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PostPosted: Sat Apr 15, 2017 7:55 pm 
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Joined: Thu Jan 14, 2016 2:36 pm
Posts: 313
Location: Wilmington NC
Another Piston, Again

A little history on the first three pistons: I would rebuild, pressure test and start with a fat jet - like a 172 (original rebuild rode great for months with a 160 main in it) but was never able to tune the spark and then out of the blue and usually within the first 15 minutes it would burn up the rings.

Rebuilt with piston #4 and compression of 140, brought assembled Pilot to the local Honda shop for a dyno run with the A/F sniffer in the tail pipe. While testing on the dyno, started up and was idling well for warm up but A/F ratio was a little high. After a few minutes started dyno pull but was unable to get any change in A/F ratio despite adjustments and then, all of the sudden A/F spiked to over 15. Shut off immediately, removed carb, disassembled and soaked in carb cleaner vat overnight. Reassembled and started back up the next morning and everything fell in line. After fine tuning carb and A/F at 13, left it running with a 165 main jet I knew was too rich but didn’t want to test my luck at this point. It was a little sluggish off the line, plugs were always wet and oil was seeping around exhaust. After a couple of months, I went to a 162 and seemed a lot better but still occasionally fouling plugs and plug still visibly wet when pulled. Went to a 160, warmed her up for a few minutes and 10 minutes into a run - she is dead. Compression is now around 30 . Haven't pulled motor (( Internal Combustion Engine ? )) yet and will do a pressure check once removed.

Engine Specs: Paul Turner Pipe, Stock muffler, 39MM Keihin carb, modified airbox (3" intake hole w automotive cold air elbow on original lid), K&N inside airbox treated with oil, K&N on elbow dry with a prefilter on it, Powerbloc clutch. Oh, and this is the part that is really kicking my A$$ - an 82MM piston which means I now need either another jug that hasn’t been bored out as far or get this one sleeved.

Shouldn’t I have been able to get a nicely browned plug at some point before eating a piston? Is it an intermittent issue with my carb leaning out? Any input is appreciated.

Really would rather have continued to deal with fouled plugs than another piston but too late to look backwards.
Typed this a week ago and was dead set on getting rid of the damn thing. I knew I’d have to get it running again before I sold it and now I’m thinking if its running, maybe I’ll keep it.

Sure is fun when it runs…


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PostPosted: Sat Apr 15, 2017 8:14 pm 
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Location: Hope, B.C Canada
Yup this sounds very familiar to me.
What was the fuel flow rate of the fuel pump ??
Octane rating of the fuel ??


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PostPosted: Sat Apr 15, 2017 8:25 pm 
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Joined: Tue Jan 17, 2012 3:19 am
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Location: Hope, B.C Canada
On a positive note here, just because you lost another piston does not mean you have to re-bore after every blow up. Most shops do this just so they can scam a bunch of $$ out of you. If there are no deep gouges in the cylinder your good. In fact even if there is a light gouge your good. Clean out the smeared aluminum and give it a light hone. Good enough. I have an Engine sitting on the shelf with 82mm and a couple of good gouges. It has 154psi compression even with those scars in the cylinder. This was the Engine that blew the connecting rod because my stock intake had a crack and it leaned out.


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PostPosted: Sat Apr 15, 2017 8:38 pm 
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Location: Hope, B.C Canada
A 165 or 172 , I don't give a poo. That Engine will run fine if everything else passes the test.
1) fuel flow (4.5oz in 10sec) -- I just can't say this often enough here on this site
1B) fuel MUST meet or exceed min octane rating -- I just can't say this often enough here on this site
2) fuel pick up tubes must be clear
3) very very very close inspection of intake for cracks
4) "MUST" pass pressure and vacuum tests

I know you are mad right now (I was when it happened to me 9 times in a row) but it will run eventually so just take this as a learning curve. Wrenching has to be fun or your done. Some people hate pulling wrench but I like it more than driving.
You may not have to even buy a piston or rings. How bad is it ?? Pics please ?? (Pressure test before tear down. Yes I know you said you would). Skiv the rings out of the grooves -- clean up piston with flapper wheel -- file out ring grooves (use the wife's nail file) -- put it all back together. Don't laugh, I have done this and the Engine ran fine until the stock intake cracked and blew the con rod. It ran two years like that.


