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Old 10-04-2019, 04:01 PM
opisopus opisopus is offline
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Default Valve Springs

Apologies if this isn't in the correct section. The recommended valve spring upgrade for a Coleman CT200 bike seems to be the 18lb option. When would it be necessary to go any higher than that? Such as 22 or 26lbs? Would that be overkill or possibly counterproductive for the 196cc/gx200 clone?
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Old 10-04-2019, 05:18 PM
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If you're using a billet rod (and flywheel), then the 18# springs will be a great upgrade. However they allow the engine to rev 7k rpm, I believe, depending on the cam, so I wouldn't use them with a stock rod or stock flywheel, since the stock cast rods have trouble staying in one piece over 6k rpm, and the cast iron flywheels like to grenade at those speeds. And that brings me to my question for you, is this engine staying governed or is the governor being removed. If the governor is staying, the springs are a waist of money, since you won't gain any rpm. And If the governor is bound for the junk bin, then I'd recommend a billet rod and flywheel for safety reasons, both the engines and yours.

Now, a quick disclaimer, I do not recommend that you do this, since the retainer can slip off and drop a valve in the cylinder, but I have been running my Baja warrior with a stock rod and flywheel, ungoverned, but with stock springs for about a year now. I have taken it to valve float, but not very often. The stock springs will float at around 5200-5500 rpm iirc, which will keep you from snapping a rod (as long as you don't stay there for more than, I'd say 20-30 seconds max). But on my bike valve float occurs somewhere just north of 55mph, and it takes it about 1/8th of a mile to get there. But I don't go there very often, because I don't want to be that guy that, because of his own stupidity, and inability to back off the throttle, ends up pushing his bike home with a valve in the piston and other various cylinder damage. Also I have a job, and I'm going to get myself a billet rod and flywheel (and maybe a cam) for Christmas.

And, yes this is the correct section for engine questions. And I'm sure that itsid will be here shortly to correct any mistakes I may have made.
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Old 10-04-2019, 07:33 PM
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Was planning to keep it governed. My son drives it so I don't want it to be out of control. For now I intended on the standard performance kit (open air, exhaust, .38 jet), and possibly a bigger rear sprocket. Is there any advantage to a new flywheel and/or rod if I'm not removing the governor? I'm looking to do minor increases here and there just to build it up. Don't really desire speeds beyond 35mph. Assuming I'll lose a little top end with a bigger sprocket. Thanks a lot for all the info. I saw a video where someone didn't take the governor out, but zip-tied the spring that sits under the gas tank? Claimed to be "similar" to removing the governor..Is there any harm in doing that?
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Old 10-04-2019, 07:40 PM
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That would be bypassing the governor, and is liable to blow up from the plastic governor gear going too fast.
Upgraded rod and flywheel has no advantage without governor removal.
If you plan to keep it governed, just do Stage 1.
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Old 10-05-2019, 01:19 PM
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The only advantage to using a billet rod with a stock engine is longevity, since the billet rods have bearings in them and better oiling. But this is an engine that makes about half a horsepower per cubic inch (12ci and 6.5hp), so it would be about like spending an hour polishing a new mirror. And JT is right, these governors don't like being bypassed. So it's either pull it or leave it.
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Old 10-07-2019, 09:15 AM
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If I were to pull the governor, would the throttle limiter screw suffice to keep it toned down enough for my son to ride it? I wouldn't mind ordering all that stuff over a period of time just to give me a project to work on, and I also thought if the limiting screw would work I could always back it out to make it faster.
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Old 10-07-2019, 09:22 AM
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If you plan to let your son ride it, I'd keep the governor in. Bad wrecks can happen at governed speeds even.
With a centrifugal clutch, unless it's geared reeaally low, it'll probably burn up the clutch with a limiter screw. TCs are fine usually.
A good rule of thumb with a centrifugal clutch is to run it pedal to the metal or not at all.
At least, that's what I do.
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Old 10-07-2019, 03:13 PM
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The governor will be more effective at limiting speed because that’s what it’s designed to do. If you remove it and use the limit screw then you’re limiting how far your throttle can open and killing power everywhere. The governor lets the engine run at wide open throttle until it reaches the speed that the governor kicks in and closes the throttle.
We run restrictor plates in both of the JR karts that the boys race which could be likened to limiting speed with the throttle screw and they can not still achieve pretty high top speeds, it just takes them longer to get there.
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Old 10-07-2019, 08:37 PM
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Quote:
Originally Posted by opisopus View Post
I saw a video where someone didn't take the governor out, but zip-tied the spring that sits under the gas tank? Claimed to be "similar" to removing the governor..Is there any harm in doing that?
YES!

the governor is a plastic gear with some metal parts embedded in it..
at high enough rpms it will break apart and release metal shards
into your crank case.. they can end up anywhere
causing MASSIVE destruction if they lock the camgear for example.
even the best case (where you just end up with a nasty scratch in your cylinder wall..)
you have a scratch in your cylinder wall you didn't want.

and that's not IF it breaks.. it's WHEN it breaks... get it out or leave it functional...no in betweens!

'sid
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