40cc bizeta to 50cc bizeta?

I have a 13hp grc rsr. It has a BZM motor. I am wanting more power. it is fast, but I would like it to be faster. I was told that when I do a compression check it should be around 140psi and if it was anything below 120psi to replace it. Well I did a check and it is only 55psi. So could I just re-ring it? What should I do? I raced a friends blata elite 13wr? It is supposed to be 9hp and it has some stuff done to it so it is supposed to be around 10.0 - 10.5 and I am faster then him.
I am thinking of going to the 50cc big bore kit. I have heared a bunch of different stories though. I was told if I got a polini 50cc it would be a little stronger on bottom end, but lose power on top end. I think it was around $150. Next was a ZPF 50cc big bore kit. I believe it came with its own head. I was told it would give me more bottom end and keep the top end. $450. Last option I have heard of was to get the bzm 50cc big bore, keep my head, and get a top end gasket I believe. $250.
What I was thinking is I can get a BZM 50cc piston and rings for $35 and take it in to a friends dirt bike shop and send it off to lencor or milinium technologies and have my block bored and re-plated with nicka sil. He said it is around $140 to have it nicka silled though. If it had a metal liner I could have it done locally for cheap.
How does a bizeta block come? Nicka silled, or metal linner? Can I use the head that is on my 40cc with the 50cc? Other options?

Wow! Sounds like you've been getting lots of bad advice. If your bike truly does have a BiZeta Motor then none of the 50cc options above are valid. There are too many specifics to get into here but very simply:

1. It sounds like the main problem with your engine is that it needs a complete rebuild, a somewhat cheaper option than buying a new top-end, depending on whethere there is any internal damage. The rebuild includes the crankcase, so it also points out that just replacing your top-end won't solve all your problems, i.e., just buying a new top end ONLY would be a waste of money.

2. If you do want to upgrade to 50cc, your ONLY choice for a top-end is the BiZeta top-end (the Polini, Malossi and ZPF top-ends are not compatible with the BiZeta bottom end). You can choose a factory stock 50cc top or a custom-ported 50cc top.

If you have not rebuilt an engine and know what to look for and what to set everything at (most people don't and end up with mediocre results), then you should send your engine to an experienced Minimoto shop.

Call or email Advanced MotoSports in Fairfax, Virginia. They can help you with the different options.

(703) 246-9003
AdvancedMoto@aol.com

Can I keep the head that I have right now or do I have to buy a new head if I put a 50cc bzm block and piston on it. How much would it cost to do a complete rebuild on it. It is only one year old and has been ridden maybee 15 times. A couple hours each time.
What should the compression ratio be?

checking cylinder pressure on a 2t reed valve motor is difficult to do,hence erronious readings,55psi your motor shouldn't even run right,if at all.

the bzm cylinder is nicasil,and it's not worth the money to bore,because once you bore it you'll need to re-port it to make up for the changes in the transfers,most likely,once you bore your 40 to a 50 it will be a paper weight anyway,that's alot of material to remove and will change port timings and area dramatically.

I would suggest as Bill did,do a rebuild on it,your crank seals and ring are most likely toast from lack of use,the seals will dry out from not being used.

Tom

thanks.

If the bzm block is nicasiled then it is better off to just buy a whole new 50cc block and piston. Can I use the head that I have right now on my bike or do I need to get a new one for the 50cc.

Yes, buy a new top-end, factory stock or custom-ported as I indicated above.

The head is the same for the 40 and 50, only the insert is different. I've used both size inserts with our 50 and haven't yet noticed a significant difference, but it certainly wouldn't hurt to get the 40mm (50cc) insert.

You can send your engine to Advanced MotoSports and they will do a complete rebuild for $50 plus parts and shipping, pretty cheap to get it done right, get worn out parts replaced and get your engine settings adjusted properly. If you don't have a good clutch you can have them set you up one of those at the same time.

Oh also, the usage you indicated (15 times, 2 - 3 hours each) is alot. That much riding is equal to a race weekend each time out. It is recommended that a high end racing engine should be rebuilt every 2 - 3 race weekends. You would certainly do it after every 6 at least.

Sounds good. I will re-paint it and re-powdercoat the frame this winter. When I do it I will send it to advanced. Just call Tom @ capital USA minimoto?
thank you
jeremy