tjstinson
RCTalk Basher
DESPERATE! Suddenly Does Not Shift (Good Tune)
This truck (HPI Racing Savage X F4.6) is fairly new (purchased in February 2014) and I had a good tune and shift point established on it until recently when it suddenly (overnight) would not shift to second.
I realize everyone has their own idea of a good tune, but I can only ask that you give me the benefit of the doubt as to explain the tune might only lead to discussions that divert from the what might be the actual problem.
This might get murky, but I am going to explain some things that might have attributed to the problem, but not necessarily. I feel, however, to omit these details might prevent one from coming to the right conclusion.
First, when I started the truck out of the box, the throttle trim was set to 100% on the transmitter. Before I could understand why it was seemingly lean and the wheels were increasing speed, it was too late. A spur gear was melted and smoke billowed from where the spur gear and bell gear mesh. The spur gear was also stripped of teeth and it is anyone's best guess as to what damage this could have caused the piston and sleeve.
I had the truck shipped to HPI and they say they looked it over. They did report that the truck had a good shift and that everything looked fine. I doubt they opened the engine, but either way I have compression and combustion. The engine seems to have survived.
I ran it for weeks following and until recently, with the exception of not seeing wheelies, I felt the truck was operating fairly well. A couple weeks ago it was shifting and I put it up for the day. The next day I took it out and no shift. I also noticed that the low-end torque was leaving much to be desired, but it is possible this was always the case since I got it. The absent or early shift was completely new to me.
One thing I hadn't considered to be damaged from the time I first started the truck and blew the spur gear, but should have, was the clutch shoes. Well, they went out this week and when I was replacing them they were horrible. I suspect that heat generated from the first run melted the spur gear and certainly the shoes. I should have checked them when it happened, but I assumed HPI would have looked it over as this was a concern.
I installed the HPI aluminum clutch shoe upgrade. I hoped that this would fix the missing low-end torque (the truck moves, but is requires more throttle than I would think necessary in the grass and has NEVER popped wheelies).
I have tightened spur gears. I have tuned it to the point that I reach temps of 270 and 280 and have to back off. I get a decent speed without the shift and a fair take off when I mash WOT, but early power and a shift is missing. I am almost CERTAIN the RPMs are present to pop into 2nd.
I have adjusted the transmission screw (yes, the right one) and I saw NO difference at all. I moved it back to stock position- still no difference. Turned it IN 3 turns- nothing. I tightened the grub screw that holds that gear in place as well. I have not checked to see if it was broken, but it is in there firmly. The finger on the transmission gear seems fine too. At first I thought it was broken because it was angled to a point, but I have looked at the stock fingers and they are the same.
I am at a loss. I have checked diffs front and back. I have smooth movement in the transmission gears. I have a stock tight drive line from rear to front as best I can tell. There isn't slop.
What am I missing? What could be going on? Does the overheating from the first start come into play in this? Is there something else that could have been damaged like the clutch shoes that I am not thinking of?
This truck (HPI Racing Savage X F4.6) is fairly new (purchased in February 2014) and I had a good tune and shift point established on it until recently when it suddenly (overnight) would not shift to second.
I realize everyone has their own idea of a good tune, but I can only ask that you give me the benefit of the doubt as to explain the tune might only lead to discussions that divert from the what might be the actual problem.
This might get murky, but I am going to explain some things that might have attributed to the problem, but not necessarily. I feel, however, to omit these details might prevent one from coming to the right conclusion.
First, when I started the truck out of the box, the throttle trim was set to 100% on the transmitter. Before I could understand why it was seemingly lean and the wheels were increasing speed, it was too late. A spur gear was melted and smoke billowed from where the spur gear and bell gear mesh. The spur gear was also stripped of teeth and it is anyone's best guess as to what damage this could have caused the piston and sleeve.
I had the truck shipped to HPI and they say they looked it over. They did report that the truck had a good shift and that everything looked fine. I doubt they opened the engine, but either way I have compression and combustion. The engine seems to have survived.
I ran it for weeks following and until recently, with the exception of not seeing wheelies, I felt the truck was operating fairly well. A couple weeks ago it was shifting and I put it up for the day. The next day I took it out and no shift. I also noticed that the low-end torque was leaving much to be desired, but it is possible this was always the case since I got it. The absent or early shift was completely new to me.
One thing I hadn't considered to be damaged from the time I first started the truck and blew the spur gear, but should have, was the clutch shoes. Well, they went out this week and when I was replacing them they were horrible. I suspect that heat generated from the first run melted the spur gear and certainly the shoes. I should have checked them when it happened, but I assumed HPI would have looked it over as this was a concern.
I installed the HPI aluminum clutch shoe upgrade. I hoped that this would fix the missing low-end torque (the truck moves, but is requires more throttle than I would think necessary in the grass and has NEVER popped wheelies).
I have tightened spur gears. I have tuned it to the point that I reach temps of 270 and 280 and have to back off. I get a decent speed without the shift and a fair take off when I mash WOT, but early power and a shift is missing. I am almost CERTAIN the RPMs are present to pop into 2nd.
I have adjusted the transmission screw (yes, the right one) and I saw NO difference at all. I moved it back to stock position- still no difference. Turned it IN 3 turns- nothing. I tightened the grub screw that holds that gear in place as well. I have not checked to see if it was broken, but it is in there firmly. The finger on the transmission gear seems fine too. At first I thought it was broken because it was angled to a point, but I have looked at the stock fingers and they are the same.
I am at a loss. I have checked diffs front and back. I have smooth movement in the transmission gears. I have a stock tight drive line from rear to front as best I can tell. There isn't slop.
What am I missing? What could be going on? Does the overheating from the first start come into play in this? Is there something else that could have been damaged like the clutch shoes that I am not thinking of?
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