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 Post subject: The Grenade
PostPosted: 24 Aug 2010 21:30 
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proff. patpending
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Current ride: Victoria Sponge
Location: Bristol - Gateway to all things good
In the light of anything exciting to read in the Tech Section, I thought I would cobble something together about my S1...

Some of you may know that I have a 97 S1, with the super sexy smaller tank. I chose to keep this in preference to an S1W, which is now under the loving care of restone.

Anyway, those of you that know their stuff about Tubers will be aware that the 96 and 97 S1s (aswell as other Tuber models of the same era) came with Lightning heads. These have a 10 degree squish band, mated to a flat topped piston, which basically equates to poor performing combustion chamber, which is prone to knock. The later Thunderstorm heads came with a 15 deg squish band, and a piston to match, in addition to a bigger inlet valve. The squish band was a token effort, being cast into the head, rather than machined, so is a little compromised, but it has the right idea, trying to force the last bit of mixture up towards the plug, from where the flame kernel is growing. All the White Lightnings, Lightning Strikes, later M2s, later S3s and X1s came with these heads. If you read the 25 Years of Buell book, coupled with a 200RPM higher rev limit, they are worth 10bhp.

When the XB came along, the head design was changed, probably as part of a cost cutting exercise. The 15 deg squish band was reduced to a 0 deg squish band, or put another way, a flat face.

Image

The head design also had better flowing ports... And again, using 25 Years of Buell, coupled with a fuel injection system and a more configurable ignition map, this was worth another 2bhp.

In addition to these changes, the position of one of the bosses for the front engine mount also changed and the carb mount bosses/breather holes were not drilled and tapped, meaning it was not so easy to retro-fit them.

From the word go, my S1 was a great bike to ride, the CV carb had obviously been set up by someone who knew what they were doing (the Mikuni that I later fitted was no better for throttle response). It felt nicer to ride than my Firebolt (91bhp on Tubbs dyno) and Daywalker and I were surprised when it only made 80bhp.

Some months before getting the S1 on the road, I had picked up some XB9, cylinders, pistons, heads, rocker boxes and rocker box covers on EBay. These sat on the shelf for nearly a year. During that time, I went through a "Oh no I have no money" period and I tried to sell them to robs, he didn't like my price and ended up getting some from the states (which he sold on in preference to Thunderstorm pistons and heads).

Also during this time, I got a front engine mount off spondon440 (as the original mount was never going to fit) in readiness for... well something...

*** I need to say here that nothing that follows is new - Steely has done the same and more on his Sportster, O3 has a similar setup on his M2 Razorback and I am sure other people have gone the same way ***

A few months ago, I was sick of seeing them gathering dust in my grease-eater, and egged on by Gunter and Daywalker, I decided to get them fitted.

First job was to machine the carb bracket bosses (it was going to breathe through the XB PCVs in the rocker covers), so taking measurements off my Lightning heads, I used my old man's Bridgeport to face off, drill and tap the bosses.

Image

I then lapped the valves in and replaced the valve stem seals.

The next thing to think about was what pistons to use. I had a set of XB9 pistons, however, there were three reasons I did not want to use them, certainly in their stock shape. Firstly, the crown has a design flaw, that being the bulges on the eyebrows for both valves, this means that the piston to head clearance is going to be limited at these points and hence the clearance at the crown sides, where the majority of the squish area is, will be large.
Image

Secondly, the crown shape, along with the increased stroke of the 12, would result in a compression ratio knocking on the door of 13:1 with a decent squish clearance. Thirdly, when I tried them in the S1 cylinders, I found the the cylinders and pistons were 10 thou oversize :o

Gunter sent me some pictures of 9 and 10 piston crowns for my education, and the dimensions of the nipple on the top of the, otherwise flat topped, 12 pistons. So I was all set to machine the 9 piston crowns to make them into pseudo 12 pistons, but a voice at the back of my head (a bit like Herne the Hunter in Robin of Sherwood) said "no", get some 12 pistons, or some posh pistons from NRHS.

Now, I am largely a fan of making the stuff from the factory work better, I am not really into big bore kits, cams, nor posh pistons, not for the road anyways, so I opted for what I knew would be reliable, a set of standard XB12 pistons. Of course, I could have used the S1 cylinders and pistons, but I wanted that nipple for more compression ratio...

Herne was right though. Measuring the crown thickness of the 9 and the 12 showed that machining the crown of the 9 to drop the compression ratio was not a good idea...

