I was experiencing random ignition cutting at arround 11.5k on my std, wire spliced 21.

Yesterday I went for a test ride with sealed exhaust and new tyga reeds. Whent out for about 20 miles calmly and returned "with a big smile".

Now the engine pulls clean and nicely up to redline. My rear sprocket is 42T, so it can do this in 6th gear even with (slight) uphill. I tryed this for a couple of km, and calmed down. While still riding at high speed, not WOT, I noticed a sudden power loss. Grabbed the clutch and the engine stopped. Once the bike stopped on the side, it started at first kick, keptt idle OK. Continued running home calmly. Once I was relatively close, tested the engine again and it revved up OK.

Could it have seized? This bike has been a full day on a track less than 500 km ago...
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You promised no more problems

as a minimum get the exhausts off and have a look up the barrel. To d it properly, get the barrels off and inspect the entire piston. Hopefully it's just your cable ties playing up and not holding your white PGM connector.

Maybe you had a partial seizure situation you should check it before riding hard again...

nxrsr20 wrote:You promised no more problems

Ja, ja, I was expecting this one. In any case, I was announcing the installation of new reeds and how well the engine revs...

I can look through the exhaust ports, but that probably will not tell me anything with naked eyes. Of course, getting the barrels off is the way to go. But, Is there another way of checking the piston/barrel state? Difficulty to start? Performance loss? Instable idle? Compression drop? Plugs? Oil consumption? Temperature? Sound? cold/warm behaviour? Vibrations?

Should I check the barrels yes or yes? Or can I continue in the absence of any symptoms?

To elaborate a little bit more on the potential seizure causes. The engine had proven reliable on the track. Later mods are:

- installation of tyga reeds (with new gaskets). This can not endanger the engine health!
- sealing of exhaust port. Same.
- removal and installation of airbox. If I miss assembled it (airbox to carb joint) I would be putting more air in and leaning the mixture, but there was no power increase in the engine.
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if the bike was pulling sweetly thru all gears, sounds good.

need more details of the power loss.. was it either of the following: 100% power loss or choking type of loss?

While the engine was dieing, did it feel like there was resistance, ie. something physically stopping the engine in its tracks? or did it just die like you flicked the kill switch?

Oh, and are you running premix
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You can see lots from up the exhaust port without removing the barrel.
Get you hands on a tiny inspection mirror like this.

Ideally you want a mirror small enough to get into the cylinder to check the bore side of the exhaust bridge.

To answer your questions with my limited knowledge:

Looking through the port you'll need a torch to see things, that mirror helps a lot more too With the piston at BDC you can also see the opposite wall.

Anotehr way to check may be to take the head off, less work but the proper way is to remove the barrel. You own a two stroke now, part of the ownership is swearing as you take it apart.....again

Yes you should check the barrel. You're gambling on the potential cost of replating your cylinder just because you did not check your piston.

Anything that changes gas flow either on the intake or exhaust means you should as a minimum check your jetting.

I've read the last two responses and I am of course considering them. Not only one has to see but also to understand what is seen. And has to be prepared for the job.

To answer Kubira's questions:

- power loss was 100%, sudden.
- While the engine was dieing it died like I had flicked the kill switch. But I grabbed the clutch immediately, so can not really tell
- I am running with the oil pump

because of a situation i had with my bike cutting out while turning, try this. start it, put it in neutral, now turn steering full left and full right. With a bit of muscle involved, repeat, but lean the bike over left an right side, put the front brake on, give the bike a shake etc.. you want to simulate all possibilities, try to re-encountrer the fault from the stationary position

Does this kill the motor at all?-
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Kubira wrote:

Oh, and are you running premix

When I reconnected the oil pump I did not bleed it. I do not know how much oil I lost when manipulating the carbs. Dumb!

I'll check the steering, but the incidennt happened on a stright line...
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Bite the bullet,and take the barreis off,it's the only way to really tell.

What do your spark plugs look like???
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it wouldn't be fun if it was easy!

If it has nipped up on one of the cylinders it will more than likely be obvious just from looking up the exhaust ports.
Use a torch and try to raise the front of the bike if you have it on a paddock stand. If you do it on the side stand you'll have to lay down on the floor.
Generally you will see the piston skirt will be scuffed and scored and maybe the top edge, (crown edge), eroded or chewed up slightly. There may be smears of piston material over the rings too.
If the skirt is very slightly polished or worn, it's probably not worth worrying about.
If you are not sure, take a picture if you can. If you can post it on this thread, someone should be able to guide you. You'll always get a lot of opinions on here!

As dunkenb said, another way will be to look at the spark plugs. If you see little silver spots/deposits of metal splattered over the plug, it's a good indicator of that plug's cylinder having a problem.

I guess you all are right. I'll start from the exhaust ports, look arround and remove the barrels if something looks suspicious. I'll show whatever pictures I make.

Dunken, you are absolutely right "it wouldn't be fun if it was easy!"

Chester362 wrote:If it has nipped up on one of the cylinders it will more than likely be obvious just from looking up the exhaust ports.

+1