SA50 upgrades

[lilredspree]

any changes i should make to a ruima bore befor i run it?

[bakaracer]

just make sure the ports are shamfered and round or put a 45deg angle on the bottom of the piston so oil can get between the piston and cylinder wall on the down stroke. check your port timing and compression.adjust where needed.

[Wheelman-111]

Greetings:

Li'lRedSpree axt:

wheelman, whats your favorite bore you have ran on a stock crank considering both power and reliability?

Baka-san has built probably 2 or 3 different engines for each of my 10 or thereabouts, so much respect. That said, much as I'd love to try out an LC arrangement I just can't see cutting panels and * with hoses, thermostats pumps and radiators. Not to mention the Colossal Trajedy of cutting into Precious Honda-ly Plastics.

My Corsa is hands-down the best performance/reliability compromise. Nikasil 49/78cc was tough and forgiving of some bone-headed jet choices, but milquetoast performance as delivered. Ruima 51s I fried like gamey bacon, twice. The Char-Mo 50mm ministroker held up, but by then I'd learned not to get too ambitious on compression and port timing and jetting.

The Corsa is faster than all but one of the Ruima 51/Ministroker 90ccs, which lasted about 5 hours after break-in. I barely touched the Corsa - installed basically as delivered and still going strong. 72cc, and with a little more tuning and cooler weather I predict 72 MPH.

[lilredspree]

i was going to say i'll go with a ruima 50mm but i think wheelman is convincing me otherwise

your hours on the ruima bore is about how long mine lasted.

i'm just slightly pushed away from these kits because of what happened. i'd hate to get another, chamfer in and go through that process just to have it blow on me again....

would it be bad to put a corsa 72cc on my block that got matched to the taiwan 50mm boost port?

[lilredspree]

Just picked up the polini corsa. Decided to try it out as I've already blown a taiwan bore. Should be here this week.

I've been doing some research on cryogenic treatment an was thinking if these motors are exposed to such high rpm's and wear... wouldn't this be something that could greatly prolong the life of the bore itself? Anyone have any experience with getting this treatment done? I may consider doing it.

[bakaracer]

in order for you to use that polini bore, you will have to fill in that boost port on your block to the polini boost port size. either with aluminum weld or jb.

[dun rite]

just a question: some people use the bores that have a larger boost port area, but don't match the case to the larger port. And report it runs fine with no problems. So if you have enlarged the boost port to match a larger boost ported cyl. and later decide to use cyl. with a smaller boost port, why is there a problem with the smaller boost port above a larger boost ported case?

just wondering

[lilredspree]

dun rite, that was my thoughts too. Will it really make that much of a difference? I understand that there will be turbulence created right before the boost port on the jug because the block will have a larger opening. Will this turbulence be enough to greatly effect the flow of the block internally? With the amount of airflow through the small area and the physical volume of air passing through these blocks at high rpm I suppose it could pose a problem.

[Wheelman-111]

Greetings:

I believe it's just a question of getting gasket seal on all sides. If the smaller cylinder gasket is used, there'll be gaps, thus vacuum leaks. If the gasket is compressed on both sides without gaps, then yes it works - albeit not optimally.

[lilredspree]

alright. so some jb weld as close as i can to the corsa boost port. if need be cut my own gasket to avoid potential vaccuum leaks. will i need extra head gaskets to lower compression ratio on this bore also?

[lilredspree]

Just got the Corsa! Will work on JB welding the boost port to match this kit. Should I be trying to change my compression ratio on this kit so I can run pump gas? Will do the measurements on my own tomorrow, but I know basically everyone has ran the corsa before. Any tips on modifying it before installation to increase longevity?

[lilredspree]

What compression ratio should I shoot for with this polini corsa? I know I can't add head gaskets to it because it the o-ring, but what about base gaskets to alter my port timing and lower the over all CR? Should I get it down to 10:1, 9.5:1?

[lilredspree]

put it together as it came... compression test shows 140-145psi. way higher than I want. Within the bore the piston is sitting at BDC perfectly level with all the ports. Will raising the sleeve to reduce the compression ratio kill performance?

[bakaracer]

you can add a metal head gasket to a oring head. adding base gaskets will only make the port timing more aggresive and narrow the power band.

[lilredspree]

where could i get metal head gaskets for this bore?