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PostPosted: Sat Apr 15, 2017 10:09 pm 
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Joined: Sun Jan 10, 2010 9:14 pm
Posts: 1779
Location: Ma
Was it ever determined if this setup was ported? It it was mine I'd find a used stock cylinder and head .. rebuild it with piston and rings to spec and run it....
Your setup still smells funny to me... I wouldn't sleeve that cylinder until I tried a stock setup first...pilots run amazing with little issue when stock providing you've got a healthy setup everywhere else..i.e. Pump, fuel quality and jetting.... regards and don't give up


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PostPosted: Sat Apr 15, 2017 11:06 pm 
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Joined: Tue Jan 17, 2012 3:19 am
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Location: Hope, B.C Canada
I had to go back and read your other thread on this issue viewtopic.php?f=1&t=16807&start=50

go oddy, hoser and adnoh made the same type of comments in that thread that jumped at me. They wondered if it is an ATVR Engine. I don't know and probably neither do you, but lets pretend it is. You are on the last bore and it has let go on you. I would slam it together with what you got, in the way I mentioned above (as long as the piston and rings still salvageable). You also said you did a flow test on the fuel pump in that thread so I guess I will have to call that good. You also had a cooling fan issue that you solved, did a pressure test and inspected the intake. So at this point with nothing to lose just try and run AVGAS. Right now I am thinking the fuel is not up to what is needed and it is causing heat. It can't be anything else from what I have read in these two threads. It's being killed by heat for some reason. Two more -- are you sure water pump is circulating fluid ?? and second I don't really like the clearance you are running (it's to tight for me (not for others though) ) but at this point it's experimental time.


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PostPosted: Sun Apr 16, 2017 12:56 am 
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Joined: Mon Jul 19, 2010 3:20 pm
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Location: saskatoon, sk, canada
i run a 39m pwk and my main jet i believe is a 190..


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PostPosted: Sun Apr 16, 2017 2:01 pm 
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Joined: Thu Jan 14, 2016 2:36 pm
Posts: 313
Location: Wilmington NC
canadian oddy wrote:
Yup this sounds very familiar to me.
What was the fuel flow rate of the fuel pump ??
Octane rating of the fuel ??


flow was good - tested previously at over 5oz. in 10 sec and octane was (according to the gas station signs) 93 and ethanol free.
water pump definitely moving water, just had radiator out the other day as it was clogged with debris from last ride through the high grass. temp light came on briefly. shut off immediately once it did and let cool before riding back. cleaned and blew out fins and fresh coolant and watched to make sure it was moving while running.
going to start digging in next week and will post pics and stats after removal and pressure test.

thanks for the feedback and positive vibes. nice to have a place to whine sometimes


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PostPosted: Sun Apr 16, 2017 2:48 pm 
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Location: Hope, B.C Canada
My honest opinion here -- it must be fuel.
You checked everything else. The fuel you get at the gas station my not be as advertised. Here in Canada they have winter fuel and summer fuel. I also don't like that methanol in it. If you run AVGAS you know what you are getting, it would be quality fuel for sure or planes would fall out of the sky. Others here might attack me for giving you this advice because they would say that they run pump gas. They would be right in saying that but at this point lets try the aviation fuel. Nothing to lose and it also solved my issues with one of my engines. Another reason I suggest this fuel is because someone may have monkey'd around with that Engine (port timing etc think atvr here). The Engine that was giving me the most grief was a modified Engine and I didn't know it at the time. I was new to the oddy world.
By the way whineing is allowed here.
Happy Easter everyone.


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PostPosted: Mon Apr 17, 2017 10:53 am 
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Joined: Wed Jan 14, 2009 2:10 am
Posts: 4678
Location: Carson City NV
You don't need Aviation fuel unless your compression is above approximately 165psi. Don't waste your money.

It sounds like you have a fuel delivery issue with one of the carb circuits.

What's that 39mm Keihin out of? What model number is the 39mm Keihin carb? Not all carbs can be used in certain applications.

If you are running a 162 and it is running rich and then you drop down to a 160 and it's burning up, you have carb issues. One of the sections of the carb isn't delivering fuel properly and the overlap in the delivery systems is masking the problem until it's too late.

Rand


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PostPosted: Mon Apr 17, 2017 4:15 pm 
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Joined: Thu Jan 14, 2016 2:36 pm
Posts: 313
Location: Wilmington NC
Randman wrote:
You don't need Aviation fuel unless your compression is above approximately 165psi. Don't waste your money.

It sounds like you have a fuel delivery issue with one of the carb circuits.

What's that 39mm Keihin out of? What model number is the 39mm Keihin carb? Not all carbs can be used in certain applications.

If you are running a 162 and it is running rich and then you drop down to a 160 and it's burning up, you have carb issues. One of the sections of the carb isn't delivering fuel properly and the overlap in the delivery systems is masking the problem until it's too late.

Rand


It is a 39MM PWK and was purchased new 13 years ago by the guy i got the pilot from - see pic.

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"If you are running a 162 and it is running rich and then you drop down to a 160 and it's burning up, you have carb issues. One of the sections of the carb isn't delivering fuel properly and the overlap in the delivery systems is masking the problem until it's too late."

