Re: Moby porting

Do not use that intake gasket, cork will fail on you. Tried it, left me stranded. The vibrations crushes the cork and it will leak on you. The exhaust is weird, no reason to dremel it out like that cause the exhaust ring will cover that part up anyways. Otherwise looks good. The back of the head may hit the top heat fin on the cylinder, maybe, maybe not. Depends on stuff. Let us know how it goes.

Re: Moby porting

Just finished dremeling the stick intake.

I may buy an aftermarket intake if I do go with a dellorto, but for now I'm just seeing what I can do with all stock parts.

Re: Moby porting

Edit: "stock intake"

Also, quick question before I leave for work:

How the hell do I get this damn piston into this damn cylinder?!

Anyone care to share any special tips before I break something... or start bleeding.

Re: Moby porting

well I found out why I couldn't get my piston into my cylinder...

My piston rings weren't lined up!

Unfortunately, I only discovered that there's a little peg that lines the rings up AFTER I broke a ring...


Looks like assembly will have to wait until my new ring set comes in from 1977.

Re: Moby porting

I saw that coming. Don't force it, when it's lined up right it will slide right in.

Moby starting issues

alright, so I've got my bike all back together.

Spark = strong

Compression = Loads

Fuel = Yes

Starts = Nope

what gives?!?!

I'm guessing I may have a timing issue...?

How do I go about setting the timing on this beast?

Any Ideas on what else it could be?

I pedaled my ass off and didn't get so much as a sputter.

Re: Moby starting issues

Hey, posted over in your other thread in repair, but if you read this one first... how old is your belt? worn drive belts cause a LOT of Moby starting problems... I know I've had plenty. Even if it doesn't look too worn, you might as well try a new belt, because you'll need it at a later date anyway...

Re: Moby starting issues

Does the motor actually turn over when you pedal? If not, you have a bad belt or a bad starter clutch.

Re: Moby starting issues

yes the motor turns over, hence the strong spark and good compression.

The only thing I can think of is a timing issue. I know when I changed the ports, it changes the intake and exhaust timing, but do I have to adjust the timing of the spark to compensate or something?

Re: Moby starting issues

Just trying to get a stock av7 up and running, I had all 3 compression(150psi) spark and fuel + a new b5hs plus.. but it would not start up/fire or anything just had run about 3-months prior so the timing being off didn't make sense to me.

I closed down the spark plug gap because it seemed like the spark was getting blown out, and I got it to fire. I havent gone back to that engine since so it hasn't started yet...but maybe take a look at that..That plug is set with >.020" gap.

Re: Moby starting issues

Damn It, I'm an idiot.

Okay, so I lied before. My compression was shit.

As it turns out, I mistook the piston touching the base of the head ever-so-slightly as compression. I only noticed this when the "compression" was still good with the spark plug out.

So i threw a gasket on that bitch. compression out the yin-yang.

I got it started with a little starter fluid... but then nothing...

It only runs for like 2 seconds on the blast of ether.

So now onto troubleshooting carb issues I guess... (suggestions welcome)

While it "ran" it was at full blast, which troubles me because it leads me to believe I the source of my original intake leak either wasn't where I thought is was, or I still didn't seal it well enough... that or I'm running super-ultra lean, which is hopefully the cause because as of right now, my carb is completely stock.

Re: Moby starting issues

Split the case, replace the oil seals and bearings, seal it back together with yamabond and use new fiber based gasket material for the base gasket and intake gasket and a metal head gasket. Air leak solved.

Are you using a 15:15 sha? what jet? 58?

Re: Moby starting issues

Stock carb= gurtner.

currently on the hunt for a 14:12 sha

Re: Moby starting issues

make sure your throttle closes all the way

Re: Moby starting issues



I took the engine all apart to check and see why I wasn't getting any fuel last week. As it turned out, I applied WAY too much form-a-gasket, and it blocked off my transfer ports!

So I got that all scrapped off and applied a nice thin layer of Toyota's finest gasket in a tube.

The engine is all back together, and I tried to start her.... still nothing.

God damn.

I've got spark, compression, gas, and all that jazz.

It's got me pretty discouraged. two minutes ago I was in the middle of typing out a FS add in the buy sell, but no... I don't want to give up just yet. I'd really like to get this thing running.

My dad thinks that because of the boost in compression, and it being a 2-stroke that it will need to get to really high rpms before it will start. I pedaled my ass off (again) but it doesn't seem to be enough. He offered to give me a tow behind the car, but I just can't believe that the rpms would need to be so high that I can't even pedal start it.

I know there has to be some magical-motobecane-modding-guru out there that know what the hell the trick to getting this thing running.


Re: Moby starting issues

you sure the timing is dead on? it wont start on fluid at all? seeing as the thing has all new seals, and apparently strong spark, thats all i can think of.

Re: Moby starting issues

Are you using the decompresison valve when you pedal? That should negate the added compression due to the milled head and get the motor to turn over better.

And again, are you 100% freaking sure the motor itself is turning over, are your lights lighting up and can you see the flywheel spinning over and does it sound like the motor is turning over (it's pretty loud on a stock pipe even without combustion).

How does the spark plug look, it better be new, after all of that? Is the diode spark arm thing wet with gas? If not, you have a fuel flow issue. Does it look still brand new? It probably should since it is not combusting anything in the motor to discolor it.

Is the gap between the arm and the diode to great? Check that by lessening it, tap it against the ground once or twice, it that doesn't work, try it again a few times to be sure.

Set the timing again and then repeat above if all else fails.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account