Aussiebikerdave

My first foray onto the track in 35 years was last weekend so you might say I was a race virgin all over again!

The weekend has come and gone, the BEARS Challenge (British, American, European Racing, no jappers... get it) races were run and won and all objectives meet. Concerning the last, the main one was to ensure that I could drive myself home instead of being driven home with my arm in a sling (or worse!)

The bottom line... the Scram ran perfectly, heaps dropped by in the pits to ape at the bike, pass admiring glances and take their pics. Due to a small number of entries in the BEARS formula 4 section in which we were entered, formula 3,4 & 5 sections where run together to form a total field of about 25 bikes.

We finished a stong last, second last, third or fourth last in all races but in so doing managed to accrue the most points in the Formula 4 division so we got to cart home the trophy!!!! Hows that! Here's a couple of pics but the trackside photographer took a whole bunch of action shots which I'll post when they arrive on CD in the mail.



For those interested in lap times, my best was 1min 19.8 secs but was generally circulating in the 1min 20/21sec bracket. The lead riders were riding 125kg Aprillia RSV550 supermotards doing around 1min 7 sec to 1min 10 sec laps. Morgan Park at Warwick is a curcuit of 2.1km with an extension of .9km to be added later this year which will make it an awesome place to ride. My personal challenge was to finish the race before being lapped by these fearless young'uns on their souped up trail bikes... hey, isn't that what our Scrambler is?


The Contenental Race Attacks worked brilliantly with never an "oh bugger" type moment!

Speedtrip

Great looking bike. Don't think I've ever seen a Scrambler with tire warmers and a steering damper, cool stuff.

Congrats on the trophy.

The Prophet

Dave,

Excellent looking bike. Great job on the track. After all, 35 years of... "waiting? - and at least you finished each race, and it's your first time out in a long while! Much more than most could ever even dream of. Super.

How was the bike through the turns? Rolling out of the turns, etc. As I recall, you had some pretty decent torque on this one, and a relatively flat Powerband.

What sprocket set-up are you running?

What was the top speed achieved in the straight-aways? Did you need to do anything special just for the "track" day? Safety wiring, etc.

On a much lighter note: Good thing you listened to all the know-all "expert" opinions on the 'other' site... eh? Just kidding of course! It's unbelievably refreshing to see an educational and interesting report on an actual track day outing vs yet another "paper race" with some lame Dyno graph to post. As they say:"The proof is in the lap times".

Looks like you had a great time. Seriously, be safe out there, and let's see more pics and reports!!

Ride (and race) Safe!

Bob

__________________

• A good traveler has no fixed plans, and is not intent on arriving. ~Lao Tzu
• Motorcyles are not my whole life, but they make my life whole. ` me

Aussiebikerdave

The track foray consisted of a track day on the Friday follwed by a two day race meet so all the normal drain and filler plugs had to wired, a temporary rear sprocket guard was attached to the swingarm with zip ties and the engine breather had to vent into a catch bottle.

Courtesy of the YSS rear shocks, some front fork work and the steering damper, the bike handled well on this circuit however the nature of the bikes geometry worked best with classic sweeping race lines. There where some corners where it was good to pull the bike around tighter to line up a better entry into the next in order to get a better drive out but it was always hard to do with the comparatively slow steering of the Scrambler. During the course of the weekend we made some adjustments to raise the back and lower the front which helped.

Gearing was 18/45 enabling me to redline it in 4th at the end of the 400metre long main straight so I am guessing that this was about 160kph. I had the speedo taped over to avoid the temptation to look as I figured my attention was better served looking for braking markers rather than a speedo!

As soon as the track photographer posts out the pics I'll post 'em! Dave

The Prophet

Dave,

Just out of curiousity:

Earlier you had shaved a bit off of the cylinder heads for an increased Compression Ratio.

Then later, you went with the BB kit and the High Compression Pistons.

Did you use the same head? if so, the CR would be greater than the 11.5 as supplied via the BB Kit?

Or did you use new/different heads?

Thanks,

Bob

Aussiebikerdave

Correct, we took 39 thou (1mm) off the heads and calculated the CR at 10.32:1, up from the stock 9.2:1. We then fitted the 904 kit but turned the motor over by hand to make sure nothing was fouling. We calculated a new increase CR to 11.6:1 with this set-up but at best it was only an educated guess. We idled the motor on the first start up then gently increased the revs to be sure it was going to be OK with regard to valves clearing the pistons etc. I'll admit this was not the most scientific approach but it turned out all good.

