Yamaha G1 Golf Cart Engine Disassembly Question

[Paulm]

Hi All--

Newbie here. I've inherited a Yamaha G1 golf cart two stroke (engine # J17-014203) from a friend and have a question about engine disassembly. It has a loud knock and not much compression. I have removed the engine and have it on my workbench. I have pulled the flywheel and ignition coil assembly.

Now I am looking at the big starter sheave on the crankshaft and do not see a ready way to remove it. How do you guys do this? Any advice is welcome.

Also, it looks like I will need parts. Any recommended sources? Is there a manual available?

Thanks much--

Paul

 

[djlan99]

You need to order a clutch tool first. They are around 50.00.

If you are good with a set of torches you can almost always save the crank and rod assy.

I heat up and burn off the old bearings. Just let the crankshaft cool normally (not with water).

You can get the bearings from automotive or a bearing supplier.

They are 3306 (clutch side) and 3206 (flywheel side).

ONLY USE YAMAHA SEALS!!!! The aftermarket ones are all junk!

The yamaha seals are about 20.00 each and will last you 10 years.

Also use a yamabond sealer for the case halves number 4 was the best but now it is epa safe
JUNK.

The good case sealers are now made across the pond and you can find them in motorcycle shops. ( dirt bikes etc.)

You will need an impact driver with a number 3 phillips bit to remove the screws.

You will need pullers to remove the case halves from the crankshaft bearings.

They will almost always stay on the crankshaft.

You can use a regular puller on the flywheel side but the clutch side needs a wider puller.

You will need a press to put this engine together. Then you install the screws last

Also when putting the engine back together you press the bearings into the case halves first then press the crankshaft into one of the case halves then press the the whole thing together.

Don`t forget the sealer.

 

[Paulm]

djlan99--

Thanks for the helpful reply. Can you describe the clutch tool you mentioned. Or better yet, post a photo? I am going to guess that the tool is a puller or a bearing separator of some sort?

Also, is the clutch piece that I need to remove just pressed on the crankshaft?

If Yamabond is n/g can you recommend a good sealer?

I have the rest of the tools you mentioned.

Is there a manual?

Thanks again--

Paul

 

[djlan99]

You can use the new yamabond # 4 but there are other case sealers that are just like the old yamabond 4. (way better)

Any motorcycle shop will have it on the shelf. It is a semi drying rubber sealer.

What ever you do do not use rtv silicon it will turn into jelly!

just look up yamaha g1 clutch tool. It is a long bolt with the threads up near the hex head.
(ebay)

The clutch is pressed onto the crankshaft when you torque the bolt with an impact gun.

Once you lock the taper it is locked. Just like front end parts on a car. Taper locks can only be broken loose by hitting them perpendicular to the taper. I have done a few on these but I
would not recommend it.

I am your service manual for this engine. If you have any questions just ask me here and I will tell you all you need to know. More than any book will tell you.

When you start putting this engine together I will tell you about the timing plate.

Also make sure to clean the top of the piston off in a wire wheel or bead blaster to find out the over size. It will be a .25,.50,.75, or 1.00 mm over size.

You can hone these cylinders to the next over size and just buy piston and rings. ( with a good stone hone)

The spec is .0015 but that is not enough. I hone these to around .002 to .003 If you don`t the piston will lock up in the cylinder.

 

[Nubs]

 

[Pimp Daddy]

Nubs tell us what you think.

 

[djlan99]

I should mention that the noise you heard was most likely piston slap.

Alot of these were rebuilt by replacing the same size piston and rings along with a cylinder hone.

The piston rings are very soft and will wear paper thin. They do not leave a ridge in the cylinder.

You should not be able to wiggle the piston at the top of the bore. If it does it should be slight.

If the noise was not from piston/cylinder wear then check for a loose rod bearing at the crankshaft. ( up and down movement where piston would be at top dead center )

If the piston and rings are good and fit good in the cylinder you can just replace the rings.

It is very important to beadblast the carbon out of the ring lands or you will not be able to compress the new rings all the way into the old piston.

If the crank bearings are good ( rare if the seals are bad ) you can just replace the seals.

The clutch side seal will always fail first. You will see oil all over the back side of the clutch starter pulley.

I have seen alot of these that had been rebuilt but used aftermarket seals. I was able to just replace the seals.

You can also reuse the head gasket as long as it looks ok. They come off in one piece. I would never do this with any other engine but on these I have never had a problem.

The base gasket will come apart and will need to be replaced.

Again use only yamaha base gasket.

Head bolt torque is around 25 foot pounds. Again not a big deal here, never had a problem.

 

[Paulm]

Been a while, but I have the engine back together and running but not well.

The noise was in the clutch assembly where the weight pivot pins were worn and things were quite sticky. I made new pins about .008 oversize and this is working well. I also made the clutch puller tool once I saw how it and the clutch were made. Works good.

Problem now is that while the engine runs smoothly without mechanical noise of any kind it will not idle down to where it can be adjusted with the idle screw. Also, it spits fuel back out of the carb fairly aggressively. Seems like this might be the reed valve. I have this out on my bench and find that the petals are in good shape and closing at the tips but there is a gap along the edges where the 'soft' compound seems to be eroded away. This leaves a gap of about .020 along the edge of each reed petal. Have any of you any experience with this problem?

For reference, I have disassembled the carb and cleaned it and all passages are open. Also bushed the throttle shaft to remove excess clearance. I have checked the crankcase for both pressure and vacuum leaks and it is tight.

Thanks for any help --

Paul

 

[Nubs]

i'm not a yamaha guy but i'll take a shot, so are ya sayin' theres a factory coating on the plate where the reeds sit? can ya see light through the back side where its worn.

 

[Paulm]

Nubs--

Thanks for the reply.

Yes, you have it right. The entire landing surface for the reed petals is coated with a black resilient compound of some kind. But, some of it is apparently eroded away, leaving the .020 inch gap I mentioned. And, yes, I can see light thru the .020 gaps.

I would post a photo but do not see a way to do it. Is a photo possible?

Paul

 

[Nubs]

you would need to host the pictures on photobucket etc first and then to the forum. i have seen this coating deal on chain saw engines in the past, thats your problem for sure. if it was me and since the plate is bad i would cut the coating off with a razor blade and then sand the face with fine sandpaper on top of a piece of glass to assure its flat and put it back together and try it. most all reeds on 2 cycles laid right on the plate, got nothing to loose you can e-mail the picture to me and i'll post it if thats easier.

[email protected]

 

[Paulm]

Nubs--

OK, I have a photo on Photobucket and will include the image link below.

The photo is taken with a flashlight inside the reed valve so that the gap can be seen as well as the 'resilient' compound. The petals have been removed from one side of the valve.

And, yes, I am thinking of milling the petal mating surfaces flat and giving it a try.

Thanks--

Paul

 

[Nubs]

give it a shot and let us know how it goes, always make sure the reeds face the same way as they came off

 

[Paulm]

OK, I have milled the reed valve surfaces reasonably flat and now have the valve back in the G1. The engine will now idle down and can be adjusted with the idle screw. Also, there is no longer any spitting of fuel back out of the carb.

The engine runs fairly well but will not wind out like the two strokes I am used to. Does anyone know if there is an expansion pipe inside the BIG muffler? Also, in this regard, does anyone have recommendations for the main jet?

Here are a couple of shots of the milling job:

Paul