Bought my first 2 stroke - started for a bit & now doesnt :(

[Coyote]

You will find it quite impossible to put those angles on the ports per book. I have just been through this process on my own 550. All you can really accomplish is to remove the sharp edges with some sort of angle (whatever it might be) so the rings won't tend to snag. Even a vertical mill with a right angle attachment is worthless. The hole is just too small.
You really need to borrow, rent or steal some inside micrometers and stop just guessing. There is really no other way to tell where you're at. If you need to convert the number is .03937. Example, the stock bore is 61mm. That times .03937 = 2.4015. If your bore checks that plus .002 (2.4035), then bore is stock. If it checks 2.421 plus a couple, it is .5mm oversize. With the micrometers you can also check for out of round a taper. Also steal some 2 - 3 outside micrometers so you can tell what your pistons are.
I am fortunate that I own these tools as I was a machinist for 32+ years. The inside mics come in a set. I can check any size hole from 1 1/2 to 18" in 1/2" increments. I also own outside mics from 0 - 6". My mics in the picture read 2.419..

. I have individual outside mics from 0 thru 6". My mics in the picture show 2.419

[tz375]

61.5 is 0.5mm oversize. If you still have the old pistons and rings look at them carefully or measure the pistons and let us know what you find.

testing compression has to be done with throttles Wide open and you kick until the needle stops rising.

Low compression was not the reason it ran and then stopped, but let's deal with one issue at a time.

[Coyote]

If the pistons are oversize, it will state so on the piston crown -- OS .5 You did put the arrows toward the exhaust side?

[bpapachr]

Arrow towards exhaust side the the tapered side (side with the markings) of the piston rings up. With the old rings and Pistons its was kinda interesting. The Pistons were standard and the rings were not. I don't even they they were the correct style of ring to match the rings.

The measurement at 26mm from the bottom of the skirt is 60.85mm. The rings have no oversize markings from what I can see.

[tz375]

Stock size is 61mm bore, so the old pistons were stock by the sound of things. I wonder how large the bores are.

Bottom line though is that if it ran with those pistons, they are not the reason it stopped running. Check ignition timing carefully and then look at jetting to see if something is clogged. My own preferred way to check timing is with head off (the bikes that is) and with a dial gauge and static timing light (I have a Dyna and the light goes on when it fires). I like the timing to be spot on and when checking mine it was a full 0.1mm out on one cylinder and that piston was noticeably darker than the others.

Some engines tolerate timing mismatch and others do not. Don't look at the propeller marks. They may be right or they may be way off. On a 750 the timing is fixed by a small key in the crank and sometimes the starter will shear that key and timing is miles off but the propeller blades still match the points so it is deceptive.

Makes sure you have a consistent good spark. There may be a short of break in the wiring or a dead spot in the kill/run switch.

[bpapachr]

Stock size is 61mm bore, so the old pistons were stock by the sound of things. I wonder how large the bores are.

Bottom line though is that if it ran with those pistons, they are not the reason it stopped running. Check ignition timing carefully and then look at jetting to see if something is clogged. My own preferred way to check timing is with head off (the bikes that is) and with a dial gauge and static timing light (I have a Dyna and the light goes on when it fires). I like the timing to be spot on and when checking mine it was a full 0.1mm out on one cylinder and that piston was noticeably darker than the others.

Some engines tolerate timing mismatch and others do not. Don't look at the propeller marks. They may be right or they may be way off. On a 750 the timing is fixed by a small key in the crank and sometimes the starter will shear that key and timing is miles off but the propeller blades still match the points so it is deceptive.

Makes sure you have a consistent good spark. There may be a short of break in the wiring or a dead spot in the kill/run switch.

When should the light come on after the points have been gapped? At TDC? I'm assuming I would see the piston come to the top and use the feeler to gap. After that at what point do I need the dial gauge to switch the timing light on?

[Coyote]

You gap when the points cam is at it's highest point. do all 3 first. Time the left side first as you need to move the entire plate. Points should open 3,37mm BTDC If you have a thou, indicator, that's .133 BTDC. This info is in the sticky at the top of this section under general info and specs.

[bpapachr]

You guys rock. Will try and report back! Thank you so much all!

[tz375]

So you set the points first when they are fully open and after that you check/set timing. Whether a test light goes on or off or you sue a radio to listen to the crack as they open differs by type of ignition and technique. I think if you take a test lamp and place it between the points feed and ground it will be OFF when the points are closed and ON when the points open, but I don't use points, so I may have that back to front

[Coyote]

That's what I use. The lamp is always on. Goes out when the points open - breaking the circuit. It's a converted flashlight and runs on 2 AA batteries. No ignition or 12V needed.

