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Message started by jashmash21 on 02/22/16 at 14:06:00

Title: Savage Engine Tear down - Piston Condition
Post by jashmash21 on 02/22/16 at 14:06:00

Hi folks, quick history - bought a 1997 savage, ~6,800 miles, knowing that the engine didn't have compression when I bought it. This is my first engine tear down - and while tearing down the engine, I found the following:

- The cam chain tensioner was missing, along with the adjuster assembly completely apart with the adjuster spring in pieces (this may have been the culprit to the damages described below); I plan to order verslavy mod, and have ordered a new tensioner, and chain;

- The cylinder head seemed to have no noticable damages, neither did the cam; The cam chain had a "kink" in one particular area, so I will be replacing it;

- The top of the piston seems to have a fair amount of gashes/scratches (see picture), and clymer didn't have any suggestions on the condition of the top side except for not removing any of the carbon deposit; I didn't clean the piston at all, I found it as pictured; The side of the piston cylinder looked fine, one of the rings broke off while I was removing it... :-/

- The valves looked ok with no obvious damage, and was within the clymer specs (so I cleaned and lapped the valves );

- I took the cylinder out and have cleaned it and glazed the inside with a hone;

- The previous owner seems to have done a half-a$$ job of putting the engine together after attempting to "fix" the bike, and found goopy RTV gasket sealer used super liberally especially around the cylinder head, head gasket, and head bolts, where he tried to "glue" the bolts back to the cylinder head with the gasket sealer; >:(

Based on the attached picture of the piston - I am looking for advice on whether the piston looks re-usable because of the numerous gashes/scratches, or should I bite the bullet and buy a new piston? Anything else I should inspect?

Really appreciate the help!
MJ

Title: Re: Savage Engine Tear down - Piston Condition
Post by verslagen1 on 02/22/16 at 14:25:23

just scrapes from removing carbon

but it's a red flag, a lot of carbon means it was burning oil and you should get new rings.

Title: Re: Savage Engine Tear down - Piston Condition
Post by Srotag on 02/22/16 at 16:32:36

Those scratches when magnified look like tool marks from your previous owners poor work. They could be polished smooth if you don't want to pop for a new piston.
I have seen worse, the key is no edges/burrs that can heat unevenly at speed...causes hot spots and eventual failure. Usually on a long dark, lonely, rainy road, with no cell service....might want to reconsider that piston purchase now. 8-) 8-) 8-)

Title: Re: Savage Engine Tear down - Piston Condition
Post by LANCER on 02/22/16 at 16:53:41

I hope to have the 94mm Wiseco High Compression pistons in a month from now. What does your repair/replace timeline look like ?

Title: Re: Savage Engine Tear down - Piston Condition
Post by justin_o_guy2 on 02/22/16 at 19:00:40

In that deep, going back stock seems a shame.
How do you like to ride?

Title: Re: Savage Engine Tear down - Piston Condition
Post by Kris01 on 02/22/16 at 19:06:54

Most pistons have something denoting "forward". Is that what the triangle is or is it a hole made by the PO?

Title: Re: Savage Engine Tear down - Piston Condition
Post by old.indian on 02/22/16 at 19:32:33

From what I can see, that "triangle" looks deep into the surface of the piston's top. If so, personally I'd replace it. But you should get one of the more experienced builders' opinion.
Note: Think about where you want to be with this bike down the road i.e. Café racer, bobber, cruiser, touring, and what is your "budget" ? Right now you are in a perfect position to get the motor where you want it and if you are doing it yourself you can a pretty serious engine on a pretty reasonable budget. 8-)

Title: Re: Savage Engine Tear down - Piston Condition
Post by Dave on 02/23/16 at 04:33:00

Only 6,800 miles.....and the engine has already been apart once (and repaired badly)?

Do you know how you are going to be riding this bike? Trips around town at a snails pace.....commuter......bar hopper.....canyon carver.....touring?

If you are planning on a motorcycle for some local rides and never plan to be very far from home....and only put a few thousand miles on it before selling it - obviously you aren't going to want to throw a lot of money into the engine. If you are planning on keeping this bike for an extended period, and if you plan on putting a lot of miles on it - then you can justify putting some parts in the engine knowing you are going to get some good use out of them.

If you are going to keep the bike and ride it a lot, a new 94mm Wiseco, new cam chain, check the cam and rockers for wear, Versy tensioner and head plug.....and new gaskets.

