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Old 06-11-2014, 01:28 PM   #1
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Default Advice on what I think is bogging at lower end

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.
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Old 06-11-2014, 01:37 PM   #2
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Try richening the top just a tiny bit. Should take care of it. May need to lean the bottom back in when you do.
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Old 06-11-2014, 01:42 PM   #3
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Try richening the top just a tiny bit. Should take care of it. May need to lean the bottom back in when you do.
Thank you for your advice. So too lean HSN can do that?
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Old 06-11-2014, 01:49 PM   #4
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Thank you for your advice. So too lean HSN can do that?
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
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Old 06-11-2014, 02:16 PM   #5
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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
Wow, very helpful my friend. I will certainly try that out. Thank you.
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Old 06-15-2014, 11:46 PM   #6
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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!!
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Old 06-16-2014, 01:27 AM   #7
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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.
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Old 06-16-2014, 06:21 AM   #8
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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.

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Old 06-16-2014, 07:47 AM   #9
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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.
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Old 06-16-2014, 08:19 AM   #10
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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!!!
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Old 06-16-2014, 11:57 AM   #11
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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?
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Old 06-16-2014, 12:07 PM   #12
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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.
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Old 06-16-2014, 12:16 PM   #13
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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 .
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Old 06-17-2014, 07:01 AM   #14
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Quote:
Originally Posted by snuvet75 View Post
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.
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!
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Old 06-17-2014, 07:59 AM   #15
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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!
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.
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