Suzuki 2 Strokes

With the carbs completely off the bike, I figured this was a good time to do a compression test. Keep in mind there are only 353 miles on a fresh top end.

L = 129
C = 125
R = 120

Is this too much spread? This is the first compression test I have done so I have no previous figures to compare it to.
You might have read in a previous post "Problems Again" that I thought I may have installed a ring upside down. I think this rules that out. Or does it?

Plugs look like this. Left, center and right respectively.

IMHO, I would say the last cylinder is not getting enough oil. Being dryer and lower compression is the signs to me....... It might be worthwhile to pull the oil lines and do some kind of flow rate test.

It looks OK to me. The compression should be within 10% from cylinder to cylinder, so that looks OK to me as well.


Lane

Your compression looks close to textbook to me. They'll only get more consistant with each other as the motor continues to break in. The plugs look respectable also, though I would keep an eye on the center one, as it looks a notch leaner than the two others. Time will tell. And congrats on solving your carb issues. I know the sigh of relief you must have felt, having been in a similar position more than once. And, you were absolutely right, THOSE CARBS WERE REALLY CLEAN!!!!!! Cheers, and enjoy that bike.
Fred

You can't read a plug form that pic. The area you should be looking at is right at the bottom of the porcelain where it meets the metal. A light tan color is what you are looking for. A bright light and magnifier is necessary. that is were combustion takes place with the least amount of turbulance.

I'd say that's looking pretty good and the compression readings are too.

Don't forget the compression gauge will only be accurate to within 5% or so ...

Fred wrote:

The plugs look respectable also, though I would keep an eye on the center one, as it looks a notch leaner than the two others.

That's the that HAD the air leak.

Reading plugs is at best iffy and at worst completely misleading in terms of reading jetting.

The idea is to get the plugs up to full temperature which means high load and usually high RPMs. Once it is hot enough, it should basically burn off most or all of the color on the tips but should show a ring of color where JA-Moo mentioned - deep in the hole.

Reading plugs at less than WOT means teh plugs were not at full operating temperatures so they are harder to make any sense of.

One thing we can see on those plugs is that the side electrodes appear NOT to have any signs of overheating from wrong plug range or too much ignition advance. In fact they are showing that they really didn't get hot enough, probably still running it in.

The other thing we can see is that the plug on the right is very different to the other two. It is dry and a different color. That's odd. The tip is covered in gray where the other two are lighter brown/gray. The steel shell is also gray and not black and oily like the other two.

Why? Was it effected by the vacuum leak more than the others causing it to run leaner and hotter or was that the center pot?

What did that piston look like?

tz375 wrote:

Why? Was it effected by the vacuum leak more than the others causing it to run leaner and hotter or was that the center pot?

What did that piston look like?

It was the vacuum line on the center carb that had the air leak. I don't know what the piston looks like. I can't fit my head through the spark plug hole.

A guy never has one of those nifty spy scopes on a flexible cord that you see them running though walls in the moves when he needs one.

WAG....but 2 things come to mind looking at those plugs:

#3 is the lowest compression cylinder and has the odd looking plug. Coincidence ??? Maybe....but maybe not.....other things may be at play such as....

How is your timing on that cylinder ?? Slightly advanced maybe ??? If you are running an electronic setup DON'T rule out that the pulse coil for #3 MAY need to be checked for actual position on the mounting plate. Get out your timing light and confirm actual firing position for that cylinder.

Congrats on finding your air leak. For want of a nail, etc etc.

Rick, I am running stock points. Timing was spot on but I'll double check it today. I also swapped left and right plugs to see of it cleans that plug up as well. If it does, then I need to take a serious look at the oil line feeding the right cylinder.

Chris,

I'd suggest that you slip off the right pipe and take a quick look at the piston skirt on that side, or pop the head off and see what the bore and the combustion chamber look like.

It's just possible that it has a leaky ring on that side or it nipped up a little.