200x blown head gasket?

[hippyplz]

I pop the head gasket trikefest this year and just now getting around to tearing it apart. There was only about 30 minutes on the top end. I was a little surprised when I tore it apart and seeing how bad the gasket was. So I guess my question is why would it blow out like that?

[shortline10]

Very common problem back in the day for 200x race bikes , that's why we only ran copper head gaskets .



I pop the head gasket trikefest this year and just now getting around to tearing it apart. There was only about 30 minutes on the top end. I was a little surprised when I tore it apart and seeing how bad the gasket was. So I guess my question is why would it blow out like that?

[hippyplz]

Do you still have any of those up for sale mike? Also someone suggested I use the copper spray, has anyone had any luck using it before?

[shortline10]

No I don't have any right now. The copper spray is more for metal type head gaskets or I've used it on the liquid 25
0r when they have seepage issues lol.

[oscarmayer]

what are the specs of the engine? (bore, stroke, compression, piston manufacture)
did you run any sort of race fuel? what octane?
did you properly torque the nuts on the studs?(what turque did you use) are studs stock or aftermarket?
did you properly deck the head and jug to ensure perfect flatness?

i'm asking these questions because any number of things can cause this.
simple improper torqueing (in my expirneces when runnign performance stuff, i will torque the head to specs, loosen and redo the torque 3-4 times w/o ever removign the head. this ensures proper seating of the HG to the top of the jug and the head itself. if stuck a performance piston in w/o properly "preping it" you could have gotten hot spots on it and it pre-detonated causing the HG to blow out. not using proper level of octaned fuel (higher compression needs higher octane fuels, and so di stroker kits and larger bores stock is 65mm. anything more than 67mm should move to a minimum of super unleaded. if you run a 12:1 piston and bored to 67mm, you need more than 93. minimum in my expirneces is 100+ for stable and solid operation w/o detonations and pinging)
did you set timign right? mis-firing can detonate and cause HG to blow out.

as mentgioned there are tons of reasons for this. it is not just cut and dry. post up as many details ands you can and let's go from there.

[hippyplz]

Alright let me give ya a little back story on the motor. It has a Wiseco10½-1 66.5 piston, xr cylinder, shortline ported head, bapp hd valve springs, xr cam and carb. Pretty mild set up, but runs out really good. Anyway the kicker gear broke on the motor and there was some carnage on the case around the sprocket. While looking for some replacement cases I ended up picking up a part bikes with a good bottom end. Pulled my top end, ran a quick hone with some new ring and put it back together. I used new cometic gaskets, torqued to 21lbs but my wrenches has not be recalibrated quite a few years. Guess that's something I'll look into doing. it seems to be running really good but it literally only ran five minutes for going on the trailer. Ran a heat cycle on it while it was sitting on the trailer the next morning and another one when we got to haspin. I probably rode it about 15 minutes for it blew.

[oscarmayer]

did you prep the piston before install? if not then the issue was probebly a hot spot caused detonation. (unless you tried to torque the head with the timing chain on the cam gear.)

[hippyplz]

I set the ring gap but didn't do anything to the piston other than that. The cam was installed, but the chain or gear wasn't on. Just got of the phone with cometic and they have the gasket in copper so i am going to give that a try. I could go ahead and drop the head and cylinder off at the machine shop to check for flatness.

[oscarmayer]

yea have the jug and head checked.
it sounds liek you have pre-detonation. take the piston out. then get some sand paper and a small half moon file. file off any sharp edged around the piston top and the valve cut outs, then take like 600 grit and sand the top and remover any shinny machining marks. so it should look silky and smooth and rounded edges with no sharp corners. this will keep that from happenning.
also ensure your timing is set correctly if your using aftermarket timing gears or CDI units.
i would also recommend a minimum of 93 octane fuel and maybe even 100 if your running extremely agressive parts.
good luck with your build and i'm sure you'll get it taken care of. I myself probelby would not use a copper. on lky 12:1 200x i use a a xr100 HG. same bolt pattern and bore as 200x but thin metal from honda. (confirm the xr100 HG. as it has been a long time since I ordered one)