CG250 Performance Cam Installation.

[ChipToothy]

I watched the vid and am impressed. Way cool! I already have 12,000+ miles on my motor so it’s a lost cause but I did enjoy the breakdown and explanations. These motors are a lot more complicated on the inside than what I was picturing. Thanks for sharing.

[ChipToothy]

I noticed you MegaDan have a brake light fix too? Mine hasn’t worked in a year for the rear lol and now I have a whole new everything rear brake wise it would be nice to have a rear brake light again.

What product-method is the easiest to make work?

[China Rider 27]

Originally Posted by JerryHawk250

The bottom of the cylinder has a bevel/taper to it which allows the ring to compress as you slide the piston in. You might have to help squeeze the rings a little with your hand to guide it in.

Originally Posted by OneLeggedRider

I don't think I've ever needed a ring compressor for a single cylinder engine, but multi cylinder is a different story.

LOL that explains why no one talks about them. Obviously, I have never seen one apart. Now that may be the best reason to justify some internal work yet!

[Megadan]

No ring compressor is needed as the others stated. The bottom of the bore is tapered, so just make sure its oily and it will go right in with a bit of care.

Originally Posted by ChipToothy

I noticed you MegaDan have a brake light fix too? Mine hasn’t worked in a year for the rear lol and now I have a whole new everything rear brake wise it would be nice to have a rear brake light again.

What product-method is the easiest to make work?

Goodrich banjo bolt brake switch.

[Megadan]

So the damn rain FINALLY stopped (3 days straight, I am not kidding) so I got to take the bike out for a proper first ride...

EDITED:

So, as it sits on my first impressions, and bear in mind I am still working out the changes to my fueling, definite boost in power, and a slight shift in the power curve, but only just a slight one. I think that just comes down to the nature of the CG250. Even with wonky fueling this thing felt way stronger than it did before the cam. Engine Revs up so much faster, and acceleration just feels much more effortless.

My fueling is all wonky though, as I mentioned before. At first I thought I had lean issues, but after some tinkering I believe I have it figured out now.

As I started the carb has a 35 pilot, 140 main. Idle mixture about 1 3/4=1 7/8, needle in the 3rd slot.

I thought I was having some lean issues at the transition from the pilot to needle, and also rolling out of the throttle from the main. Turns out i had that backwards. Needle was actually just a tiny bit rich in the third slot. I discovered that after moving it to the 4th and started having actual bog issues instead of just slight hiccups.

Other issue at the same time was getting fast idles like my idle mixture was leanm when I went to tweak it it would then drop and almost stall if I tried to adjust the mixture or idle speed more than a little bit. That issue went away and my idle went dead stable with the needle moved up. Basically the rich needle setting was allowing enough fuel to mask my lean idle.

It started raining again, so I can't test my changes. I have the needle set in the second slot and I went back to the 38 pilot jet.

As far as I can tell, the 140 main is pretty close, if not entirely perfect. I do believe it is still a bit lean up top, but I am going to wait until I can determine the effects of the larger pilot and leaner needle. I do have a feeling that I may need to go up to a 145, but we shall see when I get there.

[Megadan]

Oh, and one other thing I am considering doing, once my Chromoly pushrods come in and I get them cut to size, is just pulling the head and swapping out to the thinner MLS head gasket. It should be worth half a point of compression, which will make up for some of my lost dynamic compression with the cam installed.

[2LZ]

My guess would be that no change in lift but extended duration would make it more juice hungry to feed the new top end power. You may lose grunt but it should light up on the higher R's once jetted correctly.

[MINTY DLX]

If its raining again I'll pitch in for a uhual so you can tow the bike some where dry and ride it!

[Megadan]

Originally Posted by MINTY DLX

If its raining again I'll pitch in for a uhual so you can tow the bike some where dry and ride it!

Might need a boat rental at this rate lol. It is actually supposed to stop raining here for a couple of days, at least until Saturday. Then after that it might stay clear for a while.

Originally Posted by 2LZ

My guess would be that no change in lift but extended duration would make it more juice hungry to feed the new top end power. You may lose grunt but it should light up on the higher R's once jetted correctly.

Even with my jetting being somewhat wonky I can assuredly say that there was a small shift in the power curve. Not as much as I had hoped, but I am not disappointed either. In truth, even with the wonky jetting, the engine really didn't lose that much in the low or mid range and the top end is definitely stronger. I think with the lack of lift being added into the equation the gains are going to be tempered somewhat, especially on an engine like this.

