Slabbie 7/11 thunderbike racer

[Blubber]

Attention to detail is important  

[jonny1bump]

2 hours ago, dupersunc said:

Yes he is, I could keep with him for the first 2 laps, but then I cocked up Barn, and he was gone. 

Sounds like you doing pretty good really.

Fair play.

[dupersunc]

So the important numbers on the bike are  120bhp at the back wheel as measured on Bemsee's dyno, and 185,5kg measured on my scales with 3kg of fuel. 53.7% front weight bias.

Thunderbike extreme rules are 130rwhp maximum, and 1.46kg per hp. So as it stands I need to either get more horse power, or loose a little weight.  At my weight I'm allowed 126hp. But it's cutting it fine. Most of the front runners are running @127hp and  ballast to get 189/190kg with no fuel.

My motor is as bought save for some fresh oil and filter and a set of plugs. I haven't even checked the valve clearances. The exhaust need a baffle in it which isn't helping, and the 38mm 750m carbs had guestimate jets and settings. So I'm sure I can get 6-10hp more with some setting up and a more efficient silencer. If I go over 130, I can just peg it back with the ignition.

Weight wise, I can loose a little here and there, but It's about on the money for the class. My biggest issue is the weigh of the wheels, the stock 750m wheels weigh a metric fuck ton, and you really notice that when changing direction from Chris curve to the Gooseneck, and through Hall bends.

I have a plan though.

I reckon these boys will save me 3-4kg, so along with the engine fettling should see me able to get the bike right on the power and weight limits with room to spare.

Fundamentally I'm happy with the bike, there's a lot more from me to come before I find the limit of the bike, Next year I want to be doing 1.40s around Cadwell.

My next race hopefully will be at Snetterton on the 300 layout, a circuit I know well and suits the bike better, and I intend to come home with a little plastic cup. So before then I have job list.

Fix quickshifter, shift light and rev counter,

Replace screen. Don't ask!

Finish refurbing Astralites and fit

Check valve clearances,

Fit better Silencer

Get carbs set-up on Dyno.

Make undertray smaller and tidy up fit.

Replace gear linkage leaver

Re-bush clutch leaver.

Over the winter I've a few bigger jobs planned.

Fit 6speed box

Fit Slipper clutch

Fit slipperier fairing   TT-F1 or 750rrk if I can find either at sensible money.

Extra oil cooler. My gps logger suggests I'm loosing straight line speed as the race goes on. Engine Temp? anyone any experience of this?

 

Sorry for the rambling post but it's a good way for me to make a note of my thoughts and plans.

Duncan.

 

[MeanBean49]

Loads to do.

I will be out in Sport at Snetterton so will catch up with you

If my racing experience helps i found up towards 60% weight on front helps, better if you can do it by dropping forks through rather raising rear.

Oil temp and jetting probably explains top speed drop off, used to get it with mine. Top end cooler kit helped loads, dead easy to do. Cost about £100 if you get bits together seperate. Torques do the fittings, hose is £10 a meter and JJC race rally do the coolers for about £45

[dupersunc]

I've already got the kit to fit a head cooler, just wasn't sure it would be needed with a stock motor, and worth the extra weight. I now know it is needed, and I can afford to add a little weight if I fit the Astralites.

I'm not keen on dropping the forks, as I'll loose ground clearance and rake. I'm not convinced I need anymore front weight bias anyway.

[MeanBean49]

Ahh ok. Dropping forks 10mm shouldnt affect ground clearence and will steepen the rake slightly to make it turn better. One thing i found for circuit racing oil cooled stuff is you cant get enough weight over the front, 60/40 is best you can do without making the rear unstable on the brakes. Possibly just the way i ride.

Also the lower to the ground you can get the motor the better they handle

[dupersunc]

Cheers Rob, your wisdom is appreciated.  I'm actually really happy with how it handles, rake is already 22.8 degrees, I really don't want to go less, though it doesn't shake it's head even though I have no steering damper.   The only vice it has is the slow direction change, and I'm putting that down to the weight of the wheels. So that's what I'm addressing first. One thing at a time.

I'm notorious amongst my trackday mates though for not giving a fuck about chassis set-up and ragging the shit out of any old knacker.  I do struggle with the latest generation 1000cc bikes though, they do seem much more sensitive to chassis set-up. Zx10r anyone, bloody terrible on track on stock suspension.

I've got some data from a lad on a 2013R6 doing 1.37s , when I over lay that data with mine,  I can see he's braking later or less and getting on the gas earlier almost every where. I need to re calibrate my brain to do that. The only place I felt I was near the Limit of the bike was at Charlies2, and I'm matching R6 boy there. I'm matching him on the brakes for Park too, and I know I can go deeper there, so the bike can do it.  The bike does seem to loose out on acceleration, but my gearing was too long.

Oh I need to add a quick action throttle to the list for Snetterton.

