Merc250

All I have had out of the now 2 SH engines i have had is trouble. I broke the first one in a tad bit hasty, and that brought its demise. The new engine i broke in as per the manual stated. 5 tanks, progressively faster throttle as you go along. Now, half a gallon of fuel later( Counting break-in), my pinch is gone AGAIN!!! What gives???

alvinl

You sure it doesn't just need to be tuned? How are you determining the pinch is gone? I have an SH .28 Prospec P6 in my Savage and it's been great for about 3 years and 2 gallons of fuel. SH motors do like to be run a little rich and will die quickly if you lean them out too much.

Merc250

I am basing my information that the pinch is gone off of the fact that i can pick the truck up by the pullstart and the compression won't hold up the truck. it flies to the end of the cord. That, and the fact that while running it today, i had 3 flame outs. After these, the motor was very hard to restart. Had to let it cool down in order to start it again. I brought in my kit, and then pulled the head. ZERO resistance at the top of the piston stroke! I took the motor apart when it arrived to insure no metal shavings were left from manufacturing and to seal it with RTV. The piston actually pushed the sleeve up out of the block, but not anymore.

 I hate that i am having so much trouble out of these motors...

catbob007

I got a Carb on my new Sh18 that was none like i have ever seen the high was 2 turns out and the low was 4 turns out and it would not start and when it did it would race so fast i thought it would explode in my face and pinching was not an option on my first tank of fuel durring break in. so i plugged the exhaust to kill the engine. being carefull not to burn myself. Finally i compared needles from an oldcarb, and the low was around 4mm longer so i put in an old needle and it worked fine 21/2turns outfrom in all theway low and 3 turns out on the high needle from gently turned in. and for me?When all is said and done the low is around 1 1/2 out and the high is around 2 3/4 out and i like mine rich fore Arizona desert 110 deg operating at around 165 when it stops to shoot it at an idle idle around 135 deg, an infared temp gun is a nesessity for me when the ambient temp fluctuates 50 deg every run is a reseting of the needles day to day. I hope this helped check out my up grade ideas in use as we speak www.catbob07.rcuniverse.com

lords

only way you loose pinch is when there is excessive heat...(to lean or long full throttle runs while still tuning)..
only other is the build of different cylinder makers,and the odds of that are slim but happens...
also some differ about this after each run leave the piston at the bottom....
I have about 10 good years on buying and rebuilding any engine on this....

Mickstix

Sure sounds like it's running too lean (hot) Merc? Do ya have a temp gun you can use, to make sure it's not too lean, when ya get it dialed in? There's probably not much you can do for your current engine, but maybe on the next one? I burned one up (my 1st) by running it w/o the filter hooked up, and w/o a temp gauge.. I thought the tune was el'perfecto, but now that I have a temp gun, I know I had it way too lean as well.. They sure run good that way, but dont last very long.. Good luck with your next one! (Call Kurt at URCHobby, he'll prolly be able to hook you up with a new SH.18 for a decent price!)

lords

or just grab a piston and cylinder for it
$45 something bucks....

Jgilk1

if you got 5 tanks through it see what the manual says about head shims i know some have the head shimmed higher for the break in then you have to remove 1 or so to redo your squish

should have 2 .20 shims pull 1 and check your squish again (other wise it sounds like you burned up a piston and sleeve yet again temperature is a killer)