A rider ...

[ndian22]

Yes what I meant not what I posted! Voodoo metallurgy or NASA rocket science perhaps. I once wasted a lot of time and energy in attempting to TIG aluminum, scrapped from a fighter jet fuselage...never happened, but rivets & resin did! Thanks for pointing out my post confusion.  

Pete I don't have my temp charts here but normally I'd say engine heat wouldn't be a great cause for concern in normal use, but many of us were around racing when aluminum heads often warped and blocks cracked. Alloys eventually changed along with manufacturing processes, mechanical designs and associated cooling improvements etc. Today problems are less dramatic but do occur from time to time. Some alloys could soften with enough heat & too little cooling of course, but not ordinary.  Rick C.  

[pd]

This is 60 year old metal .

I have to wonder .

Pete .

[carryall]

Agreed.  Modern metallurgy is way more sophisticated since then.  Generally an engine made from aluminum alloy, wont reach high enough temperature to affect the strength because it dissipates the heat well.  It's hardness, malleability. and wear resistance are all engineered via the composition/percentage of the various alloys added, and the percentage of carbon present.   After smelting, (both medium to high carbon steels and aluminum alloys) their properties are greatly affected by how it's cooled (time and temperature) and thus affects how the carbon atoms then "arrange themselves".  (sorry it's been 30yrs since metallurgy class)  Repeated overheating and cooling could certainly weaken aluminum components, and "old school alloys" would certainly be more susceptible I'd think?  60 years ago nobody would have been able to produce a T6 aluminum 1911 frame like my Kimber, etc...

[ndian22]

Modern alloys steel, aluminum, titanium etc. of the best quality are amazing. I tend to build frames with steel but I have several aluminum frames that have taken long term beatings and are crack free though extremely light. DOM steel tube is freaky strong in small diameters & thin wall. Bike builders 60 years ago would have loved the new materials. Though I use modern alloys I'm still using extra braces, plates and gussets to lend more strength to frames than is required. It's hard to change even when you know your designs don't reflect the advances of technology and I'll probably not alter my frames to take advantage the improved materials. I'm mired in the past it appears, but admire those who truly trust the advances in metals. I do like new things especially when they get old! lol.   

Yes the 1911 Kimber is sweet! I still cling to my 1911 long slide Colt .45, but fully acknowledge it's antiquated reliability in a tight spot.  Rick C. 

[pd]

I'm getting back to the '57 after a couple of weeks hiatus ... due to high heat and 90%+ humidity . It would be nice to have an air conditioned shop .

Anyway , I cleaned the roller last night in preparation for mounting the motor in the frame .

 I have an aluminum CPU heat sink that has a 1/4" thick base . I'm thinking I can use that base as an insulator for the exhaust manifold . So , I cut the cooling fins off and did a bit of shaping ( sanding ) . It looks like it might just be a good fit . I still have to 'form' it , drilling holes and some grinding or some such .

I'm half thinking about building a different exhaust . 1" EMT seems to be about the closest fit for the manifold and probably the easiest to shape . That whole thought is still being chewed on .

Pete .

[carryall]

You shaping the heat sink the same shape as the manifold in order to use "stock" gaskets between?

[pd]

Pretty much the same , Yes . I might leave some material 'outside' the manifold form just to maybe help dissipate more heat . I'm thinking that it isn't going to bend very much , if at all . That might be a limiting factor .

Pete .

[carryall]

      Hmm...Aluminum spacer for intake isn't a problem but, the only application using aluminum for an exhaust manifold (I can think of, off-hand) is in Marine applications where they are water jacketed/cooled?  Not sure how much heat that AL spacer "will take" at the point of exit/exhaust without affecting it?  Copper takes double what AL will, and is why they use it for heads and exhaust gaskets.

[pd]

True that^ .

The exhaust manifold itself is aluminum . I know for a fact that it can and has been affected by heat .

Example : my manifold 'was' oval shaped , until I applied a bit of heat and rounded it .



The ears are currently bent slightly , probably due to the weight of the muffler and , of course , that allows leakage .
I'm hoping that the insulating effect of the spacer and the two gaskets will be enough to curb the effect heat has on the manifold . But , I'm not really holding my breath ...
Even with the added mass of whatever extra material I can leave on the spacer , the manifold is still close enough to the heat source that there may be no positive difference .

Considering that I seem to be the ONLY one with this problem , I have to ask 'why' .
Does my motor run that much hotter than any others out there ?
Do I happen to have an inferior ( defective ) manifold  ?


Maybe I should just build a steel manifold . Hmm ...

Pete .

[carryall]

An engine running in a lean condition will have considerably higher temps.  You (if memory serves?) were having a possible seal and/or intake leak before, so is it possible your were just overheating the motor and "soft-seizing" on occasion?
    Since 2 smokes are much more tempermental to A/F mixture than 4 strokes,  I typically will tune my mopeds almost to the point of "four stroking" via "plug chops" to ensure they don't end up on the lean side. (especially at WOT)  So many little variables affect them like oil mixture percentage, jetting, pipe, timing, and even plug heat range and gap, I start with the base tune of timing, oil mixture percentage, and pipe and then try to jet them up to a decent amount of black on the plug insulator without them 4-stroking.  

[Ricks]

I always true the exhaust manifold mounting surface before installing.  It doesn't usually take much.  I put some 60 grit on a true surface, like a table saw table, and run it back a forth.

I have not had a problem with the hole getting out of round.  As for lean, that will kill your engine!  All Simplex motors should be run fat enough that they 4 stroke while decelerating off throttle.  If your motor never 4 strokes, you are way too lean.

Have you had the motor run long enough to get a head temp?

[carryall]

Seems I've had ranges from 375 to 475 on 49cc-70cc 2 stroke mopeds at the head. (Tomos, Puch, Vespa, etc.)  Exhausts much hotter...Since I don't have a Servi motor, not sure what a "normal" range would be but, 400 or less would be nice! (really hot days running hard will be "hotter" of course.

[pd]

Soft seize ? Sure , had a couple of those . But mostly , I'd call them a hard seize . There's not much soft about the motor halting in fairly short order to the point of not being able to turn over without major force .

The plug and the piston 'dome' has always been black . The piston and cylinder has always had a rich film of oil when I tear things apart .
I always have a fan on high blowing over the motor when running the motor while not moving .

How you describe your 2 stroke tuning is pretty much the same as how I do it . Just this side of 4 stroking . I have a tendency to run a bit too rich . I've had folks tell me that my exhaust smells real rich on many occasions .

Rick ,

I don't have a thermometer able to read head temps .

Pete .

[carryall]

Just throwing it out there...possible it's "seizing" from something other than piston/ring?  Crank, piston, rod bearings, etc...

[pd]

I always check all points for free travel before I put things back together . I've not had any seizures other than piston to cylinder , which usually locks the rings in the landings .

Pete .