Hole starting in Blaster piston

[cwazyduck]

After lots of reading, using the search function, more reading, and so on, i am looking for some advice. I am rejuvenating a '92 Blaster that hasn't run in about 8 years or so. So far it was running fairly decently, but seems to be loading up, so more reading and tuning. What I have done so far...
Everything stock except for Uni filter (oiled with Uni oil) airbox lid is on
Stock oil injection using Lucas semi-synthetic 2 cycle oil
Leak test done with leak tester built from instructions here (held 8 psi over 20 mins)
Float level verified using clear fuel hose
Carb completely disassembled and cleaned, every jet, every orifice soaked, cleaned, and inspected
Plug chop as per instructions here (plug is BR8ES)

Jetting started at #250, back to #230 (genuine Mikuni) needle in 2nd slot
Elevation -- 2200 ft
temp -- 75*F
The engine starts very easy, 2 kicks cold, one kick warm.
For the fun of it, while the plug was out, I put my inspection camera into the plug hole, and it looks like the piston has a hole starting in it, I couldn't get a good picture without taking the top end off.
I'm using 87 octane pump gas (it has run on that since '93 when i got it)
When I mentioned that to the shop, they said go up a couple of jets, but then it won't run at all. I'm guessing I should start out by moving up to 91 octane fuel, what else should I do?
Other than rebuild the top-end, but what to do so this doesn't start again?

 

[dirtysquared]

Good detailed information you gave.

If it was mine, I'd definitely pull the head and inspect to see if it is really a hole starting in the top of the piston. That piston material had to go somewhere, and you dont want it taking out a crank, bearings, or a set of cases. A head gasket, and some time aren't that much money, and worth the piece of mind.

How's the compression? If there is a hole in it, it should be running low.

 

[dirtysquared]

Oh, and higher octane fuel helps curve detonation. But if the detonation is caused by a massive airleak or wrong jetting, that isn't going to help.

 

[cwazyduck]

Compression is at 130 psi.

 

[Larry's Shee]

Compression is at 130 psi.

Well then it doesn't have a hole. Not to say that it might not be starting one. When in doubt, check it out.

Though it's good you're doing plug chops, you might not be doing it quite right. Should only be a smoke ring at very bottom of insulator.

Wouldn't hurt to do a leak test. 1992 blaster, that means your crank seals are old enough to buy booze . $20 to replace = peace of mind and longer engine life

At first I thought jetting might be lean with your filter, then noticed your elevation

 

[cwazyduck]

I realized I did my pull wrong for the plug chop after I posted the pictures. I'll try to do another run again today.

Here is a poor picture looking down the plug hole, I want to try to do another leak test and if it's still good get a good plug chop before I pull the head.

 

[MercMenace]

stock Jetting at your elevation and mods might still be a little lean. I would get a 240 in there and plug chop again. With your lid on i would think a 250 would be quite a bit too rich. If you took the lid off that 250 would probably be spot on. plug chop the 240 and get us some more pics.

in case you have questions here is a link to plug chopping.
http://www.blasterforum.com/threads/how-to-plug-chop.53237/

I am at 6200 ft and on my stock bike I am running a 210, i drop to a 200 when i hit 8000 ft.

 

[bansheedave]

I put a hole in my banshee piston. Turned out the aftermarket pipe didn't fit the cylinder correctly. Sucked in air and burned a hole in the piston.

 

[jus_me]

Nice detailed first post. As Larry said, It looks as if you may have not done the plug chop correctly. There should be a tan/brown ring near the base of the porcelain closest to the still existing threads.

On the other hand I have seen plenty of "new" pistons with what looks like a small hole. Maybe the size of a match head. It doesn't go all the way through, I believe it is from the castings ? Although I have yet to see a Blaster piston with one. It doesn't mean they aren't out there I just personally havnt seen one..

Are you having probs with the 230 or was it with the 250 ?
Is tors connected?

All in all what is piece of mind worth ? A few bucks for a head gasket and some time ?

Edit; After looking closely I can see a "faint" tan ring on the plug on the left.

 

[cwazyduck]

The #250 would barely run, I think I could out run the quad at WOT. Worked back to the #230 and its much better, but it still seems a bit flat at the top end. So far 18 minutes into my leak test I have lost 1/2 psi. I guess I better start looking closer for that leak.
TORS has been disconnected as well. I didn't want to remove the top end until I did a leak test, but it will come off before I do anything more than another plug chop attempt.

 

[MercMenace]

glad you found a leak. kudos for doing things right. Once you get that leak fixed set the idle to spec then start at the 250 again and chop down.

 

[jus_me]

1/2 lb in 18 min isn't bad but it really shouldn't leak at all.. Like you said before ,,,try to find the leak before pulling the top end. 1/2 psi in 18 min it is a slow leak so it may take some time in trying to fiind it. Also pay close attn to the plug chop instructions and floow them exactly. post a pic of the plug when you can.

 

[cwazyduck]

At what point do you call a leak test good? 1 hour 09 minutes and no noticeable drop in pressure this time. The leak was in my tape wraps to upsize my tester before.

 

[MercMenace]

if it is going to leak it is going to start leaking immediately. a really slow leak could take a minute before you really notice a change on the guage. that is why 10 minutes is recommended. that way if you are human and get bored and walk away you can see if it is leaking.

 

[MercMenace]

the longer you hold pressure on your engine the more chance that a seal will work it's way loose and create a leak. I usually do my leak tests by walking away and having a beer and a smoke.

 

[cwazyduck]

So I think I can safely say my engine is leak free then. I will re-visit the plug chop instructions, I think I may have let the engine wind out too much instead of make it work. I also posted a pic I took down the plug hole with my inspection camera, but it shows that's it's still awaiting moderator approval.

 

[Larry's Shee]

At what point do you call a leak test good? 1 hour 09 minutes and no noticeable drop in pressure this time. The leak was in my tape wraps to upsize my tester before.

Was going to mention testing the tester. Soapy water in spray bottle is your friend.

the longer you hold pressure on your engine the more chance that a seal will work it's way loose and create a leak. I usually do my leak tests by walking away and having a beer and a smoke.

Totally untrue if you are only using 6/7 lbs. Last Banshee I did held 7lbs +/- over night, about 12 hrs no problem.

When it comes to leak tests you either have no leak, or a slow leak.

 

[Herpderplol]

15 minutes with less than 1/2 psi drop is good.

Hour with none is perfect. Never go over 7 psi. that how you create leaking seals

 

[cwazyduck]

Thanks for all the help and info so far from everybody, I tested the tester when I first built it, no leaks, when I put it on the engine it was sitting steady, but I sprayed down every joint anyways, it wasn't until I moved the tester itself to spray around the carb boot that a pressure drop started, then I noticed fine bubbles showing up around the electrical tape I used to up size the tester to seal better. After changing the carb boot clamp, my leak went away.
The photo in post #6 was the reason for starting this thread though. The engine always ran decent, the plug would get dark quite quickly, as if it was a bit rich or a bit too much oil. If I would maintain any throttle position for a length of time the engine would start to burble a bit until a little blip of throttle then clear up immediately. When I get a chance, I'm switching to premium fuel, going up one jet and try another plug chop. I'm sure I will pull the head anyways to get a better look at the piston, I just want to see if I can have it running well before I tear into it.

 

[Fast6hand]

I like to use bearing grease around the fittings to seal. Both intake and exhaust. Always make sure the the spark plug is tight as well.