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Need a little p.a.w. advice

Old 02-06-2013, 07:10 PM
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whoopee
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Default Need a little p.a.w. advice

I need a little advice from some one that knows more than me. I have a p.a.w. .09 mk1 blue head that is pretty new, got about 5-6 runs on it good and rich, but after about the second run its got a tight spot at the bottom of the stroke. I would like to know if this is normal or is somthing wrong and how do i fix it or will it just smooth up with more running?

Thanks for info in advance.
Whoopee
Old 02-06-2013, 07:55 PM
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Default RE: Need a little p.a.w. advice

Doesn't sound good Whoopee.

It would be a good idea to take the backplate off and investigate.

The symptom you describe COULD indicate a bent conrod.

Have you started it with an electric starter? Plain bearing diesels are a prime case where Electric fingers should not go.

Regards

Greg
Old 02-06-2013, 08:09 PM
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Default RE: Need a little p.a.w. advice

No i dont have a electric starter all my engines are hand started. Yeah first place i went was to pull back plate rod looks strait as an arrow. would like to find the issue. Thanks for the advice greggles47and all advice to come.

Whoopee
Old 02-06-2013, 08:35 PM
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Default RE: Need a little p.a.w. advice


ORIGINAL: whoopee

I need a little advice from some one that knows more than me. I have a p.a.w. .09 mk1 blue head that is pretty new, got about 5-6 runs on it good and rich, but after about the second run its got a tight spot at the bottom of the stroke. I would like to know if this is normal or is somthing wrong and how do i fix it or will it just smooth up with more running?

Thanks for info in advance.
Whoopee
I have heard of PAW con rods walking off the back of the big end and jamming against the back plate.

The clearance (whatever that should be) between the back of the rod and inside of the backplate may bear checking.

Can't see it improving with age though.

Old 02-06-2013, 10:34 PM
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Default RE: Need a little p.a.w. advice

Once you manage to get the backplate off, the rest is pretty easy to take appart and check too. If it is plain bearing, it could be binding between the crank and case. Some PAW engines also have a little too much play between the prop driver and crankcase, a few extra shims there will keep the rod from touching the backplate.
Old 02-06-2013, 11:36 PM
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Default RE: Need a little p.a.w. advice

At the very least it's worth a strip down. My first plain bearing 09 "Blue head" (mk1?) had a crack in the shaft where the crankpin was pressed in even before it was run.

They sent a replacement shaft but the engine continually wore out conrods consistent with a bent crankpin.

Other than that and excessive endfloat it was a screamer. The second one is possibly a mk2(?) and is good in comparison.

Old 02-07-2013, 02:12 AM
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Default RE: Need a little p.a.w. advice


ORIGINAL: greggles47



Have you started it with an electric starter? Plain bearing diesels are a prime case where Electric fingers should not go.

Regards

Greg
I've alway cringed at the thought of someone using an electric finger on a pb engine Greg. so I agree with you 100%.What did suprise me though was talking to Dave Owen I think it might have been at the Old Phartz last year and he doesn't hold our view.
Now I don't remember if it is a school or the Air League down Daves way some where that he sold aquite a few 1.5 PAW's to a few yeas ago now
and he does yearly maintainance on them. They have never given any trouble and these engine have always only ever been started with electric fingers.
You work it out.....

Old 02-07-2013, 02:30 AM
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Default RE: Need a little p.a.w. advice

I think it's the Air League, Fred, but can't remember where they are. As you say, they never seem to come to any harm from the electric starters, although the PAW 09 is a sturdy little beast. (On the other hand, Dave has had the odd MP Jet Classic which has obviously been damaged by an electric finger, which has him shaking his head in disbelief.)

You can't really blame the Air League for using electric starters with kids in this day and age; even with the starters, it's a miracle that they slipped it past the OH&S police.

My 10-y.o. started his first diesel the other day. It was only a Schlosser 0.25, but I was still well chuffed.
Old 02-07-2013, 03:35 AM
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Default RE: Need a little p.a.w. advice


ORIGINAL: steve111


My 10-y.o. started his first diesel the other day. It was only a Schlosser 0.25, but I was still well chuffed.
TRA DA!!!!

