Fun with 40's....HS40's that is

markus

Well-Known Member
#1
So after running out of OS piston's for the HS40's I had started searching some old resources hoping I could at least come up with a spare 1 or 2 for customer rebuilds. Well I ended up finding quite a few again! The blocks I have on hand are all either new tear downs or low run time with where they all pull very low numbers for piston ring gaps and measure straight down the bores. So I was thinking I'll just pick up some used blocks off ebay and bore them. ANy other time I've been forced to buy a replacment block off ebay It was usually whipped, So I bought three blocks in past couple of months one bare, and 2 short blocks.

Well, the bare block and one of the short blocks I had inspected, and much to my surprise both were tight, smooth and clean bores o_O Talking like .014-.015" on a set of rings Ones so nice it does not even have .0005 of variation in the center typical wear area of the bore. What the hell, where were all these blocks a couple of years ago!!!!! I have not torn into the third short block I bought, it still has a head on it and I just tossed that in the pile for later....maybe I will get to bore that one (probably when I get to it, I wont have a piston available to use :rolleyes:)

So I knocked out some prep work on both I have torn down......basic rebuild stuff that needs addressed in all engines. One I did have to go oversize on the intake valve, that sucks only because those valves are pretty pricey on their own, guide was only showing .001 over ( a "+1" pilot fit tight midpoint) but for some reason even with another valve I felt worse than that and the valve itself had damage from the keeper making me thing something was not centered well and all that could be corrected when going oversize. I would have liked to have seen the tappet, but that one was purchased a bare block with just the valves in it, the cam bore and tappet bores all look good so I am not sure what was happening.

Ate up intake valve on engine 2

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OG valves on engine 1 (right) and exhaust on engine 2 Refaced nicely, Engine 1 got a 4 angle recut to the seat last week, engine 2 is ready to get the deck surfaced trued to get rid of the "good enough" job that Tecumseh did on these as well as the always present low spot around the exhaust.
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I got to cut something at least! Taking the Intake guide to OS:
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With the Guide cut its time for a valve job, Technically they all need a true valve job.......just measure the seats and compare to the measurements in the book.....or not, ignorance is bliss :D A seat recut has to be preformed with any guide work anyway to make sure everything centers out. tecumseh does reccomend a 3 angle recut to be done. I was pretty happy with this one, and achieved the .035 seat width That is recommended in the book for this particular engine size. Exhaust is next, that should be .045......
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Test spin with marker only and I am pretty happy with the results.
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I am off to work now, More on these later,.....
 

markus

Well-Known Member
#5
Yea 46 number is the degree of the cut of the valve seat, valves at 45 degree so as they break in they form a tighter seal/ match to one another. The .045” is the width of the seat mating area. For I think most of the small frame larger sized exhaust valves, but didn’t dig out the specs sheets.

got most of the items collected before I head off to work. Going to do an actual slanted application version with mechanical compression release camshaft. So I dug out a slanted intake, single/rear fill only sidecover, etc… did get the crank micro polished out and flywheel properly lapped/ mated to the crank so now I can start washing all the parts. Have some customers engines going right now as well so I am piggybacking chores that have to be done with them. They are different DAFB7F4E-34D5-41EE-A741-25B3F76E683F.jpeg sized engines so I don’t mix up any parts!:oops:
 

markus

Well-Known Member
#10
So been busy with others engines and haven't had much time to get this done, It was way too cold to paint a customers H50 this morning so I threw this one on the stand with some unfinished parts (recoil and air filter) and a test pipe to see if it would run. She did just fine, so its time to mix up some color to squirt on it, make it Pretty, and make it available! I found a 1972 slanted HS40 tag out of my parts bins, so I set it up correctly for that application right down to the dipstick and correct parts for that time period, carb Is an actual OEM HS40 size but modified into the recreational setup.

 

markus

Well-Known Member
#15
True professional....no spray bombs, check out the disposable gun cup lid. I'm too cheap for those.
Buy a can of spraypaint lately!!!! I was bitching about the the price hike at the paint shop recently, until I saw what a can of crap spraybomb was selling for now! When it was only 3M selling those cups I would reuse the inserts! I bought a shop package deal when they first came out and It was a good deal.....until I needed refills! They have some fakes now that are a bit cheaper, all though in true repop/copycat fashion they dont fit as good as the real thing. Think it breaks down to about an extra $1 per paint job on the supplies, but I can cap the little bit of leftover in the cup, stick it in the fridge and get a day or so life in case there is a touch up to do.......But that never happens:rolleyes::D

And yes, that is single stage I am using. I shy'ed away from base/clear on full painted engines, was just too much paint layered on and I had a few problems with heat.
 
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