Reversed jug AMF

[moonerdizzle]

finally got around to working on the AMF and decided it was time to do a build thread on it. I ordered a brand new motor from BGF, and i was really surprised with the quality of this motor, no bolt on weights on the crank, the wrist pin bearing was much wider than the old ones. Right away after I got my kit i tore it down and split the cases to put in some higher quality crank bearings. while the case was split i also did some work on the transfer ports to run a reversed jug. The jug has been ported out and has reworked transfers.

And yes, this intake is totally stock, port matched from the factory

 

[moonerdizzle]

I lapped the head and polished the compustion chamber then I had it Hard coated, dont know if this will help anything, but its not going to hurt anything, and I dont have to worry about paint chipping or burning off.

 

[moonerdizzle]

Engine together and mounted in the frame, still need to do the exhaust and replace the kits plug wire, and put the throttle in. And chain and sprocket, I keep putting that off because im debating on buying a shift kit. Ill get it figured out here sometime lol.

sorry about the blurry pictures, but i only had one cup of coffee and its super early for me.

 

[Venice Motor Bikes]

That head looks like one of those high compression cheesy castings... Be careful not to torque it too much or you will easily have a leaking head gasket.
I've had a few of those, & they usually end up leaking because the head warps.

Also... If the engine starts 'knocking' when it gets hot?, add a extra head gasket to lower the compression.

 

[moonerdizzle]

I don't have any problems with knocking, because I run CAM2. Not for the insanely high octane, but for the lead. Smokers live much longer on a leaded diet. And I haven't had a problem with the heads leaking due to warping, only time it was because of the ring around it, but I lapp them off now.

 

[moonerdizzle]

side note, I use a inch pound torque wrench to tighten my heads. three passes to get to the final torque specs. I then check it after the first ride, and again a week later. after that it is usually good to go and i dont have to worry about it till i pull the jug to clean the carbon and varnish deposits

 

[Venice Motor Bikes]

sounds like you've got it covered.

 

[moonerdizzle]

I try to cover all my bases, but these little motors always have a few gremlins in them.

 

[Venice Motor Bikes]

these little motors always have a few gremlins in them.

Yes they do!!

It still boggles my mind how two exact same engines can perform so totally different from each other?!?!

 

[moonerdizzle]

Finally got her all buttoned up and took her for a proper break in ride.



the intake sound is amazing sounding when your riding it.

 

[moonerdizzle]

forgot to post pics of the wrist pin bearing, it is much wider than an old bearing i had from an old kit

a proper fit on the conrod

old style on the left, new one on the right.

 

[Mr. OrangeConeRacing]

Any new updates?

 

[moonerdizzle]

Not yet, I am still breaking her in, havent had too many decent riding days, so shes only got maybe 15 miles on it. She runs pretty good tho.

 

[maniac57]

I don't have any problems with knocking, because I run CAM2. Not for the insanely high octane, but for the lead. Smokers live much longer on a leaded diet. And I haven't had a problem with the heads leaking due to warping, only time it was because of the ring around it, but I lapp them off now.

It's not the lead, it's the better formula.
Lead has no real effect on two-strokes
Any gas with lead has a different formula than the cr*& they sell as premium these days.
Any aftermarket fuel with lead is by definition, race fuel.

 

[maniac57]

Not yet, I am still breaking her in, havent had too many decent riding days, so shes only got maybe 15 miles on it. She runs pretty good tho.

Keep us posted, I'm following this thread closely because I want to do this mod myself...it's just too cool looking.

 

[moonerdizzle]

It's not the lead, it's the better formula.
Lead has no real effect on two-strokes
Any gas with lead has a different formula than the cr*& they sell as premium these days.
Any aftermarket fuel with lead is by definition, race fuel.

yamaha? (i believe, its been a while since i read the studies) did studies and it showed that in motors that used leaded fuel the big end con rod bearing lasted twice as long as with out lead, lead is a very good lubricant, and smokers live because of lubrication.

 

[moonerdizzle]

Keep us posted, I'm following this thread closely because I want to do this mod myself...it's just too cool looking.

Will do, this motor has less than half a gallon of fuel threw her, but today on her ride she has alot of low end grunt compaired to my old motors during break in. may be just the motor, i dont know yet, still a bit early, but shes running damn good.

 

[Legwon]

did u put the piston in correctly according to the jug also? or the opposite way?
im thinking about doing this on my next build.. should (by all rights) get more air flow and better mileage.. right?

 

[Mr. OrangeConeRacing]

did u put the piston in correctly according to the jug also? or the opposite way?
im thinking about doing this on my next build.. should (by all rights) get more air flow and better mileage.. right?

If you turn arround the jug, you also have to turn around the piston. I am debating spinning the head around also as I am replacing the jug and piston anyway.

Now its a waiting game for my new parts so I can get on the road again.

 

[moonerdizzle]

correct, you have to rotate the piston with the jug, if you dont you will snag a ring on the exhaust port. also, keep in mind if you reverse the jug you will have to do substantial porting to the case and jug to make the transfer ports line up