Well done young Master Thomas!
Old 02-07-2013, 11:30 AM
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Default RE: Need a little p.a.w. advice

Great Steve looks like you son has the golden touch a natural, great to see a 10 year old doing this get him hooked early on diesel , we need new blood with the "oil burners"

martin
Old 02-07-2013, 04:55 PM
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Default RE: Need a little p.a.w. advice

That's great Steve. Always good to see your young bloke start an engine for the first time....

Fredo
Old 02-07-2013, 06:16 PM
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more fun than flicking on a switch it come to life and breaths martin
Old 02-07-2013, 11:04 PM
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Default RE: Need a little p.a.w. advice

Whoopee,

I've noticed, on occasional PAWs with long-bolt uppers, that the head bolts NEED to be torqued in carefully. Uneven tightening can tilt the cylinder slightly, enough to show a bind at some point in a revolution. My blue-head .09 has 3 long bolts through the cooling cuff and into the lower case. With this and other PAWs, I've had good results by tightening down the uppers with the backplate off, watching for the conrod big end 'walking' fore and aft. That is, obvious sliding fore and aft in the +/-90° from bottom dead center.

A tilted sleeve doesn't mean much if it is across the case - the shaft, rod and piston pin bearings can handle that. Tilt fore or aft does not align with rotation allowed by the bearings.

Final check is with the sleeve and cuff attached, and compression well reduced. The only resistance through a full rotation should be the natural compression, not anything like a mechanical bind. IF such a bind is felt, slack off each head bolt a half turn and recheck. If free then, tighten each bolt an eighth of a turn and recheck. If not, back off another quarter turn. If the bind reappears, go back to the last free, loosened, position, and try a different sequence, an eighth of a turn at a time.

You'll soon find a sequence that stays free of mechanical bind down to where all the bolts are fully seated. ...Takes longer to describe than to do.

The advantage of the screw-on .049 and .061 method is that alignment is guaranteed. The disadvantage is that it is more complicated to make sure the uppers are tight enough. A problem common with most, if not all, such systems. PAWs don't have spanner flats or holes for a pin-spanner... as with Cox glow heads, or several screw-top diesels.

My .09 is a delight, and very economical on fuel.
Old 02-08-2013, 07:05 AM
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Default RE: Need a little p.a.w. advice

Well i tore it down last night and the crank is free, and rod is free both places and strait, the piston is free in the sleeve when out of the engine. But when i put it together she binds a little at bottom of stroke. Lou Crane i will try that today that sound like a logical problem and will report back when i try that.

Thanks for all the advice.
Whoopee
Old 02-09-2013, 03:02 PM
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Default RE: Need a little p.a.w. advice

Lou Crane you were right but i have to tighten the front screw a good bit tighter than the back two to keep it free. will it be ok to run it like that or should i try again to get it better??

Thanks
Whoopee
Old 02-09-2013, 03:06 PM
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Default RE: Need a little p.a.w. advice

Whoop, those long bolts run hard in their threads making them difficult to torque evenly.
Old 02-09-2013, 05:33 PM
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Default RE: Need a little p.a.w. advice

Just wondering if the rod could be in backwards?

Most rods have a radius at the front of the journal that matches the radius on the crank pin/web joint and when you put the rod in backwards a square edge then gets presented to it .

This results in the rod wanting to walk off the back of the crank pin as it tries to get away from the crank pins radius to only ride on the flat of the pin.

Having one head bolt tight and the other two loose is not good as you are using two wrongs to make a right and actually goes against what Lou advised.
Old 02-09-2013, 11:05 PM
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Default RE: Need a little p.a.w. advice

Sounds to like the rod is slightly bent then. The cylinder has a seat so it should not really be able to rock unless the cylinder screw are really off.
Try turning the rod around to see if that changes anything, if it is straight it shouldn't change anything (appart from the chamfer talked about above). If it is bend the cylinder would now need to lean in the opposite direction, compared to before the switch around.
Old 02-11-2013, 02:54 PM
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Default RE: Need a little p.a.w. advice

Well i put the rod on backwards still have to tighten front bolt tighter than rear two for free operation threw bottom of stroke the rod is strait. if you all have anymore advice i will listen but otherwise i will get it as right as i can and finish running it in and run it like that.

