2010 Black oil / Hard to start

Maybe it's improper ring sealing cause this particular engine needs to be broken in a certain way. I read a good article about how running the crap out of your engine right away from the first time you start it after it's assembled creates a superior ring seal to those that do not do this.

um...... dont suppose its from your clutch slipping/ over heating???

Clutch is within spec, isn't grabby and it's not slipping. Good guess though. It was the first place I looked.

Maybe it's improper ring sealing cause this particular engine needs to be broken in a certain way. I read a good article about how running the crap out of your engine right away from the first time you start it after it's assembled creates a superior ring seal to those that do not do this.

I read a similar article where many shared this opinion. I've never broken any of my bikes in that way. This bike was broken in with three heat cycles (1/4, 1/2, 3/4 throttle)

I heat cycled mine twice, then ran it for about 20 minutes at 1/4 throttle, let it cool, then an hour at full throttle.

Next time, I'm going full out on a fire road up and down the gears for 20 minutes. First time it starts up after a rebuild it will be at the fire road, warmed up to operating temp and then I'm going full out.

Remember I said nothing unusual was found; well I may have spoken to soon. The mechanic that handles the things I either cannot or choose not :busted: to followed up with a team mechanic out of Cali that wrenches for Kyle Cunningham. I'm not a name-dropper, hell I'd never heard of the kid even though he's from my neck of the woods. Just relaying the info that my guy thought Cali guy would be a good source of info as this is the model they run. I digress...

He echoed Bretn's opinion that this particular model puts the oil "through the ringer" and turning black is not a red flag. I made the mistake of mentioning I'd run Rotella which of course was a no no. Wants me to run something thinner and stay away from "diesel oil". Never mind that the good stuff smokes just as fast. What is a red flag is what appears to be premature wear on my cylinder. While you can't feel the groove / imperfection, you can see it. His opinion was that my crank sounds like the culprit. Huh? Of course he changes the team cranks at a ridiculously low hour mark; he was of the opinion that with my estimated 60 hours, I'm overdue.

***? I rode a used 426 everywhere without knowing what the hell thumpertalk or a shim ever was. I changed my oil and cleaned my filter religiously as I do this bike and never had one problem. Now my pampered 10' supposedly needs a crank? :excuseme:

Edited by BlakJak
makes more sense

Wow.. .lol.

ok, well, there are alot of people who replace parts at ridiculous intervals, and this sounds like one of those people.

It sounds like he wants to replace the crank at 60 hours and that's his only reason, I'm going to guess that the bearings in the case and for the connecting rod are going to be perfect.. Shell rotella aint so bad either, lots of people use it. Either way your a religious oil changer so... shouldn't matter.

As for the cylinder, not being able to feel the groove with your finger nail is a good sign but without getting it under a bore gauge how the hell does he know it's shot?

I've seen cylinders with streaks before that have a nikasil coating and they were fine for a rebuild...

This mechanic might be right, but it sounds like he's wrong, and sometimes all they want is more money to pay for unnecessary labor that you don't need for your bike.

I agree.

Although the Cali guy isn't trying to get money out of me b/c he's not doing the work; I agree with your point. He's giving his "race mechanic" opinion. His crank theory sounds a lil excessive to me. Of course there are better oils; I ran rotella in the last few non 2t bikes with zero issues. He also used his crank theory to explain the hard to start when hot issue. I haven't tried you and another poster's starting suggestion but can't wait to give it a try. I hate when a negative possibility gets planted in the brain. I know anything is possible, but you think the crank theory is going in the wrong direction?

It sounds like his crank theory is BS, but I don't know for sure.

I don't have the crank in front of me, and I don't have the tools to properly check the cylinder. He may be right but the odds are he's wrong.

This is why I do my own work and buy my own tools and do a ton of reading before hand. Not everyone has the time or the motivation to do their own mechanical work, but at least for the ones who do, know what their engine needs.

I don't how the crank has anything to do with anything you are concerned about???? If you replace it I'll take the original :excuseme:

I've noticed that when a 4 stroke doesn't have good ring seal it turns the oil black quickly. My YZ450 turned the oil black and when I took it apart I could see it wasn't sealed up well.

After I replaced the piston and cleaned up the cylinder the oil stayed clean. I have noticed that when I ride them hard from the start they seem to run better.

It sounds like his crank theory is BS, but I don't know for sure.

I don't have the crank in front of me, and I don't have the tools to properly check the cylinder. He may be right but the odds are he's wrong.

This is why I do my own work and buy my own tools and do a ton of reading before hand. Not everyone has the time or the motivation to do their own mechanical work, but at least for the ones who do, know what their engine needs.

Yeah, his crank theory won't stop me from riding. If it goes it goes. I usually do my own work but he owed me, so let him bust his knuckles.

I don't how the crank has anything to do with anything you are concerned about???? If you replace it I'll take the original :busted:

Yeah here's the title of my ad on ebay; "2010 YZ450, my crank was yanked". :excuseme:

I've noticed that when a 4 stroke doesn't have good ring seal it turns the oil black quickly. My YZ450 turned the oil black and when I took it apart I could see it wasn't sealed up well.

After I replaced the piston and cleaned up the cylinder the oil stayed clean. I have noticed that when I ride them hard from the start they seem to run better.

Good point, but I checked and the bike never smokes.

Mine didn't smoke or use oil it just turned the oil black quickly.

It ran good. I didn't notice any more power after I rebuilt it.

Oil stayed cleaner though.

A little follow-up report:

I flushed the motor, new cam chain, replaced the auto-decomp spring, checked valves, (haven't moved), checked cylinder (looks great), filled with distilled and wetter to just above the fins (not one boil since) and got rid of my flexx bars for the original tapers (no more pump). I got the starting drill down now (thanks guys :thumbsup:). It starts so easily now that I no longer worry about a stall. When hot, crack the throttle just a bit and one kick; boom. I've put about 7 hours on her since I last wrote. I raced it in a local Iron Man 100 and she performed well. The more I ride it, the more I like it. The faster I go the lighter it feels. I've been going back and forth between it and my 07 2T setup for woods with smart performance. On the track the 2T is crazy for me and 450 is perfect. In the trees it's been the opposite; until this past weekend. While of course it takes a bit more to move it; it just feels better at speed. Hittin the dunes next month, can't wait! Thanks again to all that helped.

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