Cagiva Planet Compression Ratio control

speeddevil68 · L Plate Warrior Joined: 01 Apr 2009 Karma :

Hi,

I have just bought a Planet and had to replace the cylinder and piston. The new kit came with 3 base gaskets, and the manual says to choose the correct one to maintain the correct compression ratio. The manual specifies between 61 and 63 thou for the clearance of piston to explosion chamber. I bought a comparator and with the thickest gasket i have the clearance is ~55 thou. Is this that critical, am I likely to ruin the engine if its not right?

I put the engine back together, and now I need a new starter bendix gear, so can't tell you much about the running condition, but I did get it started before the gear gave up.

Thanks for any advice in advance.

MaybeGuy · Super Spammer Joined: 12 Mar 2007 Karma :

bump start it

also, do a compression test. should be about 140psi give or take a few after a rebuild.

i dont think it will do any damage either way, you'll just notice the performance difference maybe if theres too little compression.
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!! Mr. Green

Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

speeddevil68 · L Plate Warrior Joined: 01 Apr 2009 Karma :

I dont have my CBT yet, I am a late starter.

The compression is 150 PSI, as it will be higher with a smaller clearance from piston to chamber top. I do have the option to double up gaskets to lower the compression, but i would have to dismantle the whole top end again Evil or Very Mad

MaybeGuy · Super Spammer Joined: 12 Mar 2007 Karma :

150 sounds fine
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!! Mr. Green

Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

Blau Zedong · Banned Joined: 26 Jun 2006 Karma :

speeddevil68 · L Plate Warrior Joined: 01 Apr 2009 Karma :

Thanks for all your comments.

BlueX5 - that is why i used the comparator. My squish clearance is currently ~0.055 inches. but the manual says it should be 61-63. I think I'll just strip i down and insert the two smaller gaskets to increase the squish gap.

What happens if my gap gets bigger than .063in?

Blau Zedong · Banned Joined: 26 Jun 2006 Karma :

If the squish is too big the engine may be a bit down on power and less crisp, but it won't do any harm.
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18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

speeddevil68 · L Plate Warrior Joined: 01 Apr 2009 Karma :

Thanks again. I will update when I have completed the work.

speeddevil68 · L Plate Warrior Joined: 01 Apr 2009 Karma :

Ok, Re-assembled the engine and it runs fine. THe squish clearance is now set to 61 thou, the manual recomendation.

I need to change the oil in the crank case too. it is a 2 stroke engine. Can I use engine oil flush from halfords to clean all the parts out?