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| Bigger valves; What's the cost? | |
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| Tweet Topic Started: Mar 28 2016, 02:45 PM (580 Views) | |
| Gonzo250 | Mar 28 2016, 02:45 PM Post #1 |
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Working-class moto psycho
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So, in my trawling of the interwebnets, I came across Mez Porting among others. It appears that one can have one's valves swapped out for 37.5mm inlets and 32mm exhausts, and obviously the head ported to suit. Has anyone here had theirs done? Gary, Johnny H, do you offer such a service at Sportax? If so, how much? I'm gonna say that my requirements are a little more... Unique than your average job as I need the inlet port opened up to suit the HSR48 that's going on... |
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I drink too much, I swear too much, I ride too fast and I crash too often. It is a universal impossibility for me to leave my tools alone and my bikes standard. 'It must go faster!!' | |
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| jonny h | Mar 28 2016, 04:00 PM Post #2 |
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this is how i roll!
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would need to speak with the tuner that's used, iv'e only hear of over sizing to the 40mm inlets, and i only know of two people who do this service, this costs a fuck load of money, i think the porter brothers was about £1000 for their head, which they machine them self's , so at a guess that's where i would start if you're serious. have you tried your carb in your frame yet? |
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| Rob 110 | Mar 28 2016, 04:40 PM Post #3 |
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God
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inertia is a problem at some point bigger valve, more residual weight making it go up and down quickly gets harder therefore it won't neccesarily open/close as quickly as a smaller/lighter valve so the gain in greater gas flow by volume, is lost by less opening/closings get some titanium valves? |
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CLICK HERE TO DONATE TO THE FORUM DIRTY R30 644 '03 TPS done, gubbins gone, GSXR can, 150 main, 27.5 pilot, needle 2nd position, K&N no lid FILTHY 404DS '04: 152 main, 70 pilot air jet, 38 pilot, emm needle 4th clip, Quill T3. Sold :( HUSKY FE501 missile
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| lahauteur | Mar 28 2016, 05:19 PM Post #4 |
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Rider
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Mez Porting closed with the death of George Mansfield in 2006. |
| 2001 Rotax 640e Supermoto and 1998 350 Enfield Bullet. | |
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| motomaniac | Mar 28 2016, 05:25 PM Post #5 |
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King
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Was gonna say mez porting has died , sadly, along with a lot of information ... |
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| Gonzo250 | Mar 28 2016, 05:55 PM Post #6 |
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Working-class moto psycho
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Yes indeed, I was rather sad to hear of the loss of such an engineering legend. The 37.5 and 32mm valve upgrade was a service he offered. There's another company in the US that offer the same upgrade. Here's a link: http://www.enginedynamics.com/kits/rotax.shtml Bear in mind, these valves will fit in the same place as the originals, meaning no need for extreme head work, custom rockers and everything else that's involved if you were to want 40mm inlets. I understand where you're coming from Rob. Bigger valves = more weight. However, considering you can only realistically rev a highly tuned Rotax SAFELY to around the 8k mark, I wouldn't foresee the extra few grams being a limiting factor as it would in an engine that was revving to, say, 12k or above, as in the case of most Jap fours and to a lesser degree twins. |
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I drink too much, I swear too much, I ride too fast and I crash too often. It is a universal impossibility for me to leave my tools alone and my bikes standard. 'It must go faster!!' | |
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| Gonzo250 | Mar 28 2016, 05:58 PM Post #7 |
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Working-class moto psycho
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Oh, as to the carb in frame trial: that's a negative as yet. However, I has grinder, welder and piles of steel that I can play with to make it fit, so that's a bit of a moot point. :p |
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I drink too much, I swear too much, I ride too fast and I crash too often. It is a universal impossibility for me to leave my tools alone and my bikes standard. 'It must go faster!!' | |
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| motomaniac | Mar 28 2016, 07:20 PM Post #8 |
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King
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Hsr48? Whats that? Flatslide? I tried one of those, no way it was going to fit without frame surgery... So flogged it on |
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| jonny h | Mar 29 2016, 01:26 AM Post #9 |
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this is how i roll!
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the thing with the valve upgrade is ... you dont really need to look in to it till your breaking the 70 or even 80bhp mark at least ... and as history has proven, if you do that the crank cases will fail at some point. hence proter bros i would spend my time on getting the carb in first, as that will be a pretty major job. |
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| lahauteur | Mar 29 2016, 08:48 AM Post #10 |
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Rider
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How to stop the cases from cracking. https://www.highpowermedia.com/blog/3272/error-and-trial-and-error |
| 2001 Rotax 640e Supermoto and 1998 350 Enfield Bullet. | |
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| Gonzo250 | Apr 2 2016, 08:51 AM Post #11 |
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Working-class moto psycho
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I'm going for the big power. 75bhp is my goal with this engine. I think it's doable with what I'm planning. The Ron Woods 676cc kit, along with the big valve head, Ignitech and HSR should easily get me there. I realise the cases are then the weak point, but as mentioned, if I stick to the 8k rev limit (and as I'm not using it in a full-on racing capacity) they shouldnt't be a major issue. Motomaniac, the HSR48 is Mikuni's biggest flatslide usually found on big-bore Harleys etc. I realise it's gonna be an interesting experience getting it in, but I have the technology and the mindset.... |
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I drink too much, I swear too much, I ride too fast and I crash too often. It is a universal impossibility for me to leave my tools alone and my bikes standard. 'It must go faster!!' | |
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