Engine Blown Out!!!

Mexicano

Mexicano
I blown my cylinder during a "Street Race" last saturday...... :-(

I was racing on the street against a Gilera Runer 125....the guy didn't know what "hit" him....he never could get me...funny...he couldn't believe a fucking Vento was so fast and powerful...I was runing at 120 Kms./Hr. 8,200 Rpm's, suddenly my engine made a weird noise and shut down!!!, tried several times to make it run again...but no way to do it.....two hours later I got a pick-up truck to tow my baby back home.

Today I start checking what is wrong with my engine, spark O.K., fuel O.K., but when I checked compresion it was very low (40 P.S.I), I checked the reed cage and it was O.K., so I removed the head from the cylinder and find some small scratches at the head and piston crown...oh God!!.....removed the cylinder and piston and find this:

DSC02969.jpg


DSC02975.jpg


The piston wrist pin retainer broke and demaged the piston and cylinder:

DSC02970.jpg


Today I ordered my new cylinder and piston kit, but this time I will use Teflon Buttons instead of fucking steel retainers...as I used years ago in 4 stroke racing engines:

TeflonPinRetainers.jpg


Of course I have to modify this teflons to make them fit into my small piston but this is not an issue......the BIG TASK is that I have to modify the cylinder again to make it fit my cases and modify the piston too!!!, but you know what??, it worth the time and money just to see the other guy's face when he couldn't get me!!!!, fortunatelly he didn't see me when I was aside with my blown engine...

Do someone ever had this same problem with those reatiners???

Thanks,
 
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Never saw those king of circlips used in pistons...just the steel wire ones.
Those ones look too scary to use though..those ears that make them open/close are too big and thin to withstand a 10000rpm engine.
Try using steel wire clips without any kind of ears (those that look like a C, not the ones that look like a G).
 
different pistons are made with different grooves for the specific clips. If the groove is round then it's made for a wire, If it's squared off, one should use the expanding clip. I would not mix and match. Those clips usually work fine but they are directional. There is a sharp and a smooth edge. The sharper edge should face out. Even if you have it flipped they could work fine for most low rev applications. But it just happens sometimes when you push parts to their limits and beyond.
 
I had this problem to a few years back. No i use just the steel wire ones. One good advice, double check the area where your crankshaft is, and make sure there arn't any pieces off the broken circlip in there. If you don't such a piece can come up again and damage your piston and cilinder for the second time, happend to me also then :(

And last but not least, the opening of your circlip in the direction of the movement of your piston. Don't know if it's a myth, but i always make sure it is.
 
that is nice, you beaten up an Italian Job :D they should never under estimate the power of a Jog90 styled engine ;) what cylinder is that?
 
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Freezer said:
And last but not least, the opening of your circlip in the direction of the movement of your piston. Don't know if it's a myth, but i always make sure it is.

But the piston in my engine moves both directions, up and down! :) Sometimes sidways a bit but then the circlip is the least of my problems.
 
Guys:

I can't use the tinny round steel clips (stock) because the modification made to my piston, the piston uses a 14 m.m. pin from factory(Aerox 100c.c.) and my crank uses a 12 m.m. pin, so I modified the piston to accept an smaller pin and need a bigger circlip.

If I use a stock retainer, it just hold the small inner liner (Modification) but won't hold the pin, look at this:


DSC02619.jpg

The cylinder and piston is a 120 c.c. Malossi.
 
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That's a riot! with all the work you put into it, why not switch out to a different connecting rod so you can put the propper wrist pin and circlip in? If the piston was made for a wire clip the expanding clip probably won't hold.
 
Brookespeed:

I couldn't find a connecting rod for 14 m.m. pin and the BIG END size for my crank...believe me this has been thousand of hours of research and development!

I wish I could have an "REAL" Aerox scoot but it's not an option here.
 
Mexicano said:
Brookespeed:

I couldn't find a connecting rod for 14 m.m. pin and the BIG END size for my crank...believe me this has been thousand of hours of research and development!

I wish I could have an "REAL" Aerox scoot but it's not an option here.

or maybe rebore your conrod to fit in a 14mm if it still has a good space.. what is the lenght of your conron & what is the size of the other end?
 
Have you tried a KT100 kart engine? those have a 14mm wrist pin and a stroke even shorter by a bit. I saw a job lot of about 10 different conrods for different applications on ebay a few months back. there always seems to be spares.
 
Another issue is that I don't know what it takes to disasembly the crankshaft.....never done before...maybe no tools or facilities to do it.....
 
Mexicano said:
Another issue is that I don't know what it takes to disasembly the crankshaft.....never done before...maybe no tools or facilities to do it.....

here we can remove conrod by using Hydraulic Press Machine.. maybe you have that on your local bicycle repair shop & industrial machine shops..

you can check out SYM Jet 100cc's conrod or Kymco Topboy's conrod, both have pin14 but i'm not sure how long their rod is..
 
Mexicano said:
Emo:

Just I guess a press is needed but how to align it again in the same position? Is an special tool needed?

You have to balance it again, after the reassembly, check it with dial indicators, in a special tool.

Like this:

rebuild%20crank.jpg
 
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