Yes. The Cheetah Cub will be a lot peakier
The Serval Cub and the Cheetah Cub are both made by the same company – CPI industries and the blocks were originally designed for the Yamaha Banshee. The biggest difference between them is the porting if you compare the port map of the Serval with the port map of the Cheetah Cub (below) you will see that the ports on the Serval are a lot “lower”.
For example the top of the exhaust port on the Cheetah Cub is at 1.070 inches from the top of the cylinder and the top of the exhaust port on the Serval is at 1.218 inches from the top of the cylinder. The transfer ports are also lower, as is the inlet (to a large extent)
So basically, the effect of “lowering” the ports will provide an engine that is much less peaky but tends to develop its peak power lower in the rev range and can produce a lot more torque.
If the Banshee is for racing or drag-racing, the Cheetah Cub will probably be a better barrel. For playing around in the sand dunes or on trails, or the street, the Serval is a better barrel.
You can build both with a standard crank (392cc) a +4 crank (421cc) or a +7 crank (443cc) and they will always maintain these characteristics and they will translate through to your road bike. You can also get a Cheetah with power valves but that’s a whole different story - and price
You don’t have to go with a +7 crank for the Serval. I did just because I had one. The +4 will work just fine and no trenching. I wouldn’t expect there will be a lot of difference anyway. If you use the +4 its a drop in.
You can buy the Serval at most places that sells Banshee parts. I normally deal with Jeff Wendorff at Farm and Sand toys and his prices are great and there is no quibble over anything if it needs to go back
These are the barrels you will need.
http://www.farmandsandtoys.com/partdetail.asp?partid=403 Jeff also does a cleanup port so they are ready to drop in and can supply the right pistons for a Standard, +4 or +7 crank.
You will also need a head. There are a number of good options including the CoolHead and Roger’s Banshee over at Wicked ATV. I have been running this Noss one on my Serval bike -
http://www.nossmachine.com/banshee_heads.htm
- You can also buy this head from Jeff.
You’ll notice that it comes in three pieces. The head its self is really just a holder for the combustion chambers or domes –
that are interchangeable. That way you can change things like the combustion chamber volume or the squish just by swapping in new domes at $60 a pair. With Noss you can also use the ProDesign or Coolhead domes. Domes for this cylinder start at 15cc and work up. I would start with 21cc and go down from there if you have to but 21 will be very close. I’d also run about 0.8/0.9mm squish on the road. Tell them you’re using Wiesco 10018M’s with the 68mm bore and Jeff will be able to mill you the right domes. Just check the squish clearance when building the engine
These heads are also o-ringed which is nice. You can see the groove for the o-ring around the combustion chamber and around the outside of the water jacket –
.
Almost all performance 2 strokes are o-ringed today. They seal much better than a gasket and need much less torque to seal properly + they are reusable.
The problem for a street bike is that these heads don’t have a thermostat. If it’s race bike you can generally get away with it but I noticed in the spring (April/May) and fall (September/October) the temperature gauge sits in the cold, I just got a KTM inline thermostat from GP Bikes and put that inline between the head and the rad.
The other thing that you will have to do is have the outlet cut and welded so that it no longer sticks straight out but bends upwards at 90 degrees. The RZ rad and Banshee rad are different and mounted in different places.
As for cranks you have many options, just stay away from the ebay cranks. I have had good success with cranks from TSS (closed down), Wicked ATV, PJME, and Hot-rods. If you do go the Hot-rods route, I normally have someone like Willie at WASP press them apart and install genuine TZ350 big ends. I’m not a huge fan of their big ends but the do make some good rods. They are probably fine as is though. There are there are a lot of +100HP Banshees’ running them. These are 4 after market cranks I have personally tried and would be willing to recommend.
For the cylinder base gaskets try to stay with a one piece in recommended thickness – 0.020”. CPI recommends 0.020” for this block and it keeps the port timing right. Tony Doukas does a nice one. A good trick is to put a light coat of spray copper gasket on both sides as it sticks like glue the crankcase. It’s a PITA to get the barrels off and scrape the gasket but it cuts down on the possibility to get an air leak on the right or left side of the block. That will kill the motor. They also need to be torqued correctly (18 ft/lb). You need a crows foot wrench on the torque wrench or torque wrench extender to do this. Not torqueing properly is the #1 cause of leaks between the barrel and crankcase.
For Carbs I like Keihin PWK’s I think a set of 35’s will work really well on this motor. You can order them from Jeff or from Sudco but you will have to jet. I would start with 165 mains, 45 pilots and a CGL needed one notch from the bottom, air screw 2 turns out and work down from there. I would take it to Pro6 and have Sandy do it on the Dyno. That man has forgotten more about 2 strokes that the rest of us will ever know
PWK 35’s are used on a number of Kawasaki and Suzuki dirtbikes. I’ll dig out the models but it’s generally cheaper to buy a replacement carb from a dealer. Sudco want about 150 each for PWK28’s. I just bought a set from a Kawasaki dealer as they are fitted to a KX85 and KX 100 for $95 each. You have to rejet anyway.
As for pipes the choices are becoming limited. There is TSA in the UK or Matt Shearer in California. GPL is no longer in the tuning business. I don’t believe Roger at Wicked is doing pipes any more. Let me think about this one. JL may do a set for this motor
You will also need one of Wicked’s billet manifolds to lift the big carbs above the clutch arm.
You won’t be able to use your air box any more so a set of foam pods work well. Just make sure they are all foam and don’t have the metal on the ends
You will need a high flow fuel tap from Pingel or Norbo in the UK does a good one. Get rid of that stupid Vacuum thing.
While you are in the motor get a set of these -
http://www.fastfromthepast.com/97-0290 - No point taking a chance with 30 year old transmission bearings. You also want to pull the gears from the transmission shafts and make sure there is no galling between the gear and the shaft. You can’t see with without removing them. New circlips are cheap and good insurance.
The standard clutch basket will support up to 100Hp, but they are getting old and the fingers tend to get grooves. This is a nice alternative.
http://www.farmandsandtoys.com/partdetail.asp?partid=494 I’ve been using them on my track bike and it’s been bullet proof. It’s been on there 5 years.
If you’re running the oil pump send it to Arrow in the UK to have him re stroke it for the bigger bore. I’m not running a pump at the moment so it’s a real pain in the ***.
I think that’s about all you need to do although I'm sure I've forgotten something.
You may want to think about replacing the motor mounts as 30 year old rubber is not good
Just my impressions of the Motor. I don’t really miss the power valves. It pulls like a train from around 3.5 or 4 to around 8.5 and it’s very linear. It seems to make its peak power around 8.5. It will still rev over that but why? It’s much more powerful that the standard 350. It was around 87 on Sandy’s dyno but it is ride-able. The power doesn't come in like a hockey stick. You can play around with gearing to get something you like. for the street I'm running 17/39
Edit: I knew I forgot something. A Zeeltronic would be nice but not a necessity. I have a few good curves you can try
Edit: I knew there was something else. you will need a set of VForce 4 reeds. and I made a mistake on the Wiseco part number. You need 795M's. The 10018M's are for the Super Wampus Block. You can tell what I'm thinking about
