GM90 Head and Piston

[veggie]

For anyone interested, I removed the head on my GM90 today.

Two points of interest for anyone considering burning alternative fuels.

1] The Aluminum piston has 5 rings. 3 compression rings and 2 oil scraper rings.

2] The engine is a direct injection head but the injector seems to be a single hole pintle type.
   Can anyone confirm this from the pictures?

veggie

[veggie]

Here's a better shot of the injector...

[mobile_bob]

look very closely at the injector near the tip, i can't tell from my netbook pic
but i think you will find there are 5 tiny little holes coming  out of the tip at a bit of an angle

i think i can just barely make out two of them in the pic, just a bit up from the very tip

they will be very small indeed

bob g

[billswan]

Guys

The setup looks much like my 16/1 metro and that injector has 3 holes.

Pull the injector and reconnect it to the high pressure line roll the motor over and look see what kind of pattern you have. Don't get to close to the spray use caution the fine mist can even be breathed in.

Your piston pix if you look close I believe shows 3 darker spots, take a rag wet with some type of solvent and wipe out the piston cup the spots where the injector mist hit will be much harder to clean and you will then know how many holes you have in the tip without doing what I mentioned above.

Now back to polluting this thread with what I notice as differences to MY 16/1

I see the valves look to be above or flush with the heads face, on my 16/1 they are .057 inch below heads surface. I also notice the valve to piston clearance is cut into the face of the piston the 16/1 has no cuts in the piston like veggie's gm-90.

Veggie is the bore and stroke the same as a regular 6/1 roid.

How about the gaskets are they all different or will some interchange with regular 6/1's

Billswan
PS if you want me to edit out my off topic comments just let me know I will be glad to pull them

[billswan]

Veggie

More questions gm90 is that a model or a brand?

If it is a not a brand then who builds them?

I went to your pix of these engines on your web site and the head design is interesting in how the injector is placed.

I see they are rated 8 hp, what speed will you run the one you are having bearing problems with?

Billswan

[playdiesel]

To my memory that piston, injector and cylinder head layout are very similar to the parts in my 6/1 direct injection Metro. Would be interesting to have the parts side by side and in hand as I had wondered about spares down the road? Bothered me enough that I had purchased a set of IDI or "normal"? 6/1 parts for future overhauls, head, piston, injector etc.

[playdiesel]

Sorry to pull this thread off topic a bit but  some pics from an old post of mine when I went through my engine, Hmmm very similar partys used, maybe same?? What yall think?
Piston?

Bare head?

General layout, what do you think Veg? same parts or no?

[veggie]

Veggie

More questions gm90 is that a model or a brand?

If it is a not a brand then who builds them?

I went to your pix of these engines on your web site and the head design is interesting in how the injector is placed.

I see they are rated 8 hp, what speed will you run the one you are having bearing problems with?

Billswan

Hi Billswan,

- GM90 is a model number. However a few makers are buying the parts from the original mfr. and still calling them a GM90.
Lovson calls it an LG90. Imex calls it a GM90

- The head is direct injection and seems to be designed just for the GM90.
It has two ports for water outlets so you can discharge from the side or the back of the engine.
I am using one of the ports as a temp. sensor location.

- Cylinder is the same bore as a 6/1 but the stroke is a bit less.

- The engine is rated at 8HP / 900rpm,  6HP / 700 rpm,  and I am running it at 5HP / 650 rpm.

veggie

[veggie]

Hi Playdiesel,

"General layout, what do you think Veg? same parts or no?"

No, they are different.
Your head has two bolts within the valve chamber and two outside the valve chamber.
The GM90 has all 4 bolts inside the valve chamber. (Completely different casting)

veggie

[bschwartz]

You people with clean shiny engines make me sick.... 

[d34]

Keep the GM-90 info coming.  I'm sure I will need to reference it in the future. 

[flywheel]

You people with clean shiny engines make me sick.... 

You probably won't like my Perkins then!   
                                                                     flywheel