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JohnF2015
JohnF2015, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1081
Experience:  Owner/Service Technician at S & J Small Engines
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Husqvarna 125 BX 125bvx: I have a no start condition on a husquavarna

Customer Question

I have a no start condition on a husquavarna leaf blower 125BVX series. I have tried everything I know of yet I can figure this one out.
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
Is there someone working on this question?
Expert:  Curtis B. replied 1 year ago.
When did it last run? You replaced the rings? Did you check the flywheel key, to be sure timing is correct? If you put fuel direct into the spark plug hole, re-install the spark plug, will it fire for a few seconds. ???
Customer: replied 1 year ago.
It fired up for a few seconds about a month ago. Putting fuel in chamber or thru carb did not even get a fire. Checked spark several times and it is very blue and strong. No issues with flywheel key for timing. Looks great. I did replace the one ring as I had it apart to replace the crank seals which I found no problem with.
Customer: replied 1 year ago.
I even took muffler off to see if it would start. Same situation...no fire at all.
Customer: replied 1 year ago.
The unit is less than two years old and maybe 3 hours on it.
Customer: replied 1 year ago.
I removed all coil grounding and switch to be sure there was not an intermintant ground.
Expert:  Curtis B. replied 1 year ago.
What is the compression? Needs to be 140 psi. ??
Customer: replied 1 year ago.
How many pulls with tester hooked up to get 140?
Expert:  Curtis B. replied 1 year ago.
4 to 5 pulls
Customer: replied 1 year ago.
Ok, I will hook up my guage and give you the results in a few minutes.
Customer: replied 1 year ago.
5 pulls the compression is 75. 10 pulls it is 120.
Customer: replied 1 year ago.
rechecked again at 5 pulls. 80PSI
Expert:  Curtis B. replied 1 year ago.
Did you hone the cylinder for the new ring? Compression is too low for good start.
Customer: replied 1 year ago.
Yes I honed the cylinder with tool a little. Cylinder looked good and so did the piston. No scoring at all. You would think it would fire at 75 PSI but hard to start and run poorly. Am I correct or will this low of compression cause a total no start.
Expert:  Curtis B. replied 1 year ago.
Yes, low compression, you could try it with starting fluid to try and get it running, it has a lower ignition point. If you get it running, it might seat the rings and help!
Customer: replied 1 year ago.
OK, I will use some starting fluid in carb and see if I can get it to fire. But it would not start prior to replacing ring with starter fluid. I will use the fluid and get back to you. Would a wet compression test help in diagnosis on 2 cycle?
Customer: replied 1 year ago.
No luck with starting fluid in both the carb and a tiny bit in cylinder. will not even fire.
Customer: replied 1 year ago.
Recheck spark plug gap .028. Moved it to .030 and no start. It does not even pop. just like if the coil was grounded.
Expert:  Curtis B. replied 1 year ago.
You do have spark if you remove the plug and ground it to the metal?
Customer: replied 1 year ago.
Yes, very blue and strong.
Expert:  Curtis B. replied 1 year ago.
Spark,fuel, timing, all good. Compression is too low! Did you by chance check the ring gap in the cylinder before you installed on the piston?
Customer: replied 1 year ago.
No I did not do that as everything looked so clean and no scoring at all.
Customer: replied 1 year ago.
Is there a spec for that on this unit and I guess I will tear it down and check. Like I said the unit has very few hours on it but I have seen weird things happen in the past.
Expert:  Curtis B. replied 1 year ago.
Ring gap has to be around .010 inch. Over .020 you loose compression.
Customer: replied 1 year ago.
So on a 2 cycle it would be a matter of removing piston from cylinder, removing the piston ring and measure with feeler guage on one side the clearance between the piston and the cylinder wall, correct?
Customer: replied 1 year ago.
If it is over .020, then it would be needing a new cylinder, correct?
Expert:  Curtis B. replied 1 year ago.
Yes, just put the bare ring into the cylinder, and measure the end gap.
Customer: replied 1 year ago.
OK, got it. Just the ring itself...
is there oversize rings available as they used to have where you just put in new ring that is oversized to meet the spec?
Expert:  Curtis B. replied 1 year ago.
Check the piston top for any numbers that might show it being not standard. It could have been oversize to begin with. Sometimes manufacturer does that to use cylinders that will not make standard size.
Customer: replied 1 year ago.
I just disassembled and there are no numbers on the top of the piston. clean and no markings.
Customer: replied 1 year ago.
Ring gap is basically zero. maybe .001
Expert:  Curtis B. replied 1 year ago.
zero? no room for expansion.
