GY6 Project By Bashan (Read 37,502 times)

[Bashan]

I've had a lot of requests for a step by step guide for a GY6 tear down and rebuild so I thought I'd post what I've did so far. I'd like anyone that feels like adding their thoughts or pics to feel free to do so.

I removed the flywheel with an impact, strap wrench, and flywheel tool:

Then the stator:

Variator and clutch:

Starter and carb:

Remove the cam chain tensioner:

They're kinda clever, the plunger will only move out while installed in the engine so they're self tightening on the chain, they never need adjusting:

The screw on top is there to release the plunger when you install it:

Then the rockers and cam:

A little tap tap on the workbench and the pins fall out (sorry GTI):

A two armed gear puller gets the kickstarter gear off. You can't use a three arm, it won't fit into the space:

Slide the head off:

Expose the starter clutch and oil pump:

Starter gear:

I keep saying I'm going to get a starter clutch wrench but as long as the BF screwdriver keeps working I guess I'll procrastinate. Remember, it's a reverse thread:

Oil pump:

Get the cylinder off:

Remove retaining clips and pin from piston:

Tap the case with a wood hammer and split it:

I'll post some pictures of the crank and timing chain tomorrow and start on the transmission. Rich

[Alleyoop]

EXCELLENT RICHARD!!! Beautiful pictures and shows just how to do it step by step.
Alleyoop

[terrdnf]

nice job Rich! on teardown and photos Thanks
terry

[Gti]

Those are some awesome pics, first silly question, when you remover the starter clutch, the washer on top of the thrust bearing has a fat side and a rounded side (edges). Which side makes contact with the thrust bearing.

Second question - What kind of Camera are you using?

[Random Hero]

The rounded side faces out. If you get it wrong the scooter will not turn over.

in my pic just slide the bolt on the washer and it is correct.

[sprocket]

I always mark the face of the starter clutch washer..because as Randon Hero says (and knows too well) the washer only goes on one way...

Great job Rich! When you do the rebuild can you do some closeups of the chain guide pivot points...it seems to confuse people...

[Gysixxer]

What did you use to pry the case other than the hammer?

[Random Hero]

The case should come apart fairly easy..i would not get a hammer near the cheap case.

[Bashan]

• Yep, rounded side out on the washer.
  
• I kinda shorted out on the chain guide pivot points myself. I had to look a few times to remember where the slot is. I'll sure make a point to go over that, (like the bullets?
  
• I just tapped the case a few times with the hammer and a crack appeared. Then I slipped a small block of wood into the crack and hit it a few more times...boom, it's apart. One day I'm going to run into all these nightmares like the case not coming apart, the clutch won't come off, the rocker pins won't come out...etc. But so far I've been lucky and really wouldn't know how to address those problems. Hell, even the allen nuts came out of my brake rotor!
  
• It's a Nikon Cool Pix P100:
  
  
  
  
• With my last camera I opted for a lot of manual function because I was into all sorts of close and long photography. I swore if I ever bought another camera I wanted it to do all the thinking for me, hence the P100.
  
• Here's the crank coming out, I forgot to post this one:
  
  
  
  
  
  
• Rich

[Bashan]

Here's a few views of my crank.....I think it's glad to see me :

Sorry, couldn't resist. Everything looked good on it, the bearings are nice and tight and the connecting rod is solid.

And here's the transmission tear down, once you get the cover off it basically falls apart. The bearings are pressed in and I saw no reason to pull them out, they look fine:

Now I'd like y'all's opinions on this next part. One of the reasons I tore this engine down is that it was starting to make a pronounced slap/knock noise once in a while when I hit the starter. Also the engine just doesn't have the power it once did. Take a look at the cylinder and head, there's a thick build up of carbon wherever combustion occurs:

And now maybe the slapping noise?:

Also, I think this caramelized cam chain guide might offer a little insight:

Well let me know what you think, I'm sure I'm going to have to order some parts. I also want to look at the valve seats but some bonehead borrowed my spring compressor and can't find it. I'm probably going to have to order one...sheesh. Rich

[Random Hero]

You know BumbleBee makes a slapping noise when I start her sometimes. The only way to get it started is to rotate the engine by hand a 1/2 turn. I cannot figure out what is causing it. The 63mm bbk is almost 2 yrs old and has hardly any miles on it.

I'm not trying to hijack the thread just wonder if it is related to you issue.

[sprocket]

I don't hink the chain guide is a problem, but i would replace it just for chuckles..ya..the piston has been slapping...it is a design flaw in these pistons the rings should be spaced out more to pervent the skirts from contacting the cylindar walls...get some wear on those oil rings..and the slappin' starts.

[Bashan]

May 20, 2012 11:56:12 GMT -6 sprocket said:

I don't hink the chain guide is a problem, but i would replace it just for chuckles..

I posted that pic of the guide because I think it shows the engine got overheated. The dipstick worked loose on a ride and the oil ran way low before I noticed. I'm pretty sure it roasted my oil pump. If your chain guide looks like that on tear down I'd factor overheating into parts you order.

May 19, 2012 19:10:03 GMT -6 Random Hero said:

You know BumbleBee makes a slapping noise when I start her sometimes. The only way to get it started is to rotate the engine by hand a 1/2 turn. I cannot figure out what is causing it.

May 20, 2012 11:56:12 GMT -6 sprocket said:

ya..the piston has been slapping...it is a design flaw in these pistons the rings should be spaced out more to prevent the skirts from contacting the cylindar walls...get some wear on those oil rings..and the slappin' starts.

There's your answer RH, considering what BB went through it's not surprising. I think my overheating contributed to the ring problem along with the design design flaw. So I'm going to order:

• Piston and rings
  
• Cylinder
  
• Oil pump ( they burn up with heat)
  
• Head
  

Rich

[sprocket]

And chain guides? and I would replace the cam chain too...unless it is not showing wear.

[Bashan]

I looked over the chain guides and they look good except for some discoloration. I was going to order OEM replacement parts but I was looking over Scooter Elements' new site and realized some upgrade parts wouldn't be that much more. Walter, who was very helpful and knowledgeable, suggested going to a 58.5mm cylinder and head which would not require boring the case. He also said that most guys that did this upgrade found the A12 cam worked best. The parts arrived today and are very high quality:

The cylinder kit comes with everything you need, rings, clips, wrist pin, etc.:

The head comes with some gorgeous stainless steel valves preinstalled:

The spring side has a clever PAIR port blank so I can use my old valve cover. Saved me $15.00....what the hell, I can take the wife out to lunch :

I love a nice camshaft:

I'm in the middle of remodeling my business but I'm going to try to find time to move ahead on this project. I plan on starting the reassembly this weekend. I want to use this motor to build a new scooter from the frame up. Rich