066 RPM's creep up at WOT, ? about fuel filter

[Mastermind]

Great thread. Good reading.

 

[mtngun]

Since you are running it on a mill are you going to heat the allthread up to OT before installing?

No, they'll actually tighten up at OT since the aluminum jug expands more than the steel bolts. i wonder if that's what caused the bolt to pull out ? It doesn't take much to damage those magnesium threads.

 

[Justsaws]

No, they'll actually tighten up at OT since the aluminum jug expands more than the steel bolts. i wonder if that's what caused the bolt to pull out ? It doesn't take much to damage those magnesium threads.

I see what you are saying and that could be possible. Certainly might explain the cause of the air leak.

Having more than doubled the length of heat soaking expandable steel between a hot end and cool end attachment I would be concerned with the amount of torque it would require to keep everything clamped down over time. As the saw cools down things having to be getting loose, certainly as the hot/cold cycles start to add up and with the added vibs of the saw running, especially mounted to a mill.

The traditional cylinder mount keeps all the steel in the same temp range most of the time, even those will loosen up over time.

Hopefully it will work out, maybe a round of ceramic washers might be a good investment.

A new round of successful milling with that 660 is long over due, good luck.

Editting to add-
At the moment the work around I see working best is to use an mag alloy rod(mounting pole) between the cylinder head and base. Steel threaded rod from the crankcase to the alloy rod and steel threaded rod from the mag alloy rod through the head top. Something that can distribute the expansion of the cylinder and help isolate the threads in the case. Hopefully you would not need to do that but that is where I end up.

Editted to put the word steel in front of threaded rod. The purpose of the mag rod is to provide a metal that might expand at a similar rate as the cylinder along the length of the cylinder so that a torque value can be found that will not pull the threads out of the crankcase. The homemade timesert that was used is also an excellent solution but may still not be enough to make it a long term solution.

 

[tdi-rick]

Geez, you've had some fun with this one.

We have a few sayings here that describe this situation that I probably can't repeat in these PC times, suffice to say you've worked through it all admirably.

I think a steel stud is fine into the crankcase and just use nuts on the head although I'd be opting for some HT booker rod or make a stud from a long SHCS by cutting the head off and turn a thread on the end. (something I've done on racecars)
If you want, use some Loctite 243 into the case. (I'd hesitate to use anything stronger) As much as I hate using Loctite on mag and aluminium sometimes it's necessary and some of the manufacturers stipulate it these days, Dolmar for one.

 

[David (saltas)]

I may appear to be talking out of my back side but "all thread" will leak air into the crankcase along the thread.
When the nut is done up it is only touching one side of the thread.

The original bolt had a solid head and a flat surface to seal on.
The nut can seal on the flat surface but there is a helical air gap up through the nut along the thread
When you put a nut on a thread there is free play until the nut and washer make contact and start to stretch the bolt.

Lock Nut /Jam Nut work because each nut press against each other and by pressing on opposite sides of the thread try and stretch the thread inside them.

edit finally found a image of what I'm dribbling on about

 

[bullseye13]

I would encorage swapping the cab for a known good one should anything further arisse. I did a complete rebuild on a husky 288 for a buddy of mine, new bearings, seals, fuel lines, i rebult carb, bunch of other stuff too. This saw was through 3 top ends previously, i got it together and started it. it had wot creep pretty bad, i could kinda sorta adjust it out of the carb, blip the throttle, go wot again and it would creep back up. went through carb again, no luck. Rebuilt a spare carb, threw it on and success. I ran the crap out of that saw before i gave it back to be sure there were no problems.

Something in that carb was screwy, but i never had a spot on the inlet screen. Didnt keep it to fiigure out what was wrong.

 

[angelo c]

I would encorage swapping the cab for a known good one should anything further arisse.



Something in that carb was screwy, but i never had a spot on the inlet screen. Didnt keep it to fiigure out what was wrong.

Color me ingorant but there seems to be a lot more "mystery" carb ailments suddenly popping up since we've been force fed the corn gas. One can only expect it to get worse when e15 becomes law of the land.

tell me again...why are we putting up with this stupid lie called "ethanol"...

