Chainsaw Repair
How To Basics - Carb Fixes + Mods - IPL and Service Manuals => How To Basics and Fixes => Topic started by: aclarke on May 06, 2015, 06:29:44 pm
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Had some 3120 crankshafts stroked and balanced by Crank Works in Arizona and they added thrust washers to the big end of the crank. In the past I've used bushings on the small end side to center the connecting rod, now I'm wondering if these are adequate for centering The rod? Wide gap on the Wiseco piston boss...
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You need to make bushings to use the wiseco piston , Wiseco told me to use 6061 T6 grade or better and I never had any trouble , I leave .010 clearance on the bushing to the piston
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Sounds good Ed, I'll use the 6061 bushings I've made. Appreciate the heads up...
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Sounds good Ed, I'll use the 6061 bushings I've made. Appreciate the heads up...
I don't think you can use them with the trust washers on the bottom end. Almost all automotive pistons are located by the big end.
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I've always made spacers for the small end when using the Wiseco pistons to keep the rod from riding on one side of the crank. Thrust washers are common on the m/c two stroke kart motors, but haven't seen them on saws? If the rod is centered with thrust washers on the big end would putting them on the small end be a waste? About a .180 gap on each side of the Wiseco piston with 084 rod.
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I would think it would be a waste. Too tight and you might bind the rod, too loose and they'll never do anything.
I'd call the crank shop and see what they recommend.
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I'll see what they say. Thk
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Talked to Crank Works, they added thrust washers on the big end because the 084 rid is narrower than the 3120 rod. Helps keep the big end bearing from moving side to side. Makes sense, although the crank that Falicon made for me a few years back didn't have the thrust bearings. Odd...
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So it sounds like the washers just restored the normal 084 rod bid end thrust clearance (which should be still decently large)? So you'll would still want to run spacers on the piston pin to locate the rod.
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Yo got it, the work order he read to me said : "Make custom thrust washers for narrower rod" clearance is likely what Husky had on the oem crank I sent to them. I'm gonna us the spacers I made for the wrist pin. They still allow some lateral movement.
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use the thrust washers you made , donot run saw without them, I have seen a couple motors guys didnot use the washers and figured the rod being centred on the crank would work, it didnot . I donot use thrust washers to the big end and only use the 084 rod , never ever had a problem
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Adam check the 3120 I just sent you. I don't remember thrust washers on it...????
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I'm talking the thrust washers on the piston end not the big end , I always put a new stock 3120 bearing on the big end when stroking and changing to 084 rod , to put thrust washers on the big end they must of used a narrower rod bearing
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Ed, You're right. The big end bearing I sent them was a high quality silvered bearing but slightly narrower than the Husky bearing. Didn't think about that being the issue. Thks
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I think I've made 3 sets so far for 3120 strokers .They were 6160 aluminum.Must have worked as I never heard differently .
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Al, I remember you made some for Cliff? We're they flat or scalloped to allow more oil to migrate into the needle cage?
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They were just blanks .I don't know what he did with them .I had the ID and OD right on the money but left some meat on the length so they could be fitted at how ever much clearance he wanted .
If I recall I made several blank sets and Kevin might have ended up with a pair on that 3120 hottie he had .
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Good deal Al. I made a batch and cut four radial slots 9,12,3 and 6 o'clock with a ball end mill to let some more oil into the bearing. Probably not necessary, but...