Mods began on the Venom X22R 250

[JerryHawk250]

Originally Posted by wheelbender6

Just curious. Would the hot cam work well without the higher compression piston? I guess the higher compression helps low end power that can be compromised with a long duration cam.

There will be minimal gain . The cam works it's best for high compression and will gain more power in the mid to upper rpm's.

[China Rider 27]

Looks like that piston has some cut out for some extra lift? You should do a video on your install.

[Megadan]

The increase in static compression from the piston is often needed on more aggressive cam profiles to actually make up for the loss in dynamic compression caused by the increase in overlap or lobe center changes from said performance cam profile. If you ever get bored, take a look at some cam offerings for the automotive world and take notice of the recommended compression ratios. Get too aggressive without enough compression behind it and you can actually suffer from some fairly steep performance losses.

I am familiar with the cam that Jerry is waiting to come in. Surprisingly it has the least increase in duration of all of the cam offerings out there, but it has a healthy increase in valve lift, and the intake and exhaust lobe centerlines were moved which gives it a tighter LSA, and thus more overlap despite the lack of total duration.

It's a good combo with that 11:1 compression. Should have some really strong mid range, not lose too much down low, but it will start to wake up past 5k, be a beast from 6500rpm onward, and pull strong past 9000rpm. Torque will likely peak somewhere around 7000rpm, but be fairly strong between 5000 an 8000. With port work this combination should be able to crank out low to mid 20hp figures.

[JerryHawk250]

Originally Posted by China Rider 27

Looks like that piston has some cut out for some extra lift? You should do a video on your install.

I sure will. Dan explained or well. The piston and cam combo is perfect for a street bike. There are better cams suited for trail and off road that make more torque in lower and mid rpm's. Webcam have a couple of good choices. There are a few good write ups on Thumpertalk that explain all these cams and how they work.

[Megadan]

Originally Posted by JerryHawk250

I sure will. Dan explained or well. The piston and cam combo is perfect for a street bike. There are better cams suited for trail and off road that make more torque in lower and mid rpm's. Webcam have a couple of good choices. There are a few good write ups on Thumpertalk that explain all these cams and how they work.

I prefer the Webcam 282 profile over the Hotcams, but they are honestly so close to being the same that it really wouldn't matter much. The 282 profile just has a few more degrees of duration, but the lifts are close to the same. Plus, Webcam cams cost 2 arms and a leg.

[JerryHawk250]

Originally Posted by Megadan

I prefer the Webcam 282 profile over the Hotcams, but they are honestly so close to being the same that it really wouldn't matter much. The 282 profile just has a few more degrees of duration, but the lifts are close to the same. Plus, Webcam cams cost 2 arms and a leg.

Beside being more expensive, the Webcam is also a reground stock cam where the hot cam is a new cam. I picked my cam up for just under $147. My goal was to gain performance and not reduce reliability on a daily driver. Now if I was building it just to see how much power I could get out of a 230cc I would use a different cam and bump the CR higher.

[Chrisguga]

I bought the Athena 233cc big bore kit with the 67mm piston and claimed 11.9:1 compression although it’s really a true 11:1 that can be used in 93 octane pump gas. I will install the kit along with a cam over the winter. I’m currently leaning towards the Terry Miller 2.5 ground by Web. I’m eagerly awaiting Jerry’s results!

[wheelbender6]

Can that Hotcam and piston be installed on the Hawk and similar dual sports?

[Megadan]

Originally Posted by wheelbender6

Can that Hotcam and piston be installed on the Hawk and similar dual sports?

No, the Hawk uses a clone of the Honda CG engine, which is a single lobe cam in block pushrod motor. The engine he is installing the cam on is known as a CB clone, which is basically a clone of the engine the CRF230F has, which is over head cam. The Hawk also has a bigger bore and a different wrist pin diameter.

