NOOB BBK Install and break in gone bad

[Roaster]

Alright guys, I'm always posting bad news and stupid questions so why not just roll all that into one post!?

Saturday night I installed the CMR 46mm/63cc bore kit from VTcycles on my SE50 Elite. It came with gaskets, cylinder, piston, piston rings, pin and clips. The install went fairly easy, we put on the old head gasket on top of the new head gasket because it seemed that the piston was to big for the stock head and needed a bit more clearance, it would seem as though this extra head gasket was a bad idea...?

I added some oil to the existing tank of gas which was roughly half a tank left. I ran threw the half tank then filled up with some more premix 75:5. I rode to work today(about a 10min. ride), taking it VERY easy and things seems to be doing outstanding! Then on lunch I decided to take it out just for a short bit. I rode it harder than the morning but still didn't think I was to hard on it, but obviously I was, because when i let myself get to a bit over 50% it started making a really loud noise like a baseball card in the spokes of a bike (obvious i know now that it was the head gasket that broke and the piston was hitting the head.) I took off the fan cover and heat shroud thinking/hoping that it was just the fan or something else rattling around, well when i started it back up it made a sound like the piston ring broke and it lost compression.

I just took off the head and cylinder to reveal a pretty nasty head gasket, a chewed up head and a battered piston.

http://www.flickr.com/photos/64291011@N ... hotostream

So now on with the stupid questions....
1) What happened!?!

2) Can any of this be saved? the cylinder seemed to be unscratched.

3) What do I need to do next to get it going again?

Thank you guys for your patients and any advice!

Thanks,
Kyle

[wiguy05]

Circlip let loose

Happens all the time when top end installs aren't fully researched and understood.

At the very least the piston and head are toast.

[turtle13]

If the piston looks good and the bore look good, check the rings, replace if necessary, check your conrod bearings and rebuild.
I think I may have a spare head around if yours is gnarled.

[Roaster]

Yeah the Head and the piston are both pretty ate up. What should I do about the gaskets? What is the proper way to set them up?

[turtle13]

Either have the head machined to the proper bore diameter or check and see if the malossi head that is being sold here is the correct diameter for the cmr kit.

[Wheelman-111]

Greetings:

The Proper way is to install your 46mm piston with a 46mm head with the correct volume..

It is possible to get away with the stock and unmodified head, but unlikely that the single 46mm gasket will provide the clearance needed to keep the piston from colliding with the 41mm gasket living .15mm above it as the revs climb and the crank and rod start to flex.

At the very least, measuring clearance at the deck should have been done.

Even then, the larger volume being compressed into a stock-sized combustion chamber must have upped your compression ratio to unsustainable levels.
I'd expect at least a trio of head gaskets to be needed. Did you measure compression before ignition?


I recommend you get the head machined properly. Toboggan did one for me a while back, and very well.

[bakaracer]

you need to get the head cut to the bore diameter or find a head already that size. as for the gasket, the gasket needs to be that same size of the bore if not the piston will hit the gasket. the pits in the gasket is also a sign that it was running really hot from to low octane gas and to high a compression and thats due to using the stock head on a bigger bore.always match the head diameter to the bore.

[turtle13]

Also make sure you properly heat cycle and break in the bore, along with proper jetting of the Carb.

[Roaster]

Great, Thank you all!

Sounds like the short answer would be to simply get the correct size head?

Thanks again for putting up with my ignorance but hopefully this post can help some in the future.

[turtle13]

Hit me up if you need any help, I'm a pretty busy guy, but if I have time I'm always down to wrench and you are really close to my house. Plus there aren't many guys in KC who know these Honda's.

[Roaster]

Thank you Turtle!