CG250 Performance Cam Installation.

[Megadan]

Originally Posted by paulsstag

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

Money really isn't the issue so much as avalability of said dyno.

I am still considering hooking up a wideband to my bike to help fine tune in the jetting, especially if I determine I may need a different needle profile.

As far as different ratio rockers. I am not awarenof any. When increasing valve lift though you will quickly run into valve interence where both valves start to collide and it requires recessing the valve seats.

[franque]

Yeah, no worries, happy to advance the knowledge base. Do you think WGK does springs for them?

[Megadan]

Originally Posted by franque

Yeah, no worries, happy to advance the knowledge base. Do you think WGK does springs for them?

Not that I could see on their website.

Speaking of, I sent an e-mail to Douglas Carvalho at WGK to ask him about this particular cam profile and the type of performance it is geared for. My suspicions about the very slight shift in peak power were confirmed. This cam, while it does have a lot more overlap and duration than a stock CG, is more on the mild side due to the lack of increased lift. In automotive terms this would be a "torquer" cam. For any real higher RPM power, a cam with increased lift would actually perform better. Essentially, on the 125 they tested this cam on the peak power gains were a bit less than their 270 City cam seen here https://wgkindustria.com.br/produtos...-media-cidade/ but it had more power gained below the curve, and a little more at the top end. In short, less peak power gained, but more power gained across more of the RPM range.

I am by no means disappointed at all, it just changes my plans a little bit. In many ways that makes it a better all around performer, and as I said in my initial impressions, it really feels like it picked up power in the mid and top end with little to no loss down low really, and the throttle response and the engines willingness to rev up is nothing short of awesome. So instead of the added heat, wear, and stress of higher RPM I will just have to take advantage of the added power a different way. Plus, I should be ok in terms of valve float lol.

I will wait to see how it does before making any changes, but with as strong as it pulls now I think I could get away with dropping a couple more teeth on my rear sprocket to the equivalent of my old favorite the 17/43, but still have very strong acceleration. That would definitely put me right where I would like to be in terms of highway capability. Especially if that adjustable CDI I just got in the mail allows me to advance the lower RPM ignition timing to bump up the lower part of the power curve and toss in a bit more torque as well.

He did state that if top end power was the real goal, then their "Rodovia" or "Velocross" 289 degree cams would be the way to go. The drawback is that more potential work will likely be involved, valve seat recessing, deeper fly cutting on the piston, and valve springs. This is one of those mentioned cams, and you can see their dyno chart of stock and with that cam. https://wgkindustria.com.br/produtos...-alta-rodovia/

[mtiberio]

old rule of thumb, retard a cam to shift powerband up in RPM.

[Megadan]

Originally Posted by mtiberio

old rule of thumb, retard a cam to shift powerband up in RPM.

Not an easy to do thing with these motors, but I did consider trying. The Cam is not the easiest thing to access to make changes like that. Plus, like I said before, I am quite happy with a broad increase in power and torque over the existing RPM range, and there was a decent little increase at the top end. Instead of the power falling off quickly at the top of the RPM range, it carries a bit further and drops off less sharply.

[Megadan]

Okay, so I woke up a bit early and decided to try 1 change. Still a 35 pilot, Needle now in second slot, 140 main. Almost perfect until I hit the main jet on the throttle sweep. Now it feels just a tad dull and still struggles to pull past 62mph.

Skip forward to the adjustable CDI I was playing with. When I advanced the timing at the upper RPM ranges it started to pull a little stronger. Got a couple more mph out of it with it's not so perfect state of tune.

Another observation with my motor, it REALLY likes the ignition advanced in the lower RPM ranges. Let me put it to you this way. My big 270lb butt on a Hawk with decently tall gearing just effortlessly pulls away from a stop, and I mean effortlessly. I have to slip the clutch a lot less to get moving. It also idles way more stable.

[JerryHawk250]

Originally Posted by Megadan

Another observation with my motor, it REALLY likes the ignition advanced in the lower RPM ranges. Let me put it to you this way. My big 270lb butt on a Hawk with decently tall gearing just effortlessly pulls away from a stop, and I mean effortlessly. I have to slip the clutch a lot less to get moving. It also idles way more stable.

Funny you mention this. One thing i noticed is that leaving out my driveway this morning i didn't even need to give it throttle to move. i went through 1st, 2nd and third without touching the throttle.

[Megadan]

Originally Posted by JerryHawk250

Funny you mention this. One thing i noticed is that leaving out my driveway this morning i didn't even need to give it throttle to move. i went through 1st, 2nd and third without touching the throttle.

Yeah, me being a solid 100+lbs heavier I don't get that luxury lol. Still, it is much more effortless. I also have to give it a lot less throttle when cruising along, so as long as I can resist twisting the throttle I might see an increase in mileage.

[Megadan]

So, my little gamble on the pushrods paid off. I did some searching and couldn't find anything off the shelf for the CG250 that would work. Most options were either too small (3/16") or too big (5/16"+). Thankfully, Honda builds another engine that uses the same diameter pushrods as the CG engines, which is the GX390.

The good news is that the GX390 is a popular go cart and mini bike platform, so there is a good amount of aftermarket support for them. The downside is that most of the ready made GX390 Pushrods are too long. So that leaves option 3, which is to order a set of cut to length chromoly pushrods.

ARC Racing offers just such a thing. https://www.arcracing.com/dj-3070cl-...-individually/

They came in today, only 3 days to ship too, which was really amazing.



