Idle problem has me stumped!

[marc177u]

Ok, has anyone else experienced this? If so what was the fix? When I start my '06 RMZ it starts and runs normal, except when I twist the throttle it does not want to idle down all the way. The idle does go down but not all the way as it should. To get it to go down I have to blip the throttle a second time and then it goes down to normal. But then it idles to low. It will die if I let it. It does not do this with the choke on. I didn't do anything unusual. It started doing this on it own. It act's like a sticky slide. I checked the slide and that was not the problem. Also checked the adjustments on my return cable and pull cable, all good. Checked for air leaks by spraying starter fluid around everything, no leaks anywhere. I ran out of ideas. Maybe my Throttle Position Sensor (TPS)? But I've never heard of one going bad. Seems as though if I tap on the carb. the idle goes down, but I can't be sure on that.

[jack450]

worn needle and needle jet

[CrusRuss]

Cheapest fix is to start by cleaning out all the jets in the carby. Spray cleaner through them and make sure everything is done up nice and firm.

If it still doesnt fix it then as the other guy said you could have something worn out in the carby. I doubt its a broken electronic piece.

[marc177u]

I've cleaned it 3 times now very thuroughly. Never thought of the worn needle though. I'll give that a try. Thanks!

[dusty2221]

i am having the same issue on my rm250. We tested the Throttle Posistion sensor and it seems to be the answer. When tested with the meter, in closed throttle position it is reading that the throttle is cracked. Your case is exactly what mine is doing. I highly suggest looking up the specs in your book of what it should read and checking it.

Good luck.

[gregghealy]

Cables?

[marc177u]

Thank's Dusty, I think that's my problem. Tried a new needle and needle jet no luck. I've never heard of the TPI going bad though. Oh well, I guess it's no different then any other part. I'll be checking it today.

[GOTWHEELS]

Is the top end of motor in good shape? When A motor starts going south the idle seams to got fineky.

[CrusRuss]

When I had my RM250 a guy told me you can unhook the TPS and it makes the motor run better

Have u tried running it with the TPS unhooked?

[m1a3t0t]

the TPS will be slightly open when the throttle is closed because the bike is idling.

[Trick188]

it sounds like the fuel screw is set to lean or the throttle cable is set too tight.

[marc177u]

Update, Well I'm taking a break. This is really getting to be a pain in the a*@!! Checked the TPS with an ohm meter and it's good. I also disconnected it and no change. Pulled the carb off again and totally stripped it down even removing the slide shaft and diaphram. I double checked everything for the 5th time. Installed new needle, needle jet, main jet. I put everything back to stock settings and no change. Well, there is a slight change now it's backfiring really bad. Checked the valves, re-adjusted the timing chain and did a leak down test all in good shape.

Seems like a lean problem but I'm not sure why. Next step is change the air screw. I'm running a Sunline air screw. Maybe it's worn, who knows. Let's see what that does.

[Trick188]

i hope you didnt install an air screw in it...

[wmdspalmer]

Just a thought, have you checked the rubber around the carb for leaks?

Will

[RMZ450RIDER8]

check your slide plate on the air filter side of your carb i have seen them crack you will need too pull the slide out

[marc177u]

Okay, here's what I've done so far. 7th time completely tear down carb. and re-cleaned with carb cleaner and air and complete inspection. All the ports and jets are clear and clean. Put my OEM Hot Start button back on, put my stock exhaust back on, put all jetting back to stock, stock air screw (event though i've ran the other air screw for 2 yrs. now with no problems), inspected air boot and clamps, leak down test (which is good 3% or 3 psi loss), checked valve gap, timing chain tens, checked for air leaks by spraying starting fluid around anything that matters while running. Still no change. It's definetly a lean cond.! After running and backfiring for 1 min. the header go so hot it started melting my radiator guards and the back of my front fender. I turn the air screw out about 5turns and it gets better but still not rideable. With the choke on it's also little better. After being a dealership mechanic for 7 yrs. and building and working on bikes for 20 yrs. I never thought I would say it, but I'm done! It's going to the shop on tuesday. Luckily I still have my RM250. I'm going racing this weekend!

[capthooklv]

I had the exact same problem!

Tested the TPS sensor it checked good when ohmed out. When I disconnected it, the CDI went back into the 2 dimensional mapping. It ran good no sputter. So right now I run it without the tps connected. I use the JD Jet kit and I am up at 3500 feet elevation with lots of temperature swings. Runs good. Still wish I knew what really happened though.

[CrusRuss]

Okay, here's what I've done so far. 7th time completely tear down carb. and re-cleaned with carb cleaner and air and complete inspection. All the ports and jets are clear and clean. Put my OEM Hot Start button back on, put my stock exhaust back on, put all jetting back to stock, stock air screw (event though i've ran the other air screw for 2 yrs. now with no problems), inspected air boot and clamps, leak down test (which is good 3% or 3 psi loss), checked valve gap, timing chain tens, checked for air leaks by spraying starting fluid around anything that matters while running. Still no change. It's definetly a lean cond.! After running and backfiring for 1 min. the header go so hot it started melting my radiator guards and the back of my front fender. I turn the air screw out about 5turns and it gets better but still not rideable. With the choke on it's also little better. After being a dealership mechanic for 7 yrs. and building and working on bikes for 20 yrs. I never thought I would say it, but I'm done! It's going to the shop on tuesday. Luckily I still have my RM250. I'm going racing this weekend!

Most likely is an air leak around the carby seal or something so that its getting a lean mixture. Try running richer jetting just to see if it makes it better.

[marc177u]

I tried dis-connecting the TPS sensor and no change. I would agree with the air leak also. But after inspection of the air boot I couldn't find anything there either. Thanks for all the input!

[marc177u]

It's fixed!!?? Well I couldn't bring myself to take it to the shop and pay them to do the exact same thing I've done. So I tore it apart for the 7th or 8th time and went through it again this time with my buddy watching as a second set of eye's. Maybe I was just missing something! Re-assembled and found out the 6th time I put the slide plate in upside down. Okay, that's 1 problem but not the original. Put everything back together just as I have 5 or 6 other previous times and this time I heard the sound of a perfectly running 450:busted:. Now I just have to do the fork seals. Oh, and by the way a '06 CRF450R carb. doe's fit an RMZ450 and runs great.

Thanks for all your input!