Broke 2 con rods in 1 week HELP!

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letsrip

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17
Hi guys, I am new to this forum, so I appreciate any help I get. I own a Savage XL, I have had the K5.9 engine for about 8 years, but not with that much usage. Took it out of storage and been running well for a few weeks. About a week ago the con rod snapped (I took it as general wear and tear). I took that as an opportunity to get the LRP 32 spec 2 (new condition from eBay - not broken in). During the break in process my clutch shoes kept seizing to the bell gear, I would release, file off any barbs and resume. On tank 4 (running up to 1/2 throttle) the con rod snapped!

Two questions:
Why do my clutch shoes keep binding with the bell gear?
If I have managed to break two engines in one week, what else might be wrong?

Any help would be great. Thanks in advance
 
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Not sure about the clutch.

For the engine, what fuel are you running? What does the piston/con-rod look like after the damage? Got a photo ro two How cold is it where your running? Are you preheating the engine at all? Is there smoke coming out of the pipe when it is running when you give it throttle?
 
Not sure about the clutch.

For the engine, what fuel are you running? What does the piston/con-rod look like after the damage? Got a photo ro two How cold is it where your running? Are you preheating the engine at all? Is there smoke coming out of the pipe when it is running when you give it throttle?
Thank you for the response. I have been running 20% nitro. I preheat the engine with a hair dryer, and the outside air temperature is around 25°C (not cold). During the break in process I have been running the engine rich, with thick smoke coming out. After the damage, the bottom of the con rod has broken on the attachment part, and the piston head has also crumbled on the lower edges.
 
Can you post a photo of the damage?

I've never had that happen and I tend to run my engines on the rich side. Although, I don't let them sit and idle through the first tank like most manuals suggest to do. I drive them on flat pavement/tarmac during break-in, slowly increasing/decreasing the throttle. Usually, the first few tanks, even if you do go WOT, it won't rev that high.

I have seen it happen though during break-in. Was many years ago. A buddy of mine had been running an OS 21 RG engine in his big block tmaxx. He probably had a gallon through it and the con-rod snapped. Then he replaced the engine with a new one of the same and on tank 4 or 5 of break-in, the conrod snapped again. Didn't make any sense as the con-rods in those engines are fairly robust and he had broken it in the same as I did with the 2 or 3 of the same engine at that time. The only difference was he ran odonnel fuel whereas I ran trinity MHP fuel, both 20%. It was even the same truck, we both had big block t-maxx's.

He didn't want to risk having it happen again and went with an entirely different engine the 3rd time and it never had an issue.
 
Can you post a photo of the damage?

I've never had that happen and I tend to run my engines on the rich side. Although, I don't let them sit and idle through the first tank like most manuals suggest to do. I drive them on flat pavement/tarmac during break-in, slowly increasing/decreasing the throttle. Usually, the first few tanks, even if you do go WOT, it won't rev that high.

I have seen it happen though during break-in. Was many years ago. A buddy of mine had been running an OS 21 RG engine in his big block tmaxx. He probably had a gallon through it and the con-rod snapped. Then he replaced the engine with a new one of the same and on tank 4 or 5 of break-in, the conrod snapped again. Didn't make any sense as the con-rods in those engines are fairly robust and he had broken it in the same as I did with the 2 or 3 of the same engine at that time. The only difference was he ran odonnel fuel whereas I ran trinity MHP fuel, both 20%. It was even the same truck, we both had big block t-maxx's.

He didn't want to risk having it happen again and went with an entirely different engine the 3rd time and it never had an issue.
I really appreciate this response. I agree, it is a very strange thing to happen twice! I have never had problems with my 5.9, and when it went a new engine was the easiest solution. With the new LRP it was performing very well, I think the excessive pressure from being stuck in gear snapped the con rod. I have attached two photos below to show both my pistons (the one with the majority of the con rod left is the new LRP piston.

I am also hoping for an answer on the seizing of my clutch shoes, is there something I have done wrong with the positioning of my engine on the chassis? (I.e spur gear against bell gear?)

