CR200X - Is it possible?
- Thread starter SpeedyManiac
- Start date
- Aug 2, 2000
- 13,510
- 19
don't let these naysaying ninnies stop you, speedy. I have faith in your skills.
- Dec 19, 2005
- 193
- 0
That's really the key. Mtk's assessment is quite realistic. Don't assume that the factory engineers are dumb and unmotivated. Consider that any design is a compromise of many factors, and you can be sure the factory engineers found a far more optimal compromise than you could. If you want to do better (for some definition of "better"), then you must be willing to play by different rules. For example, sacrifice cost. Or use new technology which was unavailable to the factory "back then".SpeedyManiac said:
If you measure success by the amount you'll learn, then your journey will be a success.
Now start by investing in some books. Gordon P. Blair's book on 2-stroke engine design and simulation available thru SAE would make a nice xmas present.
Oh Speedy!
To be so young and dumb and full of energy! I've been through ALL the same thoughts and desires. Nothing wrong with that. But for you to do what you wish you still need LOTS more than desire and an engineering degree. MTK is mostly right, but you have a chance of success. You can learn from this and perhaps end up with a ridable bike. You don't appear to want advice, you've written off the logical machines. The KDX series engines could be made killer and their chassis are better than aluminum. For you to do more than design a cylinder for a CR125, to actually make patterns and cores for ports, fabricate/adapt power-valve pieces and finish a cylinder and head so the transfer flow worked for adequate power, would be a miracle. Don't give up on making something better, just don't try to reinvent the wheel. Get a 1990-1999 or 2005-2007 CR125, bore and stroke it to 155/165. It could scream if it was done/ported right. It might not be so reliable. The YZ125 would also work.
I hate to rain on your parade, but I've been there. I built a 168 lb 250 Montesa powered bike as one college engineering project in 1976. I disturbed classes in the ME building with a Suzuki TM 125 engine on the dyno doing durability testing for exhaust port shape/ring wear. I made patterns and molds for casting reed cages and manifolds as a student. I was lucky enough to work at an aerospace machine shop from age 16. That gave me some of the skills and equipment to build my dream machimes/parts. Don't give up the desire to create, just walk before you run. Make a big bore 125. Try it wthout power-valves with a low exhaust port. Try the exhaust port higher. Bring the transfers up gradually. See what these things do to your powerband. Make a cast head first. Get used to what happens to aluminum when it is liquid poured into a mold. Learn. Then go to the next step, the cylinder...
To be so young and dumb and full of energy! I've been through ALL the same thoughts and desires. Nothing wrong with that. But for you to do what you wish you still need LOTS more than desire and an engineering degree. MTK is mostly right, but you have a chance of success. You can learn from this and perhaps end up with a ridable bike. You don't appear to want advice, you've written off the logical machines. The KDX series engines could be made killer and their chassis are better than aluminum. For you to do more than design a cylinder for a CR125, to actually make patterns and cores for ports, fabricate/adapt power-valve pieces and finish a cylinder and head so the transfer flow worked for adequate power, would be a miracle. Don't give up on making something better, just don't try to reinvent the wheel. Get a 1990-1999 or 2005-2007 CR125, bore and stroke it to 155/165. It could scream if it was done/ported right. It might not be so reliable. The YZ125 would also work.
I hate to rain on your parade, but I've been there. I built a 168 lb 250 Montesa powered bike as one college engineering project in 1976. I disturbed classes in the ME building with a Suzuki TM 125 engine on the dyno doing durability testing for exhaust port shape/ring wear. I made patterns and molds for casting reed cages and manifolds as a student. I was lucky enough to work at an aerospace machine shop from age 16. That gave me some of the skills and equipment to build my dream machimes/parts. Don't give up the desire to create, just walk before you run. Make a big bore 125. Try it wthout power-valves with a low exhaust port. Try the exhaust port higher. Bring the transfers up gradually. See what these things do to your powerband. Make a cast head first. Get used to what happens to aluminum when it is liquid poured into a mold. Learn. Then go to the next step, the cylinder...
- Aug 2, 2000
- 13,510
- 19
don't let these guys poop on your parade, Speedy.
just go for it mate. theres gotta be someone that can do it.. why cant it be you?
just know that you might be in for a loss but give it your best then you can say at least you tried :) even though if you cant cast your own barrel the offset to make it 200cc will put it in the water jacket
just know that you might be in for a loss but give it your best then you can say at least you tried :) even though if you cant cast your own barrel the offset to make it 200cc will put it in the water jacket
Speedy, want a really unique bike project? Take one of the new CRF150's that is light and handles but doesn't have quite the power to be "killer" and give it some power. Sure it might break sooner but if you don't ride it all the time it could be a show piece. Figure out how to get more displacement to bring the rpm's down and make more power. Four stroke cylinders are WAY easier to make. OR, the real woods bike project bike would be a combination two/four stroke engine. The type I mean pumps with the crankcase every revolution but runs as a four stroke cycle in the top end. One of the outdoor equipment companies has a weed wacker in production with that type of engine. Yamaha tested a small version that had "twice the torque" of the normal four stroke. Think of a 165 lb CRF150 with 35 hp! This project is what I would do if I had the time or desire to make a world beater. You have the desire, go to it.
BonChance13
Member
- May 7, 2002
- 126
- 0
Not to be a know it all or anything,I thought '97 was the last year for the six speed tranny...I remember the '98 having a 5 speed and causing a little uproar because of it.A sixth gear can be had easily through SFB or via Honda.
Pete Payne
MX-Tech Suspension Agent
- Nov 3, 2000
- 933
- 38
How about just shoe-horning the KTM 200 engine into the cr chassis ?
To get the 64mm stroke the KTM uses , you would have to make new crank-wheels . I do not think you can stroke in a 5mm offset from centerline to the cr 125 original crank. Then to fit it in the cases you would probably have to plate up the cases and do a good trenching to them for the rod/ crank clearance.
As far as the cr 125 cylinder goes . You could probably squeak in a 60mm bore . 58mm fits w/o too much trouble . The studs would have to be changed over to a YZ style and the holes where the cr stud boss sits would have to be welded up to allow the head gasket some room to seal .
I don't know....... A few good weeks with the tig welder and the milling machine, a few new gray hairs , and ya might have a runner . :laugh:
I might be crazy :coocoo: but that what keeps me working on these bikes . :cool:
Now if we just had a few donor parts to work on :ride:
To get the 64mm stroke the KTM uses , you would have to make new crank-wheels . I do not think you can stroke in a 5mm offset from centerline to the cr 125 original crank. Then to fit it in the cases you would probably have to plate up the cases and do a good trenching to them for the rod/ crank clearance.
As far as the cr 125 cylinder goes . You could probably squeak in a 60mm bore . 58mm fits w/o too much trouble . The studs would have to be changed over to a YZ style and the holes where the cr stud boss sits would have to be welded up to allow the head gasket some room to seal .
I don't know....... A few good weeks with the tig welder and the milling machine, a few new gray hairs , and ya might have a runner . :laugh:
I might be crazy :coocoo: but that what keeps me working on these bikes . :cool:
Now if we just had a few donor parts to work on :ride:
Similar Topics