Since that first race meet the bug has bit so the head is currently off (again) having 2mm valves installed all round. We will certainly check clearances properly this time around and if necessary, relieve the valve pockets or fit an additional base gasket... yet to be decided.

You asked about the torque off the corners. While not a seasoned racer, it seemed excellent to me and there were times when I used a higher gear than I could/should have and it still pulled out very strongly. There are a series of esses that led onto the main straight that I discovered toward the end of the weekend, I could negotiate much quicker if I used 3rd instead of 2nd which gave a better flow. This had me coming into the straight in a higher gear (3rd instead of 2nd) but with a higher entry speed, lap times dropped. It was great fun!

I received the CD of track pics in the mail today so here is a small selection...




I lifted the foot to clear the start of that concrete curb as I was still dropping in to the turn!




Trophy presentations at end of the day on Sunday. There was no flag raising and rendition of the national anthem at Morgan Park but it was still hugely satisfying!

Aussiebikerdave

Here are a few more pics.


We ran 30psi in the rear and 28 in the front when hot.





Being chased by a pack of desperados!

The Prophet

[QUOTE=Aussiebikerdave;4250]Correct, we took 39 thou (1mm) off the heads and calculated the CR at 10.32:1, up from the stock 9.2:1. We then fitted the 904 kit but turned the motor over by hand to make sure nothing was fouling. We calculated a new increase CR to 11.6:1 with this set-up but at best it was only an educated guess. We idled the motor on the first start up then gently increased the revs to be sure it was going to be OK with regard to valves clearing the pistons etc. I'll admit this was not the most scientific approach but it turned out all good.

Since that first race meet the bug has bit so the head is currently off (again) having 2mm valves installed all round. We will certainly check clearances properly this time around and if necessary, relieve the valve pockets or fit an additional base gasket... yet to be decided. [Quote]

Thanks Dave, great info.

My take-away from this is that it MAY be possible then to shave slightly MORE (and I do mean slightly) than 39 thou (1 MM) off the heads.

I'm yet convinced of the percieved advantage of the BB Kit on an 865 cc model motor. 904 minus 865 = 39 cc's. 39 cc's is the equivalent of 1.3 ounces, which is LESS than a standard 1.5 ounce Shot Glass of swill from the local Pub! Divide by two cylinders, and you get .65 ounce for each cylinder, which is roughly a third of a shot glass each. I'm hard pressed to agree on any significant advantage, again, from this comparitively miniscule increase in capacity on the 865 cc unit.

Certainly debatable (and I'm sure it will be!) but I would suggest that the biggest change is in the compression ratio increase via the HC Pistons, not the additional cc's.

On a 790 cc, older motor, I'd agree that it's another story.

Now take that additional charge compression, add a little more with the head shaving as you had done, and we really have something.

Now add to that the carefully gas flowed cylinder heads for increased charge velocity, add a well designed camshaft, and you REALLY have a great motor.

I'm amazed at how many simply add the BB kit, then install oversize carbs and call it done. I've reviewed the interesting Dyno sheets on these types, and all that has been accomplished is more "air" passing through the motor at the upper end of the range, which results in higher RPM "horsepower", but has a negativer impact on Volumetric Efficiencies at the lower and mid RPM band, as the bigger carbs would obviously lessen, not increase A/F charge velocity, so the torque curve is then slanted uphill, sacrificing low and mid torque for peak HP numbers.

Granted, there may be a time and place for these types of motors, but on the racetrack (and the street), as you have experienced hands on (seats on?). I'd take the nice, strong, flat and usable/predictable torque band, and leave the dyno racing peak #'s to the non-racing keyboard tappers.

I sincerely like what you've done thus far. Looks great. What is your philosophy, or your thought process around the planned increase in Valve Diameter? I'm assuming you've already done the full radius bit on the intake valve seats?

I really enjoy the discussions on these well planned, and track proven mods. They're greatly appreciated.

Ride Safe!

Bob

Aussiebikerdave

Hi Prophet, re the following quote from your post above...

"Certainly debatable (and I'm sure it will be!) but I would suggest that the biggest change is in the compression ratio increase via the HC Pistons, not the additional cc's."

I would suggest that it's a bit of both. We went from a previous high of 71.8hp to 78.4hp by just fitting the BB kit. I am not to sure of the science behind it but it is a fact... same dyno similar ambient temps etc.

