jetting problems after spending $2000 on mods

i see at least 3 problems in the above statement.............

wrong case sealer.............no leakdown test to confirm airtight

pod filter directly on the carb is notorious for jetting headaches............
use a 4-6" velocity tube between the carb and filter to allow the air to "straighten out" before entering the carb

and get the filter oiled............... it will not stop dirt without the oil

just my .02.........if you don't plan on building, or purchasing a leakdown tester from slickerthanyou, and do plug chops this time around, you might as well save your loot and part that thing out
 
I did do a leak down test after the first rebuild. I lost 1/2 pd in 20 minutes. I'm going to fab up a tube for the air filter. That is something my local machinist recommended. I'm also going to clean and oil my filter.
 
/\ cool, first time around doesn't count, it must be leakdown tested everytime, the cases are split, cylinder/head or intake is removed, everytime !
7-10 lbs. max, or you risk blowing the seals out.

maybe get your machinst to lap them case halves to ensure a proper seal also, and yamabond them cases this time around,
 
I brought the case to the dealer and talked to the mechanic there and showed him pics of the piston. He said perhaps the timing is too advanced. Any thoughts?
I've got the cases back and I'm in process of putting the case bond and new seals in. Got the one side in the freezer and I'm going to put the other in the oven on low temp so I can get the cases to mate easy. Unless someone else has a better procedure. Let me know.
 
*generally* you need a crank puller to do that BUT I've heard of people being able to get the crank cold enough and the bearing hot enough for it to slide together. Sounds like you're on the right track!
 
I found an adjustable freeze plug that fit nice into my exhaust header. Hopefully I can leak test this thing with ease now. There should not be any leaks. I'm being very careful and patient putting it together.
 
Like I said, it sounds like you're well on your way.

I don't believe you had any trouble with the engine/bottom end before. I still think you are having an ignition problem....
 
I will soon find out. I hope there will be enough ice on the lake to get a decent run in. That is the only place I can get it up to sixth around here.
 
How would I find out where the timing is at? There are no marks on the flywheel and I'm not sure how I would go about checking timing.
There is a high performance cdi on ebay for $50. What are the possibilities my cdi is advancing the timing to much and causing a lean condition.
 
You don't check the timing on the outside of the fylwheel. The magnet built into the inside of the flywheel/keyway spacing is set. What you do is set your stator plate position relative to the case (or crank, however you want to think of it) and then install the flywheel onto the flywheel key so that the flywheel is lined up to the crank/piston position.

If you have a stock CDI with stock stator position, your timing should not be your holdup UNLESS trash on the inside of the flywheel magnets is causing a false pickup by the pickup coil....
 
The magneto was clean. I checked that. I know I would have to slot the stator holes and turn it counter clockwise to retard timing right? So there would be no way to put a timing light on it? Couldn't you get a degree wheel and make a mark relative to the access hole in the case? Or do you just move it little by little and see if it makes a difference in power.
Is there anything on the market that you can install to monitor fuel mixture? Or a heat sensor mounted into the front pipe? So you can see if your going lean or not. I'm just trying to come up with some ideas so I can stop buying pistons. I only have one oversize left and then its going to be a big bore sleeve next.
 
turbowrenchhead said:
I brought the case to the dealer and talked to the mechanic there and showed him pics of the piston. He said perhaps the timing is too advanced. Any thoughts?
I've got the cases back and I'm in process of putting the case bond and new seals in. Got the one side in the freezer and I'm going to put the other in the oven on low temp so I can get the cases to mate easy. Unless someone else has a better procedure. Let me know.
Click to expand...

What is your timing and the gas octane rating you use?
 
Its the stock stator and cdi. Only thing that has changed is the flywheel was lightened by Ken Occonor. I run 93 octane and use super m 2 cycle oil premixed 32:1.
 
The pics of your piston sure show signs of over heating, but obviously not from stock timing.

A lighter flywheel will make no difference to timing.

The piston looks like it has suffered detonation due to poor jetting practices.

In future is would sugguest that you jet on the rich side.
 
I had a 160 main in it. I tried a 178 and it fell on its face when you hit 1/2 throttle. I didn't have anything in between. I ordered a 165 and a 170 main. They are on there way. The thing is why can guys with the same carb and bigger displacement run 155 and smaller jets then my setup? That's what is discouraging. I think the problem is elsewhere.
 
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