cracked head

[Yolandi]

bike has been feeling like its been loseing a little bit of power each day for the last 5 days, and occationally could see puffs of black smoke coming out around the exhaust gasket on high revs, assumed it was the head gasket had gone at one point so pulled it off to change, found the head has cracked in a Y shape around the plug area!
does anyone know why this has happened? every time i start it up i leave it to idle until the throttle responce is crisp, it has been extreamly cold the last 2 weeks here (maybe the engine going from minus temps to hot fairly quickly then to cold again each day?)
im using a 20:1 ratio oil at the moment, (50ml oil to 1000ml petrol)

 

[crassius]

certainly looks like a crack - possibly a factory defect from the tool cutting plug threads - could be from not torquing in 'X' pattern, or uneven torque on some nuts, but I'm really leaning toward born dead at factory

 

[Steve Best]

I've had a center plug head go like this.
It was fine. I installed it carefully with proper torque, but with more compression than stock.
Cylinder was broken in so this was a test of center plug head only. Drove 5 kms warming it up.
Hit a pretty steep long hill, it made it half way up working well and then loss of power, characteristic noise.
Limped home under power. Headgasket blown and several cracks.

These heads are thin and made of brittle cast. Improper torque, heat or compression overload will crack them.

These engines are well engineered to *just* strong enough. Push them and find the weak spots.

Steve

 

[Deleted member 12676]

overheating due to excessive spark advance and loss of compression at head gasket

 

[inspectorcritic]

Well, looks like you got the right fuel mixture chocolate brown if I ever get mine running again going slide needle don a notch.

 

[inspectorcritic]

Look at mine ported cylinder broken chip at the port cost me time and money only one place I know that sales gasbikes the place I hate I don't know if I can buy a standar 66cc cylinder and just use that will it work?

 

[crassius]

got one badly machined like that from factory - they sent me a new one - gave old one to a homeless vet with some small files and a dremel - couple hours working at a small table at my shop & he had a nice cylinder for a dead motor he had (rings rarely reach to bottom of transfer ports with most of the port mappings used in these)

 

[Gio]

Yep I've got a cracked head on mine too only been using it for a day.tried some milliput on it.but don't think it will hold ..let's hope they send a new head..

 

[inspectorcritic]

You may be in luck you may have it on warrantee send it back or snap some pics tell em no need for you to use your garbage can I got one here can save money on shipping returns.
Got another heart ach on mine Gasbike I could'nt beeelieve sent me a cylinder it was defective had a bore flange broke off put it in hoping the goddamn thing would fire, put,put,puff nothing wellI said s**t one last ditch I will take it to pros have them look at it for a price quote from Motor Sports their speicalty wait 2 f***ing weeks for them to look at it the mechanica had a familyt break up he had to go to Los Vegas his wife was being a whore to support the kids I finaly walk back pick it up bastard damage my clutch relay at the handle bars and damage my kickstand and something else, so I thought f*** all the problems I'll just buy anothe motor stop wasting time and money well finaly got in this weekend took my motor off turn it and s**t water ran out of the exhaust port I turn it on its side more water during all the time maybe 3 months of waiting hoping for a cure I left it outside there had been several snowstorms I have a CNC carb has an open airfilter all those storms drip into it flood carb I thought when I took out the plug look at a drop on the electrode s**t dosent look like gas looks like water ....! but how when it first went down I pulled the cylinder off turn it upside down a few drops of oil ...? Well I put the cylinder on after it had sat out side now Im piss in more agony I went out spent over hundred bucks waited weeks all I had to do is turn the motor over drain and dry the water be ready to ride and I was very careful on being a good mechanic make sure got the system right but never once came over any article it could have water in carb and crankcase or there might have been a mention and so I drain my gas tank made sure I replce with good fuel. So I got another goddamn anchortoo many big expensive parts but I like the GT80 it had more accelearation power could pull a load I got a Flying Horse from Spooky Tooth it smoth not broken in only got 15 miles on it but feels like a little girls love bike the other was tuff so I got 2 motors got to part with one want to keep both but other problems maybe I'll build a bike try to sell it to a DUI lawyer first fall out of the nest for thousand bucks so the guy can ride keep his, oh s**t the dynamic agony i have gone through never ends. Have a good day.

 

[KCvale]

oh sh*t the dynamic agony i have gone through never ends.

Ya, kind of like that huge paragraph you posted.
Did you know that you can hit Enter in your posts to give to some breaks?
It is very helpful for those reading as I didn't even try to read your post.

Just a tip ;-}