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Seized Again

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So here's a few pics of the damages. Not even 50 hours on the piston.

I was able to clean it up last time and after the cylinder looked new. This time it'll have to be replated. I'm considering abandoning the 2-stroke for another big bore thumper to keep my 450R company.

Bore Shot to Hell 1.jpg

Bore Shot to Hell 2.jpg

Easter Seize 1.jpg

Easter Seize 2.jpg

I know better than to hold these pingers wide open for extended periods of time which is when it locked-up today (93.3 on the GPS). I may have sucked debrie in the cylinder last Sunday when it hydolocked crossing a stream. Who knows? I'll post video of when it locked-up for anyone who interested. Scary at that speed for sure.:thumbsup::bonk: It runs a 40 PJ, JD red 3rd, and 168 MJ with 45ish:1 Motul 800.

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obviously your main is lean

why you run so low a oil ratio?

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Main jet bigger # 170 or # 172 , 45 - 1 is fine. When you lock up wide open on top end it is your main jet , not you mixture of 45 - 1.

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One seizure could just be a freak, but with two there clearly is something wrong. Any particular reason you are not running 32:1? I would jet for that ratio after a rebuild, and check carefully for air leaks.

Also, what was the recommended main for your JD kit at your altitude? I found that the recommended main was too lean for my SX. I got it running good with the JD kit, but I have since gone back to the stock needle and main for the kind of riding I do now.

I don't really see why extended full throttle operation should be a problem if you are jetted correctly, as outboard engines, jet skis, and kart engines very often run wide open with no problems. I have heard however, that some guys will punch the kill button periodically with the throttle wide open under those conditions. This will briefly flood the engine with a cooling and lubing fuel/oil mixture that is not ignited.

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obviously you dont have enough oil. 20:1 castor type oil next time

can certainly run more oil, as long as the bike is jetted richer to accommodate the leaner air/fuel mix. If not, a seize is even more possible.

cubera, running such long times at high speed, high stress on the system, I would run as big a main as you can get by without loosing power. IOW, I would raise the main till the power drops off and lower it one size. You may be surprised at how much more main you can run. They are hungry for fuel at those speeds.

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Why the red needle? I would think the blue for wide open stuff not the red. Anyway you are lean. Richer needle and main is needed. Feed that 2-stroke you don't have any wash coming over the top of the piston. Your oil ratio is fine you just need to richen it up. A colder plug might help as well. Go up on the main if you like that red needle down low 175 -178 or more until it will not take the throttle and back off one. Just richen it don't go 4-stroke.

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Can't really fatten the jetting anymore. JD calls for red needle 3rd clip which is what I'm running, 35PJ, 165MJ, AS-1. I'm running a 40PJ and 168MJ which is as fat as I can run it at sea level and high ambient temps (85-110F). KTM calls for 60:1 on the full synthetic and I run 45-50:1 of Motul 800 right now. I believe a ring cracked today causing the seizure. I'll have to grind the Aluminum off the ring in that area and see if it's broken. I know better than to run the motor like I did today (and yesterday) but it's really not that long or severe of a run....crop duster runway strip. Here's the vid of when it shut off (fast foreword to about min 30)....http://vimeo.com/22817759

Somewhere on that strip is 93.3 on the GPS. This is how to kill a 300 motor lickity split.

I do about 10 hours of seat time a week split between my two bikes and a maybe 10% is WOT on either bike but for sure the 4-stroke is good at the high speed stuff like the pinger is at tight stuff. Here are some short vids that'll give you an idea of the kind of stuff I do quite a but of on the pinger:

http://vimeo.com/22583221

http://vimeo.com/22582277

http://vimeo.com/22240261

http://vimeo.com/22141990

Edited by cubera

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Sorry JM, I remember reading in Dirt Rider that they seized their test bike with WOT riding on a couple of occasions. Damn glad I'm slow now.

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In my world I keep going bigger on the main until it won't pull it anymore, then I back it down 1 size. Then I adjust around that for conditions.

I seized a 200 with JD's recommended settings, while thinking I was on the fat side of their specs......... Since then, I have managed to go as much as seven sizes bigger on the main and no less than 4.

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Sorry JM, I remember reading in Dirt Rider that they seized their test bike with WOT riding on a couple of occasions. Damn glad I'm slow now.

Yup.... I read that too.....chasing the 530 WOT. Chris your not as slow as I am:thumbsup: I've been working hard trying to get some skills at technical stuff since I got the 300....I've done a couple of gnarly events over here in AZ. Come on out and ride with me sometime:ride::thumbsup:

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In my world I keep going bigger on the main until it won't pull it anymore, then I back it down 1 size. Then I adjust around that for conditions.

I seized a 200 with JD's recommended settings, while thinking I was on the fat side of their specs......... Since then, I have managed to go as much as seven sizes bigger on the main and no less than 4.

I believe you:thumbsup: We do it the same way here. If I go larger than a 168 in triple digit temps it won't pull at all. I'll try again with the new cylinder though....for sure:ride:

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Ignore JD's guide and increase the main jet. If you used 60:1 you'd feed more gas to motor thereby cooling it further. Fatten up that main. It's like trying to ride sand dunes with a standard main jet. Disaster will occur.

I'm already considerably fatter than JD's recs but I'm open to trying again. I'll order a few new MJ's while I'm ordering a new cylinder. Does anyone run 60:1>>>:thumbsup::lol::thumbsup:

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You definitely have to ignore the charts with that type of riding and it just go to show that those charts are only a guideline. I ran a 188 in my 200 and most ran 182 or so, but it liked the added fuel when I was on it hard.

A person running full bore in the dunes or like you has completely different main jet needs than someone running the woods. You have to adapt the jetting to meet YOUR BIKE'S needs.

FEED IT, it will tell you when you are giving it too much. FATTEN THAT MAIN! :thumbsup:

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You definitely have to ignore the charts with that type of riding and it just go to show that those charts are only a guideline. I ran a 188 in my 200 and most ran 182 or so, but it liked the added fuel when I was on it hard.

A person running full bore in the dunes or like you has completely different main jet needs than someone running the woods. You have to adapt the jetting to meet YOUR BIKE'S needs.

FEED IT, it will tell you when you are giving it too much. FATTEN THAT MAIN! :thumbsup:

Yup. Generally the 200 and 250 take larger jets. The owner's manual (and JD) have recommended sizes as a baseline but I'm increasingly suspicious these numbers are irrelevant. I can't very well stop and re-jet during a ride and if I jet is fat enough to run WOT it'll be a blubbering loaded up mess on the tight stuff. I thought I found good middle ground and am probably very close. It sure was running great before it hung a ring and locked-up. She'll get a fatter MJ along with a brand new cylinder and size A stock piston. Like I've said before, the 300 won't live with the same piston longer than 40 hours so I'm not going to push it beyond that. Every time I do it bites me in the arse. Parts are on order now....$800....Stupid is expensive.:cheers::lol::thumbsup:

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it shouldnt be hard to ride in tight stuff if it's jetted right, the main is not really used at low throttle

I do what others said they do, I keep going to bigger jets until it wont run right, then I back off one size

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"I can't very well stop and re-jet during a ride and if I jet is fat enough to run WOT it'll be a blubbering loaded up mess on the tight stuff."

Not true.

Edited by Ralphtogo
clarity

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