Rebuilding Mini Bike

Heidle

Heidle

New Member
#1
#1
Hey guys, so this is my first time posting on here. I'm currently rebuilding my Hisun motor from my Coleman CT200 and I was wondering if I should get rid of the plastic camshaft gear soon. It just seems very sketchy to me to have a plastic camshaft on the motor.

Here's a list of mods I have done (Nothing advanced so far)

  • Billet con rod
  • Aluminum flywheel
  • 18 lb valve springs
  • GoPowerSports stage 1 kit
  • Governor removal
I was thinking about getting a bigger carb that was bored out, but the plastic cam stresses me out a bit. I was thinking about getting a .615" carb from NR racing to add a bit of power, but I don't know how much more stress this will actually put the engine under. I'm not incredibly experienced by the way. This is my first time actually upgrading a small engine.
 
SAS289

SAS289

Well-Known Member
#5
#5
Heidle said:
Hey guys, so this is my first time posting on here. I'm currently rebuilding my Hisun motor from my Coleman CT200 and I was wondering if I should get rid of the plastic camshaft gear soon. It just seems very sketchy to me to have a plastic camshaft on the motor.

Here's a list of mods I have done (Nothing advanced so far)

  • Billet con rod
  • Aluminum flywheel
  • 18 lb valve springs
  • GoPowerSports stage 1 kit
  • Governor removal
I was thinking about getting a bigger carb that was bored out, but the plastic cam stresses me out a bit. I was thinking about getting a .615" carb from NR racing to add a bit of power, but I don't know how much more stress this will actually put the engine under. I'm not incredibly experienced by the way. This is my first time actually upgrading a small engine.
Click to expand...
If you are concerned get a cam for it while the engine is open. Research cams that you can use with your already purchased 18lb valve springs. Unless you don't mind getting heavier springs that some cams require.

Jackshaft or torque converter?
 
Last edited:
M

MJL

Active Member
#7
#7
My kids put 100+ (mostly governed) hours on their Hisun before it died. Surprisingly, it was the crankshaft that broke, not the plastic cam gear. The crank did very little damage when it broke, so I replaced it (with a 3/4") and threw the engine on my Baja. I wound it up to 5200+ for over and over again for 5-6 hours without the plastic failing. So while I still have my reservations. It did not fail. They even sell plastic lobed cams on Ebay, but I've never heard any reports on them.

I just swapped the cam for a CS grind, but haven't had a chance to run it yet. If you don't want to spend the money, you can probably find a stock all steel cam someone pulled out for cheap. I believe the Predator Hemi cam may fit as well, but be sure to double check.
 
M

MJL

Active Member
#8
#8
I believe that .615 carb is pretty much stock. They just sell them for the kart racers that are looking to make sure they get the largest "stock" carb they can vs one that may have come out of the factory a few thousandths smaller. I'd give them a call to see what they recommend, but a .625 or a .650 might treat you better. There is also the Chikuni option.
 
Heidle

Heidle

New Member
#10
#10
SAS289 said:
If you are concerned get a cam for it while the engine is open. Research cams that you can use with your already purchased 18lb valve springs. Unless you don't mind getting heavier springs that some cams require.

Jackshaft or torque converter?
Click to expand...
Jackshaft
 
M

MJL

Active Member
#12
#12
Heidle said:
http://www.nrracing.com/product-p/dynomod2.htm?1=1&CartID=1

Here's the cam I'm interested in. I'm pretty low on money so I think I'm going to wait on the new cam and keep the money if I find any other problems on the bike.
Click to expand...
Let me preface by saying I am no expert, but I just spent a TON of time picking out a cam. As it mentions in the description, the cam you linked is a "cheater" cam, in other words, designed to sidestep rules in sanctioned kart racing. So while better than stock, since those rules do not apply to you, I think you can do better.

Multiple different sellers seem to recommend cams with .265-.280 lift for minibikes. Perhaps this is the Goldilocks range to preserve low end torque while picking up some top end. But, but they will probably require 22 or 26 lb valve springs.

When I first started modifying my engines, I fell for a few products designed to maximize performance on restricted kart engines, ie 3910x plugs. And while they may have been legitimate improvements, the improvements may only be worth a kart length or two on a 10-20 lap race, not enough for me to really notice on the trail or in the field with my minibike. I think I know better now, maybe...

I certainly agree with saving your money.
 
SAS289

SAS289

Well-Known Member
#13
#13
MJL said:
Let me preface by saying I am no expert, but I just spent a TON of time picking out a cam. As it mentions in the description, the cam you linked is a "cheater" cam, in other words, designed to sidestep rules in sanctioned kart racing. So while better than stock, since those rules do not apply to you, I think you can do better.

Multiple different sellers seem to recommend cams with .265-.280 lift for minibikes. Perhaps this is the Goldilocks range to preserve low end torque while picking up some top end. But, but they will probably require 22 or 26 lb valve springs.

When I first started modifying my engines, I fell for a few products designed to maximize performance on restricted kart engines, ie 3910x plugs. And while they may have been legitimate improvements, the improvements may only be worth a kart length or two on a 10-20 lap race, not enough for me to really notice on the trail or in the field with my minibike. I think I know better now, maybe...

I certainly agree with saving your money.
Click to expand...
For what he's doing there so far he really doesn't need a cam immediately. He's using the jackshaft and will be able to run his Coleman 38 mph at 7K RPM or so with stock gearing.

But yeah cam choice should be carefully considered. When I built my 196 last year I hit the easy button and didn't really "build" anything. I simply threw parts at the stock engine. Going in I wanted a better engine with a little more power than stock with a max RPM target at 5K. It got a .010 over rod, CL1 original cam, stock head with Champion rockers, PVL flywheel, and max stroke clone crankshaft. Yeah runs nice but what set my bike off was gearing with the torque converter. IMO you could have a pretty fun bike without a lot of engine if you are geared properly.
 
You must log in or register to reply here.
Top