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blower 'knocking'


duigoose's Avatar
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06-12-07, 01:30 PM   #1  
blower 'knocking'

Neighbor asked me to look at his Homelite blower (UT-08107). He said it starts and runs fine but makes a knocking noise. Sure enough, pull the cord and there is a distinct knocking noise. Sounded like plastic on plastic to me but the farther I took it down the more it sounded like metal on metal. I took it down to just the block and the internals but still can't determine where this noise is coming from. My gut thinks the rod is making contact with the cylinder wall at the bottom of the cylinder but just looking at the rod that doesn't seem the case. Another thing I think is wierd is removing the spark plug doesn't make that much difference in the resistance felt when pulling the cord. The most resistance seems to happen when the crank weight is in the 'bottom' of the sump area (as far away from the spark plug hole as you can get)
If this was a car I would say it sounds like a rod knocking. Any ideas on what it is or how to find it?

 
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06-12-07, 02:26 PM   #2  
Check to see if th blower fan is loose or has a stick or something stuck in it.

The engine should turn over almost effortlessly without the spark plug.

 
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06-12-07, 02:56 PM   #3  
No stick and nothing loose, I took this thing down far enough that there was no plastic left, only block, flywheel and coil. I was figuring it should turn over almost effortlessly by hand w/out the plug in it, almost freewheel, but I never work on 2-cycle so. I can't really spin it over fast enough to recreate the sound without the starter attached but there is still resistance by hand there in one spot.

 
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06-12-07, 05:23 PM   #4  
Is the exhaust port or the spark arrestor screen in the muffler plugged tight with carbon? Did you notice any unusual fuel puddling in the crankcase upon removal of the crankcase cover? How is the condition of the piston and cylinder as viewed through the exhaust port? Is the ring free in the piston ring land? At mid stroke is there any noticeable lag between flywheel movement and rod movement when the flywheel is rocked back and forth?

 
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06-12-07, 05:50 PM   #5  
There is almost no carbon on the arrestor screen, not clogged at all. It looks like this machine has seen very little run time in my inexperienced eye.

I don't really know what usual fuel puddling is so I can't say what unusual is. There is what I am guessing usual because after spinning it over several times there is a film in the crankcase.

Piston and cylinder through the exhaust port look fine, I don't see any scratches and really everything looks good. Minimal carbon is seen on the piston (thru the spark plug hole) as well.

I'm not sure the ring is free in the land. How could I check this? Thru the exhaust port? The ring gap is visible thru the exhaust port.

I'm not sure about the mid stroke lag question but there was nothing immediately noticeable to me.

I forgot to ask him if the blower always had this condition or what, we were in a rush. It just seems like something is catching somewhere. It was somewhat easier to rotate the flywheel backwards if that helps. Shouldn't it almost freewheel without the plug in it?

 
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06-12-07, 07:52 PM   #6  
Just courious,did you happen to check the cylinder bolts,I found on a lot of blowers that the bolts will vibrate loose from the crankcase,it could be in a bind,just a guess.

Jerry

 
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06-12-07, 08:17 PM   #7  
Didn't check, I put it back together before putting it away this afternoon. I was gonna (hopefully) let some ideas/posts build overnight and try again tomorrow.

 
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06-12-07, 11:30 PM   #8  
From the second I saw your title to this post, I thought about loose cylinder bolts. I've seen this on many blowers....especially homelites.


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06-13-07, 10:15 AM   #9  
why can i never get the 'easy' fix?

Here is what I have done today and thanks everyone.
First I checked the cylinder bolts hoping that would be my 'easy' fix. No such luck as they were as tight as could be.
I removed everything down to the short block (block, cylinder, piston, ring), the rotor (what I would call flywheel but the IPL said rotor), and the carburetor (just couldn't see how it would factor). I removed the ignition module (what I would call coil).
In my mind there should be no resistance anywhere at any point in the rotation and it should turn easliy now.(?)
I can't turn it fast enough to recreate the noise but a hair before the piston is at TDC there is a definate firm catch then a smaller catch then rotation. It takes some force to move it past that spot. The spot it catches is consistantly at TDC.
I see what appears to be a bearing, looks to be a roller bearing on the crank in the block. The only thing I can think of is there is a flat spot or something wrong with the bearing.
Any other ideas? Does my conclusion sound plausable?
If that is the case the IPL doesn't show this as a replacement part and he would probably rather buy a new one of the same caliber than pay what I would charge to fix this, heck the replacement short block is close to what I would charge to fix it

 
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06-13-07, 12:11 PM   #10  
Plausible but I'll bet you have carbon deposits on top of the piston or in the squish area (head) of the cylinder. If it were rod bearings/bushing I'd say it would happen regardless of pistion position.

 
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06-13-07, 12:54 PM   #11  
puey you very well could be right (imagine that) because it does feel like something not allowing the squish to squash, like a spring that has to compress although I wouldn't call the bearing I kinda suspected a rod bearing/bushing. I would call it more of a crank bearing as it is attached to the crank on 'top' of the motor where it goes through the block. It did seem odd the catch was at TDC though.
I've got a chicken to throw on the smoker so I will hit it again tomorrow probably.
I sent the owner an email asking what the history of the noise was. Figure if it is carbon it would worsen over time. This has become a personal challenge.

 
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06-15-07, 12:15 PM   #12  
Well, I tore it apart...again....and no the ring was definately not free in the land. There was also a small piece of metal just 'floating' around in the cylinder (roughly 1/4 inch long and the dia. of the piston ring but the ring was intact). I still can't find where that came from and would have though it would have escaped by now. It appears the thing overheated just from the coloring on the piston and most of the ring seized onto the piston. Does that sound right? There is very little carbon in the cylinder and on the piston (to my eye). Anyone want me to take pics while it is apart?
Owner said it ran fine 3 months ago, he went run it couple weeks ago and it started making that noise and wouldn't stay running.
Homelite wants around $5 for just the ring. At this point I want to know what happened and why but I am guessing it ran lean either due to improper mix or old gas.

 
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06-15-07, 01:02 PM   #13  
from the last post it, i got the impression that you found one ring on the piston. that other piece of metal was probably the other piston ring.

Im guessing that a new set of rings wont be enough, there is probably damage to the cylinder.

 
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06-15-07, 03:32 PM   #14  
Only one ring and it was completely intact just seized onto the piston other than about 20% of it. I have no clue where this floating piece of metal came from and just used the ring diameter reference to compare the size. Cylinder looks to be in great shape visually. Homelite shows part number PS01359 for the ring (1-5/16), anyone have a substitute because I'm sure when I call my local parts store tomorrow they will have no way of getting it or have a clue. Owner gave it to me for the work I've done but if I can get it going I'm sure someone could use it.

 
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06-15-07, 06:16 PM   #15  
anyone need parts?

alright, set it down for after dinner. It took a hammer and small screwdriver to remove part of the ring and once removed the piston would not go back in the cylinder (without a ring at all on there mind you). My new guess is the overheating has done it in and I would have to measure the piston and cylinder to see what is out of range and order parts from there. It took an amount of force to pull the cylinder apart too so....

 
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06-16-07, 03:27 AM   #16  
The metal object in the cylinder may be a part from the carburetor such as the throttle shaft or a throttle plate screw or the choke shaft or plate. The fact you can't reassemble the piston to the cylinder without the ring in place would indicate overheating and warpage of the piston now being out of round. Take accurate measurements of the piston at three points and compare the measurements.

 
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