My HS 50 build up

#41
Epoxy clear coat will hold the flywheel together.:laugh:
With this cast iron wheel i'am not that much worried about it exploding. Won't turn it past maybe 6k . And as much as people talk about wheels exploding , you don't see many that have . Plus this is not a China made flywheel . It also has magnets that are held on with two big ass rivets .
I know of all the talk but hey it's talk . And one more thing this motor was bought new in 1993 by the original owners of the Powell that it's on and the motor has very little run time and has not been taken apart . So the flywheel has not been beat on or over torqued and I just feel good about it .:thumbsup:
i've heard so many people argue it don't matter as long as it's cast it will explode HOWEVER you and one other life time kart racer are running cast iron wheels at well above 3600 RPM. The other life time racer guy was telling me for my HS40 there exists a cast iron fly wheel that should work AND has the lighting magnets. i'd love to to see how it's shaped because maybe if it's more square it would be easier to band. if its shaped similar to yours than it should be a cinch to band. i'm not sure if i can band my existing fly wheel. mine has been abused. also thinking about building a test rig to spin the RPMs so it can explode on the test rig and not in my shroud and under my legs/butt.
 
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#42
Well today I got the bottom end buttoned up . I did find one thing out , for those of you that are going to use the DYNO 255 cam take note .
On the exhaust side the lobe hits the crank shaft just a little but enough to stop it . With it installed and no side cove you don't notice it , once the side cover is on turn it over and it stops at that point . Here are some pics of where a clearanced the crank
 
#44
Well today I got the bottom end buttoned up . I did find one thing out , for those of you that are going to use the DYNO 255 cam take note .
On the exhaust side the lobe hits the crank shaft just a little but enough to stop it . With it installed and no side cove you don't notice it , once the side cover is on turn it over and it stops at that point . Here are some pics of where a clearanced the crank
Haha, I thought I was the only one!!

I ground the exhaust lobe with a grinding wheel and polished it. Turns over fine now.
 
#45
hhhhmmm i'll have to keep that mind. on my hs40 i plan to send of the internal for balancing. perhaps the balancer can shave off some metal in the area in the balancing process.
 
#46
hhhhmmm i'll have to keep that mind. on my hs40 i plan to send of the internal for balancing. perhaps the balancer can shave off some metal in the area in the balancing process.
Sounds like a good idea , but I don't think the little bit I toke off will matter that much . The motor is not going to spin that hard and these cranks can't be balanced in all the RPM ranges anyway .
 
#47
Actually they can't be balanced at all. A single cylinder engine will always have a primary imbalance that increases with RPM. Balance factor at 50% more or less keeps the vertical and horizontal forces at a minimum but is not always the best. The reason you can feel vibration bad at some RPM and not others has to do with the resonant frequency of the part the motor is mounted in in our case a minibike. As the rpm increases so does the frequency and strength of the vibration. When the frequency is identical to the resonant frequency of the minibike the whole thing shakes at that frequency with maximum force when the engine frequency (RPM) is 180 degrees out from the resonant frequency of the mini you feel little vibration. This is a very simplistic explanation but all a balancer can do is make sure both sides of the rod throw of the crank are in balance (rocking couple) and then balance to the balance factor which you tell them and nobody knows what it is for any particular frame. The factories balance the engine so the resonant frequency of the engine itself is around 180 out from the governed RPM that keeps it at a minimum.
 
#48
Actually they can't be balanced at all. A single cylinder engine will always have a primary imbalance that increases with RPM. Balance factor at 50% more or less keeps the vertical and horizontal forces at a minimum but is not always the best. The reason you can feel vibration bad at some RPM and not others has to do with the resonant frequency of the part the motor is mounted in in our case a minibike. As the rpm increases so does the frequency and strength of the vibration. When the frequency is identical to the resonant frequency of the minibike the whole thing shakes at that frequency with maximum force when the engine frequency (RPM) is 180 degrees out from the resonant frequency of the mini you feel little vibration. This is a very simplistic explanation but all a balancer can do is make sure both sides of the rod throw of the crank are in balance (rocking couple) and then balance to the balance factor which you tell them and nobody knows what it is for any particular frame. The factories balance the engine so the resonant frequency of the engine itself is around 180 out from the governed RPM that keeps it at a minimum.
I got a quote from a guy a who has speed shop for these types of engine, i think he does primary kohler performance stuff. gave me and quote and every thing, says the primary imbalance can be reduced.
 