Expert:  Curtis B. replied 1 year ago.
Same at top and bottom of cylinder wall?
Customer: replied 1 year ago.
Yes, both top ...middle and bottom have very little clearance . Same gap
Expert:  Curtis B. replied 1 year ago.
Do you have old ring? What would it measure?
Customer: replied 1 year ago.
the old ring is .006 end gap.
Customer: replied 1 year ago.
New ring is .002 to be exact.
Expert:  Curtis B. replied 1 year ago.
That should work. Now why does it not have compression? Could the cylinder be cracked? Rod has no play in it, that would keep piston from going to the top?
Expert:  Curtis B. replied 1 year ago.
Piston cracked?
Customer: replied 1 year ago.
I checked them both very carefully prior with bright light. I will check them both again right now.
Expert:  Curtis B. replied 1 year ago.
OK>
Customer: replied 1 year ago.
Piston top and skirt look great. Cylinder is also great with no scores or marks or cracks. Spark plug hole is solid with no cracks.
Checked both inside and outside of cylinder for cracks and leaks. Nothing wrong as far as I can see. The cylinder may need a little more cross hatching with hone as it is a little polished. Not bad but needs a little more. No cracks anywhere.
Expert:  Curtis B. replied 1 year ago.
I'm at a loss, let me opt out and see if someone else has ever seen this!
Customer: replied 1 year ago.
ok...I am going crazy on this unit. I work on numerous units but this one has got me stumped big time.
Expert:  JohnF2015 replied 1 year ago.
Hi, my name is***** will try to continue to assist you.It sounds like you have one that has you stumped. From the prior conversation I see that you have tried just about everything that could be suggested to you.In my experiences these machines will not start or attempt to start with less than 90PSI compression, by your indication of 75-80PSI I can tell you that you definitely don't have enough compression for the machine to start.There are no oversized parts available for these machine, only standard sized. Based on your provided information I see no reason as to why this machine should not have better compression unless the ring is just not seated at this point. Maybe try a little bit of oil dropped in on top of the piston to help form a better seal between rings and cylinder to see if that helps your compression for the moment.If the ring gap is at .002 as you say all the way up and down the cylinder wall then I wouldn't think that it would be a wear issue. If the seals were damaged or bad it should still at least fire when you spray carburetor cleaner into the spark plug hole or carburetor.Are you an authorized Husqvarna servicing dealer?
Customer: replied 1 year ago.
Got your message. I have not done a wet compression test. The seals on the crank are new as well as the bottom plate for crank. I am not a dealer for Husquvarna. I wish I could find out why it has low compression. everything looks great.
Expert:  JohnF2015 replied 1 year ago.
You may want to try a wet compression check just to see if anything changes.Since the machine is less than two years old it is still under the original manufactures warranty and could be repaired by an authorized service center as long as you haven't voided the warranty by working on it yourself. That call would be up to the service center to determine.My thought is that the rings just aren't seating well to the cylinder wall and is causing low compression.
Customer: replied 1 year ago.
Should I hone it some more?
Expert:  JohnF2015 replied 1 year ago.
I would not recommend honing it because it will only increase the end gap on the ring and cause more possible compression issues. Since there is no oversized parts available for these engines if you hone it too much you will end up having to replace the cylinder.
Customer: replied 1 year ago.
Any further suggestions? I really do not understand how this unit with less than 3 hours on it have a compression issue? Have you seen this before?
Expert:  JohnF2015 replied 1 year ago.
I have seen them especially with little or no use as this one has. I see a lot of times the rings stick in the piston and will create low compression. You have a new ring which should not be a ring stuck issue. The only other times that I have seen it is if the cylinder is damaged from not running the proper fuel mixture. Again you indicated that the ring gap was .002 on the new ring all the way up and down through the cylinder so I don't see how that could be an issue.
Customer: replied 1 year ago.
do you know the difference from a 125bvx and a 125bv?
Customer: replied 1 year ago.
I used my Snap-on compression tester I use on cars and I would assume it is accurate. Let us say that the compression tester is wrong, could I be dealing with a serious flooding issue? When ever I pulled apart there was a lot of fuel in compression chamber etc. I have to assume it is from fuel going in and not being burnt. This is a big challenge for me and so far nothing is making any sense to me.

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