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ASP 70 FS un-usual wear

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MikeS24/04/2014 17:16:58
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818 forum posts
240 photos

Having a strange starting problem with my ASP 70 FS lead me to checking everything from the fuel tank to engine bolt tightness.

Having the back plate off to check the bearings I noticed metal wear marks which looks like the con rod has been hitting the inside of the case.

Heres a photo,

dsc_0732.jpg

 

Mike

 

Edited By MikeS on 24/04/2014 17:20:30

Brian Lambert24/04/2014 18:46:07
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339 forum posts
6 photos

Mm, Judging by what looks like rust on the crank shaft, I would look at the bearings for more rust.

Brian

MikeS24/04/2014 18:55:37
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818 forum posts
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After each flying session I put afterun oil through as I do all my engines. I was surprised to see the scraped metal markings and possible rust.

Mike

Engine Doctor26/04/2014 13:32:01
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2511 forum posts
39 photos

If that piece of swarf in the pic was inside when you took the back plate off then there is definately a problem . Strip the engine down and check where its come from .the bearings would have to be very bad to cause it and you would surely have noticed the noise. Let us know what you find and more pics . If the engine sill has good compression ts probably easy and worth fixing.

E.D.

MikeS26/04/2014 23:40:19
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818 forum posts
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E.D, I thought that it looked like swarf in the photo but it is a small piece of cloth from cleaning out the inside of the case looking for any small metel peices.

The bearings look and feel ok and no noise when running the engine, I am still try to figure out what has caused the damaged. I could imagine a broken bearing cage causing it but can find anything inside to confirm that. The engine ran very well unitl it started to load up when at idle.

No amount of adjusting the low end has had any effect.

Mike

Martin Harris27/04/2014 00:17:21
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9337 forum posts
249 photos

I've seen quite a few engines with broken crankpins over the last few years (mostly SC/ASP but also a Saito). These pins are very hard and I've assumed that they fracture instantaneously but I'm wondering if the pin has half broken allowing a little movement of the big end?

Obviously, if this is the case, any more running will break it completely. Even if this is an unlikely hypothesis, I'd strip it and take a careful look for any hairline crack at the base of the crankpin.

There's even a possibility that the crankshaft itself has broken and is being held together by the proximity of the backplate - which does appear to have some recent wear in the picture.

Edited By Martin Harris on 27/04/2014 00:31:59

MikeS27/04/2014 13:01:34
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818 forum posts
240 photos

OK Martin I will strip it down and and have a look.

Thanks Mike

Stevo27/04/2014 18:14:19
2699 forum posts
419 photos

+1 for the loose crankpin - I've had one and had to braze it back in!!

MikeS28/04/2014 12:55:36
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818 forum posts
240 photos

Started to strip down the engine but need to get the liner out but it is stuck. Will have to put in the oven for ten minutes. I have noticed on the inside of liner very fine lines from top to bottom you can feel with you nail.

I am thinking small particles have got past the ring as some minor impact marks in the head. Will get some photos up later.

Mike

Edited By MikeS on 28/04/2014 12:56:04

David P Williams28/04/2014 13:12:58
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913 forum posts
318 photos

I would bet on main bearing cage breaking up. I've had this happen and the damage looked like yours. Mine was a 2 stroke though so quite big bits could pass up the transfer ports. Was hard to start and 'blew' a couple of plugs - actually they were being shot blasted. The piston crown looked like the sutface of the moon. Hope your's isn't too bad.

David

cymaz28/04/2014 14:02:53
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9253 forum posts
1195 photos

As you probably know ASP parts are readily available from JE. If any part looks dodgy - change it yes

I had a big end pin snap off. All repaired under 5 days thanks to JE.

Looks like a collapsed rusty bearing. Simply Bearings are very good at shipping out quick.

Edited By cymaz on 28/04/2014 14:04:31

Edited By cymaz on 28/04/2014 14:06:02

Edited By cymaz on 28/04/2014 14:06:25

MikeS28/04/2014 21:37:08
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818 forum posts
240 photos

The head looks ok on closer inspection and those valves need a clean.

dsc_0818.jpg

 

However the inside of the liner looks bad. Those lines are on each side of the liner however compression is good. The engine bearings did not make any noises when running but i still need to get the liner out.

dsc_0819.jpg

Mike

Edited By MikeS on 28/04/2014 21:37:41

Steve Hargreaves - Moderator28/04/2014 21:44:25
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Ooo that liner looks poorly Mike.....broken ring possibly??

Get the case good & hot & the liner should push out OK....don't burn your fingers...wink 2

MikeS29/04/2014 11:38:51
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818 forum posts
240 photos

Steve I thought that but after removing the liner and piston found the piston ring in one piece. The piston is bad.

dsc_0005.jpg

dsc_0006.jpg

The bearings feel and look to be in good order. No missing bearings or cages. I am starting to wonder if dirt has made its was in. I also wonder if it is my engine after care that may have caused it.

After a session with my four strokes, all ASP, 70, 91 & 120 I remove the rocker cover and run oil down the tappet rods to get oil inside the engine as the breather pipe behind the cowl. However after stripping down the engine I see this that the rods have cam followers so the oil will take for ever to reach the engine. I have always put after run oil in all my engines since my two stoke days.

Liner removed

dsc_0007.jpg

I am yet to check the pinon for cracks etc.

Mike

Edited By MikeS on 29/04/2014 11:39:22

cymaz29/04/2014 11:42:57
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9253 forum posts
1195 photos

Depending on the age of the motor, could some manufacturing scarf have been left in the engine? Given enough time it found its way around the engine? As the bearings seem fine .

Edited By cymaz on 29/04/2014 11:43:59

Edited By cymaz on 29/04/2014 11:44:22

MikeS29/04/2014 11:51:13
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818 forum posts
240 photos

Cymaz its possible. The engine ran fine right up until it started loading up at idle and moving the low end screw had no effect. If not for this I would have not stripped it down and carried on flying. My point is the engine had bags of power and run well.

So far I need a new Piston, Piston ring, Liner, and two bearings as might as well change them. Already up to six notes. if I need much more I'm not far off a new engine.

Mike

cymaz29/04/2014 11:57:53
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9253 forum posts
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I know from passed experience some of the o rings on the carb do not seal at all well. I have put a thin washer of fuel tube onto the high speed needle before screwing it in. This has stopped any air leakage. Though I see you adjusted the LSN.

MikeS29/04/2014 13:34:40
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818 forum posts
240 photos

Cymaz. I have heard of that tip but never tried it. Yes the low end I adjusted, I am still puzzled at what seems to caused the damage.

Mike

MikeS30/04/2014 09:28:23
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818 forum posts
240 photos

Removed the conrod and found no damage other than where contact with foreign object and the casing. Piston pin ok. So I need to remove the bearings to completely rule them out but its looks either manufacturer swarf or dirt ingres somehow.

Is it possible that a hot run could cause contact between conrod and case from a cold start. When starting my four strokes I run the at full throttle for 30 seconds to warm them up. I was advised to do this.

Mike

Bob Cotsford30/04/2014 09:34:28
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8581 forum posts
477 photos

and do you warm your car up the same way Mike? I doubt you do.  I warm up engines a little more gently, a fast tickover until it will run smoothly without the glow connected then short bursts of throttle gradually raising the max revs over a minute or so.

Edited By Bob Cotsford on 30/04/2014 09:35:00

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