5 mill stroker,best transfer port timing?size spacer plate?

[masterblaster]

I have a 5 mill billet long rod rad crank,what would be the best size spacer plate to use with a 61 x northwest big bore sleeve kit installed? Im going to be using flat top pistons to try and get the cylinder as low as possible for low port timing.what is the maximum distance I can have the pistons come out the top,the old cylin had yami pistons and they were 2 mills out the top with a 7 mill spacer plate.
The sleeves are 85 mil I believe they are 760 sleeves setup for freestyle in this 61x cylin. Will 701 ada domes seal ok.I am going to have them recessed for stroke and flat top pistons with a squish around 48

 

[#ZERO]

I'd say use a 2.5~3.8mm spacer plate with two stock base gaskets and it will give you around 121~123 Tx & 183~185 Ex duration with that setup.

You'll need to use a degree wheel to check this port timing or have an engine builder set this up for you so the power band hits in the right spot.

When the top ring comes out of the sleeve that's your limit and when the o-rings blows out because the domes are too thin, that's the other limit. :smile:

 

[waxhead]

Whats the timing now ?? you cant attempt to guess a figure with out knowing some measurements

Why do people constantly think that short pistons will reduce your port timing

The pistons do not effect the port timing figures
They open the port of course
But its the stroke and the rod length that effect it

Whats the measurements of that cylinder in mm and i will let you know what sort of port timing you will have with a 5mm stroke
But changing pistons will not effect this

 

[MTRHEAD]

What kind of power do you want? racing or rec riding?

 

[masterblaster]

#0 thanks for the input,but can you really push the piston up to the where you can just see the top of the ring safety,cause I think this is what im going to need to do to get the port timing im looking for.As far as the domes go,maybe I could use a stock head gasket as well then?Not sure how thin the o ring retainer will be machined for 85 mill flat tops? I was thinking a 2.5 with 2 stock gaskets would do it also,but it will be close to the ring coming out.I on a budget here so im stuck using stock cylin for now,this one has already been setup with big bore sleeves for freestyle use,but stock stroke,so 5 mill long rod will complicate things a bit.Im prolly going to send the entire motor off to chuckie for final porting to get it just right,I just need to do most of the basics myself getting this thing together with port timing in the range where its workable. I dont have a fortune to pay someone else to do it all. setup will be enhancer,rad flywheel,dual 48 carbs,bpipe,av100 fuel.I have no use for stupid $ flatwater back flip motors that wear you out in the surf,although I would like it to have enough linear power to pull backies on small surf.

wax.what im saying is that with the lower pistons I can drop the cylin down more with a thinner spacer without the pistons coming out the top past the rings,Every bit I can run the cylinder lower without this happening is effectively giving me lower transfer port timing correct?the thicker the spacer the higher the higher the transfer port timing will be. this why im trying to fig out what the max distance I can run the piston out the top so I can keep as thin a spacer as possible.do you think a 2.5 mill spacer will work with this setup and still have low enough transfer port timing to work well with freestyle use?I dont have degree setting for the new cylinder yet,will have that soon.the old 62t cylin Im dumping had a 7 mill plate with a 2 mill recessed head,its transfers port was 132 and the exh was 195 or so

mtrhead,sorry bud but i didnt think i even had to mention in the X it is going to be for freestyle/freeride use only

 

[waxhead]

if you drop the cylinder lower by using a shorter piston then the timing will stay the same
the shorter piston will have less difference between the top of its crown and the transfer port

think about this way
the distance in mm between the top of the piston crown and the transfer port on the short piston will be the same as the distance between the top of the crown and the top of the transfer port on a longer piston

If its sticking out the top on the long one and you put a shorter pison with out changing anything the timing goes up as the piston now doesnt come as far up the bore and so you have to drop the cylinder down the same heigh as you just took out to get the same timing .Result the piston now come out the bore the same amount

I cant make a judgement call on your porting till i see some figures

 

[masterblaster]

hmmm. I was thinking being able to lower the cylinder would result in lower transfer duration. How is it that some motors are running 5 mill strokes with no spacer plate and still keeping low enough transfer timing for freestyle then?Are the sleeves just pressed higher in the cylin and machined off on top?

#0 I read in one of your posts that you used northwest sleeves #1588-bb because they have 2 mill lower transfer port timing. Im getting a 61x cylin in the mail soon that was setup by Lamey for freestyle use I believe for a stock stroke motor,Do you think the transfers in these type sleeves will lower as well,or is that a sleeve specifically for a 5 mill stroke crank?the only other sleeve it may be is the #1492 760 yami sleeve they offer. I would think that lamey would have used the 1588 though.I guess one has to have the cases cut and the other doesn't though to fit? the outside diameter is not listed for the 1588 on their site for some reason?

 

[waxhead]

hmmm. I was thinking being able to lower the cylinder would result in lower transfer duration. How is it that some motors are running 5 mill strokes with no spacer plate and still keeping low enough transfer timing for freestyle then?Are the sleeves just pressed higher in the cylin and machined off on top?

#0 I read in one of your posts that you used northwest sleeves #1588-bb because they have 2 mill lower transfer port timing. Im getting a 61x cylin in the mail soon that was setup by Lamey for freestyle use I believe for a stock stroke motor,Do you think the transfers in these type sleeves will lower as well,or is that a sleeve specifically for a 5 mill stroke crank?the only other sleeve it may be is the #1492 760 yami sleeve they offer. I would think that lamey would have used the 1588 though.I guess one has to have the cases cut and the other doesn't though to fit? the outside diameter is not listed for the 1588 on their site for some reason?

yes lowering the cylinder would help but your lowering the piston at the same time

so the end effect is nothing

 

[SUPERTUNE]

Cases need cut out to about 3.615 depending on how centered they are for the 1588-BB.

 

[masterblaster]

chuck,I was thinking the BB sleeves would need this,I assume the 760 sleeves #1492 fit ok on stock cases

 

[Matt_E]

They don't.