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gobeer net

'06 YZ450 - been sitting for 3 years.

11 posts in this topic

Summary: '06 YZ450, sat three years. Clean carb - What could be wrong to need a 50P/178M jet?

Long story:

'06 YZ450, DRD exhaust , K&N style filter, believed to be stock internals.

-parked in 2010 by a guy in California who go injured and couldn't ride it.

-bought in 2012 by a guy in Tulsa as a package deal, started it, supposedly had it rejetted, it still ran bad, parked it

-I bought it this weekend. Seller (consider the source) claims 30 hours. Chain/sprockets look stock and cases have moderate wear.

When I bought it, it would start and run, but ran like complete crap. tons of backfires, could barely get above throttle, etc. I didn't try to ride it. Previous owner changed fuel/oil.

Brought it home, pulled the carb, lots of tarnish/buildup. It had a 45P, 178M, stock needle on 4th clip. Valves measure in tolerance. I have to rotate the crank a degree or so past TDC mark to align the cam dots with the head. Pipe is clear of debri (bee's nest/etc)

I drained the tank, cleaned the strainer/petcock. New non ethanol fuel. I read the jetting thread, cleaned the carb as good as I could and put it back together with a 45P, 170M. It would barely run, idled high, would die if I blipped it. I could ease it up in the RPM's but it ran like crap.

I kept going up in jets till I got to 50P, 178M. It starts easy (maybe too easy) and runs "good" with moderate popping on decel.

The 45P wouldnt run with the mixture screw less than 2 turns out. Had to be 3 turns out to give it any throttle.

The 48P would run at 2 turns, but would pop/die if I blipped the throttle. 3 turns out and I could baby it up in RPM's

The 50P seems to idle/respond well at a hair less than 2 turns out.

50P/178M seems awefully big to me. I haven't had much seat time (15 minutes?). The bike is now in Super Moto Trim. I hope to tag it this week so I can get it out more.

Thoughts?

Edited by gobeer net

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Has the function and sealing of the hot start been checked?

I have only ridden it about 20 minutes today. Moderate throttle. Its in super moto trim and not plated yet so riding area is limited. Haven't ridden it enough to need the hotstart so dont know how to test the function of it? I dont know how to tell if it is sealing. I took the plunger out, cleaned the bore and reinstalled. The o-ring showed some wear. I guess I could replace the o-ring and see what happens.

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Be sure there is free play in the cable, then, when starting it cold, with the choke still on at idle, operate the hot start. Pulling the lever should raise the rpm, almost like a thumb throttle. Releasing it should cause it to drop again.

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Be sure there is free play in the cable, then, when starting it cold, with the choke still on at idle, operate the hot start. Pulling the lever should raise the rpm, almost like a thumb throttle. Releasing it should cause it to drop again.

This is one way to check it. An alternative would be to disconnect the hot start air feed from the intake port and plug both holes (no air into intake port hole, no unfiltered air into carb boot). See if it runs any differently. Hope this helps.

If it dies when you turn the throttle, and you also have to baby it to get the rpms to increase, that definitely points to an accelerator pump issue so jojo's suggestion is spot-on as well.

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An alternative would be to disconnect the hot start air feed from the intake port and plug both holes (no air into intake port hole, no unfiltered air into carb boot). See if it runs any differently. Hope this helps.

That won't work on a 426 or 450, as the whole hot start circuit exists within the carb. Only the 400 had an external setup.

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Not much time to work on it tonight. I hope to tag it tommorrow and I'll tinker on a few things as well.

I'll check the hot start by operating the lever while idling and notice the difference.

The accel pump squirts, but not very long. My '03 squirts for about a second it seems. This squirts for .1 seconds. Its a quick squirt & done. I didn't test after the o'ring mod.

Since everyone loves pics - The '03 is the donor vehicle.image.jpgimage.jpg

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I bought a 2009 yz450f not to long ago. It ran very badly when I got it and the jetting I believe used to be set to an aftermarket pipe ( but cant say for sure, maybe ignorance was the motive for bad jetting). The owner put the stock pipe back on and never jetted the bike back before selling it to me (theory). Anyways the bike would bog and shut off, take ten kicks to start, back fire a lot and pop on decel. What I did first was set the carb completely to stock, the main and pilot were wrong (not stock). The leak jet was way off at 70 when 50 is stock. I set the leak jet to stock but never set the accelerator pump adjustment screw back to factory specs. I set all the other things to stock but still my bike ran badly. I then looked in my manual and saw that their was a certain way to adjust the accelerator pump adjustment screw to stock. I next did that and put the bike back together with also doing an o ring mod to my accelerator pump adjustment screw. After that the Bike ran ok but still not to my expectations. I then bought a easy adjustment pilot screw and tinkered with that figuring out that my bike ran best with the pilot air screw at 2 and 3/8 turns out. The bike now ran better but still hesitated slightly in mid/ low rpms. Finally I found the last piece to the puzzle and I raised my needle from the 3rd position to the 4rth to slightly enrich my mixture at those rpms that were hesitant. Finally my bike runs great, as compared to before it feels like a factory line fuel injected race bike, even though its bone stock. Now It starts first kick, goes from idle to rev limiter in less than a heartbeat, has no more decel pop, and never backfires. Now I love my bike, anyways I hope this helps in a way to solve your jetting problem, best of luck, dont give up.

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I've had a few 450's and realize a glowing header is "normal" but how much is normal? Attached is my header after 3 minutes of idling.

After conversing over a few beverages about this carb in the garage, I realized the slide height on this carb is ALOT larger than the slide height on my '03. My '03 closes completely at no throttle. This throttle plate stays open approx 1/8". This didn't seem normal to me and seemed to explain pretty much all my conditions.

What do you set closed throttle position by? I realize its set by the remote screw (idle adjustment), but what should it be set at? Closed, mostly closed? How much is mostly?

I closed it and installed 68P/170M jets in it. Now I can't get it started :-|

Edited by gobeer net

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Took an hour of kicking and 14 turns of the idle adjustment/throttle stop. She lives. Just put a few miles on her. Now to clean her up and start the fine tuning.

High on the list is suspension. I have a set of fresh '07 WR suspension with stock internals and the bike has its current leaky '06 YZ suspension with what I'm guessing to be stock internals. I don't know which set I'm going to set up for super moto use.

Edited by gobeer net

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