G1 Problems: cranks, but will not run

[sontag1]

I would be VERY surprised if this cart has had any major work done on it during its ~30 year lifetime. I am going to start breaking it down this weekend on Sunday (there is never enough time...) I got it a few months ago and I have had to run it with the choke on ever since. Like I said in my original post, it had plenty of get up and go up (it would run about 23-25 mph once drilled out the governer arm) until the total loss of power that day on the big long hill.

I have not noticed any oil leaking out from behind the flywheel, but I have not really looked for it either.

Do you have any info/thread links about the reed valve? How do I check if it is leaking?

Any info/thread links on the honing process?

Thanks,
Kevin

[sho305]

If not seals then it is either not getting gas in the carb or it has a big vacuum leak in the intake. You can get it running and spray carb clean or wd40 all over the intake boot. You can get the carb out pretty easily and inspect the boot. You can clean the carb and blow it out, check fuel pump flow, etc. You can pull the muffler loose from the cylinder see if it runs to check for plugged muffler, that might act that way. Could have a blown headgasket or other odd problem that is not common.

[sontag1]

Fuel system is solid. That is one thing I actually know something about. If the muffler was clogged (I have done the BBQ, by the way), what could fail due to the back pressure? Rings, headgasket, etc.?

I am going to dig into it on Sat afternoon or Sun after church. I will post what I find.
Kevin

[sontag1]

Well it has been 7 months, and I finally got to tear into my G1 last night.

I guess having a baby will do that to you.
Anabelle Kate Sontag Feb 22, 2012

Let me start by saying that this is the first 2 stroke I have ever worked on. I know how to turn a wrench, but most of my experience has been with autos or "60" series tanks.

My initial plan is to replace both crank seals and go through the top end. Everything in lower end looks good. I have been reading through some of the rebuild threads, and I am highly motivated.

I removed everything on the clutch side down to where I will need the puller.
In the pics, you can see that the inner sheave(?) is a little rusty. I will clean that up once I get it off of the engine.
What do I lubricate it with on the install (anything)?

I did have evidence of oil leaking behind the clutch, and from the lower part of the Jug on the passenger side.
I am going to remove the fan side tonight (Hopefully).

I know I need to mark the plate that sets the timing. Is there anthing else I need to mark for when I put it all back together?

There is quite a bit of carbon on the top of the piston and the top of the cylinder. The walls of the Jug(?) look nice and smooth. I have not checked to see if they are parallel. I intend to hone the walls and get the correct rings, but I have never done that before. Are there any stickies or threads out there showing how to hone the cylinder walls? I want to do it right the first time.

What do I need to look out for when I examine the Reeds?

I do not have the SM yet. I hope buy a downloadable verson soon. I have been taking notes on what I am reading trying to dig out all the torque specs that I can (from the threads).

What are some of the general things to look out / plan for? What else sould I consider doing while I am "in there"? I have read that OEM Yamaha rings make a real difference. Any thoughts on this, and where should I get them?
Thanks,
Kevin

[sho305]

Sounds like a good plan. Honing you basically run it up and down (w/oil) inside a few times until you have even and full hone of the cylinder. You don't want any marks or shine left just a nice crosshatch pattern (that I imagine you can find photos of on the net). Don't do anymore than you need to it should not take long. I would recommend you bore it or get a bored cylinder they are not much, the only way 2 strokes make full power is a fresh bore and they wear out faster than 4 strokes so they are typically toast at rebuild time. I'm not sure what way you are going just saying. You could also get the head decked it will make a little more power, they were designed for substandard gas and have low compression ratios. IIRC they do them .030 and that gets you to the squish band in the head.

Not sure on that clutch but in general you grease the center bushing where the halves of the clutches slide. I like to lube the pins/etc that move with a light chain lube I use super lube its synthetic and collects less dirt. They often say leave that stuff dry but if the clutch is closed in or on a sled I like to lube it and clean off any excess, because it will fly off and could get on the belt or of course collect dirt. I use brake clean spray to clean it. The sheave you can sand with a fine sandpaper or emery cloth to clean it up. It will actually grab the belt better but not like carts have tons of power anyway. You sand center to outside.

Usually you can advance the timing a little for the forward rotation direction for another little boost in power, that would be turn the pickup opposite engine rotation in forward. Usually you can't move it far and have to enlarge the holes to get much advance at all. Otherwise just move it advanced a little from where you mark it.

