air cooleed 250r crank

[atc330r]

air cooled 250r crank has anyone used a 87/88 trx long rod crank ( wiesco hot rod) in a air cooled motor? the water cooled has a longer strok than a air cooled, but the same crank. just checking be for we get in to deep

[Fuzzy]

Dose that make it in to a stroker then. How much longer is it? How high of compression would that give you? Would octain become a problem?.

[atc330r]

yes that would be a longer stroke by 4.8 mm. compressiom well depend on the cut on the head and barrel spacers.what i,am not sure of is the rod clearing the case. we can fix that with a little grinding. then theres the port timing after the barrel is spaced, i,ve got a guy with a bike shop thats willing to help try this idea. it should smoke a watercooled. oh and this is with a 75 mm piston

[Fuzzy]

Sounds like it would make a great mod. I am afraid i am no help at all on it. But would be very interested in finding out if it works out. Please keep us posted with what you find out. It sounds like it should be doable. But i imagaine carb jetting could be a bugger with the longer stroke and all. Going to be lots of little problems to work out. Good luck:headbang:

[Wankel]

I Too would be very interested, please keep us posted.


Chad

[atc330r]

the crank we are looking will be 6 mm longer stroke.the case will have to be welded then opened up .030 and the crank narrowed.the welding will just be extra webbing on the trans side. may not need this , but i,am going to do that anyway

[Fuzzy]

Wow you have tons of work ahead of you. Sounds like a lot more then i would like to get in to. But it will be a monster when you get it done:headbang: :headbang: :headbang: :headbang:

[250sx]

maybe someone at lasleeve or powroll can shed some light on it for you. usually when you do a longer stroke you have to get a custom piston that's had the pin location moved upwards to keep the top of the piston in the bore.

[atc330r]

right.we have that taken care of. it,s already running 3,4 mm stroke.with the 87 250r crank the concren maybe with oil flow to the big end bearing plus the air volumne or pressure to move the fuel at an upwards flow, speed that the engine will demand. some guys think we may have to remove the sheet metal housing that the 87 crank has on it. honda is saying it has to have that sheet metal to oil the bearing.not recmended,but they say that about everything. unless honda is racing it. then it,s the factory way. hum bug :wtf: :wtf: :wtf:

[86waterpumper]

I'd just find a mugen 360 kit like the one on ebay:eek:

[atc330r]

i,am already up to a 328 cc. with a piston i can replace. the idea is to incearse the stroke. the cc,s are good but it,s the longer stroke thats going to build the rpms. no way around that. i can go even bigger that that mugen by using a polaris top end ( cyl & head ) but i need to keep the stock honda cylinder. i tried to get mr atc to tell about his crank. i guess he wont. if i can remove the sheet metal cover from the webs and run it with out those. it will fit the case with less clearancing

[Mr. Kasey]

LONGER STROKE ,less rpm's shorter stroke more rpm's think about it ,, your adding more weight which is going to lead to a bigger explosion,,, more rotating weight,,, more recipricating weight = less rpm's ,,,,,it should yield a different powerband so you shouldn't need all the rpm's

[Mr. Kasey]

me again,,, the trx long rod motors have the same stroke as a short rod motor too!!!! thats why youy can run a trx cylinder on a atc,,,,,,,, same stroke different piston,, different pin height to accomodate longer rod ,,,,,,,,,,,,

[atc330r]

kasey; your right. i guess i,ve enter this subject in so many web sites now. i forget to put it this way. ( so it will build quicker rpm ). not a higher rpm, but say from 3900/4100 to 8500 rpm will be much quicker with a longer stroke yes ? no ? we are doing this in a air cooled 250r. this thing is fast now, but i,d like to get it as a full balls up drag motor. i have the help of the local bike shop. there focused mainly on 250r trx and banshee stuff. you dont find many trying to get an old air cooled to out run a banshee. we need to say with the stock cyl & head. to make the class we,re after. the stroke incease will be almost 7mm.

[Mr. Kasey]

to get extremely quick throttle response you shave all the weight possible,, on old moto-x bikes they came with a small rotor on the ignition which made for quick response but hard to handle so they made flywheel weights to smooth them out and slow response time down!! if your building a all out drag racer i would find a moto-x engine with the same bore and stroke as your shooting for or close and drop that sleeve in it grind the excess aluminum out of the way of the much larger ports , if your using a trx crank go get a esr 370 sleeve just cause its not a h2o pumper don't mean that you can't run any internals that you want,,,,, :headbang: :headbang: :headbang:

[atc330r]

great idea. the stator your talking about. is that one that the flywheel ( rotor )is on the inside of the coils like a old 90 ? i tried to get mr atc to tell me about his lighted flywheel but no reply. the cylinder is already a done deal. its up to a 328 cc and a old time rocky case piston. i may be able toget this crank stroke , but not at 7mm. then that would save alot of time and money. money is a object also. or i,d just dumpa chevy 502 in it and call it a boss hoss ( a$$). can you see it har har har. i,ve seen a 250r with a cr 500. i,am impressed. now thats a big boy. are going to have that at spinreelin sept? when you come down here do you use hwy 38 to reedsport. thats the fastest,easiest way. if so you drive real close tomy house. west of eklton ore 2 miles is a bike shop. they have the nology hot wires made up for 2cycle cdi engines.there prices are so so. they just stock the normal goodies

[atc330r]

on the light crank and flywheel. have you used one or either? i use both in my buggy and on a hill i lose my rpm quicker. so i slip the clutch and its back right now. it sounds like you shifted. see the drags here only during sandfest now. the rest of the time its outlaw at box car ( horse falls ) or banshee hill winchester bay. so most of the racing again is outlaw and on hills. i,am sure this motor will be retired after next summer. i,ll never be able to replace the piston or cylinder. we also have a sand dragster the plan has been to spend more time on. that. the other interest is heading in the way of minibuggy. lets face it 3wheelers are fun, but they have there place.

[Dirtsquirt]

longer cranks equal slower but more tractable power. It won't be so peaky. (steel weights more than aluminum)


to answer all you questions got to

http://www.macdizzy.com

While I do not support Rick (Macdizzy), his content hasn't been updated in a year or so so it is (mostly) truthful and straight forward.

check out the thread spread for info on taking the "tin cans" off of the cranks. But for the most part stay away from the message board, to oppinionated.

[atc330r]

already talk on phone with dizzy. he said he "dont know". he,s more into blasters. in theory. you guys are right. it looks right on paper. in use no. try it. we have done long strokes on other 2 cycles it works quit well.