tecumseh-ohh build

delray

Well-Known Member
got to test my compression relief unit this weekend and it works and it also doesn't. it will not pop over with the valve open. just to much lost of air to ignite the fuel,but not really a big deal either. what it did help a lot was the prestart of the engine. so when the engine was cold I can open the valve and then set the choke and pull the engine over couple times without kick back.. this will allow the carb to prime the engine. then shut the valve off and choke and then just pull the engine over slowly unit I get the sweet spot and then pull it just once and off it go's. I might try to restrict the hole little smaller in the future for testing purposes,but for now it's easy to pull over with that small quick procedure.
for the engine setup i am using a 5.5 and larger style block. all ohh-engines that are 5.5 and higher horse power rate come with a 2.795 bore. this block was a big plus. it had a steel sleeve. staying with the lower half of the block i had a arc billet rod installed with a new set off rings and a quick hone with 400 grit stones. cam was a 255 dyno with a set of clone 1.3 rockers modified onto the ohh head. nice thing about the push rods they are built very big(thick). i don't think they will move around(bend). the head i installed came off a 5hp engine. they have a much small open style chamber and milling about .065 off. I got a compression rate around 11.8 and this may drop so slighty when added the piston to cylinder spacing at the top that's not calculated into the finally cc's rating. so I would put it maybe closer to 11.5. perfect with 91 ethonal free gas that is ready available in my area. set of briggs valves(seen in picture above)and ported. for the springs i had to cut the spring pockets down to run a taller spring that would be rated at 32 pounds and a set of dyno retainers/keeper.for a coil i ran a tecumseh hot coil and a aluminum flywheel of a vertical engine. this was not just any flywheel. it was a certain type with the mags casted into the aluminum like the old hs-40's where done and the casting was very smooth. i have seen them come in different ways. so i don't recommend installing just any type of stock flywheel. good example they make one aluminum flywheel that can bolt up to this engine,but the mags are roll pin into the aluminum flywheel.......not safe looking at all(stay away from them)
here is the crazy part. the carb is a 22mm mikuni/china carb with a 142.5 jet a 15 pilot that I my change OUT. reason i say that is at low cruise speed I will get a very small stumble,but if you hit the throttle it would rocket right off again right up 7000+ rpm's

correction on the jetting. it was much much lower then 142.5 that was my old race motor with a isky black mama 275 cam. this one was i believe 130? i will have to take it apart and look.
 

fistfullabar

Well-Known Member
I see u been getting busy on the track! Gotta lot races on your channel. B safe! By the way my power sport keeps blowing out the oil seal on the output shaft. Not sure what to do!
 

joshua. c.

Well-Known Member
I see u been getting busy on the track! Gotta lot races on your channel. B safe! By the way my power sport keeps blowing out the oil seal on the output shaft. Not sure what to do!
The current aftermarket oil seals for the crank side aren't made to the right tolerances they are slightly to small. my dad works at a factory with a machine shop and he made me a tool to open up the metal outer ring of the seal so it fits properly, I'll have to get a picture for you later. its a pace of round stock with a hole in the middle and the edge bevels down to the diameter of the crank seal. To use it just stick the beveled side it in the seal and give it a good wack with a hammer and problem solved, if you use the other side that's flat it also doubles an installer tool.
 

joshua. c.

Well-Known Member
hear are the pictures
one from the top, one from the front, one from the bottom. hope this helps. feel free make a copy of the tool but my dad snuck this project in for me off the clock so he wont be making any copy's himself. (The company he was working for at the time dose allow this now and again as long as its kept small and you don't make it a regular habit.)

rofle I can see my shadow clearly in the last picture. "say cheese"

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