Tec HS40 Engine Internal Component Wear

[primer_bulb]

Hi all,

I have a 1970 Tecumseh HS40-55282B (Serial # 0244 0333) and I am proceeding to inspect the internals componets. Upon disassembly I noted scoring on both the main cylinder mag. side bearing and matching crankshaft bearing. The scoring can be caught with a finger nail and is more pronounce on the main cylinder. The cylinder mag. side is plain bearing with no bushing. Fortunately the PTO side has a ball bearing and feels fine. Is this scoring a cause for concern and if so is there a remedy? (See photos below)

Part 2:

The engine's camshaft appears to be in usable condition, however, I did note level lobes on both intake and exhaust side. Are new HS40 camshaft lobes rounded/ pointed rather than level? Also is it common practice to replace both valve lifters during an engine rebuild?

Thank you for the help,
Jeffrey

[KE4AVB]

Crankcase badly worn. NLA.
Camshaft lower lobe badly worn. NLA.

With parts no longer available a re-power with an used or new engine is the only options; unless, you can find used donor engine.

[bgsengine]

Yep - or if it is a "restoration rescue" project and money is not a concern - take it to a machine shop and have the block line bored and re-bushed, the crank and cam turned - the lobes look relatively normal though - they should not be at a sharp point - the lobe lift and duration specs should be checked but they look fairly normal for that old L-head - tappets are not usually replaced in an overhaul unless there's something found wrong with them (excessive wear or breakage) But if going with the machine shop option, be prepared to spend 5-10 times the cost of a replacement engine just on the machine shop work. and then hope and pray that you can even find rebuild parts (rod, rings, piston, valves, etc)

[KE4AVB]

BGS, When I zoomed on the cam image that intake lobe looks to be flat topped and tear dropped as I normally see. On this cam intake is next to gear if the IPL part labels are correct.

[bgsengine]

BGS, When I zoomed on the cam image that intake lobe looks to be flat topped and tear dropped as I normally see. On this cam intake is next to gear if the IPL part labels are correct.

Like I said...

the lobe lift and duration specs should be checked

Looking at the upper cam image in the post, which more clearly shows the intake lobe (which compression release works on) , considering the shadows in the photo, looks relatively normal to me compared to others I have seen - lighting and angle of the photo is a factor in these photos.. trying to compare it to the exhaust lobe pic - the angles of the photos are different so, the lift and duration will appear different - perhaps if there are no specs available just take a measurement of the intake and exhaust lobes at max lift and compare that way - if they are relatively close (but they will differ, as I recall) for *lift* , I would not worry terribly about the "duration" (roundness of the narrow end).

[primer_bulb]

Thank you both for the informative information. This is indeed a restoration project for a Rupp mini-bike. Below are more photos of the camshaft lobes. Hopefully my local machine shop is willing to take on the work required to overhaul this engine.

BTW how is the [url] featured turned on? I could not find the settings in the user control panel.

Thanks,
Jeffrey

[bgsengine]

Yeah from those photos now, I would tend to say it is your *exhaust* cam lobe that is worn out, oddly enough - it looks almost re-ground - I cant recall seeing them with such a size disparity - looks like intake cam lobe is much larger - but as you have discovered - it's gonna be expensive in any case, and with luck you may be able to find "NOS" (New Old Stock) parts on ebay or elsewhere - should be able to look up part numbers and then run a number search in google.

As for the url thingy - it is actually a forum restriction until you have had enough activity and experience posting in the forums, url's wont work no matter how you do them - but when you get past that limitation you generally don't even need the url tags to make a clickable link in a post. (though it is handy to make shorter "click here" links when you have a long-@$$ url to paste)

[creia]

Hello gents,
"primer bulb" is my son and that is the original engine off a 1970 Rupp Roadster mini cycle. Yes Brian, you are 100% correct it is a "restoration rescue"! Having an OEM matching model/serial numbers engine is critical on this particular project and SIGNIFICANTLY adds to the overall value of the bike. This engine actually starts, idles, and ran fairly good except it smoked like hell and was just starting to get a rod knock. After he took it apart we knew we had to do a cylinder OS bore after measuring the specs. Fortunately, my son located a NOS Tec 0.020" OS piston/ring set for a very good price and we have a very good engine machine shop to OS bore and hone. As it turned out also the crank was excessively worn at the crankpin as well, and the rod had too much play, hence the rod knock starting. New cranks for this engine are NLA, so We are looking at having the machine shop weld the crank and turn it back down to specs for the NOS Tec rod he purchased (also at a terrific price). Yes, the machine shop can install a bushing in the block for the crank flywheel end and turn down/smooth the crank on that end too. The cam (lobes) is what we were not sure about. The machine shop tech was of the opinion that the cam lobe was worn out (flattened), however, I am not so sure. I wonder just how many 1970 Tecumseh engine cams they actually see to make a comparison?- hence my son's question to this forum. I believe that my son (Jeff) is sending some better pics of the cam shortly for your review and critque
I realize that many reading this thread think we are absolutely nuts to expend this much time, effort and $$ into this old engine! (We probably are!) My son, however, has been on a mission to revive this bike back to its glory days, since he first rescued the bike from a slow death last year. Really and truly it HAS come a long ways. He has already made many repairs and/or replaced parts to the frame, wheels, brakes, cables, lighting (the bike is full lighted with headlight, tail light, and brake light- as this engine has a "lighting coil" charging system. Interestingly, this particular bike was fully street legal/registered back in the day,(We have the original registration and plate/sticker) so we will be trying to get it legal again with the CA DMV as well (Wish us luck!) . Overall, it has been a labor of love for us and very gratifying to see the progress.
Thank you all very much for your help...
Michael
Edit: Oh yeah, the valve guides were worn out too!

[creia]

Yeah from those photos now, I would tend to say it is your *exhaust* cam lobe that is worn out, oddly enough - it looks almost re-ground - I cant recall seeing them with such a size disparity - looks like intake cam lobe is much larger - but as you have discovered - it's gonna be expensive in any case, and with luck you may be able to find "NOS" (New Old Stock) parts on ebay or elsewhere - should be able to look up part numbers and then run a number search in google.

Brian,
You are correct (no surprise) about the size disparity of the cam lobes! I've never seen anything like that in any Briggs or Tecumseh engine we have ever worked on. Our research has revealed that this particular cam was a bit of an odd-ball (The lifters are also different lengths). From 1971-on Tecumseh went to a cam with lobes and lifters identical in size in the HS40. A OEM replacement for our 1970 HS40 cam is NLA, however, we have been informed from a reliable source that the 1971-on cam and lifters are a direct fit in our block and THEY are available for not too bad of a price.
If it turns out we definitely need a new cam, that is the route we would likely go.
Michael

[KE4AVB]

I realize that many reading this thread think we are absolutely nuts to expend this much time, effort and $$ into this old engine! (We probably are!)

Not I as I have done the same thing on some antique chainsaws for customers. I even did upgrade rebuild of a Poulan 4218AV that cost nearly as much the saw's new price of 129 USD but it was a great learning experience that I have been able to apply to other repair projects. BTW after the upgrade that saw would now cost 189 USD to buy new around here.