Author Topic: fl250 cylinder swap?  (Read 5489 times)

mikeatchison123

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fl250 cylinder swap?
« on: February 21, 2011, 08:02:59 AM »
hey guys i got a 78 fl250 im putting on my racing kart and i herd the old air cooled cr250 cylinders made more power so i was wondering if i could use my fl250 bottom end  and just swap to a cr250 cylinder thanks to all with help, why did Honda go with a piston port on these odysseys and have a reed port on the bikes is their any advantage with piston port? i also herd the fl350 cylinder will swap to the bottom end of a fl250 is this true?

mike

1982fl250c

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Re: fl250 cylinder swap?
« Reply #1 on: February 21, 2011, 03:25:30 PM »
Quote from: "mikeatchison123"
hey guys i got a 78 fl250 im putting on my racing kart and i herd the old air cooled cr250 cylinders made more power so i was wondering if i could use my fl250 bottom end  and just swap to a cr250 cylinder thanks to all with help, why did Honda go with a piston port on these odysseys and have a reed port on the bikes is their any advantage with piston port? i also herd the fl350 cylinder will swap to the bottom end of a fl250 is this true?   hi  for the 350 on 250 no it is a real joke..!   a 1973 - 74 Honda CR250 head will bolt on to a Honda Odyssey FL250 engine. The 73-74 Honda CR250 cylinder head has taller cooling fins and they are taller across the entire head. No shortened fins to clear a tuned pipe since the earlier CR250's had the tuned pipe go down and along the bottom of the bike. What this means is that 73-74 CR250 head can help provide a little better cooling capacity.You can use a 83-84 CR250 head gasket. The CR250 head gasket is made of copper and will fit the 77-84 FL250.
You will gain a little compression & performance because it is thinner than the FL250 gasket. Heat transfer between
the head & cyl is improved. Also this head gasket can save you money. This head gasket can be reused many times if
it is removed carefully without bending or creasing. All you have to do is clean it. Then heat it up until it glows red
hot & slowly dip it in water. This will anneal the copper (make it soft again)(copper anneals differently then iron or
steel, it does not require slow cooling to soften).Heating can be done with a propane torch.stock carb is 28mm can go up to 32mm max.will bolt on engine base 1973/74 CR250 cylinder,head,carb. 34-38 mm. for extra fun..CR250 elsinore and an MT250 elsinore. The MT250 is the same as the odyssey. The CR250 has much better porting than the MT250, and will bolt directly onto the odyssey bottom end.stock fl250 is a 70 mm bore to 72mm max over size piston only.fits on looking for W/STEEL SILENCER DG NATIONAL PIPES and DG PERF PORCUPINE RADIAL FIN HEAD CR250 MT250 for INCREASED ACCELERATION.
re NOTE You can also do it per this paper but without the flywheel key, your ignition timing may spontaneously change for 1981 to 84 honda odyssey fl250c 34-38mm carburetor. recommend a Mikuni TM/TMX or Keihin PJ/PWK Unless you are using an aftermarket ignition system, the timing needs to be changed on the models with CDI ignition for better performance at high RPM. You will lose some midrange pull but top-end will be much better and your engine will live to thank you. Here is how to change the timing to 16 degrees BTDC. With the stator and flywheel on, push the piston to BDC with a dowel or screwdriver and hold it there. Scratch a mark on the stator that lines up with the second firing mark. (There are three marks on the stock flywheel. One marked "T" for TDC and two more. The one you want to scratch a line beside now is the one closest to the "T".) Remove the stator and slot the holes about 8mm longer to the left when viewed from the top. (doing this lets you rotate the stator clockwise.) Put the stator back in and turn it roughly 6 degrees but don't tighten the screws, you need to be able to rotate the stator. Install the flywheel and key. Push the piston to BDC and hold it, turning the stator until the mark you just made lines up with the first firing mark (The one furthest from the "T" mark.) Now remove the flywheel and tighten the stator screws. Install the flywheel and key and torque the flywheel nut. Once more, push the piston to BDC and check to be sure that the mark furthest from "T" still lines up with your scribed mark. Now you can run your engine at much higher rpm's with less chance of detonation and longer over-rev The engine is the same basic design as the CR250M, which is a pretty wild machine. The easiest way to get more high revving power is to bolt on the top-end from the CR. In doing this, you will lose some bottom end power, but once it comes into the power in the midrange, it pulls hard right up to a screaming top-end at about 8500RPM. My clutch engages at about 3800RPM and it will still madly spin the tires from a stop.To make the swap, you need the following parts from a ?73-74 CR250M.The cylinder,The head , The intake manifold,The head gasket . source : http://members.shaw.ca/tjsodyssey/topswap.html
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