tag-RCU

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I have a PAW 80 Classic that I got used but looks really good so I don't think it has a lot of time on it. Using Eric Clutton's Old English mix fuel, which I believe is 33%/33%/33%.

I can get this engine to run good on an 8*4 prop but when I try a smaller 7*4 prop, it won't adjust and keep running. It will start though. I just can't keep it running.

Any ideas? Does this engine need more run time or is it worn out? I don't have any history on it but as I have said, it looks too good to have much time on it.

Thanks
Tag

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Tag,

When you go to a smaller prop you need to increase the compression. Have you tried this? Jack

tag-RCU

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Jack,
I've increased the compression and I've tried numerous compression and needle valve adjustments but just can't seem to get it to run more than a few seconds with the smaller prop. It will run out an entire tank with the larger one. It seems almost like it's running out the prime but it's drawing some fuel thru the line.

Thanks
Tag

vauxhall

Hi Tag, take out the needle valve, remove the fuel line and blow through the spray bar, sounds like it or the pickup in the fuel tank may be blocked if it only runs off the prime.........John

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Tag,

Is it a cold winter day? What is the tempature? I have been running a Drone diesel in 30's and 40's degree temps here in Northern Illinois. With a 14/6 wood zinger it is easy to start at these temps. But with an APC 12/6 it would start on the prime but die mabe 4 or 5 times before it keeps running. Sounds like maybe your engine is similar but even more difficult to start. Maybe on a warm day it will work with the smaller prop. Also some more runs with the larger prop may help. The first time I ran the Drone I used the 12/6 as that was the only prop I had at the time that was not bored out for larger prop shafts. My arm was tired before I get the engine running. I found that if the engine was still a bit warm it would restart easier. But when cold, say 5 minutes or more difficult to keep running. Try running with the larger prop until the tank runs out, then change to the smaller prop and increase the compression and try to restart while the engine is still warm.

gcb

While checking the spray bar, check that the hole is oriented in the correct position. I am assuming that the carb is wide open if it has a carb.

George

johnvb-RCU

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Tag, I have one of these as well, and mine doesn't really want to know about smaller props. It will run a 7" prop from memory, but seems happier on 8".

The Classics are a detuned .049 far as I can gather. On mine there is only one exhaust port, out the back, while there are three on the normal .049/80. I also have a C/L plain bearing 80 (with the 3 exhaust ports) which goes really well with 5" to 7" props.

What George said about orienting the spray bar is really important by the way. I set mine so that both holes are pointing downwards at wide open throttle. I know others who advocate setting it so that one hole is pointing downwards at WOT. My way works, and I presume the other way works as well. What you don't want is one of the holes pointing upwards.

If it really is as new as it looks you might find that it will get better with a bit more running.

juxy2

The .80 BB Classic PAW is described on the box I have, as "High Torque". However, although the porting arrangement is certainly different, the bore, stroke and timing are exactly the same as a regular .80. The revised transfer port size gives the increased torque, enabling it to run happliy on larger prop sizes but there is no reason why it should not run 7" or even 6" props. Mine is an R/C version with very little running time. For the sake of curiosity, I just grabbed the first 7" prop I could put my hands on today, which was a Graupner grey plastic 7x3" and she started quite normally, after a few good primes, but was very sensitive to the position of the comp screw, with less than an eigth-turn latitude between firing up on a prime and no chance at all. Once running, it settled down to 10,650 rpm, on this prop, running a little richer than optimum, on 'cooking' fuel, with an outside air temperature of approx +4c. It was happy to throttle back and pick again, which I did several times, with only a hint of a stutter. Probably doesn't help you much but thought I'd share that with you. Alan.