Thanks again, and I look forward to any other similar experiences or info. 136BB72D-8BCB-40EE-B0D9-CDABC0FCE546.jpegDC6D1AFD-E435-4FEA-AD44-28662651966C.jpeg
 
With regards your clutch shoes without seeing your shoes they must be getting to hot or the C/B is, are both a Branded make & is C/B hardened type?
Just out of interest did you make sure piston was not pitched at top when starting engine & when you put it away each time particularly when breaking in?
Did you also use After run oil after each run ?
 
With regards your clutch shoes without seeing your shoes they must be getting to hot or the C/B is, are both a Branded make & is C/B hardened type?
Just out of interest did you make sure piston was not pitched at top when starting engine & when you put it away each time particularly when breaking in?
Did you also use After run oil after each run ?
The clutch shoes are HPI, I am not entirely sure what a C/B is? And yes, after each run (therefore when restarting), I ensure my piston is at BDC, and use after run oil after each run.
 
If it seized then you need to look at Condition of springs & bearings is the only other thing I can think of!
 
Don't want to sound rude but are you positive the clutch pads and springs are put together correct ?
 
Don't want to sound rude but are you positive the clutch pads and springs are put together correct ?
I have just found out that it was not correctly installed. Firstly, when I bought it on eBay the springs were not fully pushed down. When I reinstalled after brushing off the barbs, I too did not push the springs fully down. Pissed off about that!

This has called a number of problems as you can tell. Is that enough to snap a new piston? I believe it happened as I applied the breaks (and of course the gears were still engaged).
 
If it brought the engine to a dead stop . Very possible!!
That is a nightmare!! Thank you!!!! It is also a nightmare trying to get a replacement piston and con rod - I do not want to pay for a fully new engine
 
I’m surprised you can get lrp parts . Are you in the US ? A brand new Dynamite big red is $150
 
@letsrip I CANT HELP THINKING THAT TWO ENGINES BROKE IN THE SAME WAY THAT YOUR SLIPPING / STICKING / MELTING CLUTCH SHOES ARE THE CULPRIT . THAT'S JUST MY OPINION . HOPE AFTER YOU RESOLVE THAT YOU'LL BE RIPPIN WITH NO FURTHER ENGINE BOMBS .

P.S. NOT YELLING , ALWAYS TYPE IN CAPS .
 
@letsrip I CANT HELP THINKING THAT TWO ENGINES BROKE IN THE SAME WAY THAT YOUR SLIPPING / STICKING / MELTING CLUTCH SHOES ARE THE CULPRIT . THAT'S JUST MY OPINION . HOPE AFTER YOU RESOLVE THAT YOU'LL BE RIPPIN WITH NO FURTHER ENGINE BOMBS .

P.S. NOT YELLING , ALWAYS TYPE IN CAPS .
I believe so too! Other than putting the spring correctly in the groove, is there anything else I need to be cautious of with clutches? What’s a good replacement clutch for a big engine like the .32?
 
Which way were the shoes fitted as can go forwards or backwards, clockwise or antoi-clockwise?
1590668691341.png
 
Which way were the shoes fitted as can go forwards or backwards, clockwise or antoi-clockwise?
View attachment 8087
Great diagram thank you. They were on the right way round, unfortunately the spring was not pushed into the groove on the nut, hence was riding up! This small mistake has ultimately lead to the destruction of an engine
 
Your clutch shoes slipping the whole time whilst running in a new engine will be one reason why the clutch is overheating and siezing up. Thicker clutch springs will only let the clutch engage when the rpm's get above a certain speed. During a break in period, with a rich setting, this will mean much lower rpm and a clutch that will slip and generate a lot of heat. Alloy on steel = horrible. Whilst obviously bad/inconvenient, I don't think this would cause con rod failure. I genuinely don't.
 