I am completely on board with this - it should not burn up from that small of a change unless there is something else that is getting out of line - intermittent cloggage, etc.. FYI - the pilot jet is a 55 and the needle (stock that came with it) is on the center notch.

One last item and not sure if it has any value or bearing on this situation but on the last ride, I was on my second lap and was driving hard. Everything felt good, motor (( Internal Combustion Engine ? )) pulling hard. Came up to parking area, let off gas to decelerate, hit brakes and that's when the Engine stopped and died. The end.

Will be tearing down next week and performing a pressure check prior to disassembly. Will inspect amount of damage to cylinder walls as well. If a light hone and cleaning the piston and rings will get the compression back up, i'll be surprised - but happy.

Anyone got a spare jug laying around that isn't already bored to 82MM they'd be willing to part with? Shoot me a PM if so.


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PostPosted: Mon Apr 17, 2017 8:47 pm 
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Joined: Tue Jan 17, 2012 3:19 am
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Location: Hope, B.C Canada
I agree with Randman but did someone monkey around with this Engine (port timing) ?? That's my argument here when I am blabbing about AVGAS. Perhaps I am trying to bandage a bad Engine. Rands comment about the carb is very plausible and I did not really think of it.


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PostPosted: Mon Apr 17, 2017 9:03 pm 
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Posts: 3294
Location: Oklahoma City, OK
Ill post a question that was already asked but i didnt see you answer it. Was it by any chance ported by ATVR or another unknown shop. I had a jug ported by them that no matter how fat I would set the main (but still allow Engine to run without falling on its face,black soot coming out of pipe, etc etc), it would start to lean out at WOT (Wide Open Throttle) after a minute or two. I could never get it jetted properly even with the help of the jetting gurus here. I should have just thrown the jug in the trash but I ended up selling the Pilot with new owner aware of issue. This is not the first I have heard of this problem with ATVR's jugs, not all of them but some.


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PostPosted: Tue Apr 18, 2017 9:05 am 
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Joined: Thu Jan 14, 2016 2:36 pm
Posts: 313
Location: Wilmington NC
I was able to confirm it was definitely stock jug. Spoke to owner i purchased from - second owner and friend for 25 + years - and it was bone stock when he got it. He purchased (brand new) 39mm carb, Paul Turner pipe, aftermarket muffler and a powerbloc clutch with intention of racing it in central FL. He was the first to go through two pistons - stock and 80.5 and he was running a 190 main jet. Was choking and falling all over itself off the line but still managed to lean out enough to burn up pistons. I bugged him for years to let me buy it but it sat for 12 years before he finally gave in.
Compression after all rebuilds never got over 140.


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PostPosted: Tue Apr 18, 2017 5:20 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
I have a commercial t to add when tare Down. Or pre tare done. Check your balancer oil level. If you put in new main seals and hopefully the o-ring the oil level should be ok. If low there you go. Also did you get that kerchunk fixed by the exhaust port.


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PostPosted: Tue Apr 18, 2017 5:21 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
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Location: Wichita ks
If you would be so kind let.me know what reeds and what cut away you have on the carb.
Thanks adnoh


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PostPosted: Wed Apr 19, 2017 6:15 pm 
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Joined: Tue Jan 17, 2012 3:19 am
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Location: Hope, B.C Canada
adnoh wrote:
If you would be so kind let.me know what reeds and what cut away you have on the carb.
Thanks adnoh


Based on the info I found online the 39PWK has a 6.0 cut away. (PS: I don't even know what that means LOL). I would be willing to bet that's what he got in there.
As for reeds dipnadactyl will have to tell us.
I don't know, and I bet dipnadactyl don't know what you mean by the "kerchunk" in the exhaust port. Is it that ding in the top left of that pic in the other thread ??
This is the site I got the info from: http://www.pjmotorsports.com/jetting-tuning.html


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PostPosted: Wed Apr 19, 2017 7:01 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
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Location: Wichita ks
http://www.keihincarbs.com/tips/gate.html


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PostPosted: Sun Apr 23, 2017 1:36 pm 
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Joined: Thu Jan 14, 2016 2:36 pm
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Location: Wilmington NC
Engine is removed so here is what I have so far:
looking in exhaust port, rings look like toast. burnt toast.
cut away is a 6.0 and reeds are standard boysen reeds
drained crankcase oil and had about 5 oz. manual says should be .19L (approx 6.4 oz) so little low.
all seals and bearings were replaced previously on original rebuild.
I don't know what you mean about the kerchunk by exhaust port though.
will get press test kit and test tomorrow and post results.


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PostPosted: Sun Apr 23, 2017 2:37 pm 
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Location: Hope, B.C Canada
dipnadactyl wrote:
Engine is removed so here is what I have so far:
looking in exhaust port, rings look like toast. burnt toast.
cut away is a 6.0 and reeds are standard boysen reeds
drained crankcase oil and had about 5 oz. manual says should be .19L (approx 6.4 oz) so little low.
all seals and bearings were replaced previously on original rebuild.
I don't know what you mean about the kerchunk by exhaust port though.
will get press test kit and test tomorrow and post results.


