Siezed the engine ... again

[eprovenzano]

1999 400ex. I rebuilt the engine last winter as it was still on the original piston, rings, and the valve seals. It smoked like a two stroke, so I felt it was time to rebuild. I had the cylinder honed, valve seals replaced. I put it back together and had issues with the idle surging. Within 5 hours of run time, the engine seized. The piston was toast, rings stuck (melted) on the exhaust side. I

I rebuilt it by having the cylinder bored 2 over, new piston and rings. It ran great, but still had the surging issue.

We just suffered seizure number 2. The bike was run for 20 hours. The piston was toast, rings stuck; only this time it was on the intake side. The cylinder will need to be bored to 4 over to be clean.

My concern is why is this happening? I'm leaning towards jetting. I have not opened the carb to get the current jets. I will as soon as I can. I know bad (incorrect) jetting can be masked by a worn piston and rings. I'm thinking the jetting is to lean causing the failure(s) and the surging it was experiencing. I think I need to be running richer jetting. The engine is stock with an HMF slip-on, and an opened air box. What jetting should I be running.

Theres alot of things that can change jetting but, i would say 155-160 main would be a good place to start and a 42 pilot if you havent done it yet.

[jcs003]

if you increased the bore size of your engine you usually have to change your jetting to suit the increased volume. but not always.

as for the better flowing exhaust and intake. you always have to increase(richen) jet sizes.

was your break in done correctly?

was your bore/hone done correctly?

has the bore been matched to your specific piston?

did you install your rings correctly?

was a leak down test done after rebuild? an air leak is a good culprit for a seizure.

[witech]

What was your ring gap on the new piston and side clearance?

[eprovenzano]

I feel the 1st seizure was my fault. I don’t trust the machine shop that honed the cylinder, I didn't measure the cylinder, but believe it was warn enough that it should have been bored. I take the blame for seizure number one.

I come from the world of two stroke dirt bikes, and understand that a worn cylinder can wreak havoc on jetting. I’ve learned the hard way chasing jetting problems only to find the cause was a worn top end. This is why I'm leaning towards lean jetting...

The bike is always warned up properly, both seizers were when my son was on the gas... the 1st after a nice hill climb ( it lost power after he completed the climb), the second on a dirt road between trails. It’s like the bike overheated. Outside temps are not the cause, the 2nd time the temp was in the mid 50's. Oil flow seems to be fine, as each time I pulled the cylinder; the bottom end seems well lubricated. Fuel is one of the components used to cool an engine, this why I keep coming back to jetting.

I hope later today to get the jets pulled to get the info written down.

[togup]

lean on a new engine smells like disaster,the rings are at a critical point where they are wearing in to the shape of the cylinder it doesnt take much more heat to melt the aluminum.I know where your coming from i melted a 460 stroker because the case opening was out of round ,so before you rebuild check every thing dont assume its jetting

[sixer3]

yeah, I'd just make sure you get your cylinder machined by a reputable shop this time and make sure they have the piston, sounds like your cylinder was out of round to me. not your fault. and though you could probably stand to be a little richer, these motors are pretty resilient with those mods it should have been able to take even the stock jetting without seizing anyway...

[eprovenzano]

Quick Update

I was looking at the bike a little closer last night. I see that the piston pin has seized to the rod. This also happened last time the bike seized. Last time it seized to the rod so bad I had to cut, yes, cut the piston off, and press out the pin with a C-clamp. I think I may do some more disassembly to check the status of the lower end including the rod... I need to do some more investigating before I'm confident I've found the cause.

Bad crank? bearings? seals? hmmm I may have a bigger job on my hands than I thought.

Quick question, I have split a 2 stroke motor to replace the crank with just basic hand tools, is there anything special required to split the case on a 400ex?

Thanks to all those who responded.

[rubbersdown]

Originally posted by eprovenzano
Quick Update

I was looking at the bike a little closer last night. I see that the piston pin has seized to the rod. This also happened last time the bike seized. Last time it seized to the rod so bad I had to cut, yes, cut the piston off, and press out the pin with a C-clamp. I think I may do some more disassembly to check the status of the lower end including the rod... I need to do some more investigating before I'm confident I've found the cause.

Bad crank? bearings? seals? hmmm I may have a bigger job on my hands than I thought.

Quick question, I have split a 2 stroke motor to replace the crank with just basic hand tools, is there anything special required to split the case on a 400ex?

Thanks to all those who responded.

