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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 5:50 pm 
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....or run a 9 rod front & 12 rod rear cylinder
best of both worlds :rotfl: :rotfl:
:couch:


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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 6:19 pm 
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Current ride: XB9SX
x1glider wrote:
BTW, regarding your long post about rod ratios and different accelerations either BTDC or ATDC has more to do with cylinder offset. It doesn't matter what length con rod you have when the cylinder axis is directly over the crank axis, the piston acceleration will always be the same, you just may have undesirable thrust loads on the piston side walls.

When you offset the cylinder axis away from the crank axis, that's when you see differences in acceleration. Forward (usually 2-4 mm), the compression stroke slows down more and has more dwell just BTDC allowing for more combustion heat to accumulate and allowing retarded injection and firing timing. As such, the piston has a better angle to push down on at the big end journal, allowing for more leverage on the crank, giving more torque and it also accelerates faster on the way down.

Easy to engineer in with an inline or with offset journals on vees. Can't really do it on a twin with a shared rod journal. Move one axis how you want and the other moves in a direction you don't want. You'd have to change the angle of the faces of the barrels in relation to the crank axis to simulate an offset. Our Buells cylinder axis is pointing directly at the axis of the crank so that at TDC, the piston is always pushing directly down on that axis where there is no leverage.



I think you are referring to 'desaxe' engines like the MT-09 and 07 which have offset cylinders. :?

I also read once that US versions of the XS650 had shorter rods than UK models!? :shock:

I rode a KTM 950, 990 and 1190 V, but the 990 SMT? was the best in my view. My XB9 as it is now is still more fun overall even if the 990 is faster and more comfortable long distance. ;)


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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 6:21 pm 
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Nutah wrote:
....or run a 9 rod front & 12 rod rear cylinder
best of both worlds :rotfl: :rotfl:
:couch:


That'll work after a fashion. lOl


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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 6:41 pm 
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Current ride: X1 2001
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;) :mrgreen:


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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 8:53 pm 
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There is some debate about the effects of rod length on the combustion process. I just found my long lost book on Four Stroke Performance Tuning by A. Graham Bell. A GBell no not that one!? lOl He argues that there is no noticeable rod effect its flat or low domed pistons. Which would include our Buells. :?

On the other hand read; ‘blog.diamondracing.net’ which explains dwell at TDC and piston acceleration away from TDC and effects of rod length on angular rotation in relation to piston movement and induction given appropriate cam timing. :?

Whatever, regardless of rod length, a ‘stroker’ 9 motor that doesn’t go to the extremes of a 12 would be interesting to ride. ;)


It’s not my maths that needs checking, it’s my eyesight; the XB9 rods are 7.270 in not 7.027 in. :oooops:


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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 9:33 pm 
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edd wrote:
:yt: Technically brilliant, but it’s so ugly l’d want it totally in satin black. I’d also get busted for mono wheeling everywhere as soon as it was run in. ;)


Its not its absolutely stunning and you on occasions talk such shit its staggering.


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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 9:43 pm 
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Current ride: Buell ulysses
Location: Telford
:rotfl:

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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 11:07 pm 
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Milf Hunter
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Current ride: '98 S1
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I test rode the 1290 when Tubbs was at Crescent. Bonkers bike, absolutely loved it. lOl

Sadly could never afford one. :sad1:

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 Post subject: Re: A Rod to Spare?
PostPosted: Wed Nov 18, 2020 11:35 pm 
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spondon440 wrote:
edd wrote:
:yt: Technically brilliant, but it’s so ugly l’d want it totally in satin black. I’d also get busted for mono wheeling everywhere as soon as it was run in. ;)


Its not its absolutely stunning and you on occasions talk such shit its staggering.



Each to theirs, but constructive criticism always welcome. ;) I guess the 890 R is one of those state of the art jewels that often look better in the flesh?


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 Post subject: Re: A Rod to Spare?
PostPosted: Thu Nov 19, 2020 8:35 pm 
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https://www.google.co.uk/search?q=ktm+s ... ODcrhFHbqM 8-)

Talking to myself again!


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 Post subject: Re: A Rod to Spare?
PostPosted: Thu Nov 19, 2020 9:54 pm 
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I tried the 1290 sdr
The Ebr 1190 is more fun

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 Post subject: Re: A Rod to Spare?
PostPosted: Thu Nov 19, 2020 11:12 pm 
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Never ridden a water cooled Buell, but am still happy. ;)

Read; Cycle World’s review by Kevin Cameron ‘Inside KTM’s 890 Duke R’ looking at performance from a new perspective. The future may not always be orange but it may often come in a twin! 8-)


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 Post subject: Re: A Rod to Spare?
PostPosted: Fri Nov 20, 2020 7:49 pm 
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Wasting your time reading that, it tells you nothing at all, I went to the shop, took the demo bike out, rode it reasonably hard, thought fuck me thats fast (not like I don't know what a fast bike is either) and said I'll have that.

What I would say, the 890 is £10400 and they are clearing the 790's (or they are on offer) at £7500, the 790 is a bargain and whatever your man says, its not as mental but its still a great bike.

I read all articles on bike in the press with a pinch of salt, its very easy to influence them, I ride everything I fancy, when I bought my Uly I took it back with 170 miles on the it.

Andy


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 Post subject: Re: A Rod to Spare?
PostPosted: Fri Nov 20, 2020 9:54 pm 
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Agreed if l was buying, but l have a nerdy interest Kevin Cameron’s articles.

I meant the technical one with 790 and 890 torque curves and exploded view of KTMs engine which explained the reduced emissions of the bigger motor. Cameron went on to speculate that the smaller ring seal leakage of twins over fours was significant and may lead to more sporting twins being made in future instead of multis. :?

My XB will see me until it goes bang or is banned for causing non essential recreational pollution! 8-)


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