Hey fellas, I am starting a project that will more than likely take me until next summer. Im going to attempt to create my own crank case, cylinders and head to get somewhere in the ball park of 100-1100 ccs. I plan to keep all the rest of the bolt ups the same. I will leave the intake setup and exhaust the same. I have access to a huge machine shop as well as casting. I am going to try to machine all parts but may cast some if its easier. I was wondering if anyone had any input as to what they think may be a good crank and pistons to use in this. I will make all the parts if i need to but I think it will be easier to find a crank and pistons that will work and design the motor to them. I was thinking in the ball park of 90-92mm pistons and 75ish crank. I also am thinking about maybe trying to make something bigger with about 95mm pistons and 80ish crank. Anyone know of any cranks from different vehicles that may work? I was going to start looking into snowmobiles. If anyone has any junk cranks from anything with 80ish stroke Id love to take it of your hands and get some measurements from it. I havent decided if I want to try to powervalve it or not. I think that may make it more complicated and maybe an 1100 cc boat will be fast enough. Also if anyone has any ideas for sleeves from another machine. If not I was thinking machining my own sleeves. Thanks
Ideas about crank and pistons
- Thread starter RideItLikeYouStoleIt
- Start date
I meant to mention I was also thinking about taking a crank designed for a 650/701/760 and just modifying the middle section of the crank to increase the distance between rods. That should give me the distance I need to increase the size of the pistons without losing the area for transfer ports. Any input? I know maybe a gp800 crank may be a good idea too. Anyone know how much further apart the rods are in a gp800 compared to a 61x/62t? Using 100mm pistons isnt out of the question yet considering im going to make a new crank case anyways. I wanted input before i started to do some engineering of them.
- Location
- Blacksburg, VA
wow thats some project. whats your background? i know you said you have access to all the equipment but do you have any sort of engineering experience? Also do you have access to cad software that you can perform fea and thermal analysis on? This is going to be very important.
I have a 61x motor for sale(minus head). It has a good crank so it might be a bit more money than you want to spend.
What are you trying to get out of the project?
I have a 61x motor for sale(minus head). It has a good crank so it might be a bit more money than you want to spend.
What are you trying to get out of the project?
azreark1
Live Free and Ride Hard
- Location
- Beaumont, Tx
machining everything is the easy part...port size and location are going to be a good trial and error area and also the intake on the crankcase as you would need to design it to make sure it gets good velocity into the crank and up thru the transfer ports. Could be a great way to improve and eliminate the things like reed spacers/stuffers and the like...could be a big money pit.
Bigger cases and crank for a wider spaceing between cylinders is a great idea but you have to remember...its a standup, very limited space unless you also design an exhaust system that instead of wrapping around the engine, the expansion chamber and pipe would go straight back through hull. also a smaller gas tank would work but sometimes it seems they are already too small
Bigger cases and crank for a wider spaceing between cylinders is a great idea but you have to remember...its a standup, very limited space unless you also design an exhaust system that instead of wrapping around the engine, the expansion chamber and pipe would go straight back through hull. also a smaller gas tank would work but sometimes it seems they are already too small
Im an aerospace engineer. Im also a grad student at a tech school so I have access to pretty much everything I could ever need. I am sure I can make it work. It isnt going to cost me anything but my time. I am doing it to get a sick motor and I think it will be a fun project.
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- Location
- Blacksburg, VA
maybe you could make yourself a v8 4 stroke like one of the schools did for the fsae comp. 500cc v8 standup
about the project taking you til next summer. I will be very impressed if you can get a running motor by then. It is a super large undertaking. I designed a rotary motor for a design project and probably 1/2 year of research and calculation, another 6months for design and thats with no production.
Since you have access to the stuff you should to a lost wax cast of your block. im sure you have a wax edm machine. this would also let you cast some pretty cool expansion chambers.
what school are you at? here at va tech we can't do personal work like that and i would be hard pressed to convince anyone to let me undertake a project like that. but thankfully i have a cnc and lathe in my garage
about the project taking you til next summer. I will be very impressed if you can get a running motor by then. It is a super large undertaking. I designed a rotary motor for a design project and probably 1/2 year of research and calculation, another 6months for design and thats with no production.