Thanks
whoopee
Old 02-11-2013, 03:28 PM
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Default RE: Need a little p.a.w. advice

It honestly sounds like the engine is made incorrectly (as in the crankcase is bored out of alignment and the false screw adjustment is compensating for it) and there is not much else to do but to send it to PAW for a checkup.
Old 02-11-2013, 03:54 PM
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Default RE: Need a little p.a.w. advice

ORIGINAL: whoopee

Well i put the rod on backwards still have to tighten front bolt tighter than rear two for free operation threw bottom of stroke the rod is strait. if you all have anymore advice i will listen but otherwise i will get it as right as i can and finish running it in and run it like that.

Thanks
whoopee
These engines were a popular power plant for Phantom Racing and Midge Speed during the 1990's.

As I suggested in post #5, check the pressed in crankpin in the crankweb. Mine was in crooked and the surrounding area had radial cranks.

Others here in oz have also reported crankpins that weren't perpendicular.

I've also had PAW 09 rods with the little end drilled crooked.

Both these things would produce your symptoms.

If you plan to use the engine at relatively low speed on a big prop it probably doesn't matter

a great deal and the tightness may go as the bits mate together slightly out of alignment.

Ray
Old 02-11-2013, 05:39 PM
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Default RE: Need a little p.a.w. advice

If the engine is reported as 'pretty new' (as post #1 indicates) then perhaps it is still under warranty?
Old 02-16-2013, 02:23 AM
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Default RE: Need a little p.a.w. advice


ORIGINAL: PWF63


ORIGINAL: greggles47



Have you started it with an electric starter? Plain bearing diesels are a prime case where Electric fingers should not go.

Regards

Greg
I've alway cringed at the thought of someone using an electric finger on a pb engine Greg. so I agree with you 100%.What did suprise me though was talking to Dave Owen I think it might have been at the Old Phartz last year and he doesn't hold our view.
Now I don't remember if it is a school or the Air League down Daves way some where that he sold aquite a few 1.5 PAW's to a few yeas ago now
and he does yearly maintainance on them. They have never given any trouble and these engine have always only ever been started with electric fingers.
You work it out.....

I was a bit wrong with my assumption that Dave Owen approved of electric fingers for PB diesels. I was right about the 1.5 PAW diesels that Dave supplied the Air League. These engines were specially modified with thrust washers for the electric starters and the Air League would not let the kids hand start the engines. An OHS and insurance thing. This was a ONE OFF thing with the PAW 1.5 for the Air League.
Sorry for any incorrect information that I gave out. Electric Fingers are NOT to be used on any other PB engines or used at the engines peril.

Cheers
Fredo

Old 02-18-2013, 12:46 PM
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Default RE: Need a little p.a.w. advice

well finally got around to running it again today and she got tighter so i took her apart again and the hole in the center of the crankshaft aint a circle and the pin will move up and down with stiff finger pressure. qazimoto you were right i dont know how i didnt catch that at first but i didnt.

Thanks you all. Do any of you know if the cranks in the current production .09 will fit a mk1 09??
Whoopee
Old 02-18-2013, 01:21 PM
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Default RE: Need a little p.a.w. advice

Been away from here a while, sorry not to answer your question about the tightness of each bolt. IF everything else is good, and you get all three firmly tight, even if one needs to be tighter, it should be okay.

It appears, tho, that the crankpin is too loose in the crank disk. Check the PAW site about repairs/replacements.

A comment about the sleeve sitting square if things are tightened properly - true, but... I had a PAW 29 years back that appeared to have either the base of the cylinder, or the land in the casting not square. It may have had one position where things lined up, but I couldn't find it if it was there. And the 29, 35 and 40TBR have 4-bolt uppers... That 29 was the only PAW I ever had or worked with that had such a problem. Murphy's Law: If it can happen, sometime, somewhere, it will. His Second Law: Murphy was an optimist...

Best of luck. In good condition, that is a very enjoyable engine...

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