Hi everyone!

Last weekend, 2 seasons after, my JG first time loose a power. No any carb needles changes cause good changes.
I am open it and found (with another, normal use, no serious problems) a small groove in exhaust bridge.

So, I ask the professional engine service with honing machine, and I've got a good result. (lower photo)

Small, visual checked groove is stay.

Please any comments, yours ideas, how long it will life?

Before honing:

And.... after:

That issue is one of the weak points in an engine design using a BIG exhaust port. The Bridge is there to keep the piston ring in the groove as it travels across the face of the exhaust port opening.
The bridge is subjected too direct heat of the out flowing exhaust gas's and gets MUCH hotter than the surrounding area. This HEAT cause the bridge to expand inward slightly against the piston.
Now ring pressure is greater on the bridge causing it to wear like you have. ** Likely reason for the power loss is NOT the bridge wear, but a groove worn into the sealing face of the ring at bridge contact area. This groove on ring face no longer seals against the bore of cylinder above the exhaust port once it closes.

Your hone job and a new ring should be just fine and provide years more of running. :dance2:

While you have it torn down, IF you like to do any mods on engines ? .... can show you some porting tricks for more power.

Just post if you are wanting to modify it while your at it :?

Hello Scott,

I also have a J&G motor and would like to know how to do some mods on it. Could you please provide me the info to do so?

Thanks,

Rhett

my big thanks,

it sounds well for me, I will be glad for using a repare engine without next modifications.
I saw before a Quick Draw heads with interesting undercutting, in the corners also, I have no enough bravery to do same )

I sure, our guys will be happy to see for know modifications!
Never say "no" ))

... what about I keep a silence, - about my situation of lost power -
typical way - the piston pressed a ring inside of groove and held it, after opening I found it..


once again, thanks!

OK guys,

This is going to be simple, so it will be best to have you J&G top end in hand so you can SEE what is different.

#1 widen the intake side transfer windows on liner @ .100" more.
* Scribe the new width into the cylinder and then blend it in.

#2 cut down divider bridge on cylinder @ 3/8" and resharpen as shown.

#3 square up the edges on exhaust side transfer passage on cylinder ( done to a 3/8" depth like bridge cut )

#4 sharpen up the bottom edge of liner at transfer passage cut away.

#5 blend in the bottom edge of transfer windows on liner as shown.

#6 tack in place a NEW gasket on cylinder base, trim the outside edge of transfer passages to edge of gasket. * Be careful NOT TOO go any farther than gaskets edge !

#7 View photos, copy :dance2:

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