If you are going to ride it a bit and sell it....I have a good stock piston, good used cam chain with life in it that I can sell you at a very reasonable price. Check your cam and rockers for wear......and the Versy Tensioner and head plug...and new gasets.

Title: Re: Savage Engine Tear down - Piston Condition
Post by justin_o_guy2 on 02/23/16 at 05:01:14

I'd like an explanation for the triangle. Looks like it's deep and edges look like it's punched in while Hot, as in, manufactured.
If someone wants Me to know what side goes forward, putting the mark way over on one side seems weird.
I can understand forward and rearward on a two cycles, but not sure why on a four stroke, unless the wrist pin is off center. Seems like I remember seeing something about that.
Of course, high compression, close fit, valve clearanced, naturally, gotta be One way only.

Title: Re: Savage Engine Tear down - Piston Condition
Post by jashmash21 on 02/23/16 at 07:25:36

Lancer - i'm working slow on the bike (usually only a few hours over the weekends). How much would you sell the 94mm HC piston for? I am definitely willing to wait a little for it if it's not too pricey!

Dave - I'm just an inner city commuter (max10-20miles round trip at max), I rarely take out my working savage out on the freeway; I plan on keeping the bike after repairing, and perhaps sell my old one, will see :-/. however, I am moving out to the burbs in a few months, so more freeway commuting will be in my future. I'm also considering a bobber conversion for the bike as well. Please PM me what you want for the used piston and cam chain!

old.indian, Justin_o_guy2 - I believe the triangle denotes the direction of the exhaust (?). Anyways, i'm positive you're correct, the piston left the factory with the triangle stamped on it;

Title: Re: Savage Engine Tear down - Piston Condition
Post by Kris01 on 02/23/16 at 18:49:38

Considering it's a flat top piston with no valve reliefs and only 8.5:1 compression, the combustion chamber must be huge! If there were valve reliefs I can see where there would be some sort of designation for front. Being a flat top, I can't find any reason to point the piston a certain direction.

Title: Re: Savage Engine Tear down - Piston Condition
Post by justin_o_guy2 on 02/23/16 at 20:09:24

is off center. Seems like I remember

Title: Re: Savage Engine Tear down - Piston Condition
Post by Dave on 02/24/16 at 03:53:46

447D667C3F3E0F0 wrote:

The wrist pin is not located in the center of the piston....it is offset to help even out the load and wear on the piston skirt and cylinder wall. When the crank is on the compression or power stroke, the rod is at an angle to the center of the cylinder, and sideways loads are placed on the piston. The cylinder pressure during the compression stroke is far less than on the power stroke - so the pin is offset to help reduce the sideways loads during the power stroke.

Title: Re: Savage Engine Tear down - Piston Condition
Post by Kris01 on 02/24/16 at 05:04:20

Is that because it's a long rod engine? Shorter rods puts less of a load on the cylinder wall.

Title: Re: Savage Engine Tear down - Piston Condition
Post by Dave on 02/24/16 at 05:40:39

1C253E246766570 wrote:

Is that because it's a long rod engine? Shorter rods puts less of a load on the cylinder wall.

Every engine....long or short stroke has an offset piston pin.

The amount of the offset is most likely changed to match both the stroke, and the length of the connecting rod. Even with very long strokes you can get a mild rod angle.....if the connecting rod is made to be long - the downside is that the engine becomes very tall, and becomes heavier as the height of the cylinder/block must be increased.

Title: Re: Savage Engine Tear down - Piston Condition
Post by Kris01 on 02/24/16 at 13:55:21

457E7364757962647F777A65160 wrote:

Every engine....long or short stroke has an offset piston pin.

Maybe I'm not following you Dave. I've torn down a few engines and don't remember any of the wrist pins being offset. They were all small block Fords if it matters but the pin seemed to be centered.

Title: Re: Savage Engine Tear down - Piston Condition
Post by Dave on 02/24/16 at 16:24:16

The pin appeared to be centered - but most likely it wasn't. The offset is not so huge that you are going to be able to visually tell. That is why every piston is marked with something to show you the forward side of the piston.

http://www.motorcycleproject.com/text/cows-offset.html

Title: Re: Savage Engine Tear down - Piston Condition
Post by Kris01 on 02/24/16 at 16:46:03

I never realized that. I guess you DO learn something new every day! Thanks! :)

Title: Re: Savage Engine Tear down - Piston Condition
Post by justin_o_guy2 on 02/24/16 at 18:15:35

I guess you DO learn something new every day! Thanks! Smiley

Hmm, I didn't know that!