I just purchased a high performance valve train package that will be installed on my HM80.They are Tecumseh star parts and the new valve stems are smaller than the stock valves among other upgrades for better flow.I will take pics and post them if anyone is interested.My engine has a PC 702 grind cam in it along with port work and some eye brow work performed by me.I might upgrade to a 26MM mikuni from the 24 on it now.This engines RPM is limited by its points set up but pulls hard to its limit, it is my favorite mini bike that I own right now.
8HP Tecumseh Mods
- Thread starter roccosbike
- Start date
- Tags mods tecumseh
I just purchased a high performance valve train package that will be installed on my HM80.They are Tecumseh star parts and the new valve stems are smaller than the stock valves among other upgrades for better flow.I will take pics and post them if anyone is interested.My engine has a PC 702 grind cam in it along with port work and some eye brow work performed by me.I might upgrade to a 26MM mikuni from the 24 on it now.This engines RPM is limited by its points set up but pulls hard to its limit, it is my favorite mini bike that I own right now.
I got the valves,split keepers,guides and lifters today.What a huge difference in the valves,first they are stainless and have a swirl polish tulip...The stems are 1/4" where as the stock stems are 5/16".The guides are bronze and they push all the way down...no protrusion, and the main reason for all this in the first place, I now have split keepers.Now I just have to install this stuff and I will post a pic of how it looks.
I got the valves,split keepers,guides and lifters today.What a huge difference in the valves,first they are stainless and have a swirl polish tulip...The stems are 1/4" where as the stock stems are 5/16".The guides are bronze and they push all the way down...no protrusion, and the main reason for all this in the first place, I now have split keepers.Now I just have to install this stuff and I will post a pic of how it looks.
Walt, I am going to cut seats in the block and then lap them to make sure they have a good seat together. the valve guides just tap into the original valve guide.It is a well thought out upgrade.This work is being performed by me and a guy that does this stuff for a living(he knows what he is doing)and he has all the cool tools to make it happen, so pics to follow after the install.
Finally some progress...after getting the valves all squared away I put an old set of tappets in the block,set the motor at TDC of the comp stroke and checked tappet clearance with feeler gauge then wrote down what I had for intake and exhaust.Then I took the lifters out and measured their height for in and ex then added clearance measurement to height measurement to get an overall measurement for the in and ex.Then I subtracted what I wanted my tappet clearance to be for the new tappets, (which was .006 both sides) off the overall measurements.Then I took the new extended tappets (lifters) to a machine shop and had them ground down to my specs.After installing them I checked my tappet clearance and I have .006 on the intake and .007 on the exhaust.On this particular valve train this is how its done...Mike Clements told me to clearance the tappets not the valves:shrug:who am I to argue with him.The valve train is ready and I can't wait to hear it run with the new set up.The tolerances were never this good on this engine since I have owned it, so I know its been improved.Right, wrong or whatever:shrug:this is how I got it done and I for one am happy with my results.:biggrin:
