cam specs

[flea]

alas,with them not useing the internet it makes it hard to phone internationaly (time diferences and money) maybe we,re getting spoilt.thinking about getting my cam a passport as its now gone back to the the states to mr riggs for a grind.

[flea]

May 6, 2013 18:23:05 GMT -5 jack said:

All cams work better with ported heads and depending on the valve timing events,some will pull harder or you could loose Hp out the exhaust,that's why you generally port the head to the cam.If you're are individual who looks at the theoretical side of things,like I do, you take the time and effort to obtain that little edge to add a few extra HP.

You have nothing to worry about with that cam choice you selected for your ported head, as it's quite similar to the "256 " Reverse pattern and when even combined with a non ported head and decent carburetors,pulls real hard to redline. When you start getting into the single duration patterns or cams 30 and 40,then I feel one should pay particular attention to the flow ratio details cuz to much lift combined with a high exhaust ratio could spell disaster in terms of power falling off quickly higher up in the cams power band. Didn't mean to scare you ;D

any thoughts on heidens rephased hi performance 250-30 camshaft for street use

[jack]

I don't see that camshaft listed,can you link it?

[flea]

sorry jack ,computer skills not up to it but if you go to hiedens tuning and then go to racing parts.. its 6th one down...ht-027 277 deg hi-performance cam kit (special order)

[oldnwise]

May 2, 2013 18:02:20 GMT -5 flea said:

im building a rephased motor/mikes 750 kit/5th odrive/primary high ratio gears/modified head..ported,titanium o/s valves springs etc/slightly milled/ceremic coated/vm34 carbs.will be to a performance cam grind on rephased cam.im looking for advice on the best cam grind (specs) for it.it will be for street/hway use only (no racing) and was looking for performance and relibility have already looked at the shell grind and the first 2 of megacyle cams in their catalog and im getting out of my comfort zone so any advice or suggestions would be great

I would have the XS-2 256 cam cut and welded or reground. It is the exact camshaft for this engine. It was replaced in 1973 because of the EPA regulations requiring it to be neutered. I had an original XS-2 that had only had a valve job and resurfacing the head. It resulted in a CR of 9.2:1 CR. After turning with the Yamaha performance book I went 1 step colder on plugs, set the lash, the cam chain. Pulled the BS38s and rebuilt them with the clip in the richest spot.New genuine Yamaha points and putting slightly lighter springs on the advance greased the shaft between the points and advance. I kept it a 360 no one had yet done the 270 yet or even the 277 as far asI know , but if I had one now a 277/83 , especially with points and the hot coils now. I couldn’t find a rectifier is why I sold it 3 years later. This was in 1981 before people discovered just how great they are. At 62 now, I would love to have another XS2 with the rephrase and a rephrase 256 72 cam. No need for anymore cam. The LSA at 104 could be tightened to 100 even. Study David Vizards “128” formula. The heads need no porting, and rephrasing the 256 cam putting the BS38S back on with the clip in the richest position and in any chassis you choose it is at the normal overbore of 700ccs the LS-6 454 of bikes. And it will run just fine on pump gas. I would recommend putting an oil cooler on it and if you can find it the early style geared cam tensioner and don’t get it over tight. I’m not entirely certain about interchangeability, but I can’t imagine why not. I actually filled my ports in the bottom to a D shape and joined the SSR at an downhill trajectory on intake and exhaust and have used Virago valves on other peoples bikes, I have rephrased a few by turning one cylinder 3 splines forward and using red loctite on the pin pressed them back together using Yamahas press specs, and a good time to replace bearings BTW. I love the sound of a rephrased 277 with a rephrased 256 cam at 9.25:1 CR and twin popes with a cross pipe and some nice straight through mufflers, earplugs recommended. Lol. Just my experience that tight LSA is good and the 256 cam cut and welded with a sleeve and woodruff key for the gear crimped and tigged is a monster. I ran my stock XS2 to 13.02 and 97 mph on pump gas and I was and still am 6ft 2 175 lbs. I hope that even after so many years since the question was asked that it helps other. If I had one now that is what I would do. I would sell the XS 2 minus the engine to someone who wants to keep it stock , it is the most beautiful bike ever made. Like an original 428CJ car I would sell the body to a restorer, and find a 302 car. That’s how I roll!

[oldnwise]

I really like the 277/83 because it is a great hot rodders spirit method that is quite simple to so, and it adheres to the reason for changing the pistons position at the firing interval. The 277/ 83 is very close to the 270/90 interval. Have you ever really listened to a rephrase getting after it? To me the twin sounds like a V8. Two cylinders firing each with an alternating pause makes a nice full and rounded sound because One cylinder is pushing down on the power stroke and assists the other cylinder though it’s BDC dead stop and subsequent rise to its compression and ignition and it performs the same assistance to the other cylinder after blowdown and though its exhaust stroke. Neither cylinder experiences the BDC dead stop without the opposite cylinders assistance to get through this and push back up with almost a crankcase supercharging each other alternately. To hear either rephrase is like hearing a high strung V8, it reminds me of a 427 Ford, long rod ratio at 1.71, big bore and relatively short stroke, not too short but high strung heading towards 7000 rpm’s. Can you hear it?

[oldnwise]

Oh and I meant to say that is where the XS2 cam rephased is magical because it amplifies this effect. If you just think it over, the tighter lobe centers keep the ports flowing and generating kinetic energy to cancel out the dead stop vibrations as the cylinders alternate their actions by cycles. Phil Irving took two 500 cc cylinders and mated them to a crankshaft and used these alternating strokes to create a liter bike that could have been unrideable like the 2 stroke V8 engine used for racing that was so powerful and hard to control that riders would dump then into bales intentionally. Phil’s 4,stroke VTwin fixed that. Wonderful power, predictable and reliable! I’d love to have a Vincent Black Lighting. “ Said Red Molly to James, that’s a fine motorbike….”

But I’d settle for an XS2 cam spec rephrase, 277/83 with BS38s with the rod clips on the richest notch. If for nothing but the sound and smooth application of power sounding like a 289 Ford Cobra with Webers or a 427 Ford with 2 four barrels. Sweet!