Compression Release Cam

massacre

massacre

#1
#1
I'll have to search this site, i remember reading something about this years ago.
Can an OHV 5hp compression release be retrofitted to a flathead Hs50?
Or, more specifically- can the compression release parts be installed onto an aftermarket cam?
I have an aftermarket cam and want to install a 12v starter. I'm worried about the compression being too high for the 12v starter.
 
Havasu Dave

Havasu Dave

Moderator
#2
#2
I sent a CR equipped cam with the components removed to Dyno and had them grind up the cam to .265 specs. I did not think I could accurately install the OHH CR components on a worked Dyno Cam. A better machinist could. I think you are correct to be concerned about having the starter torque required. If you could "pull" the engine past the compression a bit, then engage the starter, you might get the revolutions built up enough to fire it. Another option would be to try a good LiPo 14VDC battery, which is the route I'd go first.

Also, check here: https://oldminibikes.com/forum/index.php?threads/hs40-hop-ups.147893/post-1138997 And our friend @ole4 has gone this route.
 
massacre

massacre

#3
#3
Havasu Dave said:
I sent a CR equipped cam with the components removed to Dyno and had them grind up the cam to .265 specs. I did not think I could accurately install the OHH CR components on a worked Dyno Cam. A better machinist could. I think you are correct to be concerned about having the starter torque required. If you could "pull" the engine past the compression a bit, then engage the starter, you might get the revolutions built up enough to fire it. Another option would be to try a good LiPo 14VDC battery, which is the route I'd go first.

Also, check here: https://oldminibikes.com/forum/index.php?threads/hs40-hop-ups.147893/post-1138997 And our friend @ole4 has gone this route.
Click to expand...
Thank you for the helpful response! I'll look into that for sure.
 
Minimichael

Minimichael

Well-Known Member
#5
#5
massacre said:
Looking into that 14v battery, this engine will have a charging coil on it. I'm assuming it will charge at 12v and not 14v?
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Perhaps there's a converter you could install inline between the 12v coil and your 14v. I've looked into this a bit, and as I understand things, you'll want to be careful with the power you send to lithium battery, so a conditioner of some sort (eg: "buck" or "step down" is what I used between an 18v battery and 12v lights) can help you dial in the right charging voltage.

Wanna say someone on here also set up condensers to further condition the flow of electricity. Don't recall who, sorry.
 
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sparkwizard

sparkwizard

#6
#6
If you plan to run lights and 12 volt accessories, install a 12 volt battery into your charging system.
Use a 14 (or 18) volt tool or RC car battery for the starter and solenoid only.
This would require static charging your starting battery at home with the dedicated tool battery charger.
 
Minimichael

Minimichael

Well-Known Member
#7
#7
sparkwizard said:
If you plan to run lights and 12 volt accessories, install a 12 volt battery into your charging system.
Use a 14 (or 18) volt tool or RC car battery for the starter and solenoid only.
This would require static charging your starting battery at home with the dedicated tool battery charger.
Click to expand...
That'd be so much extra weight, tho.
 
Havasu Dave

Havasu Dave

Moderator
#8
#8
massacre said:
Looking into that 14v battery, this engine will have a charging coil on it. I'm assuming it will charge at 12v and not 14v?
Click to expand...
Good point. The charging coil of the Tecumseh will not fully charge a 14v battery. Even 12vdc LiPo likes 14.2 volts to charge. But it would charge it to your max voltage, which is going to be just above 12v. (So a waste of battery, unless you are going to charge it up manually between rides)

I would go ahead and assemble the engine and the electrics and see what I had using that Dyno cam and the Tec charging stuff, and a 12v battery of suitable AH rating. It may be that you don't even have a problem. And like I said, you could always pull the recoil past the compression stroke anyway. That is how I have to start my BSA with the kick starter, though I use a compression release to bump it past.

Something I learned playing with motorcycles using no battery, is that I get some decent saved storage using capacitors. They do store energy, and after I run the bike, there's enough juice to hit the lights or horn for a few seconds. It might serve to fool your charging system into thinking it's got more capacity, as well as provide storage when starting. 5000 micro farads and 50 volt rating on the cap. Pretty easy thing to do. You might want to look up adding a cap to your charging system.
 
massacre

massacre

#9
#9
Well it looks like i have a lot of research to do. I might just get it together first and pull past the compression stroke and see how that goes.
Thank you all so much for the replies, very helpful!
 
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