I put a Hyway 272 top end kit on a husqvarna 61. It came with a pop up piston and caber rings. I plugged the decomp hole. When I first built it I did a compression test and only came up with like 116 psi. Now I’ve got 1 tank of fuel through it and if I get the high screw where it seems right it will run ok but as soon as you lean on the saw at all the saw has no power and the chain just stops. Also it doesn’t want to start quite right. Even when warm it needs to have the choke on first. Did another compression test after one tank and still only 120 psi. Even after the piston breaks in I feel like I’m not going to get the compression. I would’ve thought compression should be 155 or better. What am I missing here?
272 new build low compression
- Thread starter Rfarr1994
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SteveSr
Addicted to ArboristSite
Using aftermarket parts and expecting OEM performance...
I completely get that the majority of aftermarket parts won’t come close to the quality of OEM but do you really think that’s all there is to it? I thought hyway was supposed to be halfway decent. Also forgot to mention did a base gasket delete and squish was .018 with no gasket.
.018 squish and only 120 compression. Like they say "sum ting wong". I am thinking a broken ring on assembly. IDK maybe??
Not sure which line of their kit you are using, but I have built a few using their Ni kits, you should be 180+ with the popup. Usually they run very well.
drf255
BAD CAD
Something wrong, I believe on the verboten site you claimed that your compression tested reads normally on your other saws? Does your comp tester have a shrader valve at the tip where it screws into the plug hole?
AM usually don’t compare with oem, but Hyway is actually not as bad as others. I’d contact them and see what they say.
Assuming your reading is real, it could be excessive ring gap, broken ring, out of round bore. Are you certain your squish is .018? Did you take that measurement at different points in the squish band and all the way to the wall of the bore?
Makes no sense. A popup and squish of 18 should be in the 180 range, unless the casting has a ridiculously huge combustion chamber. Consistency is another bane of the AM products.
Add 1-2 cc of 2 T oil to the bore, pull it over a few times, then recheck compression.
AM usually don’t compare with oem, but Hyway is actually not as bad as others. I’d contact them and see what they say.
Assuming your reading is real, it could be excessive ring gap, broken ring, out of round bore. Are you certain your squish is .018? Did you take that measurement at different points in the squish band and all the way to the wall of the bore?
Makes no sense. A popup and squish of 18 should be in the 180 range, unless the casting has a ridiculously huge combustion chamber. Consistency is another bane of the AM products.
Add 1-2 cc of 2 T oil to the bore, pull it over a few times, then recheck compression.
I had the cylinder off yesterday and ring wasn’t broken. The cylinder is nikasil with a pop up piston. Tested 2 more saws this morning with the compression tester and one was 150 and the other was 157 so I have no reason to think the gauge is off. I will try and check ring end gap and recheck squish and adding some oil to the bore this evening. Maybe I’ll give hyway a call too the website says it has a 1 year guarantee.
While you are doing end gap check P/C clearance at skirt too. Feeler gauges work for crude check. 0.002" go, 0.003" no go. Be careful not to mar piston
Checked the ring end gap this evening. I put the ring in the cylinder and used the piston so it was above the exhaust port and used feeler gauges to measure the gap. Came up with .015 had just a little resistance between the rings. Don’t know much about where it should be. Is that too loose or about right?
Pistons are tapered, bottom to top. The "skirt" is the bottom, measure there (widest place)
I think that's a little big but O.K. so you won't loose compression.
RED-85-Z51
Addicted to ArboristSite
Probably trash port timing
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Sent from my SM-G996U using Tapatalk
Wolf Creek Saw Shop was awesome in working with me swapping stuff out to get the saw running. Saw has a meteor top end on it now. I use stihl oil at 32:1. I timed the saw when I put it together and the numbers seemed on. I think I have them written down somewhere.
Pretty sure the problem ended up being a broken flywheel key. Put the meteor top end on it and same 120 psi. Eased with it for a while and finally saw the flywheel key was broken. Swapped to another flywheel and 170 psi. I thought when I checked the top end on 2 different 61’s I have here that they had 2 different flywheels on them but being almost 3 months ago I can’t remember what I did. The hyway kit was probably good to start with though, I just never thought to look at the flywheel.
So basically it was a husqvarna part that failed ?