As for my philosophy, I guess I'm a bit like Forrest Gump when he ran around the country with a hord following. There'll come a day when I will say, "I'll think I'll stop now". In the meantime I have noticed that most tuners get a top of around 85-88hp without going to stroker kits etc so I guess this is about the ceiling before the big dollars get spent. If I can acheive say 85hp and 67ft/lb I think that will be enough.

I dont think the extra HP will have a bearing on quicker lap times as much as more track time and better rider skill but we'll have fun trying. Back at the track it didn't take me long to realise that the problem was not with the hardware but more with the software!

However, as an ordinary road bike out on the road (or trail in the case of it's Scrambler roots), I'm imagining that those figures will be truely beautiful.

The Prophet

Thanks Dave, great comments.

One of the unfortunate things about posting (and especially Emailing for Business purposes) is that attempting to describe in words what is actually and precisely meant or intended, often gets left out or muddled. Always better to have a face-to-face conversation, but then again, that's what these Forums are for, written exchanges of ideas, etc.

My question was Bad: I should have elaborated more, in that the increase in swept volume via the big bore kit obviously alters the Compression Ratio, which contributes significantly to the improved Volumetric Efficiency, which in turn provides increased torque, which calculates out mathematically to more HP at various RPM's. Whew, that's a mouthful! I would also add that perhaps the singular High Compression Piston offers (minus the big-bore kits) require some heavy thought, as the high crown on these is not conducive to ultimate and efficient combustion chamber / squish area design. The "flat top" piston arguably (!) presents the best shape for the best squish and best burn efficiency, as you have in your kit.

I also agree 100% with your "Forrest Gump" scenario. Peter Egan - the iconic, and fantastic Automotive and Motorcycle Author - had a wonderful column in Road and Track magazine (Side Glances) years ago around a similar subject. The column's title was: "But I don't want to..."

What he spoke of was "Yeah, I could buy that basket case '56 Porsche, totally strip it down to the last nut 'n bolt, then rebuild it from the ground up as a beautiful restoration... but I don't want to right now". And so on. The premise was, as many of us have done, after so many years, so much time spent, and so much money spent, on various vehicle projects, sometimes you need (deserve?) a break.

Sometimes it's nice to just have a solid, reliable, clean, modern vehicle to ride around on, and not have to spent hours on your knees or back fiddling, cleaning, running back and forth to the machine shop (and Bank!),painting, wrenching, etc. It also makes sense to occasionally "stop and smell the roses" and take some time to enjoy the fruits of your labors.

Having said that, I also agree that you need to set a "Limit" sometimes as to where you want to go with these things, and your example of the 85 HP cut - off is a good one. Yes, these Bonneville's and Scramblers are fun to ride at 85 + HP, but at what price? Obviously there are tons of other, faster, more powerful bikes out there in stock form far better at a similar cost. Nothing wrong with fiddlin' around with the old Triumphs, but I agree a limitation is an extremely wise and pragmatic thing to do.

O.K., yeah, I still spend a little once in a while for doo-dads, gizmo's, accessories, experimental stuff, etc., but I try now to buy things than can easily be detached, put the stock stuff back on, and sell the doo-dads on Ebay or something when I trade in the bike for something different. Like many, I spent enough years in the garage building cars and bikes to the Nth degree, then selling them for half (or less!) of what I put into them, the labor always being free. Fun, no doubt about it, and a great way to spend time, but now at 58... I don't want to for a while.

I do enjoy exchanging ideas and so on, and finding NEW things to ponder over. I also NEVER intend for this Forum section to EVER become a "Mine's bigger (or better!) then yer's" style Forum, as so many gravitate to, or a breeding ground for braggart, or sad contrarian types.

Your comment on improving the "Software" is dead on, and no doubt the best investment ANY of us could - and can - make. Most local tracks offer mid-range to advanced, and sometimes further - courses for very reasonable prices. My Dealer in Wisconson gets a reasonable discount at the local tarck, and we have group Tracks days roughly every three weeks from Spring to fall here in northern Illinois (Blackhawk Farms Raceway). Roughly around USD$160.00 a pop, but dollar for dollar, the best "Performance" investment, as well as "fun" investment, a rider can make. IMHO, this creates "Kinetic" energy, Vs "potential" energy if we are merely looking at hardware.

After all:

"An excellent rider on an average bike is always faster than an average rider on an excellent bike"... author unknown.

So far, so good in these respects, as we have few, but extremely excellent, people and riders involved here on this new Forum. Keep us posted on your fun project, and remember... "Stuff Happens" (Forrest Gump, famous bumper sticker... remember?).

Ride Safe!

Bob