr carbs yet. Pilot is a 42, I have a moose fuel screw, seems to be aluminum. The bike performs great, no bog or flame out, just a higher idle, maybe 500 rpm. What are the guesses?

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A work connection hour meter/tech would be a good plus. Are you pushing the choke back in after it's warm? And believe it or now a low low idle is 16-17 and should be about 1,850

Edited by Diggla117

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A work connection hour meter/tech would be a good plus. Are you pushing the choke back in after it's warm? And believe it or now a low low idle is 16-17 and should be about 1,850

I have an hour meter, not a tach. Its not ridiculously high just a solid note, wondering about it. I know my 2strokes always would come back to the truck idling higher then when it left, again, not hanging, just a bit higher.

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A work connection hour meter/tech would be a good plus. Are you pushing the choke back in after it's warm? And believe it or now a low low idle is 16-17 and should be about 1,850

I have an hour meter, not a tach. Its not ridiculously high just a solid note, wondering about it. I know my 2strokes always would come back to the truck idling higher then when it left, again, not hanging, just a bit higher.

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A work connection hour meter/tech would be a good plus. Are you pushing the choke back in after it's warm? And believe it or now a low low idle is 16-17 and should be about 1,850

I have an hour meter, not a tach. Its not ridiculously high just a solid note, wondering about it. I know my 2strokes always would come back to the truck idling higher then when it left, again, not hanging, just a bit higher.

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Those alum. Fuel screws are notorious for acting inconsistant. Get a brass one. Check your hot start plunger operation also.

how can I check that plunger? Wouldnt the hot start sticking make it hang on idle or even cut out when nailed? Seems as if it would have a bigger sign then the idle just coming up a bit yet otherwise acting perfect and crisp. Now the aluminum fuel screw, im interested there, I have heard that before but dont understand it exactly, what is the issue with the aluminum one?

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The alloy fuel screw, as mentioned, is a POS, and can/will eventually break off inside the carb.

 

The hot start cable and plunger will hang up due to corrosion: pull apart, lube both, and I even stretch the spring a good 15mm more to make it stiffer.

 

I have never owned a CRF that does not take a long long time to get the CARB warmed up. 

I mean when the top of the radiators are HOT the carb is not, what ever adjustment you have done to the carb will change when the carb heats up.

 

I have jb welded a coin into my idle screw, so it's easier to turn.

I start  the bike with the idle turned in 1/2 turn, so it will continue to idle with the choke off.

 

Then a few miles in, I check the idle again, and it always has to go down.

 

I strongly recommend a 45 pilot, and R&D fuel screw, a fresh slide plate seal,  and re-visting the fuel screw adjustment using the low slide method.

 

If your motor has lots of hours, replace the needle jet too, as they oval pretty fast and start to give you false rich/lean symptoms.

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You are pushing the choke back in once the bike is warm correct?

A hour meter is cool and all buttt the works connection is a tach too and it's only 30 bucks.

Slide seal should be replaced. The manual says to replace the vacuum slide as well every 25 hours. Nobody ever replaces theirs because they are pricey but at partzilla the seal and plate are 60 bucks and you should Atleast replace once.

Thumbs up on the r&d fuel screw as well. It makes life easy and dosnt unscrew like the after market fuel screws are notorious for.

As others mentioned the hot start lets more air in as well as leaving the choke out so when it warms up it's going to idle higher.

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All are bikes idle higher once full hot , hot oil thinner ect!!' And dude I like the idea of the coin jb welded that is absolutely sweet !!! Lol

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The alloy fuel screw, as mentioned, is a POS, and can/will eventually break off inside the carb.

 

The hot start cable and plunger will hang up due to corrosion: pull apart, lube both, and I even stretch the spring a good 15mm more to make it stiffer.

 

I have never owned a CRF that does not take a long long time to get the CARB warmed up. 

I mean when the top of the radiators are HOT the carb is not, what ever adjustment you have done to the carb will change when the carb heats up.

 

I have jb welded a coin into my idle screw, so it's easier to turn.

I start  the bike with the idle turned in 1/2 turn, so it will continue to idle with the choke off.

 

Then a few miles in, I check the idle again, and it always has to go down.

 

I strongly recommend a 45 pilot, and R&D fuel screw, a fresh slide plate seal,  and re-visting the fuel screw adjustment using the low slide method.

 

If your motor has lots of hours, replace the needle jet too, as they oval pretty fast and start to give you false rich/lean symptoms.

 

 

this man gave you the proper information,

btw the cheapest place to get the vac release plate SEAL is a yamaha dealer, there the only o.e.m. that sells it separately,

Yamaha part number

4FN-14997-00-00

http://www.kawasakip...64fe/carburetor

its number 11

 

this will work in your Honda the FCR carburetors are the same. well spare a few subtle differences

 

other places like jd jetting sell it for 17$ for the seal.

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my 08 does the same thing.. tried the brass oem fuel screw, new slide AND seal ($80), aluminum housing for hot start (better seal), new hot start plunger, new choke, different pilots (42 is best in mine, 45 was too much), cleaned the carb on 2 occasions (total disassembly), tried it all. It always idles up a bit when warm, and sometimes even idles a tad high, then lower if you blip the throttle. My 04 ? idles perfect all the time.

I have a feeling it has something to do with the timing retard/gear position sensor on the 08. Retards timing in 1st 3 gears.

Edited by MELK-MAN

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