strange tuning issues...

[synnyzter]

Trx 3.3 in a slayer pro. I bought one that was lightly used however it ran very strong. the odd thing is it would not run with the factory needle settings. I would have to lean the HSN about 1 full turn for.it to even run properly. This always bothered me but, hey it ran great.

After awhile I could tell it.was starting to lose some compression and wasn't delivering enough fuel (no i had no air leaks) so, I bought a new piston and sleeve. I broke it in according to the manual as I have done many times, and as expected it.turned out strong, solved all the issues, I was happy.

I still had to lean it way out from factory to even run right, still plenty of smoke
So, I noticed while slowly tuning I could not hit 2nd gear, regardless of its.tune. the tranny is also brand new installed by me, shifted great before the rebuilt engine.

So after the engine rebuild it did run strong but refused to.shift. I then made a.few more.WO runs then it just died. Upon inspecting I realized the plugs coil had burned completely off and fell into the engine seizing it, piston and sleeve destroyed I'm sure.

Does anyone have an idea to why I have to turn the HSN so much in to even run right? Why my plug.fried so hard as to lose its coil (too lean can cause this I believe). Again it puts out plenty of smoke, is the Carb maybe hosed? I'm an experienced.nitro guy but never seen this issue...

 

[Rolex]

No engines run at factory settings. They all start very rich for the beginning of the break in process.
Proper tuning and breaking in are the whole secret to the long life of glow plugs and engines.

 

[synnyzter]

Well I have a stampede and a tmaxx that both run fine at factory, grant it they aren't at 100% but still run fine. They only.need minor adjusting for peak performance. The slayers 3.3 however needs major adjusting, I couldn't even break it in set to factory, as I said "would not run at all" nor would it start. A full turn out was needed to even start it and it was still very rich which is why I asked if it could be the Carb...

---------- Post added at 8:03 PM ---------- Previous post was at 7:54 PM ----------

Sorry I meant a full turn in not out. I had to lean it a ton, perhaps its a damaged needle?

 

[dub c]

not only are no two engines the same, But no two carburators are built the same.

The shifting problem may be a complete different issue. What has me interested in your situation is the fact you replaced your piston/sleeve. Also I find it hard to believe the bottom end of a 3.3 can survive breaking in 2 pistons. Most of us replace our engines as a whole.

 

[synnyzter]

not only are no two engines the same, But no two carburators are built the same.

The shifting problem may be a complete different issue. What has me interested in your situation is the fact you replaced your piston/sleeve. Also I find it hard to believe the bottom end of a 3.3 can survive breaking in 2 pistons. Most of us replace our engines as a whole.

Sure this is true but having to crank the needle down so much to lean it enough to running condition is strange, I've had many 3.3's... Not that shocking to me that the bottom end can handle that though, they are fairly sturdy crank cases, while typically I do swap engines occasionally I come across a good deal on piston/sleeves so it made sense to go that route, and I did inspect the case before rebuilding.

I strongly believe the shifting is part of the weird engine behavior, I'm 99% sure a new engine/carb will remedy this, I just replaced the tranny, technically the whole drive train and tested prior to this.

It's just a mystery to me why it fries plugs the way it does, and is so difficult to tune with new parts when 3.3's are generally very easy to tune, but oh well, time for a new engine. I really just wondered if anyone had encountered this before as I have not. I just hate....not knowing lol.

Thanks for the responses though. I'll update once I work myself up to buying yet another new engine.

 

[dub c]

When I say bottom end I mean con rod, crank, and bearings.

 

[synnyzter]

Yes.I meant that too. Sorry I should have been more specific but yes everything in the crankcase was tip top. Still is :/

 

[2revo1maxx]

If you're frying plugs you're running it way too lean. You have to also make sure the engine is warmed up before you turn any needles. I believe that's part of your problem, so now you should richen the needle back out until you know it's too rich, then work from there. A well tuned engine will always run rich until it warms up.
What kind of fuel are you burning?

---------- Post added at 4:15 AM ---------- Previous post was at 4:14 AM ----------

Have you ever replaced the bearings in this engine?