 

[Mastermind]

Color me ingorant but there seems to be a lot more "mystery" carb ailments suddenly popping up since we've been force fed the corn gas. One can only expect it to get worse when e15 becomes law of the land.

tell me again...why are we putting up with this stupid lie called "ethanol"...

Good question! Everyone knows it's a bad idea, yet we are still being forced to use it.

 

[mtngun]

Thanks for the comments and suggestions.

Re: trying the other carb, it makes sense to try one thing at a time. No point trying another carb if the saw keeps spring air leaks.

Saltas, it does not matter if the cylinder bolts leak air because the threads are in a blind hole, and the gasket seal is on the inside of the bolt holes.

I took it to the woods this morning. Ran super strong for about a minute, then the RPM's started creeping up again. At the end of the pass I attempted to re-tune the carb, but it alternated between over-revving and not wanting to run at all. I'm guessing it sprang yet another air leak.

Will leak test and tear down. If I find another problem with the jug threads I'm gonna set the 2 piece aside and go back to a conventional jug, as the dissimilar thermal expansion issue on the 2-piece setup worries me.

I would be concerned with the amount of torque it would require to keep everything clamped down over time. As the saw cools down things having to be getting loose

Actually, the concern is that the bolts are getting too tight as the aluminum jug expands with temperature. That may put enough stress on the threads to pull them right out of the mag case. SOMETHING has to give.

I am certainly not the first person to use a 2-piece head, but most 2-pieces are used for racing where it's only run for a few seconds at a time. Milling is always the ultimate test of a chainsaw.

Will report back after I leak test it and tear it down.

 

[RiverRat2]

Good question! Everyone knows it's a bad idea, yet we are still being forced to use it.

Seems we need some new direction @ head quarters to change it!!!!! so say we need a breath of fresh air!!!!! sorry about the derail,,, Good luck with the saw,,, did I mention it's hot outside????

 

[Mastermind]

I was aware that you were running a two piece head on a milling saw and have been wondering if or how it would hold up. As you said milling is the test of a saw's durability.

I've toyed with the idea of using a two piece head on a work saw, but I don't think that's a good idea now.

As always, thanks for the posts. We all need to post the good, the bad, and the ugly.

 

[mtngun]

Jug bolts seem fine.

Leak test was mostly good.

But there was a teeny weeny leak at the base of the jug. The leak rate was well within spec, and I wouldn't be worrying about it if the saw was running right. It's surely too small a leak to cause the creeping RPMs.

Pic of saw under water with 5psi pressure. No bubbles visible at the source in this pic, but you can see where bubbles accumulated by the exhaust block-off as they floated up from the base.

This is the same place where I found a small leak a while back. Dunno why it leaks here, as the gasket was smeared with permatex #2 (I switched to permatex after it had leaked there with hondabond the previous time).

I'm back to being puzzled about the creeping RPM's, and ready to try the other carb. Plan is to pull the top end, try once again to get a good base seal, and then put it back together with the other carb. I brought a small log home from the woods so I can test the saw at home and not waste time and gas running back and forth to the woods.

 

[albert]

If it leaked in the same area before, it could be the base of the cylinder has a small blemish or slightly warped. Same goes for the crankcase deck. Hard to tell from the pic, but does it originate near the crankcase seam? I hope you get it solved. I forgot if you use the saw mainly for milling. I know milling is about the toughest duty a saw can do. I have very limited experience with milling. Most miiling saws are probaly stock, and are tuned very conservatively on a 32:1 or heavier mix.

 

[tdi-rick]

[snip]
Actually, the concern is that the bolts are getting too tight as the aluminum jug expands with temperature. That may put enough stress on the threads to pull them right out of the mag case. SOMETHING has to give.

I am certainly not the first person to use a 2-piece head, but most 2-pieces are used for racing where it's only run for a few seconds at a time. Milling is always the ultimate test of a chainsaw.

Will report back after I leak test it and tear it down.

