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Doogster85

I'm completely lost

17 posts in this topic

I'm having more trouble than I know what to do with and it's got to be something stupid that I'm missing. So let me start at the beginning and I'll walk ya'll through what's going on. Bike has 40 hours on a pretty thorough engine rebuild performed by a TT member and has ran with no issues until this point

March 28th: First race of the year with IXCR, a local HS series, bike ran fine with no issues until my clutches decided that they were finally going to let go on my 2nd lap. Get a quad to tow me in and I loaded onto the trailer.

February 29th: Give the bike quick wash as it was getting dark and I didn't want the bike sitting with a boat load of mud on it.

March 6th: Trailered the bike over to a friend and fellow tt member to change a set of clutches and change the rear tire now that we were done with our obligatory sand race. So I changed the oil, and swapped the clutches. Pulled it out of his garage to start it up to get the atf fluid removed from the clutches. Bike started on the first couple of kicks but didn't run very well, and ended up dying as it was idling. After that I was getting a no start and still needed to get my tire changed, so I pushed it off till later

March 9th: Found time to breifly work on the bike. Bike would not fire to save my life until I decided to try it with hot start and the choke at the same time. Bike ran, but ran incredibly rough. Changed the plug to see if that would make a difference but it didnt.

March 12: Pulled the carb believing that the pilot jet was potentially clogged giving me a super lean condition. Saw a few specs of what I believe to be fine sand in the float bowl, so I went ahead and pulled the Jets, cleaned and blew them out. Pulled the accelerator pump and cleaned it out. Re-installed and yet again ran into a no start.

March 13th: Hauled the bike over to aforementioned tt member and went through everything mechanically on the bike. Did a leak down test, which was inconclusive as we couldn't seem to keep it at TDC. After piddling around for a little while we decided the only thing that could potentially be wrong was a stuck valve. I bounced them a few times off the buckets and didn't see anything wrong, but we went ahead and pulled the head. No scoring in the cylinder, valves were fine and no notice of anything going wrong with the guides. Decomp moves freely and the valve clearances were all within spec. While putting back together I had Kevin go through the carb yet again just to see if I missed something. So with fingers crossed we tried to kick it over. 2nd kick the bike acted like it wanted to start as it went through a few revolutions but it never materialized. After that we couldn't get anything from the engine.

March 14: Tested stator and coil again minus the secondary coil as I'm not able to measure in kila ohms that small, and everything checked put ok. Decided to try starting it once more and it fired on 2 occasions both times with hot start and choke on but it ran roughly, was able to blip the throttle and increase rpm's but with the same rough running as it was at idle. Removed hot start on the first try and bike died. Removed choke on the 2nd start and bike died.

So any ideas? I'm at a total loss as to what could be going on, unless the cdi box is doing something incredibly funky. Sorry for the incredibly long post, but I wanted to ensure that I was as thorough as possible in trying to explain the situation

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Still kinda sounds like pilot jet or its circuit to me. Possibly valves.

Try replacing the pilot jet, getting some fishing line and run it threw its passages and floss/ream it out then use air and cleaner and repeat. AF passage to.

Why was the leakdown test "inconclusive"? Not able to hold at tdc? A 12pt socket on a breaker bar resting on the peg works great. Or remove the cam chain then test it.

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That's what it sounds like to me as well, or excess air finding it's way in somehow, but the boot looks good. When we tried the leak down we kept knocking it off TDC when we applied air, lowered psi to 80 but still knocked it off tdc. We had a breaker but the way the breaker sat was right in the middle of the peg and neither of us were able to hold it, and at that point, we conferred that if it was rings we wouldn't be feeling that strong of a pressure. I never thought about removing the cam chain, that would have worked much better.

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You could use less air pressure, too.

 

You say you can't measure 4.6-6.8 KΩ?  Measure it either as 4600-6800 Ω, or as 460-680 on the Ωx10 scale.  

 

The '08 had a little bit of trouble with stators.

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How much lower could you realistically go. It was a motion pro gauge and had a suggested 70 psi minimum.

I can't remember if that's the primary or secondary gray, it's too early in the morning, but it was the other one, the .03-.10. I haven't been able to get an accurate readout from my multimeter on it

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That's for the ignition coil.  The stator is a more likely suspect.

 

You could use 50 PSI. 

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I was working on a 2006 YZ450F for a friend of mine that was doing something very similar to yours. I put a new pilot in, checked timing and the valves all with no luck. The problem ended up being with the slide and the slide plate that "floats" on the engine side of the slide. I first found that the plate was upside down and also that the thin rubber seal that goes on the plate was old, wrinkled and wasn't working anymore. I ordered a new seal and put the slide and plate back in correctly and the bike has ran fine ever since.

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Sorry gray, I thought your were asking about the coil as the spec you posted was for the coil. I've now tested the stator twice, once on the stator, and again at the plug for good measure, both times same results. Can the stator be crap even though the windings are testing out fine

Stator test:

Pickup coil resistance: 248-372

Reading: 282

Charging coil 1 resistance: 720-1,080

Reading: 826

Charging coil 2 resistance: 44-66

Reading: 52

Neutral switch: good

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Hey, fox , yea fellow ixcr'r. Trying like hell to get the bike up and going for the race this weekend, unfortunately with not much success. Your day sounds a lot like mine, I wiped my clutches out back in the mud pits, well they were already going, but I went ahead and finished them off.

Thanks for the tip WYO, I'll give that a look see once I get the carb back off of it

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Sorry gray, I thought your were asking about the coil as the spec you posted was for the coil. I've now tested the stator twice, once on the stator, and again at the plug for good measure, both times same results. Can the stator be crap even though the windings are testing out fine

 

 

Yes, that's the point.  Test it immediately after it quits. 

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I haven't seen anything about how much fuel comes out of the pepcock without it hooked to the carb.

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The symptoms you describe sound somewhat like a pilot jet issue. As another member mentioned earlier it is also possible to put the slide plate in upside down, so that's something to check. Another issue I've seen that can cause a hard start/no idle issue is a seized or dragging cam shaft. With the tolerances as tight as they are it doesn't take much to warp the caps when tightening or even a small piece of dirt to gum things up. Easiest way to check that is simply release the cam chain tension and see if you can roll each cam back and forth slightly while installed in the head. Hope you get to the bottom of this soon!

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Any resolution on this Doogster85? I'm having the same behavior from my 09 YZ450f and haven't been able to sort it out.

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