6,5hp Clone block crack, help...

[jada555]

So today I was riding my trike on a field. While riding slowly back to the car it suddenly stopped.
After inspecting the engine I saw a huge crack on the block.
Anybody got any ideas on why this happened?

Modifications I've done.

Milled head 0.080.
Ported and polished head.
Flat top piston.
18lb valve springs.
Original Honda alu flywheel.
Jetted carb and gx140 emulsion pipe.
Straight exhaust.
1,3:1 rocker arms.

Ps. Sorry for my English, I'm Norwegian...

 

[Bonanza BC1300]

I feel your pain!

Appears to be the result of an internal failure of an over stressed part .... Looks like you took it apart, did you see the cause of failure?

 

[Moedog07]

I wonder if the crank hit the governor arm while rotating?

 

[jada555]

wow

Thanks for the quick replies.
I could not see any sign's as too why this happened.
The governor is removed except the arm. And it's not bent or got any marks on it so I don't think its that.
All the parts look fine, no marks at anything.

Oh well... Need a new crankcase now..

But got a bargain on www finn no (our answer to Craigslist)
A gx160 with 2:1 transmission on it for about 85 of your American dollars

 

[lawn-boy biker]

Have witnessed this kind of damage a handful of times.

Appears to be the result of an internal failure

I would not have assumed that.
Please articulate.

 

[jada555]

So what do you reckon did this? Did I mount it wrong in any way?
Is it safe to buy a new clone case? Or should I buy a Honda one?

 

[David wulf]

I'am pretty sure that gov arm got hit by the crank at speed . My brother did the same thing with predator didn't take out the arm and it hit the crank, but did it at start up so it just cut the motor off . When I took the side cover off the arm and crank jammed together . Did no damage but he was lucky .
Take the arm out on the next motor cause it will happen again .

 

[David wulf]

Oh a Honda block is stronger but you did not have enough motor to blow the jug off it . Get rid of that arm !!!!!!!!

 

[Prowler08]

Milling the head .080 and a flat top piston bumps the compression enough that it is not if the block will split but when the block will split...

We have split enough blocks just running a box stock class...
If you look where it split you will notice that it is VERY thin there...

 

[jada555]

There is no mark on the arm, and I use the top part for throttle linkage. With a spring on it.
I would think there would be some signs of the crank hitting the arm, either on the arm or on the crank. Or?
But point taken, the arm will be removed in next block.


From the charts I've looked at my compression was about 12:1 is that too much?

 

[cheezy1]

No billet rod?

 

[Prowler08]

After a while it is... A engine that was designed to run 3600rpm, at 8-1 comp. Going to 12-1 expotentally creates more force on every part of the engine...
I blew 2 jugs off last year running, one Honda and one clone 12.5-1 comp ratio, my dad ran all year with no failures... Some hold up some don't...

 

[jada555]

On it's way. Along with a new cam.

 

[jada555]

After a while it is... A engine that was designed to run 3600rpm, at 8-1 comp. Going to 12-1 expotentally creates more force on every part of the engine...
I blew 2 jugs off last year running, one Honda and one clone 12.5-1 comp ratio, my dad ran all year with no failures... Some hold up some don't...

So what comp.ratoi is safe?

What should I do with the gx160 I bought.
Port job, governor removal, straight exhaust and 18lb springs?

What comp.ratio is a gx160, and what ratio can it handle?

I have a new flat top piston, should I use it?

 

[ole4]

While I would think the arm hitting the crank would show more damage to the arm it appears that it was not the jug trying to come off but something right where the arm is that pushed up as the crack is largest right next to the arm. If the arm was held out of the way of the crank then there is no way it could have hit the crank but if that arm could move enough to hit crank I would expect the damage to look just like yours. In the future remove that arm if you are taking out the governor.

 

[jada555]

Okay, seems like the governor arm was the problem then.

It will be removed in my new engine,
Which just got delivered to me at work now
Not a gx160 but a Honda gx200!

Are all clone and Honda part interchangeable?
What mods are safe?

 

[David wulf]

Do you have a real HONDA piece or clone . The clone parts will work in the Honda . If you have a real Honda then they are the best to start with . And what OLE said about where the block broke , that why I know your crank hit the arm . You are so far from having enough motor to break the block . It take a lot of power and RPM's to do that .

 

[cheezy1]

Okay, seems like the governor arm was the problem then.

It will be removed in my new engine,
Which just got delivered to me at work now ��
Not a gx160 but a Honda gx200!

Are all clone and Honda part interchangeable?
What mods are safe?

Billet rod...and remove all traces of governor while you have the case apart and plug the holes. Don't be a half @ss.......

 

[jada555]

Billet rod...and remove all traces of governor while you have the case apart and plug the holes. Don't be a half @ss.......

Billet rod is on it`s way. hopefully this week.

I`ll remove the arm completely.
I will have to remove the head, shold i use the head i have milled and ported? or just port the honda head, and no milling.
I have a spare flat top piston, use or not?

If I want parts I have to order from US or UK.
Costly shipping and takes what feels like forever to arrive...

What cam should i go for? I see the CL1\2 are cheep, what do they do?
They only shipped in US, so I have to order a new one another place.
I want torque and HP, but I guess I will have to choose one or the other..?

 

[cheezy1]

There are a lot of variables when building a motor. For instance...bike, gearing, your weight, what you are using it for...etc.
And as far as ordering parts...it is simpler to find one place and try to order everything you need at once to save on shipping and waiting on parts.
The head....depends on what CC each one is. And the milling and work are something you need to figure out once you have the piston in the hole and can measure a few key things for clearance. But the Honda is a better casting and can take more abuse. The flat top is the piston to use also.
As far as the best "bang" for your buck cam..Black Mamba Cam & 26LB Springs
That seems to be a nice middle of the road cam that develops nice power and isn't too crazy. The CL1/2 cams are nice for a almost stock motor or small build. They are basically the same lift..just more duration that causes the valves to be open longer and in return more fuel and air into cylinder.
I am sure there will be tons of opinions on this matter....so you will have a few options I am sure.