Non scooter question?

[aschrauth]

I have a question that is non scooter related that Im curious about. If this is not allowed on this fourm just message me and I will delete the post.

About a month ago I picked up a leaf blower off marketplace for $10. It is a Poluan pro BVM200. It runs fantastic and came with all the attachments and even the owners manual, I changed out the fuel lines and replaced the primer bulb as they were eaten away by ethanol. I measured the compression and I got about 90 PSI after about six pulls. I follow this gentleman on YouTube ( Great channel by the way if you are interested in fixing lawn equipment) and he worked on the same blower and managed to get up to 110 PSI. So I followed his instructions and started off cheap by replacing the piston ring for about five dollars. Once I reinstalled everything I was getting about the same 90 PSI as before. when I disassembled the head and looked at the cylinder I saw minor scuffing on the piston but nothing that would catch my fingernail. However, the Jug had several deep scratches. So I opted to replace it for $25.00.

  I reassembled the jug and piston with assembly lube and buttoned everything back up together, Pulled the cord about ten times and was still getting a reading of about 90 PSI. For a minute I thought my gauge was faulty so I rented one from AutoZone and the numbers were pretty close. 

Now I know that these small engines are somewhat disposable and not many people would bother fixing one But I would rather fix this one then getting another one in the next five years. My question is why am I still getting 90 PSI. Im wondering If I should have replaced the piston as well.

Here is a cost list so far if you are curious.

Blower itself - 10.00
Fuel lines and primer bulb 8.99
Cylandar jug- 25.00
Piston-

Let me all know what you think. Here is a link to the gentlman that I mentioned earlier in the post.

[CROSSBOLT]

I harp about some things on here because they are simple, easy to check and many times the primary cause. On two smoke engines, my favorite harp is "piston ring end gap." Too little and the engine stops when it gets to temp because the ends touch each other and the ring acts like a brake. Too big and compression is lost.

The only down side to checking this is dis-assembling the engine.....again!

Other than that, what is it supposed to be according to Poulan?

[JJJoseph]

2-strokes have tremendous power output - for a while.  Eventually the piston and cylinder gets scored from riding over the ports in the cylinder wall.  Compression slowly goes down until eventually it won't start.  That's the end of the unit. Low compression is the villain. The required fix is a new piston/ring set and cylinder. It's routine maintenance when racing dirt bikes, for example.  Chinese piston/ring sets are machined so accurately, you don't even have to gap the rings. The time-consuming part is finding gaskets.

[stuo]

The compression will probably rise as the new ring "seats" (becomes worn in to the cylinder). If it runs OK and does the job where is the problem?

[Stig / Major Tom]

Wait...!?
"It runs fantastic"..?
And we're fooling with it ...because?
You're already about 10 bucks over the price of my electric leaf blower....and it runs great every time I flip the on switch.

Stig

[aschrauth]

2-strokes have tremendous power output - for a while.  Eventually the piston and cylinder gets scored from riding over the ports in the cylinder wall.  Compression slowly goes down until eventually it won't start.  That's the end of the unit. Low compression is the villain. The required fix is a new piston/ring set and cylinder. It's routine maintenance when racing dirt bikes, for example.  Chinese piston/ring sets are machined so accurately, you don't even have to gap the rings. The time-consuming part is finding gaskets.

I only have about an hour of usage on the new ring and cylinder Jug. Do you think I should purchase another piston or leave it alone at 90psi?

[aschrauth]

Wait...!?
"It runs fantastic"..?
And we're fooling with it ...because?
You're already about 10 bucks over the price of my electric leaf blower....and it runs great every time I flip the on switch.

Stig

I know Im OCD when it comes to my machines, maybe I should let it alone as long as it runs.

[aschrauth]

The compression will probably rise as the new ring "seats" (becomes worn in to the cylinder). If it runs OK and does the job where is the problem?

\
I just wanted to see if I could get the unit back to "new " condition so that way I do not have to replace anything for awhile.

[aschrauth]

I harp about some things on here because they are simple, easy to check and many times the primary cause. On two smoke engines, my favorite harp is "piston ring end gap." Too little and the engine stops when it gets to temp because the ends touch each other and the ring acts like a brake. Too big and compression is lost.

The only down side to checking this is dis-assembling the engine.....again!

Other than that, what is it supposed to be according to Poulan?

Crossbolt. I purchaced a new OEM piston ring from Polan. As far as specs I am not sure, I don't think leaf blowers come with a service manual.

[stuo]

A new engine needs to be run until the ring seats itself and then the compression will increase. It's what was once called "breaking in" an engine.

 Use the blower and measure the compression after maybe ten hours of use. Even if the compression doesn't rise to 110psi, so what?  Maybe the Youtube dude's gauge was off or he misread it. You could also call the manufacturer to find the correct compression ratio if that's still bothering you. I take a lot of what I see on Youtube with a heavy dose of skepticism.

[aschrauth]

A new engine needs to be run until the ring seats itself and then the compression will increase. It's what was once called "breaking in" an engine.

 Use the blower and measure the compression after maybe ten hours of use. Even if the compression doesn't rise to 110psi, so what?  Maybe the Youtube dude's gauge was off or he misread it. You could also call the manufacturer to find the correct compression ratio if that's still bothering you. I take a lot of what I see on Youtube with a heavy dose of skepticism.

I think Ill just wait to break the new ring In and take a new reading then. Ill try getting ahold of the manufacture to see what the optimum pressure is, Most internet forums state that it needs between 90-100 PSI to run. Sometimes I think my OCD gets out of control when it comes to my Small engines. 

[CROSSBOLT]

Crossbolt. I purchaced a new OEM piston ring from Polan. As far as specs I am not sure, I don't think leaf blowers come with a service manual.

Pretty much nothing comes with a service manual! Har, har! But there will be specifications that may be found on the internet. I foung end gap for my Echo string cutter and chainsaw engines on the internet.

Like Stig said, if it runs great, run it.

By the way, ALL piston engines have ring end gap specified by the manufacturer. The piston WILL lock in the bore if the end gap is too small. Compression WILL suffer if too large.