Your clutch shoes slipping the whole time whilst running in a new engine will be one reason why the clutch is overheating and siezing up. Thicker clutch springs will only let the clutch engage when the rpm's get above a certain speed. During a break in period, with a rich setting, this will mean much lower rpm and a clutch that will slip and generate a lot of heat. Alloy on steel = horrible. Whilst obviously bad/inconvenient, I don't think this would cause con rod failure. I genuinely don't.
In your opinion, what would be a likely cause of con rod failure in this situation then? I am trying to diagnose before getting a new engine - can’t have it happen 3 times and still no working car.
Could there be anything wrong with my hearing/differentials?
 
It's unfortunate that you have 2 con rod failures, but your clutch ain't the cause of it. Conrod failures can occur for numerous reasons:

Lean sieze
Piston failure/breakage
Debris/Swarf (particularly relavent on a brand new engine)
Hydro locked engine
Corrosion

In your case, the first engine may have failed due to corrosion related failure Your second engine may have had a horrible life before you bought it. Eg, been disassembled re-assembled incorrectly. There are just too many variables.

Don't give up though. All the years I've enjoyed nitro, I've only broken 1 rod - on a Rossi .21 when I was in my early teens, over leaning my engine. I pushed the envelope and it went Bang.

I've seen others put their broken con rod through the block of their engine - twice. So you're doing well, really! ?
 
Get a new engine though, dude, from a reputable brand. It's risky getting second hand engines, because if they've been abused, the seller is hardly likely to advertise the fact.

I'm a big fan of Novarossi 28 8 engines. They scream! Easy to break in, tune and run.
 
I think it's your clutch system and one or some of your bearings. You meeting enough rotational resistance to break a part that I never been able to break. Get yourself a new clutch system and start looking for a bad bearing. You already know it's not in the engine so start by checking your transmission. I'm taking a guess but I would bet you have a steel spur otherwise I think you would have stripped it by now. Also it may help to loosen your slippers. Good luck. I hope I help solved your problem.
 
What starting method pullstart or rotostart? If rotostart what type of starter, battery type/voltage?
 
It's unfortunate that you have 2 con rod failures, but your clutch ain't the cause of it. Conrod failures can occur for numerous reasons:

Lean sieze
Piston failure/breakage
Debris/Swarf (particularly relavent on a brand new engine)
Hydro locked engine
Corrosion

In your case, the first engine may have failed due to corrosion related failure Your second engine may have had a horrible life before you bought it. Eg, been disassembled re-assembled incorrectly. There are just too many variables.

Don't give up though. All the years I've enjoyed nitro, I've only broken 1 rod - on a Rossi .21 when I was in my early teens, over leaning my engine. I pushed the envelope and it went Bang.

I've seen others put their broken con rod through the block of their engine - twice. So you're doing well, really! ?
Very helpful response thank you. What would be the top tips going forward when I get a new engine, I am looking to get another LRP.32 (if you think that is a good shout).

Anything I should closely look out for or do as extra precaution would be great.
Thanks
 
Just make sure clutch shoes/springs installed as per pic and clutch bell spins with no resistance and little movement forward/back. Check you can turn engine over by turning fly wheel by hand with glow plug out. Make sure truck rolls forward back at idle throttle position with engine off. Check brakes work and release as you roll it. As your using a pull start then there is very little strain on engine when starting. Always best to remove cooling head and backplate from new or used engine to inspect and rinse out with fuel. Make sure needles at factory settings. Preheat engine to 200F with heat gun on new engine, hair dryer not sufficient, loosen glow plug a touch if pinch too tight but retighten when running.
 
If the clutch was siezing due to heat, this would result in clutch bearing failure - yes - and a clutch that fails to disengage will stall the engine every time you apply the brakes and attempt to stop. Which is inconvenient, but nothing that would cause a conrod to fail.

The clutch is a separate issue, the remedies mentioned above will no doubt cure that side of things.

The simple truth is, you may never get to the bottom of why either con rod failed and it's entirely possible that both failures are unrelated.

You need to go ahead and fix your clutch at any rate. So do that.

Get a fresh new engine - no unknowns to deal with - and fresh fuel, fresh glow plugs. Take it from there. If you have a 3rd con rod go with the new engine - I suggest you try brushless! ?
 

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