The next thing on my mind was some new cylinders, after all, XB pistons don't some oversized, at least not in the parts book. I don't think I have seen any come up on EBay.co.uk, but there are plenty at places like Pinwall in the states. Just prior to taking the plunge and ordering a set, Herne the Hunter turned up and said "look at the XB9 cylinders, understand how they differ from the 12", so like a good boy of the forest, I checked the cylinder length, and also the part number. Wow, I was astounded, they were the same part as the 12, so too were the pushrods (which I haven't used), which means the only real difference between 9 and 12 in this area is the crank, the con rod (longer on the 9) and the piston... Nice to know...

I honed the cylinders and checked the 12 ring gaps, all was in order...

Using guidance from the NRHS website and Tubbs, I armed myself with some Cometic gaskets (10 and 20 thou base and 30 and 40 thou head), the 9 cylinders, 9 heads, the 12 pistons, some grease and some 1.1mm diameter solder.

Image Image

I selected my gaskets to ensure I had a min squish clearance of 30 thou, however, I had to repeat the job cos I cottoned on to the fact that the small folded paper in the Cometic package was actually some instructions, and the torque values used were somewhat higher than Erik tells us to use. I ended up with a further 10 thou on the base gasket to get the clearance right.

In actual fact, I ended up between 36 and 40 thou as a result of concentricity errors from the crank centreline to the head face, the connecting rod bearing centreline parallelism and the wrist pin centreline to piston crown parallelism. I was limited to a minimum of 36 thou cos of the minimum step in gasket size was 10 thou, I could have done with a 5 thou base gasket or, if I was feeling really adventurous, could have marked the pistons at their tightest spot and then pulled them down with a draw bar onto shim material on a face plate on the lathe, then "squared" the face up... Maybe a job for another engine build project...

I then checked my eyebrow clearance using some modelling clay. Even though this was essentially a stock setup, Tubbs hammered into my brain not to take any chances, and I'm glad I took note.

Image Image

The front exhaust clearance was a little low (less than 60 thou) at the top of the pocket, so out came the Stanley knife to get the desired value.

The S1 gives you access to do all this with the engine in the frame, I'd love to repeat the exercise on my Firebolt, but it would be a frame-off-job... :evil:

When I bought the bike, it came with adjustable pushrods and collapsible covers. Maz warned me it was potentially a grenade engine, but what could I do? Well, I pulled the cams out and they appeared to be stock, the first dyno run suggested it was nothing special, but I digress...

Anyway, those of you that have played with adjustable pushrods will know a bit about the tappets too and how to set them up. Bascially, the tappets have 0.2" of self adjustment, so based on this "fact", and with the engine on the compression stroke, but some way either side of TDC, the adjustable pushrod is extended by hand until it goes tight. Then, allowing the tappet to bleed down throughout the process, the pushrod is extended a further 0.1", commonly done by a knowledge of the thread pitch (mine were 25TPI) and hence the increase in length per 6th of a turn (a nut flat). Just to make sure I was on the right track, when fully adjusted, I took the pushrods out and measured them against stock. They were close to 2mm shorter than both the S1 length in the manual, the XBs and some I had kicking around from a Sportster engine which were all the same length. I was a little concerned, so I set them up again, and they were still a similar amount different. So, what was that telling me? Either the tappets have more than 0.2" of travel or the stock pushrods are longer than they need to be... Or my adjustable pushrods are shorter than they need to be :?

Anyway, I drew stumps and get the rest of the engine together, finishing on the Thursday before Em's day. Took it for a 20 miles test that evening, then with it holding together, apart from an oil leak from the plugged oil gallery which I cut through when cutting down the cam cover (take note pre-98 engine owners - I later fixed this by drilling and tapping the hole 1/4 UNC and Loctite Hydraulic Seal-ing it in), I rode it to East Kirkby and back, a good 400 miles, to do the running in...

Then I took it to Tubbs to tinker on the dyno:

viewtopic.php?f=8&t=7732

The results were encouraging. Of note was the ignition timing. The standard ignition curve had too much advance for the engine. If we assume that Erik did a good job at the factory by selecting the optimum curve for the combustion chamber, the engine response to a reduced advance suggests that combustion occurs faster. I am down to 30 deg advance (see this post) from 5250rpm onwards at WOT. Compare this to an XB and you will see that the XB ECM demands a few degrees more. Does it need it?

