I dont know history of tractor was in bad shape when I got it.Have been working on it about a year off and on.I have engine together but cant get it started.Carb rebuilt by a professonal mag is hot new wires blue spark and in time Valves set at .020 by the book pistons are .045 oversize 4 1/2 inch pistons Compression comes up to around 30psi and leaks back through crankcase.But am only hand cranking.It wil almost take off sometimes but never been very promising.Should this air leak back I know with engine cold the compression will be lower.I miced the block before putting pistons in but only at the top read 4.5+.045 with very little ring grove.I have put air in plug holes with both valves closed and air comes back through crankcase but my air pressure is about 120psi.Is my block more wore than I thought or is this normal for blowback on these engines cold.Please help me Im ignorant and stump at what to do.This hand crank and no prize has gotten old.Thanks for your help anyone.
- Thread starter MAF
- Start date
Would of been nice to know the wear in the worst part of the cylinder which is usually at the top of the ring travel in the straight up and down position.
Were the end gaps of the rings staggered ? was the end gap of the rings measured ? were they NEW rings ? if so maybe they were only for standard bore ?
I've had low compression on fresh engines from valves being held open from assembly lube. Tapping on them seemed to help. Sometimes the initial start up can be a challenge due to oil in the cylinders and such.
Got another tractor to hook up a flat belt to crank it ? I'd try that and check your compression then too.
Were the end gaps of the rings staggered ? was the end gap of the rings measured ? were they NEW rings ? if so maybe they were only for standard bore ?
I've had low compression on fresh engines from valves being held open from assembly lube. Tapping on them seemed to help. Sometimes the initial start up can be a challenge due to oil in the cylinders and such.
Got another tractor to hook up a flat belt to crank it ? I'd try that and check your compression then too.
Yes rings are new and box said .045 I did not measure the rings just assumed they were right And made sure gaps were staggered I have also checked both cylinders with both valves open and closed with air hose no air through intake or exaust with valves closed.So you think my compression leaking back is o.k. I have never rebuilt any thing this old or hand start so its all new to me what to expect.Thanks for your help and anything else you might come up with.I will keep trying.
golfcartman
Member
You just gotta get it turning faster than hand cranking, like the others said by pull starting or belt pulley from another tractor. I love hand start tractors but that first start can be a booger
BushogPapa
Well-known Member
Some feel the Rings can loose their seal from oil draining down over long storage.
Such was the diagnosis from a JD Service Tech.
The problem (non-starting) 530 had the cylinders fogged with oil, compression picked right up and it has started as it should since..
I have heard this several different times and it does seem to have merit.
Ron.
MAF, Turn your PSI down to 50-60 psi. These engines never had that much cylinder pressure when new. So, what makes you think you can make the rings seal at almost three times the psi now then when these machines were new ? Maynot be the problem either. The condition of the bores and rings work together for a good ring seal. Did you bore the block ? Did you hone the cylinders ?
No I did not bore the block But I did hone cylinders The engine had .045 pistons in it when I tore it down.The ring groove is barely visible and I mic the block myself showed .045 above 4.5 inch bore I know 110psi pressure is more than it ever had my main question is should the pressure it creates itself blow back almost imediatly I assume someone else bored it long back.Again dont know the history.
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