Hole starting in Blaster piston

I went to do another plug chop yesterday, and the engine would just stutter and bog out so bad that I couldn't even get out of fourth gear, when my neighbour, a long time sled head wandered over to take a look. He suggested to pull out the choke when it was running at its best to see what happens, and the engine would totally die, then he suggested taking off the air box lid since I didn't have any other jets on hand to try. The machine really smartened up, and he said that that is how a 2 stroke is supposed to run. I only did one pull through the gears that way as I didn't have another plug to do two runs on, so the lid went back on to get home.
As mention before, my leak test showed no leaks, compression at 130, everything is completely stock except for a uni filter, and a new genuine Mikuni #230 jet, with the old #230 it ran better. Float level has been rechecked for adjustment, and it is within spec.
It just seems odd for the engine to be happy with a stock #230 and open air box with a uni on it, I think I'll go do one more chop with the lid off, but that just feels all kinds of wrong in my gut, but the quad seems happy.
Doesn't the old saying go "Your 2 stroke runs the best just before it dies!"
 
The old saying is true, a 2 stroke always runs best just before it dies, but the following must be added!

Because of a too lean a mixture mainly caused by an air leak or by poor jetting!

Have you checked the fuel level in the float bowl by attaching a clear hose to the bowl drain, crack the drain screw open and holding the end above the bowl gasket.
The fuel level should be level with the carb body above the gasket halfway along the carby body.
The engine should be running and the petcock on.

If the needle and seat is faulty or has a varnish buildup is possible for the carby to flood even with the float level correct!

When trying the choke trick, one needs to pull it out only a little.
 
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If the motor is saying a 230 main is what it wants and a 230 main plug chop comes out correct than a 230 main it is.

Yamaha also supplied a 220 main for certain locations.
 
I just did the clear fuel level check as you described, the fuel level sits roughly in the middle of the flange of where the bowl bolts on, looks to be just above the gasket.
Any movement on the choke when the engine is warm starts killing the engine.

I don't think there is much point in this plug chop photo, I might not have run it long enough this time, but I am certain I am Way too lean as well now. That was my last new plug, so I'm sitting until I get another handful.
As soon as I put the lid on the air box, the machine is only good for putting around at a jogging pace, but the lid off and it goes like stink. I also put a #240 in with no lid again, and there was a slight drop in performance.
Maybe I am having issues with the air box lid. Anyways, I think I'll be running lidless, so I will pick up more plugs and maybe start plug chops at #260 maybe even #270.
 
With lid off and a 240 and it runs best and with a lid on it runs worse is suggesting that you are rich. Try the 230 again with lid on and see how she runs. Then pull lid off and compare.. Going up on the main is only going to make it worse as you have already seen. Smaller jet # = leaner Larger jet # = richer. Air box lid off makes it run leaner air box lid on makes it richer.
 
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With the lid on, it gets better moving from my starting point of 250 down to 230, I haven't tried a 220 yet, it was easier to just to take the lid off with the 230.
With the lid off, it ran great with the 230, and very good with the 240, with any jet, anytime I put the lid back on, it would run poorly, I just never got around to trying the 220 with the lid on.
It always seemed flat at the top end, this is my first attempt at tuning it since I bought it back in '93.
I thought I'd play it safe and start again around 260 or 270 with no lid and go down from there. 240 or 250 just might be the sweet spot if I go without the lid.
 
At your elevation. Stock I would guess a 220mj. Uni air filter 230. Lid off 240.

The 88 and 89 came stock with a 220. In 90 they richened em up with a 230.

I like your thoughts with starting higher. One nice thing about all the guess work and tuning is that you will know your bike well.
 
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I've gotten to know more about this quad in the last few weeks than in the previous 22 years that I've owned it!
I bought it used, all it had done to it before was the TORS was disabled. It always seemed to run rich, but the previous owner said he had it running the best he could get it for doing quad rallies, I just used it for zipping around on the farm, the odd trail ride with friends, and for crop scouting, then it just sat in the barn for about 15 years only coming out for a day or two a year. Now I'm resurrecting it for crop scouting again as well as get back into trail riding, but my wife thinks she might want to get into riding.
Even before I registered to this forum, you guys have been a huge help in getting this thing going again with all the helpful posts, and even more so with educating me directly with my particular issues. I was contemplating giving my pink Blaster to my wife, and getting a bigger machine for myself like a Banshee or Honda 250R, but seeing the possibilities for the Blaster, I might just find another one and stretch it out for my larger size, although it's worth a laugh when "A big man on a little pink quad just beat your RZR!" comments start floating around.
I've always taken the conservative approach to building and tuning my off road toys, so I thought it would be prudent to start rich and lean out till I'm happy. Maybe this winter is a port and polish and new pipe for the ol' girl too.
 
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if my quad sat for 15years or however long was stated lol
id be checking the exhaust for obstructions/especially seeing hows you got stock exhaust with the baffle knowed to break and cause jetting headaches
check every ground and sand down clean.
free flowing gas from tank to carb.....with gas cap ventilating properlyo_O
also in my opinion seals go bad from sitting for years and years..burning tranny oil/that is not made to burn lol
i would check
everything electrical/sand clean grounds.might not have enough good spark under heavy loads:)
free flowing gas
free flowing exhaust
airscrew setting?
amongst alot more things lol
 
I picked up more plugs today, so I'm ready to go try another plug chop or two, but before I go, I would like better clarification on how to do my run, more specifically, do I short shift and make the engine pull hard, and do I keep it topped out for a few seconds, or shut off as soon as I'm at top speed, I did two runs almost identically, but one looked like I kept using the plug, and another didn't even look like I did anything with it. I think I might be cutting out too early, and I don't feel like wasting anymore plugs doing things wrong. I did read the plug chop instructions thread, the OP says when you hit full blast in 5th, cut the engine, another poster is saying you have to go 1/2 to 1 mile to get a good reading, I'm seem to be topping out in under 1/4 mile.
 
Before you make the plug chop run it is important that the float level is correct, the idle is set correctly and there are no air leaks in the system, otherwise the smoke ring may lie about the AFR.


WHEN ALL OF THE ABOVE ARE CORRECT PROCEED WITH THE FOLLOWING.


Warm up motor to operating temp.

Fit new B8ES plug, ride WOT through the gears and hold WOT in 5th or 6th gear for 10 seconds, or as long as you can safely.

The idea is to keep the engine pulling strongly all the time!

Switch off the motor and pull in the clutch, apply brakes to come to a stop quickly.

Take the plug out and replace the old one for the ride home.

Carefully cut the threaded end off the plug to expose the insulator.

There should be a smoke ring of a cardboard or biscuit colour around the insulator.

If it is non existant or a very light colour, you are lean and require a larger main jet.

If it is a lot darker you are rich and may go down a size in main.

I prefer to run a little on the darker side, I may loose a little power but it is worth it for the peace of mind that I won't need a rebuild so soon.

You have to get up a reasonable speed so that you can get the motor to pull strongly.

Then hold it Wide Open Throttle (WOT) for 10 secs or as long as you can.

The idea is not to get speed but to make it pull strong at full throttle to get onto the main jet circuit.

I find I can safely do it on a short run by applying the brakes some.

If you have not enough room you can use 4th or 5th gear with good results.
 
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#260 main
I think I still need to pull a bit longer, I also think I could go up one or two more jets.
Ambient temperature is down to 48 today instead of 75 for my last chop.
 
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