If you desire a camshaft for a Hawk or other CG powered dual sport, they do exist. I have one I am going to install in my Hawk as soon as I get in a tool I am waiting on.

[Megadan]

Originally Posted by JerryHawk250

Beside being more expensive, the Webcam is also a reground stock cam where the hot cam is a new cam. I picked my cam up for just under $147. My goal was to gain performance and not reduce reliability on a daily driver. Now if I was building it just to see how much power I could get out of a 230cc I would use a different cam and bump the CR higher.

Webcam does hardweld regrinds and then surface hardens the cams. I trust their quality to the same level as a new camshaft. That process is part of the reason they are so expensive. What I love about webcam more is that they can do a custom grind for you if you want to change something about the cam profile you are looking at for not much more money.

I know what your goals are. I think you made the right choices.

Originally Posted by Chrisguga

I bought the Athena 233cc big bore kit with the 67mm piston and claimed 11.9:1 compression although it’s really a true 11:1 that can be used in 93 octane pump gas. I will install the kit along with a cam over the winter. I’m currently leaning towards the Terry Miller 2.5 ground by Web. I’m eagerly awaiting Jerry’s results!

One issue I experienced when you start getting into the bigger overbores for the CRF engines is the cylinder starts to struggle to control heat so you tend to have to tune your carb pretty darn rich to keep it happy and not wreck the piston and rings. Just be aware of that with that high compression 67mm piston. You are entering the territory of engines that need frequent rebuilds.

[Chrisguga]

Originally Posted by Megadan

Webcam does hardweld regrinds and then surface hardens the cams. I trust their quality to the same level as a new camshaft. That process is part of the reason they are so expensive. What I love about webcam more is that they can do a custom grind for you if you want to change something about the cam profile you are looking at for not much more money.

I know what your goals are. I think you made the right choices.



One issue I experienced when you start getting into the bigger overbores for the CRF engines is the cylinder starts to struggle to control heat so you tend to have to tune your carb pretty darn rich to keep it happy and not wreck the piston and rings. Just be aware of that with that high compression 67mm piston. You are entering the territory of engines that need frequent rebuilds.

Interesting. I’ll have to look into that. I don’t plan to do any engine mods until the winter so I have plenty of time to think it over. I can always sell the kit on eBay to get most of my money back.

I definitely want a reliable setup as I plan to log at least 500 miles per month on the bike and often venture 1-1.5 hours from home.

[Megadan]

Originally Posted by Chrisguga

Interesting. I’ll have to look into that. I don’t plan to do any engine mods until the winter so I have plenty of time to think it over. I can always sell the kit on eBay to get most of my money back.

I definitely want a reliable setup as I plan to log at least 500 miles per month on the bike and often venture 1-1.5 hours from home.

It's not that they can't be reliable, I just wanted to make you aware that there is a point where you start trading minute gains for long term durability. 67mm is about the limit of what I would be comfortable with.

[Chrisguga]

I might try to look into running dual oil coolers like Jerry is on his hawk. There’s room to mount another below my current one.

Also, I wonder if something like this would work to provide data on whether I’m running in a safe range of oil temps? Looks cheap and easy.

Chrome Shorty Style Oil Tank Dipstick with Oil Temperature Gauge - Black Gauge Face - Fits 1979-2003 Harley Sportster XL and 1984-1999 Harley Softail Models - Replaces HD Part# 62668-87T (40-0361) https://www.amazon.com/dp/B07WGVVJJD..._SCRREbY46DYEC

[JerryHawk250]

The oil cooler you have is big enough. You also don't want to block the air flow to the head and cylinder. I think I'll get another temperature/ volt meter like I have on my Hawk. I use it to monitor the head and oil temperature plus voltage.

Link: https://www.amazon.ca/Top-Gauge-Wate.../dp/B01M9AERIK

[JerryHawk250]

Got the bump stick in yesterday. Cylinder base gasket comes in today and i'll be ready to start working on the bike this weekend.