Image

Of course, it is not as simple as all this, the ignition timing advance is set to burn all the mixture as close to Top Dead Centre as possible. Many things affect the flame speed, such as AFR, temperature, pressure (volumetric efficiency - how well the cylinder fills) and flow inside the combustion chamber (this is where squish and other methods of provoking mixture movement - such as swirl and tumble - help). The difference between what works on my S1 and what Erik wanted on the XB could therefore be down to volumetric efficiency as the exhaust / inlet cam profile is different.

So all in all, and well over 1000 miles later, well worth the fannying about to get things to work (sure, you can use 2003 Sportster heads - but try finding them second hand).

Next on the to-do list is to get the engine to talk to an XB ECM so I can have better control over the ignition, I think I can get away with even less advance, especially in the midrange. I also want to ditch the VOES and replace it with a MAP sensor or MPX4115A which will act as the TPS input to the ECM, then it will be off to the dyno again to make it work...

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 Post subject: Re: The Grenade
PostPosted: 24 Aug 2010 21:45 
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Bloody hell Pash, did you come up for air while typing that.
Still interesting stuff, and wurth a read ;)

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 Post subject: Re: The Grenade
PostPosted: 24 Aug 2010 21:47 
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proff. patpending
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I wrote it a week or so ago then hid it... :evilh:

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 Post subject: Re: The Grenade
PostPosted: 24 Aug 2010 21:49 
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The Nagged Hubby
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Chuffin nora :worthy: :worthy:
you have been busy! You retired then?

Well done Pash, good write up you little tinkerer :yup:

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 Post subject: Re: The Grenade
PostPosted: 24 Aug 2010 22:14 
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Current ride: CB1300, Z750, R1200
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:yup: Well done. I am just missing the picture that shows the valve imprint.

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 Post subject: Re: The Grenade
PostPosted: 24 Aug 2010 23:32 
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Current ride: S1w X1 1125CR
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You will always be my hero Pashmina :yup:

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 00:11 
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Location: Wales. The land of dragons and welsh cakes
Have'nt got a bull's notion what you were on about Pash, but mighty impressive. 8-)

Now to more important matters. Have just fitted new rear brake shoes and cylinders to my Fairway Taxi and am unable to get the handbrake to function. I am informed that the system is the same as that fitted to earlier Ford Transits.......any ideas? :?

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 11:57 
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Interesting write up by Pash. He mentioned my old razorback M2 in passing so I'll add a little more info. The XB or >04 XL heads work just fine with the flatop pistons that were standard in the 96-97 Buell Lightning bikes (S1, S2, M2 and S3) yielding a CR of around 10:1. I used the >04 XL heads because they already have the carb mounts drilled and are black with highlighted fins, so they look dead posh. I fitted the heads with XB rocker boxes and breathers and NRHS front mount. With the flat top pistons there are no piston/valve clearance issues using the stock Buell Lightning (0.497") cams. I did briefly try the Screaming Eagle 0.536" cams but found the power shifted too far up the rev band for my liking and I sold the 0.536" cams and put the Lightning cams back in. Having said that, I think at least part of this was caused by the exhaust system I was using then since it had shorter than stock headers and it would be at least in part what moved the power up the rev band. Nowadays the bike has camcoated standard headers and a 2" V&H muffler so it would probably be quite different. (A note for early M2 owners, while the early M2's in the USA had Sportster camshafts, the export M2's had Buell Lightning cams fitted as standard). I used the stock pushrods in the motor, the deck height of the XB/>04 XL heads is 0.020" lower but the standard lifters/pushrods are fine with that. Unlike the conventional wisdom here at UKBEG and elsewhere, I agree with Pash that the standard CV carb is just fine on a mildly modded motor if it is set up properly and I too noticed no difference at all when I fitted a Mikuni HSR42. I remember years ago NRHS studied the differences between the carbs and their dyno work showed a little power gained at the top end with the HSR42, otherwise similar. The NRHS write up is probably still on the web. However, I did spend a long time in the early days of my ownership monkeying around with the standard carb and ended up with bits in there that I got from a place called Headquarters in Canada. The bike is also fitted with the Screaming Eagle version of the Dyna 2000 ignition system that Pash has, mainly because I could set the rev limit at 7000 rpm and, unlike the standard ignition unit, it keeps full advance right upto the rev limiter. It is set to use the standard double fire ignition coil rather than single fire mode. Interesting to read what Pash intends to do to his S1 next, I had thought several years ago (probably nearly 10 years now, time flies by) about using an X1 throttle body/injectors and converting the bike to use a MegaSquirt injection system, however, I lost interest in that idea a long while ago. I don't ride the bike any more and the next thing I will probably do to it is to put it back to standard trim when I have the time as I have all the original bits apart from the heads still in the shed.

