Say It Isn't So, HPI

[DOOBEEWHA]

While I was enjoying the idea of having my Savage put back in order since my last airial display incident, I thought that all was well with the rebuild I had completed over the past few days.

The TVP'S striaghten nicely, I actually found better screws and bolts to replace the stripped out cross member supports that are worthless for resizing bigger screws.
I installed two aluminum supports to replace the trashed ones. the chassis is now stronger than it ever was.

My consern about the tranny turn out to be an internally sprung E-clip, that seats on the input shaft, inside the tranny. A quick openning of the tranny casing, and the E-clip was reinstallled easilly.
It seemed that luck was on my side for a change.

Remembering that my one-way bearring was starting to slip abit durring my last time bashing, I thought it best to clean it up from the oils beginning to infiltrate the roto start plate.
The motor, having close to 4 gallons through it, never really had a propper seal job.

I figured,... just do it, as burnt out as I was from rebuilding 90% of thr truck.

Now keep in mind,.... The mill was running fine, up until this rebuild.
It showed no indication of what I'm about to show you guys.

As a matter of fact, the mill was just becoming in to the realm of having a P & P job in the very near future.....NOT.

=============================================== This is what I found in my four gallon k4.6 ======================================================.

 

[DOOBEEWHA]

What the?...

 

[DOOBEEWHA]

What is so strange to me is:
There's no evidence of any fragments anywhere in the crankcase.
There's no indication of scoring, scraping, or shafing to speak of in the sleeve, whatsoever.

Did I just catch it it time before major failure, or what?
The skirt around the piston is 85% GONE. And what remains is a choppy, unevened edge where the skirt once was.

I looked everywhere to find some indication of anything that would be considered, remains of residue or particals, ect.
Nothing..... and only four gallons through it.

Outside of a defect in the piston, I find this a very bizare developement.
What are the chances of the mill blowing out the material fragments of the pistons skirt without leaving a clue to the cause?

Admittedly, I do not have a train eye for nitro "ware and tear" signatures to say what occured here.
Its almost as if the piston was installed at the factory this way which is just as unbelievable than that fact this mill still runs now, as it is.

I do know this. Four gallons does not an engine life, make.
I had a pretty good history with this mill. It always stayed in the low-mid 200's, degree wise.
It had a methodical break-in procedure, leannig towards factory reccommendations.

I just am supprised to see that I'm looking at a new piston & sleeve to get this mill back in a healthy state.
I don't want to assume anything with warranty yet, but I don't have much to work with here.

================== Anyone got some insight on this one?===============================

 

[Crash]

holy cow, I always think I'm the only one with the nitro mill demons. I bought a hpi 4.6 (not the k), last year. I got through break in no problem but, 1/2 gallon later it was hard to start and onces it got hot it would run like shi........t.
So, I tore down my new engine and here is what I found.

looks like yours doobee. wow

 

[DOOBEEWHA]

Hey crash, looks familure, for sure.

 

[HopIt]

I run the K4.6 at the mo, it's not had quite so much fuel through it, maybe just over two gallons. This could mean it's already more than half way through it's life, which really sucks because the replacement parts ain't cheap ! Looks like the .32 upgrade I was thinkin about is closer than I imagined :jumpers: I'll just wait till it's toast then get a new mill, for the price of a new HPI piston, conrod and liner I should be able to get a decent .32 !!
How much wear you guys got in the conrod bushes and on the crank shaft pin where it fits ??

 

[Jeremy]

Thanks crazy for a piston todo that
why mmmm not sure.... lean mabey other then that weird

 

[savagecre]

Yeah it is I can vouch for DOOBEE that he's motor was running KILLER. he might of had a bad spell in the beginning but that was gallons ago..it is weird though I'm thinkin mabey you guys had a stress crack from the manufacturing process, and it took a while but finaly gave? but still DooBee you had no signs of this in your motor. we looked at it inside and out...thats what puzzles me. no scrathes and dings inside the sleeve or crank case? those peices would have been alittle too big to not have an impact point.

 

[HopIt]

That is just pure wear you can see on DOOBEEWHAs piston. The aluminium dust particles would have just passed out of the exhaust without a trace. I bet if you stick a mic on that piston, it will be well and truely oval.
The damage you see on crashes piston is another story. This has happened in one hit, not sure how though !

 

[Jeremy]

had the same problem w/ my sts ... I sent to rb modds and he told me that I ran it VERY hot and the piston warped.. there also was no scratches or anything on the sleeve

wasn't that bad tho

 

[DOOBEEWHA]

In this case, It's probably going to be a 50/50 chance, HPI is going to kick back a piston & sleeve for warranty coverage.

I'll give them a call to see where I stand with this.
I won't be supprised if they tell me that there's no warrranty because I got the savage over a year ago. Four gallons or not.

On the other hand, maybe they'll consider the fact the It's an awfull short life span to have for what they cost to replace.

 

[HopIt]

It's an awfull short life span to have for what they cost to replace.