#49
Well today I got the engine mounted in the frame and started . I don't have the throttle hooked up yet cause with not using the GOV I'll have to fab something up , not sure how to do this . But back to the motor I did shave the head some and she pulls a lot harder than it did stock , but not as bad as the raptor with the 107ss cam and .040 thou off the head .
So put some gas in her and a shot off starting fluid and two pulls and she fired up . This HS 50 does not sound like it did stock , it's got a slight bit of a Lopey idle . Even with the tech carb she seemed to rev effortlessly . She's louder than it was and got that Briggs flat head sound going .
 
#50
Lowest primary imbalance would be to balance at 50% but that usually doesn't work as well as a higher balance factor. The best way to reduce primary imbalance is to reduce reciprocating weight. That means small end of the rod (which you cant do in the Tecumseh case) and a lighter piston, or lighter wristpin. How does he plan on reducing the primary imbalance if he is just using a balance factor? That just moves the imbalance around the horizontal or vertical planes. While this is a complex subject, there are good articles explaining it. I used to do what you are doing send it out to get balanced and wound up with bad results so please before you spend money getting it balanced read this over a few times so you understand what balancing a single cylinder engine actually does.

http://www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf
 
#51
Oh I did have a pretty good oil leak when I got her running the GOV arm hole had not been plugged . So when she was revved she blew oil .
Had to pull the motor and I used a self tapping to seal it .
 
#52
Lowest primary imbalance would be to balance at 50% but that usually doesn't work as well as a higher balance factor. The best way to reduce primary imbalance is to reduce reciprocating weight. That means small end of the rod (which you cant do in the Tecumseh case) and a lighter piston, or lighter wristpin. How does he plan on reducing the primary imbalance if he is just using a balance factor? That just moves the imbalance around the horizontal or vertical planes. While this is a complex subject, there are good articles explaining it. I used to do what you are doing send it out to get balanced and wound up with bad results so please before you spend money getting it balanced read this over a few times so you understand what balancing a single cylinder engine actually does.

http://www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf
Good info here Ole knows his shit !!!!
 

markus

Well-Known Member
#53
Well today I got the engine mounted in the frame and started . I don't have the throttle hooked up yet cause with not using the GOV I'll have to fab something up , not sure how to do this .
I leave the arm assy intact or nip the inside down (so it could never rotate all the way up and get into the cam) when I gut the gov gear/workings out of the small frames. that leaves the throttle assy on the outside still useable and stock looking :thumbsup:
 
#56
That was a great idea now it looks perfectly stock wish I had seen this before I plugged up mine. Great tip Markus. David very nice stealth job!
 

markus

Well-Known Member
#57
Now that I see Davids idea/fix I'm thinking of running a bolt or pressed in pin...something of that nature through the next one I do. The arm can just pivot off that, the hole gets sealed up tight, and it still retains a pretty stock look :thumbsup:
 
#58
Lowest primary imbalance would be to balance at 50% but that usually doesn't work as well as a higher balance factor. The best way to reduce primary imbalance is to reduce reciprocating weight. That means small end of the rod (which you cant do in the Tecumseh case) and a lighter piston, or lighter wristpin. How does he plan on reducing the primary imbalance if he is just using a balance factor? That just moves the imbalance around the horizontal or vertical planes. While this is a complex subject, there are good articles explaining it. I used to do what you are doing send it out to get balanced and wound up with bad results so please before you spend money getting it balanced read this over a few times so you understand what balancing a single cylinder engine actually does.

http://www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf
hhhmmm.... maybe snake oil? i
ll have to dig up the email and ask more questions.
 
#59
Been out running the Powell around the neighborhood and what a bike now . The low end power is amazing compared to what it had before . The top end is not quite there yet , either carb adjustment or maybe bigger carb .
 
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