I ordered a set of GX390 lifters to assist with pressing them together. They were cheap, so why not. Prevents me from damaging the ends. I can always pass them along to someone else when I am through with them.

Anyway, I just figured I would prove that the ends are the same dimensions, so this first picture is the GX390 lifter and the original CG250 Cam follower.
The second picture is the end of the pushrod in said cam follower.





So on to the details. The CG250 Pushrods are 153mm long, or 6.024" long. Since I milled down my head 1mm, I am going to cut these pushrods to be a bit shorter at 6 inches even.

The pressed in tip is 5/16" long from flange to end, so I need to cut my pushrods to 5 11/16" long. Pretty straight forward. Hopefully I have the time tomorrow, but I may hold off until next weekend because I want to finish getting my jetting sorted and repack my muffler.

The jetting might not actually take very long though. Currently my idle mixture, pilot, and needle settings are spot on, and the bike pulls strong until you hit the last 1/8th bit of throttle, and it just goes flat, so it needs a bit more fuel. I just got my 142-150 main jets in, so I should be able to get it sorted fairly quickly. I might even take it out tonight and test one or two jets if I feel up to it.

[Megadan]

Jetting update: Ready for this? I ordered a 142, 145, 148, and 150 main jet right? The 145 improved the lean condition, but it still felt flat. The 150 cured it, but I think there is just a little bit more in it so I am going to order a 152 and 155.

Current Jetting Setup is as follows.
Pilot Jet: 35
Mixture: 1 5/8 Turns out
Needle: 2nd slot.
Main: 150.

So, if there was any doubt that there was an improvement in airflow, let's consider that before this point I was running a 132 -135 main jet depending on the air temps earlier this year.

Verdict on the cam. Definite improvement in power from 3000-8000 rpm. My bike will now pull to 8500 much stronger than before. In 5th gear I was able to pull to 8200rpm before I ran into traffic (that's 77mph), which is pretty heavy today being an almost perfect day and a Friday afternoon. I think with enough room on a flat bit of ground I could pull to the factory rev limiter and hit 80mph.

One thing I do think I can get away with now is to drop 2 more teeth on the rear sprocket and go for that 17/43 type gearing. I have enough power to spare to pull that off and have a true road capable highway machine.

If there was a shift in peak power, it was just a few hundred RPM, but more importantly is it helped level off the top of the power curve. It doesn't fall off as quickly as it used to. The best part is, it hasn't really lost any mid range, and maybe just a tiny bit down low, but the advanced Ignition curve on the CDI I have brought a lot of that back.

Do I think the chromoly pushrods are necessary? Not really, but I wouldn't shy away from them if you plan on doing this cam. I plan on installing mine once I get a couple of other things in to do all of it at once. I am then going to install the TT250 head gasket to increase my compression another half a point as well.

[Megadan]

Time for a little bit of educated bench racing. For the heck of it I decided to spend the time doing a little VE calculations based on jetting changes, both from a proper jetted stock bike (105 main jet), which likely made right about 15hp give or take a half a hp. Considering RPS rated them at 14.1hp with their too lean jetting I thing that is a fair assumption.

Now, give me some latitude here, because I already said this is a bit of educated guess work, but that 30% increase in air and fuel at WOT would put my bike right in the 19-20hp range. For a bike with port work, a full exhaust, compression increase, and a cam. I think that would be a fair number to assume. I will try to get a dyno session schedule sometime later this year if at all possible to confirm that number. That would put me around 18ish hp at the rear tire. Obviously that number could be higher or lower because there are so many other factors at work, but if it made around 18-19whp, I would be quite happy. Considering CCW's Heist made 21hp to the rear tire with a more aggressive cam profile and revving out to 9200rpm, I don't think it is that unreasonable to assume.

[mtiberio]

On my race Guzzi I had to tighten up valve clearances when I went to CrMo pushrods. They expand Less than Aluminum .

[China Rider 27]

Originally Posted by Megadan

I will try to get a dyno session schedule sometime later this year if at all possible to confirm that number. That would put me around 18ish hp at the rear tire. Obviously that number could be higher or lower because there are so many other factors at work, but if it made around 18-19whp, I would be quite happy. Considering CCW's Heist made 21hp to the rear tire with a more aggressive cam profile and revving out to 9200rpm, I don't think it is that unreasonable to assume.

Alright! It is time for the numbers. How to get a CG motor to approach CCW's results is the quest!

[Megadan]

Originally Posted by mtiberio

On my race Guzzi I had to tighten up valve clearances when I went to CrMo pushrods. They expand Less than Aluminum .

Yeah, I was actually considering that possibility as well. Not quite sure how much I would want to tighten the clearances, but I had considered going to .05mm intake and .06 exhaust. That would bring both settings in about .01mm from what I run now.

[Megadan]

Originally Posted by China Rider 27

Alright! It is time for the numbers. How to get a CG motor to approach CCW's results is the quest!

If that were my goal, then I would start with this cam. https://wgkindustria.com.br/produtos...-alta-rodovia/

Port the head and use proper multi angle valve seat cuts with back cut stainless valves, The above pushrods, better valve springs because you WILL have valve float issues, mill the block a couple of mm to reduce the quench gap to less than .035" And then have a custom forged piston made because your compression ratio after that jug being milled will be right around 12:1 on a stock one.

Then you just need a 32mm carb.