 

[Childresshunt]

I strongly believe the shifting is part of the weird engine behavior, I'm 99% sure a new engine/carb will remedy this, I just replaced the tranny, technically the whole drive train and tested prior to this.(

Imo the engine not running tip top has nothing to do with your shifting problem. As long as it is reaching wo and not going any faster the truck should be shifting. Have you tried adjusting your shift point. (backing the grub screw out for sooner shift) I know one time when i replaced my drive hub bc of a messed up spring in it i couldnt get it to shift and i thought i had backed the screw out enough but i had in fact not. backed it out about a turn and then it started shifting.

 

[2revo1maxx]

It wouldn't be hard to rule out the engine tuning if you put up a video. It's pretty easy to tell if an engine is reaching it's max rpm.

 

[Snook Man]

You said it locked up? Did you disassemble the engine to see what failed? We love engine carnage pics. At least I do...

 

[synnyzter]

Well as I said it wasn't actually to lean. I had as rich as I could get it while still able to.run, there's plenty of smoke. But you are correct in that would be the typical answer.

I pulled.the engine today and bought a new 3.3, and when I pulled my clutch bell I realized kits bearings were blown up lol. So...it would seems the crankshaft was warped, probably due to a combination of wear and tear and 2 beakins. (Too much stress on it).

I'll gladly post up a pic of the top of the cooling head where you can see the remains of the plug.coil mashed up.

So, knowing the bearings were thrashed and the shaft probably warped its.safe to say no Max rpm wasn't reached which explains the lack of.shifting. I believe the hsn needle is also damaged or.something explaining the number of.turns away from factory that were required, didn't pull it yet but.I'll look later and post pic of it too if it.is.

---------- Post added at 11:41 PM ---------- Previous post was at 11:37 PM ----------

As.for.the glow.plug.exploding it.was the first time I ever used a traxxas plug, and last time!

Stupid . Is next to the space bar on phone grrrr lol

 

[synnyzter]

You can see the coil in the cylinder, it looks fused into one mass lol. Tomorrow I will take it apart and well see what the sleeve looks like. It's not very dramatic but it doesn't take much!

 

[2revo1maxx]

The bearing will wear out easily on most engines. The biggest problem with that is it will cause the crank to ruin the block. You need a new engine this time. That crap in the cylinder is probably junk from the bad bearings.

 

[Childresshunt]

Take the head off and post a pic. can't see much of anything like tht besides a lil mashed up stuff

 

[synnyzter]

OK the pics arent the greatest, best i could do with my phone. In the ones thats more blurry you can barely make out the pits in the cylinder but theres tons of em and the coil was fused into 2 solid pieces lol. This is the most I can break it down because I have to turn in the engine at my hobby shop sorry =/

 

[Snook Man]

That damage wasn’t caused by the plug coil (the damage/shrapnel is what caused the coil to break). That's either a bad bearing and/or a broken piston skirt most likely.

 

[synnyzter]

That damage wasn’t caused by the plug coil (the damage/shrapnel is what caused the coil to break). That's either a bad bearing and/or a broken piston skirt most likely.

Well either way a coil in there is still bad news lol. You dont think the coil could have done that? Brass is very malleable and doesn't take much to score it. The only bad bearing I had was the outer clutch bell bearing, it exploded. Internals were fine other than warped crankshaft, which killed that bearing. Anyhow thanks for all the replies, muchos gracias.

I did buy the new 3.3 and installed it today. Gee, 2 days ago I broke in my engine, tomorrow I get to....break in my engine lol.

I'm trying really hard to stick with nitro. I am somewhat a mechanic and love to tinker, customize, rebuild, get greasy, but I tell ya what, on the daily it gets tiring!

 

[2revo1maxx]

A plug coil will most likely get shot out the exhaust with only a minor scratch to the piston and sleeve assembly, your crankshaft is not warped either.
The engine most likely had worn bearings when you bought it, and then you put in a new piston and sleeve without replacing the bearings. A lot of engines are known for bearing failure within the first 2 gallons of use.

 

[synnyzter]

A plug coil will most likely get shot out the exhaust with only a minor scratch to the piston and sleeve assembly, your crankshaft is not warped either.
The engine most likely had worn bearings when you bought it, and then you put in a new piston and sleeve without replacing the bearings. A lot of engines are known for bearing failure within the first 2 gallons of use.

Actually I did replace the clutch bearings when I rebuilt the engine. They were trashed when i removed them, in fact one was blown completely apart lol. The new bearings didnt even make it through break in. I may have forgotten to mention that? Anyhow today is break in day for the new engine!