Well I reserve judgement on the rings until I see them. Lets pretend they are burnt toast. Then you can order just rings, I think they are about $50. The real question for me is how bad is the piston and the cylinder. My money right now says they are salvageable. The pre-tear down pressure test is crucial. It will tell you if a seal is gone or you have some kind of air leak.


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PostPosted: Mon Apr 24, 2017 7:38 pm 
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Location: Wilmington NC
Leak test is complete. It was quite a process too. Put the tester on and pressurized, almost immediately noticed pressure dropping. Checked all the stoppers with soapy water - Intake, exhaust and vacuum tube - and they all seemed good. Sprayed the entire Engine down and nothing on any seals or areas where there are gaskets. Hmm, maybe it's the tester itself?

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Sure enough, the two lower lines on the tester AND the squeeze ball all leaking. Cut the two lines back and reattached, pressurized and held my thumb over the intake on the ball and voila! No leaks. Pumped up to 9 1/2 lbs and after 5 minutes with my thumb as the seal only went to 8 1/2 lbs. Just checked it and after 20 minutes with no thumb over the seal and still at almost 7 lbs. Safe to say there is not an air leak in the Engine. On to the tear down.


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PostPosted: Mon Apr 24, 2017 9:54 pm 
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Lets see it. Pics Pics Pics Pics Pics !!!!!!!!


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PostPosted: Mon Apr 24, 2017 11:00 pm 
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work calls, gonna be a few days but will update with pics when I get into it.


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PostPosted: Wed Apr 26, 2017 5:17 pm 
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I was able to locate a cylinder that is on it's first piston so it will need to be bored to 80.5 and cost is comparable to getting the current one sleeved. Spoke to the local shop and asked them which way would be better to go and seems their thinking is that either way should be good - Unless the problem is with my current cylinder. Is there any possibility of a cylinder heating up and leaking - sometimes? This is a very frustrating issue and i feel like i'm grabbing at straws but nothing else is making sense.

One other thought that may or may not have any bearing: I mentioned the burn up happened when i pulled up to a stop, let off the gas and hit the brakes. While coming to a complete stop, motor (( Internal Combustion Engine ? )) shut down and was done from there.
When i removed the drive pulley prior to removing the motor (( Internal Combustion Engine ? )), I loosened the bolt on the dust cover but it stayed compressed. My first concern was it popping off unexpectedly and removing one of my digits so i re-tightened the bolt to snug and put a small vice on it to make sure it didn't release until i was ready for it, backed out the bolt a little and tapped it with a rubber hammer and pop, it was off. The shaft has some scratches and not a problem to clean up but is it possible the clutch didn't spring back out and my momentum continued to drive the rear wheels, spinning the crank with no gas/oil and that caused this?
Any thoughts?

Like i said, grabbing at straws...


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PostPosted: Wed Apr 26, 2017 8:31 pm 
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Location: Hope, B.C Canada
dipnadactyl wrote:
I was able to locate a cylinder that is on it's first piston so it will need to be bored to 80.5 and cost is comparable to getting the current one sleeved. Spoke to the local shop and asked them which way would be better to go and seems their thinking is that either way should be good - Unless the problem is with my current cylinder. Is there any possibility of a cylinder heating up and leaking - sometimes? This is a very frustrating issue and i feel like i'm grabbing at straws but nothing else is making sense.

One other thought that may or may not have any bearing: I mentioned the burn up happened when i pulled up to a stop, let off the gas and hit the brakes. While coming to a complete stop, motor (( Internal Combustion Engine ? )) (( Internal Combustion Engine ? )) shut down and was done from there.
When i removed the drive pulley prior to removing the motor (( Internal Combustion Engine ? )) (( Internal Combustion Engine ? )), I loosened the bolt on the dust cover but it stayed compressed. My first concern was it popping off unexpectedly and removing one of my digits so i re-tightened the bolt to snug and put a small vice on it to make sure it didn't release until i was ready for it, backed out the bolt a little and tapped it with a rubber hammer and pop, it was off. The shaft has some scratches and not a problem to clean up but is it possible the clutch didn't spring back out and my momentum continued to drive the rear wheels, spinning the crank with no gas/oil and that caused this?
Any thoughts?

Like i said, grabbing at straws...


I think your really grabbing at straws there on the drive pulley scenario.
As for the other cylinder, good you found one but you may blow it again until you find the issue. I would try to slam the old one together as cheap as possible and try the better fuel suggestion. If it lives you know the answer. Everything else you posted checks out so my money is on crap fuel. That's why I want to see that piston.
Just my opinion.


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