I wouldn't be too concerned, Karts and bikes have used studs into the crankcase and bolts to hold the head and barrel down forever.

Ok, they are designed that way, but it works, and we only ever used 150Nm tension on a kart head and their BMEP's were a lot higher than a saw.

 

[mtngun]

If it leaked in the same area before, it could be the base of the cylinder has a small blemish or slightly warped. Same goes for the crankcase deck. Hard to tell from the pic, but does it originate near the crankcase seam?

Cylinder base is fine. It was leaking about 6 mm away from the case seam -- could be a slight mismatch between the case halves, but you'd think the gasket goop would seal any imperfections.

Karts and bikes have used studs into the crankcase and bolts to hold the head and barrel down forever.

That's what I wondered. Of course, carts and bikes use aluminum cases, don't they ? And prolly larger diameter threads ?

OK, just to be safe, I pulled the top end and gave the leaky spot a look-see. There may be a slight mismatch at the case halves at the seam, but it's certainly not bad or unusual.

I made a couple of paper gaskets out of manila folder. Two, to give me the thickness I needed. Smeared both sides with a thin film of hondabond. Cleaned up all mating surfaces, and put it back together. I'll give the hondabond 24 hours to cure before I fire up the saw, even though that shouldn't be necessary.

Why paper ? Even though paper gaskets are dissed, I've used them several times before without incident. I'm thinking the paper will have more "give" than the steel OEM gasket, and should conform to any imperfections in the mating surfaces.

Will put a carb kit in the new-to-me WJ69 and give it a whirl later this week. If the ghost problem is still there, I'm not sure what's left to try that hasn't already been tried. :msp_confused:

 

[angelo c]

Mtngun,

If you want to try a different jug just for chits and giggles let me know. I got one on my bench you can borrow...if for no other reason then to eliminate failure possibilities one by one. I could stick a known WJ 69 in for good measure too.

I wouldn't be too upset if it got ported on the way back !!!!:msp_thumbsup:

 

[David (saltas)]

Saltas, it does not matter if the cylinder bolts leak air because the threads are in a blind hole, and the gasket seal is on the inside of the bolt holes.

I'm glad now that I said I may appear to be talking outa my backside.

 

[mtngun]

Another update on the ghost problem. Since the last trip to the woods, I :

-- fixed the itty bitty air leak at the cylinder base. No bubbles seen with submerged pressure test, vac leak 0.5 inHg/hour.

-- pressure tested the fuel line (again)

-- vac tested the fuel line to see if hose was collapsing. No, it did not collapse under 10 inHg vacuum.

-- verified tank vent was venting (again)

-- new-to-me WJ69 and ultrasonic bath and carb kit.

Tuned to 11,500 WOT. Idle was a bit inconsistent and didn't respond normally to the L screw, but otherwise it seemed to run OK out of the wood.

However, by the end of a 12' cut, the WOT had crept up to 13,000. Plus, it didn't want to idle well. I tried playing with the idle without success.

-- put the old carb back on and tuned to 11,500 WOT. Idle seemed good and responded to L screw.

At the end of a 12' cut, idle was still good, but WOT easily hit 13,800 and was still climbing when I said "enough."

I'm ready to try another top end. Will install a used BB jug. Can't understand why the 2 piece top end would be inherently prone to creeping WOT, but I've tried everything I can think of and nothing seems to fix it. We'll see if the problem goes away with the BB.

 

[komatsuvarna]

Interesting thread. Im just as curious as you to see what it is!

You think maybe the 2 piece head cant disapate the heat fast enough in a hard cut, making it go leaner and leaner? That combined with the extra heat from the extra mods and porting. Maybe im thinking out my ass.

 

[mtngun]

You think maybe the 2 piece head cant disapate the heat fast enough in a hard cut, making it go leaner and leaner?

No doubt the higher compression runs hotter. Though why that would make the revs creep up is beyond me. Maybe it is detonating ? I don't hear any funny noises, but then I'm not sure that one would be able to hear detonation on a chainsaw.