[bpapachr]

That's what I use. The lamp is always on. Goes out when the points open - breaking the circuit. It's a converted flashlight and runs on 2 AA batteries. No ignition or 12V needed.

I'm using a test light that I grounded on the bike and use 12v from the battery. The light will be off for my use until the points break where the plug is fired (3.37mm BTDC)?

[bpapachr]

Okkkkkk...so I finally got back to the rebuild this week and here is my report back.

1. The bike sounds ok when started and sometimes it seems like either the right or left cylinders don't fire. I'll feel for back pressure from the exhaust and reach upfront and touch the exhaust and it will be lukewarm at best. The other day it was the right cylinder, tonight it was the left cylinder. Checked for spark and it was there. The biggest problem with this bike is that it turns over no problem but as it heats up and stays on for about 7 minutes, the rpm's come down and it starts to bog down and sound flooded or starving like it did previously. I changed the piston rings, and found out that the shipper sent the wrong rings and now I'm up to 130psi in each cylinder. This is with the carbs off and exhaust buttoned up.

2. The battery seems to be draining so I want to get everyone's advice for testing the charging system (alternator, rectifier, regulator, etc.). At this point with all the money if spent, is it worth just changing out the system and going with electric spark? Or if anyone has a recommended solution I would love to hear it. At this point I'm just hoping to get this thing out for a few rides before the winter hits! haha. When I was running the bike the other night, the battery stayed static at 11.38 volts with the bike running and no increases when revved. Tonight, I charged the battery over night and was around 12.58 and started to slowly drain and the same happened with the bike running, volts were around 12.18 and no increase when the bike was revved.

I also noticed a lot of smoke the other night coming out of the left cylinder, (the cold one) after the bike cut out. Trying to research more into this but I think its just the oil heating up and not burning properly. The carbs from my perspective have been thoroughly cleaned, inspected 3 times over, new floats, new jets, everything buttoned up properly. I have attached short video of what is happening when the bike heats up and shuts off.
https://www.flickr.com/photos/131622719 ... res/112435" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

And a picture of the plugs from the other night when I was having issues with the right cylinder not firing.


Once again, appreciate all the help!

[Alan H]

You MUST have good voltage to the points and coils or the bike will not run right.
Lots of threads about charging on here, but basically power is supplied to the alternator rotor via a voltage regulator. This excites the rotor so that 3 phase power is produced by the alternator stator coils, and turned into DC by the rectifier. Normal voltage with engine off should be about 12.5v, and at least 13.5v when running.
If not, then you've more fun coming!
First check is to see if you have power to the rotor, check rotor brushes, then check power is coming out of the rotor to earth.

You didn't expect this to be straightforward did you?

[Coyote]

I wish you were closer. I'd mail you a copy of the triples manual on CD. Trouble shooting the charging system is laid out pretty well. Maybe I can copy those pages and post them up here. One thing you will need is a multi-meter for checking the electrics.
The left plug looks dry. Can you smell fuel on it? Could be the float level is slightly off. With it running, try spraying some starter fluid into the carb intake. If it begins to fire on that cylinder, you'll know it's a fuel delivery problem. Ain't this fun?. It's dinner time. will try to post those pages later.

[Coyote]

Sorry Bob. No can do. To make it large enough to read, then each page has to be split up. That makes the illustrations and text not match. frustrating.
There are 2 options I can offer. I could mail the CD to you and you can reimburse me for the postage. No charge for the manual or the media. Just postage
The other option we would need to get together while I email you packets of the file in pieces that can be assembled with an included tool after receiving all the packets. There are 17 in all all are 5mb in size. The reason I say we need to be together is so you can email me after receiving each one so I can send the next. You need to copy all of the to a single file. You can't leave them in your mail box because it will get full and I won't be able to send them all. Probably take 2-3 hours to do..
Are you familiar with changing file names? I ask this because the assembly tool is a .exe. It won't mail because your or my spam filter will see it as spam or a virus. So I would have to change the extension to something like.jpg or .bmp. You would have to change it back to a ,exe once you get it.
The finished file size is 80mb
Do you know what your limits are. It's possible I could email the whole thing at once -- ready to run. I also have the GT550 parts list. That one is 10mb. Both files are in PDF format.