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Idle stay's up when coming off of full throttle?

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R

rfraser

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Savage xl. I know, its an air leak right, but I sealed the engine,its seem's to be working great, wheelies pretty well and shifts through all 3 gears great. Throttle trim is set and return spring on the carb, throttle always seem's to return to idle position when doing a prerun check.Am I misssing something.
Appreciate any help,Thanks, Rob
 
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Could be the tune, too lean on the HSN or too rich on the LSN. If the idle speed steadily increase after a WOT pass, the LSN is too lean. If it stays revved up then starts dropping then it is either the HSN is too lean or the LSN is too rich or a combo of both.
 
abovelegit- yah,I do have a 1 mil gap, if your refering to the carb slide adjustment

Scrogg- It seems that I have it a little better with the tuning you recommended, some times it doesn't do it at all but it still does it after a longer hard pull.

Can I still be too lean running at 260? It doesn't quit or start breaking down at full throttle and still has some smoke.

When I pinch the fuel line 1 inch from the carb, it will rev up a bit and quit in under 5 sec.

One last thing, is it common for these XL's to wheelie better on the lean bottom half of the tank,(lighter with less fuel as well I guess)I'm assuming you tune for the top half. If you leaned it out more for the top half could you be to lean on the bottom half?

Appreciate any comments. Rob
 
The shape of the savage tank sucks. Usually guys adjust tune when the tank is half full. Then when it's full, it's a bit rich and when it's running low, it's running a hair lean. The way the tank is shaped doesn't spread out tank pressure/liquid pressure evenly and as it empties, the shape changes so much that the tune changes with it.

To me, it sounds like your a bit lean on the HSN and possibly LSN if it's doing it after long WOT runs. When you let off the gas and you drop to idle, the fuel in the crank case is a lean mix and takes a little bit for it to build back up. If you richen it up a hair, it may help.

That tank shape may be why you are seeing this problem off/on. Full tank would be less likely to cause the issue than a half or 3/4 empty tank.

Personally, I find an alternate tank that is more symmetrical from top to bottom. I'm currently running a 125cc tank with my LRP28 on it... I get about 6-7 minutes of run. I really need to pull the pin and just buy a couple tanks off tower that are 150cc, but shaped better then figure out a way to mount them. The MGT tank I was running fit well and looked good, but it leaked air like a sock. So I ditched it and my erratic tune went away. Hopefully better luck next time!
 
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You have the tune very close, sounds like you could go a tad leaner on the LSN. 3 secons on the pinch test is pretty much max performance. 260F is fine for that mill.
Again if you lean the LSN a little more, you'll probably have to drop the idle speed a touch and richen the HSN 1/16th or so. Glad that helped you. You now know how to properly tune. Tune every engine you get your hands on this way and they will scream and run reliably. If at any point you start to experience tuning trouble or glow plugs failing later on down the road, that usually means it's time for new engine bearings.
 

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