top end trouble on te300i

[rubberduck1]

I have a 21 TE300i with a riot 120. I rode it the first year with no trouble. Before the start of the second season I put in a new piston at 100 hours. 10 hours later, the piston seized, had some scratch on the sides and the ring caught the exhaust port. Bored and nikasil the top, 10 hours later another piston fail. Had it bored/nikasiled to match the piston to be sure it wasnt too tight. Rode it 5-10 hours at the end of the season. Put 10-15 ours on the dirt, on the 2nd winter ride, I lost the piston again.

Each time has been on groomed trail leaving the parking lot riding on hard groom. I make sure its warmed up and not too hot, this time I looked a the temp guage when it had issues and I was at 190 (I am told this is warm but not a problem).

Any thoughts on what could be happening? Am I running too long on hard pack in a high gear? It does have a high compression head (0-6000') but I am riding around 6000+. I have ridden it pretty hard in deep stuff without issue. Plugs looks med/dark brown. I have the Injectors moved back to the intake and a Coober ECU.

 

[eric82930]

Probably too lean somewhere in the mid range. If you didn't change anything from the first 100 hours may be one of the injectors is starting to plug up and not flow as well as it used to.

 

[rubberduck1]

Pulled the top off, and found this piston and sparkplug look a lot different. The end of the spark plug is burned off and there is a cavity burnt out of the piston after 18 hours with metal splatter.

Is this do to lean, too much compression, too much heat? (first picture of the head has a new sparkplug in it).

 

[portgrinder]

Probably too lean somewhere in the mid range. If you didn't change anything from the first 100 hours may be one of the injectors is starting to plug up and not flow as well as it used to.

Piston pics pls

 

[eric82930]

Yep. Too lean. If you didn't change anything since it made the first 100 hours then you have a plugged injector, low fuel pressure or some other tpi sensor gremlin. If problem started when you added the head then you need to reflash to add more fuel.

 

[eric82930]

It's definitely not coolant temperature heat. Is heat generated from the lien combustion which is thousands of degrees to melt aluminum. I've seen sleds that burn a hole straight through the piston from being too lean.

 

[rubberduck1]

Is it safe to say it's NOT an oil injector problem and must be not enough fuel?

Is it possible the high compression head is doing it?

I did an injector relocate and ECU reprogram at the 60 hour mark, don't think that's the issue as it ran another 50 hours before failing.

What's the best way to test injector output (I would like to see what they are doing before I clean/replace stuff just to be sure I found a problem).

 

[eric82930]

No .Lack of oil won't melt the spark plug or piston. YesThe high compression head will want more fuel than a stock head that's why I asked what you changed since the first 100hrs. But I sounds like your head is a low altitude head so you aren't crazy high compression so that's probably not enough to be the issue.

 

[GlennRMK]

What are you setting the ring gap at? Need at least .011" or so. I am wondering if that was maybe the original ring snag issue?

The pictures look like a different lean issue though.

Double check fuel pressure and check injectors are spraying properly. Maybe have them cleaned/checked? Check or replace crank seals. Check for any other air leaks.

Maybe the mapping is just lean?

Air filter setup? I had trouble sucking a lot of fine snow with just the prefilter setup.

Double check oil pump is working but premix or added premix is a good idea since you already have the injectors out of the cylinder

 

[CATSLEDMAN1]

running too hot and that causes a leaner condition , your incoming fuel at 130 degrees would likely keep the piston cool enough to avoid this for a longer run time, all of this heat anneals ( softens the aluminum material )the crown of the piston making it even more likely to surface melt and this likely took hours of run time, as the piston crown anneals the rings get looser and looser and won't then transfer piston crown heat to the cylinder walls , if you measure your ring land clearance it way out of spec and rings are fluttering and work in efficiently. If you truly want to know this and hear the truth, send your piston and rings to a engine lab and they will explain this common problem to you in graphic detail. 25 years ago building big bore snowmobile engines and complaining about lousy piston, our piston supplier had us send several sets of pistons to a lab for analysis . So we had to eat crow, lousy tuning /poor jetting/ inadequate cooling system will destroy any piston/ring/nicisil jug.

 

[eric82930]

It's just too lean. If the engine can't survive 190 degrees coolant temp going down a road with the correct fuel to air ratio you might as well throw it in the trash. Dirt bikes in the sand dunes run way hotter. Yes keeping coolant at 130 might let it survive being lean for a few more seconds but that doesn't make the coolant temp the root cause. It needs more fuel.

 

[portgrinder]

Yup. Add fuel.

Snowbike load takes a lot more fuel than an enduro bike.

Should Cc the dome while you’re at it. Here’s how. Get your cylinder level, (might have to lift front of the bike up) and get the piston to top dead center. Add oil thru the spark plug hole with a syringe and measure the cc’s. Take the stator cover off and you can slightly rock it back/forth to make sure your piston is at the top. Note how many cc and take of 2cc if you fill it to the top of the spark plug threads.

If you screw it up just rotate the piston thru it’s stroke a few times and the oil will go out the exhaust.

With your dome volume we can calc actual compression and tell you what fuel you need to run with.

 

[rubberduck1]

Yup. Add fuel.

Snowbike load takes a lot more fuel than an enduro bike.

Should Cc the dome while you’re at it. Here’s how. Get your cylinder level, (might have to lift front of the bike up) and get the piston to top dead center. Add oil thru the spark plug hole with a syringe and measure the cc’s. Take the stator cover off and you can slightly rock it back/forth to make sure your piston is at the top. Note how many cc and take of 2cc if you fill it to the top of the spark plug threads.

If you screw it up just rotate the piston thru it’s stroke a few times and the oil will go out the exhaust.

With your dome volume we can calc actual compression and tell you what fuel you need to run with.

I agree it needs more fuel, but I am not sure the cc calculation will help this case (or at least I wouldn't know how to add more fuel). This is fuel injected and already has an aftermarket map that is supposed to add more fuel.

As this point, taking everyone's thoughts, I am hoping I just have a slight clog in the fuel system that Maggie's when I am running at high rpm for extended periods of time (on groomed trail). I think I am going to test the fuel pump pressure, replace both fuel filters, clean the injectors, pull the snow kit, return to the stock compression head, and then ride it on dirt and keep a very close eye on the head temperature, compression, and visually inspect the piston to see if it returns to normal.

 

[portgrinder]

You need to add fuel. Just because you can’t doesn’t change that fact. This is the problem with fuel injection.

Cc calc will tell you WHAT fuel you need. If it turns out your 16-1 you can add as much 91 as you want but it’s not going to end well.

 

[JimBridger]

Buddies bike was doing the same thing. Welded in a koso egt gauge to keep tabs on temps. He has a get ecu so he can add or subtract where he needs to. You could always do a JD Jetting fuel controller. They can add fuel. I have one I'd sell cheap if you're interested.