Heck, for all I know that 140 main is actually a touch too rich and causing many of my issues. If I get a chance I may try to swap in the 135 main tomorrow and see what happens. I ran the 135 before the cam and it was on the rich side so I stepped down to a 130. It's very likely the 135 might be the ticket now.

It wouldn't be the first time my jetting was optimistic after a mod. I just want to keep realistic expectations as to what this cam can do with one of these engines. I still don't expect to hit 80mph, mostly because of my gearing, which would require me to bounce off the rev limiter.

I do believe that if I dropped two teeth out back I could do it. The engine feels like it has the power to pull that kind of speed, honestly. I just don't feel the need to do it, and I am absolutely loving how strong this bike pulls even with the current gearing.

There is also the concern at the back of my mind that I may be approaching valve float past 8000rpm now with the more aggressive ramp profile. This cam is supposedly designed to work with stock valve springs on a CG125 engine, but I have actually started looking at valve spring options just in case. I am wondering if the CRF150/230F valve springs are similar dimensions to the CG engines, because that would give an off the shelf option from BBR for a measly 56 bucks.

I know the rough dimensions of the outer springs. I can't remember the inner spring dimensions off the top of my head.

Outer Spring
Length 40mm.
OD 26.2mm
ID 20.6mm
Wire Dia. 2.8mm

[franque]

I can get you some specs for the NX (ohc) vs CG 125s, as long as they're specified in their respective service manuals.

[Megadan]

Originally Posted by franque

I can get you some specs for the NX (ohc) vs CG 125s, as long as they're specified in their respective service manuals.

If you can find that information I would definitely appreciate it. Otherwise I will have to order an inner and outer spring to measure just to be sure. That's 25 bucks I would rather not have to spend if I didn't have to.

[franque]

They didn't give diameter figures, just length. Outers for the CG were 40.9 mm, inners 33.5. For the NX, it is 44.85 intake, 45.5 exhaust, and 39.2 intake and 39.4 exhaust. I just looked it up for a 230, and the spring specs are 44.9 and 39.2 respectively.

It looks like it won't work, sorry!

[paulsstag]

Originally Posted by Megadan

Oh, and one other thing I am considering doing, once my Chromoly pushrods come in and I get them cut to size, is just pulling the head and swapping out to the thinner MLS head gasket. It should be worth half a point of compression, which will make up for some of my lost dynamic compression with the cam installed.

Thank you yet again Dan

You have given us a great insight as to what it takes to do the cam and roller finger up grades to our bikes. I enjoyed seeing how far you have to go in order to do it.

The cam comparison was neat and was easy to see that the valves would indeed be open for a longer period of time.

Its all well and good to get too radical with a cam and end up with an engine that has no low down grunt and everything in the upper part of the rpm band but it seems your cam choice has retained the low down tractability that makes these engines fun and easy to ride but given it a little more in the mid and upper area.

Do they offer a different ratio roller follower ? As i would be curious to have a different ratio on the intake valve (more) and a stock ratio on the exhaust?

Thanks again for pushing the boundaries and giving us a glimpse of the possibilities .

[paulsstag]

Originally Posted by Megadan

Oh, and one other thing I am considering doing, once my Chromoly pushrods come in and I get them cut to size, is just pulling the head and swapping out to the thinner MLS head gasket. It should be worth half a point of compression, which will make up for some of my lost dynamic compression with the cam installed.

Just an idea

Dan your bike has mods to it that i think we would all love to have.

Do you have a dyno in your area to actually put it on?

I realise money is the issue but i would be willing to put some money in a go fund Dan account to pay for a few hours on a dyno.

Find a willing partner or two , say one with a bone stock bike , and another with say a bike with carb and exhaust work and use them as base line.

Take your CDI units ( sounds like you have several you would like to test), jets, spark plugs and anything you can think of to get your bike dialled in.

You will get the idiots that will say you did all that work to get say 2 HP but in the scheme of things 2 HP is a huge gain as a percentage

Give it some thought and count me in to chip in some money

Paul

[Megadan]

Originally Posted by franque

They didn't give diameter figures, just length. Outers for the CG were 40.9 mm, inners 33.5. For the NX, it is 44.85 intake, 45.5 exhaust, and 39.2 intake and 39.4 exhaust. I just looked it up for a 230, and the spring specs are 44.9 and 39.2 respectively.

It looks like it won't work, sorry!

It was worth a look. I reached out to the company that made springs for CCW for their heist build to see if they maybe have the specs on file for what they used. If now I am sure I can find something that may work with a bit of digging. Thanks for taking the time to look those specs up!