I need engine help please!
 

So i thought it would be a good idea to buy a 95 600 F3 with a blown engine and then fix the engine. The guy blew a rod and obviously destroyed that piston, cylinder, and all 4 valves. So what i did was buy another engine with no carbs. The engine i bought without the carbs will be called engine 2 for simplicity. so i took the lower case from engine 1, because engine 2's lower case/transmission wasnt that pretty. I then took engine 2's upper case/cylinders, engine 2's head, and pistons. then took engine 1's miscellaneous covers. I did everything you are supposed to when building an engine, new rings, new gaskets, lapped my valves, new valve guides. And yet i still have a HUGE loss of compression.

The problem: i have 50 pounds of compression in every cylinder, since they are all exactly the same and i had new rings and what not this lead me to believe i had something mechanically wrong. I did a squish test and it turns out i have something like 1.4 mm of squish and i need .7ish. so my pistons are not coming up anywhere near far enough. This is all what my grandpa told me, who used to race bikes. but he has been wrong many times before. He suggested that a deck the top of my cylinders- shave about .8mm off the top of the cylinders.

Can anyone please give me some help! tell me what i could test that may also be the problem, i am brand new to sport bikes so if it seems obvious to you it might not be to me. HELP PLEASE!

Hello,

For starters it is not a good idea to mix cases, they are machined as one piece so each case is a matching set, when you take two different case halves they Will not match up 100%. that being said, in some instances it may work, or...... it might end up resulting in a bigger problem. Me personally, i would look into getting a whole case that is in good condition with no parts, just the case. Tha'ts just my two cents, take it or leave it, its up to you.

P.S.

You say the pistons are not compressing enough, that could be a result of the bottom case not being the same exact size as the other one.

yeah, i realize now it wasn't such a good idea. but i have too much money into it and am committed. The other lower case had a large crack in it, thats why we didnt just put the whole engine in as it was. Would decking the cylinders be a good way to go? I have talked to a few mechanics and they said it could be a good way to go.

That could solve your problem temporarily or for good, dealing with two case halves from different sets is a gamble, you could be fine or have major problems, or you can prematurely wear out parts like rings bearings and such, and I know how you feel bout putting money in the bike, I just dumped $2000 into my 96 to rebuild it, but you might be able to get away with it, or it could cost you loads in the long run, I would personally buy a case for a couple hundred bucks and know that I won't have any future problems or expenses.

So if i were to buy a new case, would the pistons and crankshaft and other parts like that match the case? Or would I, for example, end up having my pistons not come up far enough and end up having to deck my cylinders anyways?

If you buy a new case the only thing you will need to do is take the case, rods, and crank to a shop to have the bearing tolerances measured to find out which color bearing you will need, or if you have to proper equipment and know how you can do it yourself, i just had mine done a few weeks ago and they only charged me about $95 which isn't bad, but other than that, just hone the cylinders (Do you know how to hone) and all should fall in place after than that my friend.....

And unfortunately you might have to buy new bearings again, or you might get lucky and it call for the same color coated bearings you already have.

Alright, thanks for the advice. I am going to look into that but i am also not ruling out the idea of decking the cylinders and just being done with the bike. I am going to keep looking into both options and talk to mechanics and people who race bikes just to give me more opinions.

Thanks much for the help!

Np anytime glad to help, if you have anymore questions message me, i literally just rebuilt my F3 a couple weeks ago so its still fresh in my head, but either route you take good luck and i hope the best for your bike, let me know how it turns out.