Timing was around 20 degrees just to play safe and plugs were Iridium 9s to make sure they did not overheat, and ignition is a custom DYNA S with stock coils. Fuel was 93 Octane from a normal pump at a gas station on the way to the dyno shop.
Started with stock pipes which smoked a lot for quite a while until the motor was run under load and got the pipes hot enough to burn clean. After that they were fine - only the slightest smoke. The motor is higher compression that stock, mildly ported A block and uses stock carbs with UNI filters. Main jets were raised one size from stock and the rest of the BS40 CV carbs were stock. Just to get a baseline.
It's hard to get an accurate Air:Fuel reading on two strokes when the baffle is stock because the probe doesn't go in far enough and air gets into the back of the pipe. Sounds odd, but it does. The right pipes stayed very cool and the center one was way hotter than the left for some reason. Exhausts had the crossovers (L pipes) in and repacked cleaned baffles (one was new) and all had new clean packing.
A:F was terrible - very lean overall though teh right side showed almost normal and the left showed way lean. Jets were new, At least that's what the system was telling us. Plugs showed clean to slightly rich on the left and way rich on the right, so who knows what was going on with the mixture. I'll have to pull all three plugs and strip the carbs for a post mortem exam to see if we can determine what was going on there.
Baseline with no fine tuning or jet changes was around 58 RWHP with 51 Lb Feet of torque.
Next up were a set of Jemco pipes I borrowed from SuzukiDave and Kevin the Hatchet. The port mods worked well with those pipes and lets just say that they are really good pipes. HP is no where close to the levels that they made on Kevin's drag race bike, but they didn't lose much to teh stock pipes at the bottom end with this set up. We kept revs down in deference to teh fresh tight motor but they made a significant improvement. I'd recommend those pipes.
Very little smoke from the Jemcos which came from a race bike and were clean. Air: fuel appeared to be better than stock pipes but still showing lean on teh gas analyzer.
Next up was the Strader 3 into 1. That thing sounded unreal and smoked more than than our local council's mosquito fogger. Seriously bad from accumulated oil in the carbon inside the pipe. That pipe came with a stock A model I rebuilt a few years ago. the owner/seller said he used stock jetting and he thought it perked up the bike at the bottom end and was similar to stock higher up.
Dyno results confirm a similar curve to stock but lower at the top end and with so much less weight, it explains the performance. Air:Fuel on that pipe was showing much closer to correct which was a surprise given how short the available tailpipe access was.
We ran out of time and money to try much more other than an ignition swing and adding more advance made surprising little difference - within the margin of error.
Now I need to work out what's going on with those carbs. and see if I can fit the set of 34mm flatslides that are lying here gathering dust.
This stuff is addictive. I need to win the lottery so I can spend more time on the dyno checking out a few ideas and a thousand and one other combinations.
For the street I'll be happy to use the Strader and if I'm silly enough to take it to the track I'll need to keep those Jemco's - Sorry Dave....
Listen to the music coming from this awesome machine. Fantastic!!
Man that Strader sounded great. Nice to hear actual comparisons on those pipes too, although I trust you have a good reason for keeping us in suspense on those Jemco/Strader numbers...?
