Seeley (replica) Framed Project Road Racer

[Pete O'Dell]

Geoff, dont lock wire your split link, the guy who said that on crmc site is a bloody idiot.

[Zunspec4]

Evening Pete,

I must admit my take is with you, never had a split link fail. However I was imagining this was now standard practice.

On another note. How much running will those new pistons need before making any meaningful dyno runs. it's not as if I can take it for a dozen laps etc.

Cheers Geoff

[tz375]

3D mapping may not be an option with that ignition, but it's what you effectively do with jets. It's a lot less sophisticated than a digital FI system but the principle is the same.

We are familiar with the fact that the different jet circuits operate at different throttle openings, but each jet circuit will also change mixture with engine speed. Fuel:air ratios are not linear - they all curve. But that's a second order effect.

For example let's take WOT on the main jet. Dyno operator slams the throttle open at say 3000 revs and holds it to say 8,000. Typically the A:F will start high (lean) and trend lower (richer) as revs rise and in some cases, flip that the very top and go lean again.

The two things at work, that we have any control over, are the main jet and air jet. In some circumstances, the A:F looks fine low down and goes lean further up. If we go to a larger main jet to get top end right, it's too rich lower down. The other way is to change the air jet to change the rate at which it changes from lean to rich. What we are looking at is the fuel slope.

On some of our engines with Bleed type nozzles (needle jets) we find that changing needle position makes a difference even at WOT because the main jet is small and the needle end NJ are effectively controlling the mixture through part of the range at least.

So yes it is possible to look at 3D, we treat it a fine tuning when the base is close and something needs to be tweaked. In reality, we pretty soon reach a point where it's close enough and just adjust the throttle to ride around any minor issues.

I'd do three heat cycles first and the operator should run it on the dyno and gradually increase load and RPM as the motor settles in.

If a dyno guy takes your bike and immediately runs it at WOT, feel free to punch him in the nuts and tell to never touch your bike again - unless it's for drag racing where they run hard and cold.

[Pete O'Dell]

half a dozen heat cycles is what i would do, check head bolts after 2 cycles, pretty sure I set the timing to 2.9 its what I normaly do.

[Suzukidave]

From what i have read and used myself with what seems to be good results ( others comment please ) is to not hold a steady load on the engine to break it in . Not to extreme but warm to operating temp then load the engine at higher throttle for say 15 or 20 seconds and then ease off for 15 ~20 seconds and then load the engine again etc for several cycles . As you put load on the engine it forces the rings with combustion pressure agnist the cylinder walls seating them and cleaning off a bit of the high points caused by the honing . When you back off between cycles it allows the material lost to clear the cylinder . Also it is recommended to not use a synthetic oil dureing the breakin process .

[Suzukidave]

Geoff ,could you post a picture of your racer in the "let see the custom 500's " section

[Zunspec4]

Geoff ,could you post a picture of your racer in the "let see the custom 500's " section

No problem.

Cheers Geoff

[ja-moo]

Slides and needles are not going to be needed on the dyno. It's all about WOT and that's really the main jets. Needle jets and needles also have an impact but I'd get a baseline on the dyno and get the main jets close and then ride it at a track day and get the part throttle right by feel and response at the track.

I would disagree on this, as I have seen top ends trashed from the wrong needle/needle jet on a dyno. Besides a rich or lean needle system ruining the the HP/torque curve, a too lean condition (even on a quick roll-on) Can put in enough heat to seize one or all pistons. Something to take into account when doing dyno runs.

As far as the split link, this is a vid of what I do, as I have also seen these things come apart.

http://www.youtube.com/watch?v=OlTMKMk2CIo" onclick="window.open(this.href);return false;

[tz375]

Good point John,

I could have been clearer there. I did not mean it was OK to thrash on the bike with tan inappropriate needle and jet combo. What I was trying to convey is that the needle and jet will be selected for mid throttle use at the track and not on the dyno. We have often see changes to full throttle A:F just by changing a needle position, but that didn't mean it was suitable for mid throttle position running at the track.

[ja-moo]

Totally agree, getting the needle combo has to be done on the track, as we know jetting is slightly different than on a dyno. Just a bit of a cautionary, for running on a dyno.

[Zunspec4]

Great video ja-moo, if I decide to provide secondary clip security I'll give it a go.

Well, I have my first dyno session tomorrow. I only intend to give it a gentle run as despite my best efforts I have been too feeble to bump start the Seeley by myself (just can't push fast enough ) So no heat cycles have been achieved. I hope to get enough information to determine what range of jets etc. I might need for a serious return to the dyno. I'll take video and post it up tomorrow.

My gut feeling - 46 to 48 bhp. at the back wheel (with plenty of potential to gain via ign. timing / jetting changes)

Cheers Geoff

[Zunspec4]

OK here it is, the 1st run on a Dyno. The "device" couldn't run as a set of rollers so I had to bump start and ride the bike in, I missed most of it as I was running outside to get the camera. Not too disappointed with the results . Running a bit rich but as good a starting point as I could wish for. We only did one run as the engine, apart from about 10 minutes of me blipping the throttle outside prior to the run, has hardly any time on it.



58.37 BHP was way over what I was expecting, and a broad spread of power too. Feel free to analyse. I think I could raise the needle 1 notch to rich'en up the bottom end and go 1 jet size smaller to lean out the 70 - 95 mph area (yep spot the actual lack of rpm readings, sensor wasn't connected Doh, as it was a bit of a scramble to get the bike tied down to the Dyno and run before we choked to death on exhaust smoke). I'll know better next time, Tim Blakemore (Dyno owner) was a real nice chap and was genuinely interested in the Suzuki.

Of course the video I tried to shoot will be a mess, I still have to down load it from the camera. If it's any good I'll post it.

Cheers Geoff

[tz375]

Geoff, That's a great start and more to come. Do you know/remember at what point along the X dimension the operator had the throttle wide open? It's an interesting fuel slope if it was WOT all the way. It is rich most of the way across that graph except for when the operator was presumably winding it open (the lean portion of the graph).

Air:fuel line drops up to 80MPH and then changes to head north (lean) again. That suggests that it needs smaller main jets (probably 3 to 4 sizes, but start with small steps) to lean out the main part of the graph and slightly smaller air jets to flatten it off at higher revs.

Normally on a two stroke with Primary air mix, it's not so common to play with the air jet, but if yours are replaceable, it may help to go down from 2.0 to 1.8 A more normal change would be to lengthen the spray tube which is not so simple. Making it shorter is easy

Congrats on a great start.

[Zunspec4]

Evening tz,

I missed most of the dyno run fetching my camera. Just a few seconds from the end of the run.

http://www.flickr.com/photos/zunspec/9161114128/

I have no idea of when it was at WOT, but the sounds I was hearing when it must have been wide open were....... amazing . Tim suggested that it was running on the rich side but not too far out and not worth messing about with jets/timing at this stage until it had a bit more running. Said I should take it out on a track and see how it goes as it is. I intend to take it along to a chap who has been dyno-ing a friends T500 racer for some serious fiddling about, be good to be able to compare mine with his on the same day. I have a lot to learn about interpreting a dyno chart so all help very welcome.

Cheers Geoff

[Pete O'Dell]

Geoff are you taking it too James? Good move if so, to be honest am a little stunned it could not be started on the dyno and not exhaust extraction!!! did he hook up any temp sensors?