[MeanBean49]

No probs. You can get pretty steep on the rake on these gsxr's without really upsetting them too much. I found lighter wheeld didnt make too much difference really. 

Ive never ran a steering damper either, they are that stable. I reckon you will find when you start trying to break later and get on the gas as earlier as your mate on the R6 you will find the chassis is the limiting factor. Will start twisting and getting out of shape to the point it wont go any quicker. I would be fairly confident that will before you get anywhere near a 1:37

They will lean well, go well and stop well enough. Its the transition between them that becomes the issue. 

Really cool what your doing, very interesting to see how quick you manage to get to and if you start running into same problems i had with my slingshot.

Fast action throttle is essential

[Solcambs]

13 hours ago, dupersunc said:

Thunderbike extreme rules are 130rwhp maximum, and 1.46kg per hp. So as it stands I need to either get more horse power, or loose a little weight.  At my weight I'm allowed 126hp. But it's cutting it fine. Most of the front runners are running @127hp and  ballast to get 189/190kg with no fuel.

Just remember it's not the peak that matters, it's the spread of the big numbers ... i.e. area under the dyno curve. I've always thought that classes which specify maximum hp open up the potential tuner to providing a really rideable bike with a flat torque curve and a good spread of power.

Years ago we spent a fortune getting an R6 motor to produce massive numbers ... it blew up. I put a stock motor in with  some mild work, made less power, but had a massive spread of power and the bike was quicker on the circuit.   

[dupersunc]

Yeah, if  I get a 1.37 out of it I'll be calling Davide Brivio.

 

[dupersunc]

1 minute ago, Solcambs said:

Just remember it's not the peak that matters, it's the spread of the big numbers ... i.e. area under the dyno curve. I've always thought that classes which specify maximum hp open up the potential tuner to providing a really rideable bike with a flat torque curve and a good spread of power.

Years ago we spent a fortune getting an R6 motor to produce massive numbers ... it blew up. I put a stock motor in with  some mild work, made less power, but had a massive spread of power and the bike was quicker on the circuit.   

Absolutely this. It's one of the reasons I went for the 1100. If I end up with 130+hp, I can just back off the ignition at certain rpm so I've got maximum allowed power for several 100rpm rather than just a peak number.

[MeanBean49]

Good thing i found with motors was when i ran my turbo motor in N/a form for a couple of races. Busa pistons give nice low compression and 1216cc. Was running a bandit 1200 head and cams. Motor only made 115bhp on the bemsee dyno but it was hugely grunty and had massive midrange. You could do somthing similar and with some flatslides and head work would see 125bhp.

The other thing is the low comp keeps the heat generated down, helps stop the power loss problem. Good set of busa pistons are cheap compared to new big bore pistons too.

I also run an ignitech cdi. Fully programable. Can change ignition timing every 500ish rpm. They are awesome

Edited August 3, 2016 by MeanBean49

[nightrider]

8 hours ago, MeanBean49 said:

Busa pistons give nice low compression and 1216cc. Was running a bandit 1200 head and cams. Motor only made 115bhp on the bemsee dyno but it was hugely grunty and had massive midrange. 

The other thing is the low comp keeps the heat generated down, helps stop the power loss problem. Good set of busa pistons are cheap compared to new big bore pistons too.

Hmm I was wondering about that.

 I knew low comp was good for turbos and low comp makes 2-strk off road bikes grunt better.

Occurred to me recently that it might work for Short course Roadrace bikes too just haven't heard anything on it.

Anyone know what comp Busa pistons have?

 

Edited August 3, 2016 by nightrider

[MeanBean49]

7.8:1 i think is what busa pistons in a bandit 1200 gives.

Low compression is good for bottom end and midrange but not top end

[nightrider]

so short legged course and backroads engine then. 

[dupersunc]

Nah don't agree with that at all. Compression=torque, the more the better, as long as you can manage the heat.

[MeanBean49]

Thats not what i meant. More power and torque due to bigger capacity. Has really good bottom end and mid range but not massive outright power. Really good flexible motor for power limited class. And solves heat issue 

[dupersunc]

I'm going to try heat management first.

Did I tell you about my oil cooler fetish

 

[MeanBean49]

Your not the only one :-)

[pambos1127]

i have two oilcooler for my 1246cc engine,this is the second for extra cooling.

[dupersunc]

Just picked these up from Dorset Aluminium, who've re anodised them. I'm like a dog with 2 dicks.

 

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Edited August 2, 2017 by dupersunc

[Bowler]

2 hours ago, dupersunc said:

Just picked these up from Dorset Aluminium, who've re anodised them. I'm like a dog with 2 dicks.

 

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That looks amazing! Was it hard to anodise them? (i.e. getting them apart, new rivits etc.)

[Solcambs]

They look rather nice! Bloody good job based on those photos!

[dupersunc]

She's not quite so pretty anymore though.......

[dupersunc]