best stock cylinders for 4mm stroker?
Moderator: rztom
best stock cylinders for 4mm stroker?
hey guys,
I've seen it mentioned here before when I used to come on years ago but I can't find it now,
what are the more ideal cylinders to use for a stroker engine? im about to go pick up a motor and the guy im buying one off has a few sitting around, so if I have a choice which would be the more ideal for putting a 4mm stroker crank in? 31k or 1ua?
I've seen it mentioned here before when I used to come on years ago but I can't find it now,
what are the more ideal cylinders to use for a stroker engine? im about to go pick up a motor and the guy im buying one off has a few sitting around, so if I have a choice which would be the more ideal for putting a 4mm stroker crank in? 31k or 1ua?
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Re: best stock cylinders for 4mm stroker?
I was advised by Martin at Mad Biker Designs in the UK. who did my head and cylinder work on my 385 to go for the 31k version as the porting was better suited to use with the +4mm crank. He is very helpfull and would be able to explain in much greater detail I'm sure. There a few guys on the rd crazy forum in the UK who have gone this route before also.
Good luck with the build.
Paul
Good luck with the build.
Paul
Re: best stock cylinders for 4mm stroker?
really you should re-grind if you're using a standard cylinder...
Re: best stock cylinders for 4mm stroker?
nokturnal, I will be getting them worked when I get them, but I do remember seeing somewhere on here mentioning that 1 is better than the other for use with a stroker crank... so I guess im asking which is the better base to start with if im getting a stroker crank?
Re: best stock cylinders for 4mm stroker?
people have used them with a spacer plate and stock porting... maybe that's where the recommendation comes from. I believ the only difference between years is a slight difference in porting, which would likely be a non-issue if you are reporting.
maybe not though... maybe someone has info I am missing.
maybe not though... maybe someone has info I am missing.
Re: best stock cylinders for 4mm stroker?
The 31k barrel/head combination is the preferred pick.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
Re: best stock cylinders for 4mm stroker?
My 1UA's are happy a +4 and +2.
Cheers!
Pete
'12 Tuono V4R APRC, '05 R6, '88 RZ350, '82 XV920R
Pete
'12 Tuono V4R APRC, '05 R6, '88 RZ350, '82 XV920R
Re: best stock cylinders for 4mm stroker?
Ive ridden a bike with a spacer plate on 31k cyls and it had a very linear power delivery and we (Aaron and I) felt it was dull to ride, he later fitted different pistons and removed the plate, it was a different bike. My view is that a spacer plate is not the way to go. To be honest very few (any?) on this (and other) forum ever use them if you search.nokturnal wrote:people have used them with a spacer plate and stock porting... maybe that's where the recommendation comes from. I believ the only difference between years is a slight difference in porting, which would likely be a non-issue if you are reporting.
maybe not though... maybe someone has info I am missing.
I do agree that I doubt you'd notice the difference in the porting on the cyls with a 'bum-dyno'.
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81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid
Like Watches? www.PloProf.com & www.DeskDivers.com
Re: best stock cylinders for 4mm stroker?
Just saying that’s where the recommendation MAY have come from. I have no idea.JonW wrote:Ive ridden a bike with a spacer plate on 31k cyls and it had a very linear power delivery and we (Aaron and I) felt it was dull to ride, he later fitted different pistons and removed the plate, it was a different bike. My view is that a spacer plate is not the way to go. To be honest very few (any?) on this (and other) forum ever use them if you search.nokturnal wrote:people have used them with a spacer plate and stock porting... maybe that's where the recommendation comes from. I believ the only difference between years is a slight difference in porting, which would likely be a non-issue if you are reporting.
maybe not though... maybe someone has info I am missing.
I do agree that I doubt you'd notice the difference in the porting on the cyls with a 'bum-dyno'.
I’m not sure many people use stock ported cylinders with a stroker crank either... 31k, 48H, or 1UA flavor
Re: best stock cylinders for 4mm stroker?
Using a +4 crank and a 2mm spacer at the base gasket nukes your exhaust timing to some 206 deg (think this was with a 31K cylinder).
The transfers also go up to (I think) some 134 which is waaaay too much.
And that's the reason why getting rid of the spacer and machining the head to accommodate 2mm more piston stroke is helpful.
The difference between 1UA and 31K is that the 1UA has 1mm higher exhaust and transfer ports. Depending on your other mods (like which pipes you have) and the desired application the "optimal" solution will vary.
In a nutshell: The 31K's would tend to give more rideability (=midrange torque) whereas the 1UA usually result in more top end.
In any case a simulation of the intended combination helps to pre-optimise everything.
If you have 31K and want 1UA: Simply get a 1mm spacer and machine the head just for 1mm more stroke - mission accomplished.
The transfers also go up to (I think) some 134 which is waaaay too much.
And that's the reason why getting rid of the spacer and machining the head to accommodate 2mm more piston stroke is helpful.
The difference between 1UA and 31K is that the 1UA has 1mm higher exhaust and transfer ports. Depending on your other mods (like which pipes you have) and the desired application the "optimal" solution will vary.
In a nutshell: The 31K's would tend to give more rideability (=midrange torque) whereas the 1UA usually result in more top end.
In any case a simulation of the intended combination helps to pre-optimise everything.
If you have 31K and want 1UA: Simply get a 1mm spacer and machine the head just for 1mm more stroke - mission accomplished.
Bye
Martin
Martin
Re: best stock cylinders for 4mm stroker?
thing is, porting on a stock cylinder is not "optimal" when EVERYTHING is stock, not sure why anyone would throw a new stroker crank at an engine without having the engine ported/machined properly. seems like a waste.
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Re: best stock cylinders for 4mm stroker?
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Re: best stock cylinders for 4mm stroker?
That would have been that Dumb ass Rogernokturnal wrote:
Just saying that’s where the recommendation MAY have come from. I have no idea.
31k are best EX port will sit at 196/197* and your be able to change the transfer roof angles with out going to high on the timing!!!!
Re: best stock cylinders for 4mm stroker?
I was going to say, 31k is Glyn's preference for port timing and head rework, although he can make either work with a recut dome. But Glyn responded.nokturnal wrote:why
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine