Engine Trouble Whats this noise? (Video) 66CC 2 Stroke

[66CC2019]

Hi!, I have a newer build currently at 104 miles, running 30:1 full synthetic. Its a CDH 66CC with high compression head, copper head gasket, upgraded C Clip CW10, and upgraded open port jug running a NGK B7HS. I have one gasket on bottom of jug. This thing rips all the way to 37 MPH with a ton of low end torque, there is no need to red line it.... BUT. for the last couple days when starting cold, i heard this sound like air escaping from some where but would go away after a few secs, and would always start, until i was really ripping on it when warm, it started making this sound again, but this time it stalled out, and gave the feeling of low compression. I thought the rings or piston were shot, took all apart, and everything is like new tight, clean, with no abnormal wear. The only thing that seemed questionable, was the one or two of the head bolts are slightly stripped because of the acorn nuts. But i was able to tighten them down enough, and the sound went away. Does this sound like a lose head because the bolts are not holding enough tension?

As of right now, they are semi tight, and it runs perfect, and i did not see any damage to engine, piston, rings, or jug...

Am i over thinking this? I am going to upgrade nuts today.

Thanks!!

 

[Chainlube]

Those acorn nuts are not very good, half the time they bottom out before they ever get the head tight. I always bin those and replace with good ones. Take your head off, mark the gasket area with a sharpie and lightly sand the sharpie marks off on a piece off on a sheet of 329 grit sandpaper on a piece of glass. This will tell you if the head warped from loose nuts. Sand it a bit and examine, see if the marks are coming off evenly. If you see any kind of high spots, sand until flat, and then check the top of the jug.
Put the head on the sandpaper and sand a few strokes then turn 1/4 turn and repeat, etc..

 

[66CC2019]

Thanks!, Will do today, and update

 

[Chainlube]

Thanks!, Will do today, and update

That should say 320 grit sandpaper. Just go slow and keep the head flat, you're just checking it. not trying for any added performance.

Do you have a new head gasket? Examine the old one, and see if it has an impression on one side and not the other. That is a sure sign on uneven torque.

 

[DAMIEN1307]

Am i over thinking this? I am going to upgrade nuts today.

Those acorn nuts are not very good, half the time they bottom out before they ever get the head tight.

Be sure to use a torque wrench when retightening the head if your mechanical knowledge is limited...The proper torque on those head bolts/nuts is only 12 ft pds...If your using an inch pds wrench, that translates to 144 inch pds...That should hopefully prevent any more damage/loseness to studs/nuts due to over torque/tightening...DAMIEN

 

[Wrench]

Best to use an Inch lb torque wrench. A ft lb torque wrench can over torque when it's @ 12 ft lbs
That's why we have inch lb torque wrenches, to be accurate
Inch lb torque wrenches usually only go up to 20 ft lbs = 240 inch lbs

An inch lb torque wrench usually cost 4 times as much or more than a ft lb torque wrench

 

[DAMIEN1307]

An inch lb torque wrench usually cost 4 times as much or more than a ft lb torque wrench

Might be cheapest if bought from "Harbour Freight:...DAMIEN

 

[wan37]

I got a inch pound one . I purchased it at Harbor Freight but I’ve had mine 8 or so years it was cheaper than the foot pounds ones.

 

[Wrench]

I bought Craftsman inch lb torque wrench But my Ft lb torque wrench is a $20 Pittsburg and yea the Craftsman costs 4 times as much.
But it is a beautiful tool

 

[66CC2019]

Thanks for the replies to update problem fixed and put over 90 miles on new headbolts and lightly sanded head.