Well you just answered your own question right there. Did you lube the wrist pin well last time you rebuilt the motor? Did you check the wrist pin clearances? There has to be enough clearance for the wrist pin to be properly oiled or else it will seize and force the piston to "rock" and force the rings into the wall and they will stick like yours did. Not all parts come 100% ready to go, sometime (especially in parts with super tight clearances) things have to be fit. Sounds like you need to "fit" your wrist pin to your piston or rod. You may have to hone out the piston or rod to fit the pin or run an oversized pin to fit. May even be easier to start with a fresh crank and or piston if the pin galled the rod at all. Your wrist pin to piston clearance needs to be between .002-.014 and the wrist pin to rod end clearance needs to be between .020-.047 or else you will keep having this problem.
To answer your other question, theres not much difference in splitting 2stroke vs 4 stroke cases. 4 stroke is actually a little easier because you dont need a case splitter.
I did a full write up on putting a 400ex bottom end together...http://www.exriders.com/vbb/showthread.php?s=&threadid=449203

[eprovenzano]

Originally posted by rubbersdown
Well you just answered your own question right there. Did you lube the wrist pin well last time you rebuilt the motor? Did you check the wrist pin clearances? There has to be enough clearance for the wrist pin to be properly oiled or else it will seize and force the piston to "rock" and force the rings into the wall and they will stick like yours did. Not all parts come 100% ready to go, sometime (especially in parts with super tight clearances) things have to be fit. Sounds like you need to "fit" your wrist pin to your piston or rod. You may have to hone out the piston or rod to fit the pin or run an oversized pin to fit. May even be easier to start with a fresh crank and or piston if the pin galled the rod at all. Your wrist pin to piston clearance needs to be between .002-.014 and the wrist pin to rod end clearance needs to be between .020-.047 or else you will keep having this problem.
To answer your other question, theres not much difference in splitting 2stroke vs 4 stroke cases. 4 stroke is actually a little easier because you dont need a case splitter.
I did a full write up on putting a 400ex bottom end together...http://www.exriders.com/vbb/showthread.php?s=&threadid=449203

Everything was lubed, but I did not check the wrist pin clearances. I agree, with the new tight tolerances from a fresh bore and new piston / rings and a suspect wrist pin rod tolerance that was (is) my issue. At least that's what I'm thinking at the moment. I still need to disassemble to confirm, but I agree I think I've got a bad rod. Now do I get a hot rod kit, and have the rod replaced, or replace the crank, new crank, used crank.... etc.
The next problem, getting the swing arm bolt out .... yea, this is not going to be fun.... I need to go get some PB Blaster and start soaking the bolt. Once I get the engine on the bench, I'll begin the disassembly process.
I need to start stock piling some parts… as while I’m there, I may as well replace bearing, seals, timing chain, chain guides, piston / rings. Oh well it’s a good thing its winter, as I will need some time to scrape the parts together

Thanks for the link. It will really come in handy.

[honda400ex2003]

sounds like a jetting issue to me at quick glance from the sounds or the issue in the OP. they wont run long if lean, esp if ridden hard. I am actually quite surprised it made it 20 hours if it still had the stock 148 main in it. It also sounds like there was a leak in the intake system somewhere by the surging problem that was experienced. this would also lead to a very lean condition.

steve

[rubbersdown]

Originally posted by eprovenzano
Everything was lubed, but I did not check the wrist pin clearances. I agree, with the new tight tolerances from a fresh bore and new piston / rings and a suspect wrist pin rod tolerance that was (is) my issue. At least that's what I'm thinking at the moment. I still need to disassemble to confirm, but I agree I think I've got a bad rod. Now do I get a hot rod kit, and have the rod replaced, or replace the crank, new crank, used crank.... etc.
The next problem, getting the swing arm bolt out .... yea, this is not going to be fun.... I need to go get some PB Blaster and start soaking the bolt. Once I get the engine on the bench, I'll begin the disassembly process.
I need to start stock piling some parts… as while I’m there, I may as well replace bearing, seals, timing chain, chain guides, piston / rings. Oh well it’s a good thing its winter, as I will need some time to scrap the parts together

Thanks for the link. It will really come in handy.

If your going to swap the crank you just buy a whole new one. Cheaper then replacing just the rod in the long run.

[RATPACK Z400]

You should definitly change or check jetting ! Thata the first thing to be done before riding it if its lean all that work is ruined !

[beastlywarrior]

are you doing a lot of wheelies and are you getting proper oil pressure

[eprovenzano]

While I have it down I will get into the carb, if for nothing else to get the jetting info written down. The previous owner claimed to adjust the jetting when the HMF slip-on was added, and the air box open.

No wheelies, the oil pressure was fine. The oil was full as we always check before we ride.

[rubbersdown]

Originally posted by beastlywarrior
are you doing a lot of wheelies and are you getting proper oil pressure

Wheelies wouldnt matter sense the 400ex uses a dry sump system and it has no pickup. And being that the oil pump is 100% mechanical the odds of oil pressure being the problem are very slim.