TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: trx250scar on May 14, 2014, 08:02:07 PM
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the cases i ordered from esr the invoice says the cases were set at .250. what would be the correct spacer required to run with a 4 mil crank if it was on an oem set of cases. really dont understand deck height, port timing,etc. pretty much everything about setting up and engine. maybe i did something wrong but when i convert .250" to mm i seem to come up with 6.something mm? i know there needs to be something figured also for a base gasket. can someone (who knows what they r talking about) give a simple explanation? or even just do the conversion.
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Is the extra because of ESR uses 86 style pistons and I have a long rod 4 mil stroke?
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Is the extra because of ESR uses 86 style pistons and I have a long rod 4 mil stroke?
it should be right, .250" = 6.35mm minus 5mm for a long rod on a short rod style piston = 1.35mm
+4 stroke will travel +2mm higher than stock stroke. So it depends how the cylinder is setup, if it is stock height then the piston will stand around .65mm above the deck height.
It is more than likely setup this way because the cylinder being lower(piston above the deck) has the port timing lower for more low-mid range power.
Arlan has done this many times, so hopefully he will chime in but it sound like its correct to me.
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One thing I've never understood, why the after market cylinders are cast & machined to be used on a short rod crank, when most everybody will be using a long rod or a stroker.
Neil
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One thing I've never understood, why the after market cylinders are cast & machined to be used on a short rod crank, when most everybody will be using a long rod or a stroker.
Neil
So they only had to cast 1 cylinder for 86 and 87-89 would use a spacer. That was what they were thinking in 1987. True now hot rods cranks are set up with a long rod because 1989 was supposed to be the superior way to go. You know thats why Calvin set his cylinders up to go with a +4 crank! Evolution!!! I am glad Eddy casts his cases to get rid of the spacer plates. Last thing you need is the spacer plate leaking.
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Yeah, Tony, like you say way back years ago, but far back as I can remember, even before the R riders site days & when I was a new Mac Dizzy member, there were maybe 4~5 people even had 250Rs with short rod cranks.
Way back to my first day on Mac Dizzy, even before that, say like the late 80s, the hot set up on the 250R was the 85/86 crank webs pressed apart & 87 to 89 rod kit pressed in, so even that far back most all 250Rs had the long rod, at least the racing ones.
There must have been something about the aftermarket cylinder castings, the reason for them being machined on the base so much.
Now you take an OEM Honda 250R cylinder, either year model & using it with a long rod crank & 85/86 style piston, you'll need a 3mm spacer plate for it to work, but you take a Pro-x or ESR cylinder with long rod & piston the same style as the 85/86 & you'll need a 4.8mm spacer plate.
The short rod was something fazed out years ago, but cylinders have not followed along with that & its hard to figure out why not, unless theres a need just to sell spacer plates.
Figure this one out, quite a few years ago had a guy was wanting a 265 Pro-x & we couldnt find a used one anywhere, so I talked to Allen at CT & he said maybe, but he would have to see if he could dig his old molds out from in the shop to cast one. I was thinking & asked, should I just contact LA Sleeve since that is where the Pro-x comes from anyways & he said LA hadnt cast one in years.
I was thinking the Pro-x 250~265 & the 310 casting was the same, but he said they were not & that there were 8 different cylinder casting for the Pro-x cylinders between the PV & non PV cylinders.
Kinda funny how it has all turned out, finding out that info & then knowing Calvin did the first Pro-x cylinders.
Neil