tuning - os carb
 

Just getting back into nitro offroad. I always ran OS and could tune with my eyes closed. Seem to be having problems getting the perfect tune on my novas. After some reading I discovered the long needle vs short needle comments. I have some left over OS speed carbs from the vzb days. Any reason not to run one of these? I'm assuming it will change the tuning method to that which i am used to? I'm guessing the mid range needle may need some TLC.

Just wondering if there are any reasons I shouldn't mount the OS speed carb up?

THANK YOU!!!

because its an OS carb on a Novarossi engine. :lol:

All kidding aside whats the issue you are having with your tune? Novas do not like a rich LSN. Once the motor is broken in, about a gallon and half, I hardly touch my needles more then an hour either way for weather.

maybe thats why
 

Maybe that is why. With the OS, I would typically tune it so it was crisp, idle dropped ok, and after sitting for 3 seconds it would take off crisply and after sitting for 10 seconds it would take off with some additional smoke and a very slight build up. This always worked perfect. I'd also routinely check the top end on the box by quickly holding full throttle (very very short pull), and passing my finger over the exhaust smoke to insure there was some small amount of oil.

On the Nova, I have a hard time gauging the tune and which needs the adjustment. Perhaps I need to tune my LSN leaner? It is about flush now. It Even hear the idle go up a little sometimes which would typically be evident of an airleak or a lean lsn. I don't remember seeing a larger idle gap with rich low end raising the idle?

Also, motor seemed ok before. Now that it's lost the mechanical pinch it seems diff. Maybe I need to take the deck height down a little but that shouldn't change the tune that much.

About 1 - 1.5 gallon through the motor. I can easily turn it over. Had a couple of novas feel like this after little fuel. Either I need to ajust the deck height, or they are like the old vspecs that just got like this and ran for gallons like that.
Hopefully I don't have a rich LSN and lean HSN and am wearing them out :/

I've been racing for a long time. Never had tuning problems :(

Fine tuning a Nova and OS is quite different......so if your used to tuning a OS carb you may find yourself doing the wrong things when tuning the Nova without even knowing it....

what are you seeing with the Nova carb ? exactly what symptom ?

Correct me if im wrong but after 1-1.5 gallon's that motor is just broking in? I swore my motor was tuned but i was way off (rich on bottom) and had so much more to go at that exact mark 1.5 gallons shes just coming aroud.... Why not just go back with the new O.S.?

idle gap
 

I went back with Nova because they seemed to be doing so well for everyone. The speeds seem very high priced in comparison.
I spoke to local engine "guru" and explained the symptom (idle comes down, raises back up a bit, unpredictable, can stall at idle.)
I had my idle gap set at 1 turn in from closed which I was told was about right. I should have kept leaning the LSN until it idled but did so a little and then raised the gap. I think my LSN is rich.

Try the following:
get the engine up to temp and do a high speed pass and then listed to the idle. If it starts to lower itself after a few seconds then lean the lsn and go out for another high speed pass. Once you get the idle to stay consistant adjust it with the idle stop screw. The idle gap will be around .5mm to .7mm with the venturi out, but the measurement is more of a ball park number, not an exact science. If the idle gap is to large the idle will fluctuate up and down and give you the feeling that the LSN is to lean. Once its set right and if the engine is in good shape with no air leaks it should idle for about 20 seconds before it loads up and drops.

My LSN is set to the point that 1 to 2 hours leaner and it will sound like a short lean bog coing off of slow corners.

Does anyone have a spare piston lying around.. User error on one of my mills piston is scored pretty bad.. Plan to see if I can buy a loss piston then send to ray racing for A fit.

you also need to be very gentle when adjusting the LSN. the low pitch threads on lsn means you can only adjust one minute at a a time on Novas, compared to 5 minutes at a time on OS. This is what i see moast guys do wrong, overadjusting on the needles.

Ro Grab me Friday when your about to go out to practice and I will get you tuned in. My guess you probably have it lean top fat bottom. Very common mistake by guys coming from O.S's to Nova's.

Sounds good
 

Thanks Ron. See you guys Friday! Let me know if you guys want to pit. I'm coming down solo. Ro - 949 415 4284 txt

+1 its a common problem for guys running OS's too but the OS will stay running tuned backwards. just cause it runs don't make it right. ;)

+1, this is why I think there is a lot of guys saying OS's are toast after 3 gallons, they run even with a whacked out tune frying the internals.

that is exactly why.

So on the new btt wc is a good plug to run still the oddonol 97t? I know a lot of the orininal btt guys run that plug. Was not sure if the is any major difference with the new one.