Since you have access to the stuff you should to a lost wax cast of your block. im sure you have a wax edm machine. this would also let you cast some pretty cool expansion chambers.
what school are you at? here at va tech we can't do personal work like that and i would be hard pressed to convince anyone to let me undertake a project like that. but thankfully i have a cnc and lathe in my garage
Just so you know, this whole post makes me jealous! Have fun.
maybe you could make yourself a v8 4 stroke like one of the schools did for the fsae comp. 500cc v8 standup
about the project taking you til next summer. I will be very impressed if you can get a running motor by then. It is a super large undertaking. I designed a rotary motor for a design project and probably 1/2 year of research and calculation, another 6months for design and thats with no production.
Since you have access to the stuff you should to a lost wax cast of your block. im sure you have a wax edm machine. this would also let you cast some pretty cool expansion chambers.
what school are you at? here at va tech we can't do personal work like that and i would be hard pressed to convince anyone to let me undertake a project like that. but thankfully i have a cnc and lathe in my garage
I go to WPI in Massachusetts. I can work on personal projects. I just did all the work to my cylinders and cases for my big bore and got the sleeves in.
I been brainstorming it a while and have a pretty good idea what im going to do. I am debating keeping the crank the same except for making it wider in the middle and just making room to have 100mm pistons. That would make about 1068 ccs. That would allow me to keep port timing very similar to the 61x. Then if the motor worked as I hope i could play with it from there to start to alter stroke length and get more ccs. That would make the engineering easier because I could use alot of the same dimensions on the crankcases. The idea is to be able to use the same everything else. Same bed plates, drive couplers, exhaust manifold, intake, starter, pickup, stator. I could just make it so the timing cover would sit about 1.5" towards the front.
- Location
- Blacksburg, VA
what about a 4 stroke wankel SJ
it sounds like you have a plan. If you are going to the trouble of making your own case you could always leave a 61x crank as is and mod two yz490 cylinder and make the engine a V. Although it would only be about 90mm and not 100.
biggest ive seen for a gp800 was like 84mm
There are 86mm pistons for the 760(789)
off the top of my head i cant think of anything that comes close except big bore MX bikes
it sounds like you have a plan. If you are going to the trouble of making your own case you could always leave a 61x crank as is and mod two yz490 cylinder and make the engine a V. Although it would only be about 90mm and not 100.
biggest ive seen for a gp800 was like 84mm
There are 86mm pistons for the 760(789)
off the top of my head i cant think of anything that comes close except big bore MX bikes
- Location
- Blacksburg, VA
seadoo, .120over you can get a 91mm piston for their 950.
I think If i go for 100mm I will have to make my own pistons. Ill look into yz490 pistons though. There are some 1000cc snowmobiles as well.
sfab
X
- Location
- Canada, QC
thats exactly what im doing right now, an entire engine from crank case to head. Let me tell you that its hell of a job!! Im not even designing it from scratch, just a copy of good ol rotax technology... Been 4 months right now and i can swear its a machining nightmare!!! lol Just figuring a way to do the bores for the bearing in the cases is quite challenging, measuring the last bore is kinda PITA... Im glad im not the only one with crazy ideas!! good luck!
I can angle the intake and exhaust inwards a little.
- Location
- Blacksburg, VA
this may sound stupid but if your just looking for 1000cc and you want to use 701 intake blah blah, why dont you just make your own cylinders, rods and pistons. Push the bores as far as you can while still have some water jacketing and then pump the stroke up(within reason). im not sure how close you can get or if you know what bore/stroke ratio you are going for but i assume it would be an easier process. You could even use a 701 head. That way you would have your big bore motor and you could still work on the case design from there but have a something to go on. There are several companies around the country that will do custom extrusions for you. you can design most of the head and have it extruded, then do the finial machining work and press in some liners.
just a thought.
ps, most extrusion places have a 500lb min, it ends up being about 2 grand, but if you could end up making this a big bore kit that bolted on to a stock case and use stock manifolds and heads im sure you could liquidate the rest of them. 2grand would be enough material to make about 40ft when talking about a 2cyl setup.
just a thought.
ps, most extrusion places have a 500lb min, it ends up being about 2 grand, but if you could end up making this a big bore kit that bolted on to a stock case and use stock manifolds and heads im sure you could liquidate the rest of them. 2grand would be enough material to make about 40ft when talking about a 2cyl setup.
I may make my own crank and make it a roughly 78mm stroke with a wider center section. Slap 100mm pistons on it and itll be over 1225cc.