snuvet75

iTrader: (16)

Hi. I have Novarossi Top .21 on my 977 and it sounds like it bogs at low end and I can't seem to pinpoint the problem. At beginning of race, it's fine and after a few laps, when I hit throttle out of corner, it doesn't accelerate right away (I mean it goes but slower acceleration than desired) but it takes about 0.2-0.3 seconds before it takes off fast, like booooBOOOONG.. And it definitely gets behind the other cars every corner because of that.
I thought it was clutch gap or spring. The gap is 0.6. Spring is hard. I put a new one. And I thought it could be LSN being too lean. So I richened more and more and checked every time but it only slowed down the car and didn't fix the problem. What could it be? Thanks in advance.

P.S. I've done pinch test and idling time to check proper LSN setting and temp check after 5m running and it was 225-240F.

wingracer

iTrader: (24)

Try richening the top just a tiny bit. Should take care of it. May need to lean the bottom back in when you do.

snuvet75

iTrader: (16)

Thank you for your advice. So too lean HSN can do that?

wingracer

iTrader: (24)

Yep.

Most all onroad motors have short needle carbs so the minute you touch the throttle, only the HSN is in control of the fuel. LSN only controls it at idle unless it is so rich that it floods the crankcase and can't clear it all out quickly. A good, high timed onroad motor will often not let you go very lean on HSN before the classic lean bog hits. It's kind of a nice, unintended safety feature

snuvet75

iTrader: (16)

Wow, very helpful my friend. I will certainly try that out. Thank you.

Geezatec

It sluggish after a few laps. Does it blow a bit smoke at corners? When the engine is at optimum temp and less fuel, it gradually be come lean. You can richen the LSN. On test bench, tank just a little less half full, engine at temp, from half throttle to idle, how long does it drop to idle speed? longer then 5 seconds, LSN maybe too lean. Try that! HSN is always constant, LSN mostly adjust during races on pitstops. Another way if your RX has speed control adjustment you may slow the servo. Depends on driving style. Good Luck!!

dan_vector

iTrader: (27)

My thoughts are too lean on top. Classic signs. You may also be too tight on your clutch gap and an extra 0.1 of end float might help as well.

dj apolaro

Something to consider is also the clutch spring. It may have lost its tension and when you warm up the clutch it goes soft. Just another thought if nothing else seems to be working.

DJ Apolaro

snuvet75

iTrader: (16)

Thanks all. I will richen the HSN this weekend and see. The clutch spring is new and hard one DJ. I thought it could be the problem and changed it. The clutch gap has been the same so I may need to try different gap. How cool is it to get DJ'S idea here?! dun get me wrong Dan, you have been more than helpful too.

Geezatec

Adjusting the centax clutch. Your endplay or gap is at minimum .06. Preloading the spring to a 9-10mm to the end of crankshaft, is only a starting point. Adjust the collar CCW for earlier engagement, it wont take much. Adjust by using allen wrench through hole of the pinion cluster. One thing about Centax it take a lot of maintenance, scotch brite the flywheel and clutch material cuz it glazes with it engages so late.. preload at 9-10mm it engages almost 1/4 - 1/3 throttle. You'll find the optimum that suit you. Have fun!!!

dan_vector

iTrader: (27)

What is the ambient temp on the day? This could affect plug choice and also be an area to experiment. Stick with Novarossi plugs and use the C7TGF if sub 50F and use the C8TGH above that. What does your plug look like after a run?

snuvet75

iTrader: (16)

It depends on the days but I'm in SoCal so mostly dry and hot. But this manifest has been going on for the last 4 months or so (70-85F mostly). I just haven't gone to the track much for those months though. But it has been pretty same every time. I re tune my engine like everybody else every time I go there but I didn't pay a particular attention on HSN doing that so I don't remember if it was better at certain HSN.
I used #7 Nova plug and then changed it to #8 1 month ago but it didn't make any difference. Maybe I tend to set HSN too lean. The plug is not very dry but the coil is gray when I take it out and I know it is on the lean side.
I'll just make it rich a bit to see.

Skem61

Hello ,

I had the same thing on my Nova Virtus .
I have changed rear bearing and front and now it's like new and very constant everywhere .

dan_vector

iTrader: (27)

Gray wire in the plug is definitely a lean engine. Change the plug before you run it again as once the element is gray it's now brittle and so could break and damage the piston/sleeve/button!

Geezatec

At 240degrees its critical. Depending on what % of nitro, lack of lubrication. No wonder you have flat spotting on acceleration. Flat spotting or bog
down during acceleration causes for the engine to run leaner for a split second, or starve the engine. At 220-240degree we know how lean you are. Remember, less fuel in the tank the leaner the engine runs. If you're actually racing rich to lean every 9-10 minutes, you'll find the balance of it. Being fast is nice, but being consistent is better.