A worn jug will tend to get egg shaped. Check for a ring wear mark at the top of the cylinder where it stops that can give you an idea of wear. Usually wear more on exhaust side. You can do it however, how much of what I say you do is up to you just saying what I would do.

Check the reeds for cracks or bends, anything that would make them not seal for reverting air flow. They should be closed at rest but I have seen them open a little and the cart ran fine. Also check the rubber carb boot for cracks. Check the piston skirt for cracks or excess wear very closely if you re use it. Some skirts have broken.

Carbon build up could be from the oil used, or just old age, or low compression and you using the choke is going to make it too.

Far as I know cutting the head, advancing the timing, and having a fresh new bore is the easy ways to get the most power. I hand sanded the exhaust port less than a millimeter higher on one it seemed to help but you have to cut the head if you do that. It loses compression, but will raise the powerband a little. That cart I did all of the above it topped 30mph no problem and was completely stock on the outside right down to the tires. I t had no governor. Advancing the timing mostly helps it wind up to higher rpm with no governor, it will have better top speed. You can also do stuff with the clutches to help it run a little better, but that helps more with a lifted cart.

I don't know about OEM parts. I do know some parts are not much different price from a dealer than some aftermarket parts. I worked on a lot of yamaha sleds from back then and yamaha parts were very good, these carts don't last 30+ years with relatively little upkeep for no reason. Do you have to use OEM now? I don't know if it matters but would guess they are quality parts.

[bananaman]

I thought bad crank seals would not effect compression. Correct me if I am wrong?

[sontag1]

Originally Posted by sho305

Note a 2 stroke the intake air (air and fuel actually) goes into the crank, the piston comes down and pushes the air up the transfer ports into the cylinder, the piston closes the ports to get compression while sucking the next cycle of air into the crank. This is how the bad seals mess things up, they can change the air/fuel mixture as well as leak compression out of the crank area. This does not mean you have bad rings, though if they are not fresh I would do them anyway because worn rings have a much larger effect on power than in a 4 stroke, a 2 stroke will only have max power with a new bore and rings.

I think this is what Sho was talking about with the compression loss due to bad seals. In my case the Cylinder Base Gasket had failed and that is where I was losing most of my compression. It was way low!

[sho305]

You can still see compression with bad seals, it does not drop to nothing because seals lose compression in the crank not the cylinder you are checking. Cylinder still compresses the air that is in there. So yes it should be lower but hard to say how much lower as most people don't know what it was before the problem, so it could still be in a normal range. On top of that ports operate on an air flow dynamic at speed and don't really work well at cranking speeds, so you are not seeing the air flow you would at operating rpm (as well as any exhaust reversion/etc). But bad seals can let plain air suck into the crank and trash the mixture, usually why you have to choke it then. Many of them are worse the lower rpm as there is more time for leakage. I've seen lot of them that run but hard to start and idle (slow speed). Of course it depends on how shot they are. It is better to look for oil leaking at seals or try the spray test on them, than to use a cylinder compression number to determine seal issues....is all I'm saying. Yes a bad base gasket could cause similar problems, likely not as common though. I guess lower compression should tell you there is a mechanical problem, just not exactly that it is seals or something else.

[sontag1]

I was able to get a little work done on the cart today. I cleaned the Jug, Head, Reeds, and the Exhaust/butterfly. I used some soapy hot water, a scrub brush, and a large amount of elbow grease to clean the parts. It took some scrubbing, but they came clean. I lubed the inside of the Jug. Hopefully I can hone the cylinder tomorrow, and then I can figure out what size rings to order.

I actually removed the butterfly completely. I had it wired open, but since I had it off I figured I would remove it completely. I had some ceramic engine paint, so I painted that part as well.

I also got my Primary Clutch Sheave off (with my homemade puller). http://www.buggiesgonewild.com/gas-y...tml#post725654

I was soooo excited when that sucker popped loose! I cleaned up and celebrated!

[sontag1]

Since I had the exhaust flange off I decided to go ahead and remove the Butterfly. I had it wired open anyway, and this will look a little better.

You will need to remove a few clips and the linkage for the weight will come off. There are a couple of screws to remove on the butterfly itself. I was surprised that I was able to get them out without stripping out the screw heads. They came right out though. There are a couple of clips to pop off of the shaft, and the shaft will come out with a little persuasion. Now you have a hole to fill or you will have an exhaust leak. I found a bolt with a tapered Phillips head and it worked like a charm. I had some Hi Temp Ceramic Engine Paint so I went ahead and painted the part. Time will tell if it can take the heat.