My HS 50 build up

This HS50 is off my Powell and needs some help . I already have a ARC rod for it and thinking about a cam from Tim Isky.
How big can these motors be bored ? There is nothing wrong with mine now and doesn't have too many hours on it , but bigger is better .
I plan on cleaning up the ports a little eyebrow work and just a little off the head .
David the valves sit on a cast in metal insert and are flat on the head you can't do eyebrows like on a H50 or a briggs. There are still some of the 45 dollar 255 dyno cams on ebay. I don't know what tim gets now but the cam he did for me was $150. I got a hard face one. Here are some pictures of the deck you can see there is not much you can do for eye brow reliefs. They are aluminum bore and depending on what serial number you have they have slightly different bores. They already have a very large bore so you can only go up to .030 over.
Well I got the head off and no eyebrows. What I did find was before I got it , it was run very little . The intake port looks new the cross hatch in the cyclinder looks new . I have put maybe 4 hours on it and before me very damn little ime was on it .
I'am trying to get the side cover off and can't . I remember reading here there a trick to it and I need to know , so will somebody please help .
The sump cover most likely has a roller bearing. Remove the seal, there will be a cir clip, pop that out and the cover should slide off.
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New standard rings, seals gaskets, rod, and cam and done. Maybe a little port cleanup but looks great!

Hope mine look that good inside.
Looks like a electronic ignition engine. You can buy a hot coil for it on Ebay tecumseh ignition 36605k eBay item number:

151603750375 .
Looks like a electronic ignition engine. You can buy a hot coil for it on Ebay tecumseh ignition 36605k eBay item number:

151603750375 . It's the coil used on the 5hp motorsport engine and the star engine also.
I've got the rest of the motor torn down and ready for building . Where can I finnd the dyno 255 cam on EBay? And will I need bigger springs ?
And one last question , what about the cast iron flywheel how will it hold up the 5k or so RPMs ? Is there an tech aluminum one that came on some of these ?
Well one more I really want to run a stock looking carb , will the stock one be big enough ? Or will HM80 or 100 carb be better ?
Last some pics
This will be a another cool build everything looks good.

If your looking to add some HP, the stock ports are a big problem. Intake is a mess with the dog leg intake, gonna take some work to straighten the air flow there. The Exhaust port is way too large for the valve size; I have a book from the 70's, David Vizard wrote it, mostly theory of air flow. Velocity is what makes air flow, larger ports does always not make a port flow more, he suggests about .8 of valve diameter for best gas flow. and a 3 angle valve seat with a venturi section.

Some high temp epoxy and smooth them ports!

Here's a link for Vizard's book. My copy is 30 yrs old.

ISBN 9780851130668 - Theory and Practice of Cylinder Head Modification Direct Textbook
Need to know where I can find a bigger exhaust valve and what kind of springs are y'all using ? I put a tech spring beside Honda 160 spring and they are real close in diameter and length , but the tech spring is bigger wire size and stiffer . Have y'all tried a 18 or 22 lb clone spring ?
Is your a small exhaust or regular? most of the older magneto ones had the larger valve. I used a briggs 5hp exhaust valve it is a better material a few thousanths thicker stem than the new replacement tecumseh valves and a touch larger diameter.
Ole my intake is 27.22 mm and my exhaust is 24.51 mm . I'am thinking the larger model . This all seems backwards in Honda-clone theory where the ex side is bigger . The hemi predator I have has a 27mm ex and a 25mm in what give here ?
Also everyone say the exhaust port is to big but in measures 23.4 or so , seem perfect for the size valve . Now the intake port seems way to small if it were round in would be like 22mm or so but it's got that weird shape which makes it bigger I guess .
This is my thinking leave the valves alone clean up the exhaust port and a three angle valve job . The intake reshape it to round and try to get her a a little bigger . For a carb I want to use a tech carb will the stock one work for this motor ? I want to straighten out the stock manifold or make a new one . Or would a bigger tech carb work better like for a HM80 or bigger ?