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 12:15 
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proff. patpending
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Nice one 03...

03 wrote:
With the flat top pistons there are no piston/valve clearance issues using the stock Buell Lightning (0.497") cams.


And there probably isn't with the XB pistons, there wasnt on the rear, but on the front, be it a stack up of tolderances, the exhaust valve cutout eyebrow edge was a smidgen under 60 thou which made me get the stanley knife out and relieve it a little. Over cautious? Maybe...

The Mikuni v's CV write up is here:

http://www.nrhsperformance.com/tech_mikunivscv.shtml

Of note:

Quote:
What the dyno sheets don't show you is that in either case, the Mikuni gives noticeably quicker throttle response. Twist the grip and the motor reacts right now, giving the impression that your wrist is connected to the rear wheel.


I dont think I found that much of a better throttle response compared to my CV, but then again, I think I have a tinkered CV...

Quote:
Also, the Mikuni is a tuner's dream, it's main jet is accessible in seconds via a plug on the bottom of the carb, instead of being a 20 minute job as it is on the CV. There are a lot more adjustments available on the Mikuni and although they're dialed in very well out of the box, the obsessive tuner can really get one perfect with all the adjustments available to him.


I am in agreement with this. The only thing I lack is dyno time to tinker...

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 12:19 
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Correct, the Mikuni is a nice piece of kit. I noticed zero difference on my seat of the pants dyno regarding throttle response, but my CV carb was well dialled in. There's no need for anyone to spend the cash on the Mikuni really but I guess it adds to the warm fuzzy feeling because everyone else has one and swears it's fantastic. The best mod to a bike of that age was/is to fit US gearing, by far.

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 15:17 
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03 wrote:
The best mod to a bike of that age was/is to fit US gearing, by far.


How incredibly true. I went from half US (that my bike came with) to full US quite a few years ago - and the ride home from Black Bear was a revalation.

On the Mikuni - I had mine changed over from the CV years ago - and on my bike it was an amazing difference. Everyone said it made throttle response better - and I wondered how that could ever be possible - until it was changed. The first thing I noticed was that heading out of Brighton on some twisty town bits (I had if fitted by RedStar - for those that remember Tim) the bike just seemed better in corners, which I think was/is just down to more consistant fuelling making it less lumpy and therefore more confidence inspiring. It was a straight from the off feeling.

That stated, I am more than happy to accept that CV carbs are as good, if set up correctly/differently from standard. There was an interesting short article in Classic Motorcycle Mechanics (I think) the other day - quite interesting in that it stated that CV carbs were really only introduced due to emission concerns, but that they were a theorectically better, more measured, way to feed in fuel - and that certain bikes (Ducati's iirc) they were a better solution from day one of manufacturers moving towards them.

Take one message from this - US gearing is always better on an old Tuber-thing (Norm - NO!), and Mikuni can give you a real improvement, but it is not the only path).

My tuppence!

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 15:21 
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CV carbs predate emissions regs by decades. For example, SU carbs were fitted to millions of engines over the years before emissions regs came out. They have many advantages, simplicity being just one of them. To mention just one mistake on CV carbs, many folk drill the air slide as mentioned on a lot of websites. All that it does is to encourage development a flat spot on acceleration because the slide will open too quickly. Fitting a Mikuni will then feel like you fitted a turbo in comparison. I agree, the Mikuni is a nice bit of kit, very tunable, but you don't need one in the same way that most folk need US gearing. IMO, ofcourse.

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 17:24 
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Nice write up Nick.

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 Post subject: Re: The Grenade
PostPosted: 25 Aug 2010 18:03 
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Nick & Steve ..
very interesting , wish i could afford to tinker like this
always enjoy reading others expertize , thanks guys :yup:

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 Post subject: Re: The Grenade
PostPosted: 26 Aug 2010 19:24 
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proff. patpending
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Current ride: Victoria Sponge
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03 wrote:
Correct, the Mikuni is a nice piece of kit. I noticed zero difference on my seat of the pants dyno regarding throttle response, but my CV carb was well dialled in. There's no need for anyone to spend the cash on the Mikuni really but I guess it adds to the warm fuzzy feeling because everyone else has one and swears it's fantastic.


Just been comparing the Keihin CV that originally came off the S1 to a standard one (I am guessing it is standard as it has the standard needle and the slide doesn't appear to be drilled). I noticed the slides looked different, so I pulled them out and it appears the carb I had on my S1, prior to fitting the Mikuni, had a Dynojet Thunderslide kit. :twisted:

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