SA50 upgrades

[lilredspree]

I'm doing 32:1 gas/oil. And a yamaha 2-stroke oil I have used in my quad for years.

[lilredspree]

CHT guage stopped workin in the middle of a run. Will have to investigate tomorrow. Got temps right around 300. Moved the needle clip up one (all the way at the top now) and throttle response improved a ton. Will have to try leaning out the main a tiny bit more tomorrow then I think she is in pretty good tune!

[bakaracer]

so your 55/160 jetting is on a 28mm carb?

[lilredspree]

24mm.. and i came back down to 48/145 and liking that.

[bakaracer]

make sure all the bolts are tight. retighten if you haven't yet. man the main jet is huge for a 24mm carb. the biggest I ran was a 120 and thats on my malossi mhr cylinder and msp exhaust which is like a pg typhoon or v8 exhaust but it flows better. that jetting your running is more a 28mm carb setup.

[lilredspree]

I'll re-torque the head studs before I ride next. Really like the power its got. Will keep working leaner until temps increase too much.

[bakaracer]

you can play with the air fuel screw too. that also controls the 0-1/2 throttle area along with the needle. make sure you put the clip down 1 position if you lean the main. if not your going to lean the midrange to much and you will see high temps at the 1/2 throttle area. your good to about 380deg at wot. for the street thats a good temp anything higher than that go up 1 step on the main. if you shoot for a 340-380 temp you will notice the engine will be very snappy which is good.if that pipe is to loud,try that bore setup with your stock deresticted pipe. will have really good low-midrange pull. wont rev as high but thats good for longer life of the kit too. rpms's wear parts faster.

[lilredspree]

Motor was running great. Had about 4.5 hours on it. Decided that I felt confident with it and I'd venture a little farther away from home this morning. Apparently bad idea. Temps never rose too high bout 350 or so. Was in a 35mph zone at about 8500rpm and slowed down to 25mph. Felt the bore get really tight so I shut her off. Checked my plug to see if it went bad. Looked fine, lil fouled from bein a bit rich but I'd rather be on that side of a tune. Put in a new plug. Wouldnt start. Basically I towed her home and this is what I found:

Compression test: 50 psi.
Inspected to see if I blew any gaskets: Negative
Pulled the head off: Minor carbon deposits gasket was fine.
Pulled the bore off: Piston rings stuck on the exhaust port side with piston damage and sleeve damage (only on exhaust port side).

What could cause this? Just a cheap bore? Anything more reliable I could run instead when I buy a new top end?

[lilredspree]

Anyone have opinions on a bbk? Go the same 50mm bore I had or go with the name we all know the Polini Corsa 72cc?
What I truly wish to have is a watercooled 50mm piston kit that will accept the stock crank. Don't believe one exists.

[Wheelman-111]

Greetings:

More expensive, but all the good bores end in the letter "i". Whether for reasons of machine tolerance, design or materials, the Taiwanese bores just don't seem to last very long unless tuned very conservatively and everything has to be perfect. One exception for me was the very robust, fairly affordable Nikasil 49mm from DayWot.

[lilredspree]

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

[bakaracer]

Motor was running great. Had about 4.5 hours on it. Decided that I felt confident with it and I'd venture a little farther away from home this morning. Apparently bad idea. Temps never rose too high bout 350 or so. Was in a 35mph zone at about 8500rpm and slowed down to 25mph. Felt the bore get really tight so I shut her off. Checked my plug to see if it went bad. Looked fine, lil fouled from bein a bit rich but I'd rather be on that side of a tune. Put in a new plug. Wouldnt start. Basically I towed her home and this is what I found:

Compression test: 50 psi.
Inspected to see if I blew any gaskets: Negative
Pulled the head off: Minor carbon deposits gasket was fine.
Pulled the bore off: Piston rings stuck on the exhaust port side with piston damage and sleeve damage (only on exhaust port side).

What could cause this? Just a cheap bore? Anything more reliable I could run instead when I buy a new top end?

that type of seize is due to not enough lube or oil broke down. most of the taiwan bores you should use a flex hone to shamfer the ports since alot of the bores have sharp edges so they act like squeegees.that will take the oil off the piston and cause it to seize.same with the bottom of the piston. some pistons have a rounded or slight angled edge. alot dont so that come like a squeegee. the only reason the italian stuff holds up better is because they shamfer the ports and the bottom of the piston has an angle to it so oil can get between the piston and the cylinder wall for better lube.the taiwan stuff you have to make sure those things are done to make it reliable.

[bradthreee]

Not only the cheaper bores, but seems also the fine intalian ones too...

I had to learn the hard way

[lilredspree]

The bore being robbed of oil around the exhaust port makes complete sense to me baka. So making sure I put a slight chamfer Around the ports should solve this prob?

bradthree: are you saying that the fine italian ones can rob the bore of oil and seize in a similar way too? what do you recommend getting around this problem as you say you have encountered it before.

[bradthreee]

Same exact thing happened to me last week



This is an Athena Race Kit

Listen to Baka, he knows what he's talking about