This is the thing with HPI, they charge top prices but there parts are no better, and in some cases are not as good as other brands.
There is something going on with HPI at the moment anyway, because all the Savage kits are now coming with Nosram .28 engines not HPI. Do you know anything about this ?

 

[Jeremy]

In this case, It's probably going to be a 50/50 chance, HPI is going to kick back a piston & sleeve for warranty coverage. I'll give them a call to see where I stand with this. I won't be supprised if they tell me that there's no warrranty because I got the savage over a year ago. Four gallons or not. On the other hand, maybe they'll consider the fact the It's an awfull short life span to have for what they cost to replace.

you did say right that you had 4 gallons on it right ?

if so cut your losses and get a new piston and sleeve, sure try hpi if they send you a part your lucky... 4 gallons isn't too bad

 

[savagecre]

four gallons not to bad? I thought I heard some where that the life expentancy of a nitro motor is 9-10 gallons? and 4 is a long ways away from that. so what is it that if all the things are done perfectly it will last 10 gallons or is that just another myth...

 

[Jeremy]

depends on how you run the engine !!! I get somewhere close to 6 before I have to rebuild

 

[DOOBEEWHA]

you did say right that you had 4 gallons on it right ?

if so cut your losses and get a new piston and sleeve, sure try hpi if they send you a part your lucky... 4 gallons isn't too bad

Yea... I here ya, bro.
I just figure that if your going to replace the piston & sleeve, you might as well replace the low quality bearrings as well.
Then of course, your still letting it all ride on the crank pin to hold up.

It's one of those " lets see how long it will last this time" deals which is the brakes, I suppose.

I just feel like I'm getting drawn into a spendding cycle on this mill caused by pre-mature engine failure. I feel 4 gallon is a BIG disapointment, If you ask me.
The fact that I've had the mill for over a year is why I can understand that hpi has a reasonable position in not replacing the piston and sleeve.

It's just one of those things to where I need to see if the company will stand behind there product based on principle, rather than, techicallities.

Thanks SJ

 

[Fx]

I wood defiantly check for any foreign material..........

 

[DOOBEEWHA]

Hey fxstrongside. I know I can be a little wordy in my posts, but did you read the posts in this thread? I think I went out of my way to discribe that fact that there was no evidence of any foreign or non-foreign matterials anywhere in the mill.

 

[HopIt]

Hey DOOBEEWHA, I have some exciting news about your worn out piston bro ! It's supposed to be like that, I just pulled the back of my K4.6 to check the seal and all, and I took a look at the piston through the back of the engine. It looks just like yours, but from the inside if you know what I mean ! When you watch the piston move up the liner the two cut outs line up with some ports. So maybe that's what the holes are for or maybe just savin weight, but I would say it's all about porting. Take a look in the manual http://www.hpi-europe.com/manuals/pdf/15201.pdf It's on page 5, I know it's not a proper picture, but you can clearly see the holes.

 

[Crash]

are you sure hop it?

 

[mikeh]

Wierd. I had no problems with my K4.6
Maybe a fluke? I would call HPI on that.

 

[HopIt]

are you sure hop it?

Yea, I'm sure about the holes in the side of the piston on DOOBEEWHAs, there exactley the same on mine. I can also see them on your new pics, just ! It wasn't til I looked at the piston in my own engine, that I could clearly see. Those holes are there intentionaly, no doubt in my mind !.
However, the chunk missing from your piston skirt is definately damage caused by something. I don't know what could have caused it, I not seen anything like it before, sorry !

 

[Crash]

sorry, I thought you meant the skirt on the piston, the port holes on piston were not in question just the skirt. Mine broke off same as doobee, same side if piston too. o well makes nice key chain now..............................

 

[HopIt]

Mine broke off same as doobee, same side if piston too.

Oh right, sorry ! I can't really see anytning wrong with the skirt on DOOBEEWHAs piston. That's why I thought he was talking about the holes. Maybe he can do some better close up pics from different angles.
Your piston skirt is definately damaged on the one side, but on the 2nd pic that all looks normal. That bit missing is a cut out section that goes toward the front of the engine and gives clearance for the counter weight on the crank shaft.

 

[HopIt]

I can't really see anytning wrong with the skirt on DOOBEEWHAs piston.

Ok, I've had a closer look at DOOBEEWHAs pic. I think I can see what your talking about crash, but unfortunately the picture has been taken from the wrong side. It certainley looks a bit iffy ! Need more pics DOOBEE !

 

[DOOBEEWHA]

 

[DOOBEEWHA]

 

[DOOBEEWHA]

 

[DOOBEEWHA]

I hope these are enough. I've got limited camera zoom and need to learn more on how to use it.

 

[HopIt]

Yea I can see now that the edge of the piston skirt has worn away and broken off in places. It must be very thin on the edge I guess ? Unfortunately I would say it's just wear and tear, but it may be worth speaking to HPI and see if this is within there normal life expectancy for this engine. I would definately like to hear back from you on this, because mine will soon be at that stage. Keep us posted DOOBEE, and good luck !