RILS

I think the 330s will be rich and the 290s will be close possibly a little lean but imo 290s or 300 would be very close get some pods and 320s or 330s would be about right.

The 4mill alone I would say no. You have a good crank now. A port job will bring alot more then a crank. I ran a stk crank with a drag port and smoked quite a few stk cylinder 4mill bikes. If your into drag then a cub is where the moneys at.

I have some 34pjs I will swap u and give you all my jets which is quite a few if you will do the same. I have the boots too im running the carbs now.

If you run a 4mm crank you will need to have the head or domes cut or run a spacer plate, the rod lenth has nothing to do with that. I would prefer cutting the head or domes but the plate will work. I have one if you need it. The rod lenth will determine what series piston you will run shortrod will run the 513 or whatever the #on the big bores are and the longrod crank will run 795series. As far as weather you should go with a 4mill crank or not is up to you if u are replacing the crank anyway then theres not a big reason not to stroke it if you have the funds to have the head cut the short rod would save you that much if you are going to reuse your pistons. All thats up to you. I will say the best way to do this is have the head or domes cut and have the jugs ported for the stroke to suit whatever riding you do. If you are taking out a good working crank to replace it with a 4mill then imo its not a big enough gain alone for the money, do it right and it will be a nice difference.

I assume you are saying you want to use the pistons you already have if thats the case and they are 513 series pistons then the 4mill short rod is what will work. As far as your porting goes if its not too extreme especially high on the transfers then you would be allright you can just drop the floors to the new bdc position about 2mm lower but it would run without that. The shortrod will produce just as much power and rev a little harder then the longrod the longrod usually has a little broader curve. The longrod will reduce the rod angle helping with wear, from my experience they will both run fine and be dependable.

Ive got a stock one in good shape low hour $100.

Or cook it yourself.

Ive got one. Its completly stock bearings are in good shape on it. Came out of my 04 had 30 hours or less on it replaced it with a 4mill been sitting every since.100 shipped

Ill take some pics pm being sent.

You have a valid point. Im thinking of how to best word this. Ok lets say you start with a bike with a 513 series piston from the get go and you have a 22cc chamber and thus giving you 350cc for simple math. When you figure your compression ratio you have already measured and determined that this is your actual cc. So your starting figure is 175cc that is what you are changing to come up with a different number. This just gives you a good figure not exact if you want exact you will need to measure everything and assume nothing, starting with your true bore and stroke with the piston you will be using and base gasket installed then measure your true deck height, squish. By my formula using a 513 series piston and assuming you have a true 175cc using that piston. What you are doing is changing your overall cc of the motor on the bottom side that has already been confirmed with that piston doing this will give you a slightly different number not like it will on the top side but still a different number however if you are accurate on the true starting cc with the piston used my formula will hold true. I will stick with my way and you with yours I guess. By my figures using my bike I have 385/2=192.5+18=210.5/18-5.5=16.84:1 your numbers would yeild 385/2=192.5-5.5=187+18=205/18-5.5=16.4 I hope some one like blowit will chime in here but I feel pretty comfotable im right on this if im not Ill gladly be corrected.Either way you figure it yours or mine you will be in the ball park which is all your going to be anyway without getting down to the above measurments.

No i am subtracting read the equation.175+22=197/22-5.5 you can figure any bore you choose with this method and you will not find a equation that will figure temps and such. Here is another example 4 u. 421 cub with 20cc domes. 421/2=210.5+20=230.5/20-5.5=15.89:1 This is simple math if you are not familar with this then do some reading and talking to people who build a few motors instead of arguing with me. 421cc /2 because you have two cylinders 210.5+20cc for the dome 20cc-5.5cc for the piston dome Does all that make sense to you?

This is a simple way I use to figure it. On a stock bike with 513 series pistons. 350/2=175+22=197/22-5.5=11.9:1 chamber=22 piston dome= 5.5cc I misfigured it in my first post. This is not a exact figur but a commonly used one. If I remeber correctly the japanese method uses a simlar equation but they only figure the space above the exhaust port or somethimg like that I have a book that covers it if you insist I look it up.

Blowit knows what he is talking about. The 6.5/1 is by japans method. Using a basic method about 12.7/1 with 22cc or stock head would be stock. Your flow changes alot with porting giving you a lower cranking figure however your cranking figure really has no relation to actuall compression ratio just gives you a base point to work from stock and people have transfered this over to what you can get by with from experience. Imo the guy above is fine with pump.

Drag type the transfers are pretty high and the exhaust is in drag range. How do they run?

That is assbackwards. When u run a 4mill stroker crank the pin is offcenter from stock position 2mm making the piston travel 2mm farther down and 2mm farther up. You can run a spacer if you want and do nothing or you can run a spacer and drop the transfer floors to the new piston postion or you can run cut domes and do whatever you want to the porting. The rod doesent matter if you run a 110 rod run 513 series pistons or the short rod bigbores I cant remeber the # if your running the 115 run the 795 series or the blaster pistons make sure whoever cuts the domes knows what pistons you are going to run. I have a spacer plate if somebody needs it for $25. And after typing all that I just reread his post and he is correct that you will be rasing all your timing up with the spacer but if the jugs are stock they will do ok and yes if you drop the floors to make up for the plate they will always be to low for a 4mill crank without the plate best option is to get some domes cut and do the porting right.