engine tweeks to increase hp

[clay]

You can't reduce chamber size without affecting the integrity. You show me a guy who has a 9:1 compression HT and i'll buy you a harley davidson

buy my first build back for me

 

[speedracer831]

wow, did you do that head mod yourself? i have an arc welder, can you make a thread with some sort of tutorial of how to do this, im sure it would be greatly appreciated bu many many people. any actual compression/psi numbers you can share with us?

 

[clay]

you cant do it with an arc welder. it's pretty straightforeward with a tig though, weld it up and grind it out. that particular head produced 140-145psi depending on the amount of kicks. but there was too much heat buildup with the stock fins. i ended up going with a head off another application. minimal "adjustments" were needed, and it has huge fins. the exact application will be a secret until after the death race.

 

[speedracer831]

haha wow looks like thats a well worked on engine, dual carbs and all. although i would go walbro if you plan on winning the race. custom exp chamb. too? aww what a shame your running that beast single gear!

 

[Egor]

I think someone has been called out. LOL. There are a lot of heads that could be made to work on the Happy time engine. I was going to look for a Hodaka head myself. One thing that has been pointed out here is that there is insufficient fins for cooling. I have made that point numerous times in my posts. I have a link to a source for heads. I think that if the bolt pattern is slightly off it could be made to work with a little ingenuity. Most small two strokes use the same pattern, or close. Have fun, Dave

https://www.1977mopeds.com/parts/Engine/CyH0/Cylinder-Heads/

 

[speedracer831]

Ill be getting this one https://www.1977mopeds.com/product/707/Puch-70cc-High-Comp-Head/ thanks so much egor, its gonna kick butt as far as cooling goes, and for a strong well built high compression head, hey this is just great.

 

[Egor]

I like the looks of that combustion chamber! I like the price of there parts. I would love to find a crankshaft that would go into the happy engine. I could make the ends up on my lathe. Glad to hear that you found something that you like from them. have fun, Dave

 

[speedracer831]

lathe? jealousyy... hey if you look on the intake section of engines, there are a bunch of different reeds. i cant tell well from the pic but are there any that would be easily adaptable to go on an ht?

 

[speedracer831]

i ended up getting this one https://www.1977mopeds.com/product/1908/Puch-70cc-High-Comp-Kstar-Head/

 

[bigdan]

is the puch 70cc head a bolt on replacement for the 70cc HT motors or did it need to be modified.