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how do i stop my bike siezing? (pics)

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Hey, my bike (2009 250SX but that doesnt matter) siezed this morning- the second ride since I rebuilt it. :smirk:

I was pinning it in 5th gear (high revs) for about 30sec when it lost power for half a second and the back wheel locked up . The bike had been broken in fully, and today it had been warmed up and ridden for about half an hour before it happened (so it wasnt a cold seizure).

The stock main jet was a 158 and with the jd kit its now 165. The plug had a nice tan / light chocolate colour after seizing, so I'm pretty sure it wasnt lean on the main jet. :smirk:

we took it apart and the ring gap is 0.16" / 0.4mm for both rings after seizing. This is on the large side, so its not that.

the cylinder is scored deeply and the brand new OEM piston is scored on both sides.

The scores are in the same place as the first piston the bike had as you can see in these pictures, the old piston is on the left and the new piston is on the right:

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7398.jpg

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7401.jpg

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7394.jpg

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7397.jpg

and this is the main score on the new piston:

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7408.jpg

What could have caused this? running a ratio of 50:1?

I read this really good article on the ratio and it said that you shouldn't just run what the manual says, but what you should run depends on how you ride.

I ride trails and just mess around, but because of the way I ride its more like desert racing with a little bit of just cruising. should I run 25:1 and re-jet?

Whats the issue here?

Mike.

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oh and the cylinder has some deep scores. what can I do about that short of replacing it? do i need to do a big bore kit? or hone it and then get it re coated and use a large piston? :smirk:

Thanks guys :smirk::thumbsup:

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Well, considering you seized it the first time, then it sounds like you did nothing to the cylinder to repair it before rebuilding with a new piston, its not surprising your going to eff up every single piston you install afterwards until you get the cylinder repaired!

Can you post pics of your cylinder?

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Well, considering you seized it the first time, then it sounds like you did nothing to the cylinder to repair it before rebuilding with a new piston, its not surprising your going to eff up every single piston you install afterwards until you get the cylinder repaired!

Can you post pics of your cylinder?

The even though the piston looked terrible the bore looked fine and it felt fine too - it felt perfectly smooth :smirk:. I've had the bike for all but the first "10" hours and it hasnt seized with me (100+ hours) untill now.

The pictures of the clinder are here:

Right of the exhaust port:

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7417.jpg

Left of the exhaust port:

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7416.jpg

Intake port:

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7422.jpg

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7420.jpg

Cylinder head:

http://i942.photobucket.com/albums/ad268/mikekx/IMG_7423.jpg

^The shiny parts on the cylinder head are small flakes of metal sitting there, not scratches

Edited by mikekx102
additional information

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Float level too low? wonder if you sucked it dry of fuel, running lean.

for high speed/rpm runs, I would likely want a richer indicator than what your plug shows. Bump the main till power drops off at WOT, then back off one.

There should be a decent replater in Aussie land. If you can get it to them, Millennium Technologies can replate it to better than new condition.

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I was pinning it in 5th gear (high revs) for about 30sec

that could be your problem. Extended high-rev high-load operation is different from how most people ride, and may require different jetting, or more oil. In really wide open desert race sections, i'll hit the kill switch every 10 seconds or so for a moment to let some nice wet oil gas coat the cylinder. If you're going to ride like that all the time, more oil or richer jetting may help.

fwiw, i tend to run 44:1 for general riding, and 40:1 for full on racing in open terrain.

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that could be your problem. Extended high-rev high-load operation is different from how most people ride, and may require different jetting, or more oil. In really wide open desert race sections, i'll hit the kill switch every 10 seconds or so for a moment to let some nice wet oil gas coat the cylinder. If you're going to ride like that all the time, more oil or richer jetting may help.

fwiw, i tend to run 44:1 for general riding, and 40:1 for full on racing in open terrain.

I have to mostly agree here, I like Super M 32:1 all the time, but jetted rich in the winter. I dont do the kill switch trick but have for sure been wide open for more than 30 seconds a few times :smirk:, without any issues. Where we ride in the winter the air is cold and dense and the sand deep, too little fuel/oil is a bad deal, leaner is meaner but not as safe for the motor.

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Lean on fue,l rich on good burning oil and all is well, good power and good lube..is what I try to get...

Our 300 will sing for minutes without any issue on a 168-172 main even running U4.4 fuel and 38.5 oval bored carb. (this is at 75+ degrees)...

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Personally I doubt the 50:1 ratio is the culprit.. FWIW I have been running 100:1 for the past three years in my 300 with a 150 main jet.. The usual cause of a siezure is lean jetting.. You may have an airleak someplace.. The marks on the piston are consistant with pistons I have seen over the years that have lean seized.. That said for YOUR conditions you probly need to go up on the main. At least until you get this sorted out.

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Float level too low? wonder if you sucked it dry of fuel, running lean.

for high speed/rpm runs, I would likely want a richer indicator than what your plug shows. Bump the main till power drops off at WOT, then back off one.

There should be a decent replater in Aussie land. If you can get it to them, Millennium Technologies can replate it to better than new condition.

So the float level can actually do that? :smirk: it was set way too high stock and dumped fuel out the overflow around every corner, so i lowered it but not to a specific height so i must have gone too far. does a low float mean less fuel goes through the jets and makes it lean? or just that it runs out of fuel? woops i'll have a look at that.

Looks to me like it sucked some trash and hung a ring. These things happen.

Yeah, but the rings are both intact and its happened twice now.

Personally I doubt the 50:1 ratio is the culprit.. FWIW I have been running 100:1 for the past three years in my 300 with a 150 main jet.. The usual cause of a siezure is lean jetting.. You may have an airleak someplace.. The marks on the piston are consistant with pistons I have seen over the years that have lean seized.. That said for YOUR conditions you probly need to go up on the main. At least until you get this sorted out.

I dont think there's an airleak, but i'll have a look when i put it back together. and I'll get some richer main jets and look at the float.

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The fuel bowl can empty before gravity can refill it.

yep, if you are suckin' it out faster than it can fill up...

but, I was just throwin that out there as something to check. Higher % that it is jetting related, but something to look at while you are in there.

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ok :lol: i'll have a look. you see how the piston is stuffed up below the rings right? well does that mean that there would be lots of metal in the bottom end? like do I need to split the cases, clean it out and put in new bearings? :ride:

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that could be your problem. Extended high-rev high-load operation is different from how most people ride, and may require different jetting, or more oil. In really wide open desert race sections, i'll hit the kill switch every 10 seconds or so for a moment to let some nice wet oil gas coat the cylinder. If you're going to ride like that all the time, more oil or richer jetting may help.

fwiw, i tend to run 44:1 for general riding, and 40:1 for full on racing in open terrain.

Exactly perfect advice. I say this based on hard learned expensive lessons learned.:ride:

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ok :ride: i'll have a look. you see how the piston is stuffed up below the rings right? well does that mean that there would be lots of metal in the bottom end? like do I need to split the cases, clean it out and put in new bearings? :lol:

Probably not necessary to split the cases but you'll have to spend some time cleaning it out for sure.:lol:

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Probably not necessary to split the cases but you'll have to spend some time cleaning it out for sure.:lol:

I dont understand how you could clean it out? there's no room? how would you do it? :ride:

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I dont understand how you could clean it out? there's no room? how would you do it? :ride:

pull it from the bike, flush it out.

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pull it from the bike, flush it out.

with water a few times and then petrol? or degreaser? :ride:

also, what happens with the cylinder? does it need to be bored out? and then get an OEM piston size 2?

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You should be ab le to clean the cyclinder up with some muratic acid.. Somo\eone else hit it on the head noting the low floats..

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