Kawi2strokes.com Forum

Haaahahahaha Joe, you are about becoming triples addicted. Just as I am, and remember: 5 years ago was the very first time I stepped on a H2 kick.

Suzinut:

It's hard to compare those pipes, but I will give you an assumption anyway.

The TNT are VERY revvy pipes, at least on my even more ported H2 seen in the video. In fact, peak power was around 9500 which is in my opinion, not qualified for street use. But they performed very well, great power all over. They sure works with less exhaust duration then mine, getting the peak power rpm down.

The dencoes is a completely different animal. They produced a linear curve, VERY streetable. And gave ok peak power. They really work along with heavily ported H2's, mid range is very very good.

My assumptions is they peak at about same, or a bit higher rpm then specII. But I think they may be a bit better in mid range. SpecII has not exactly a flat spot, but still the torque flattens out a bit in mid range. Dencoes did not, it is in fact difficult to see where the powerband starts as they produce the very linear curve, almost like stock, or a foulstroke.

I may put on my jolly and also stock pipes just for the test later on today. But no jetting though. The result will be interesting. I bet this bike produces 100-105 rwhp with jollymoto, and about 75-80 with stock pipes. I also have a set denco pipes, and may try them as well.
Could be interesting as stock pipes and denco pipes with ported cylinders and vm 34's are a rather common combination.

Stay tuned.......

Jørgen

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

Hi Jorgen,
I know there is no chance of getting an answer, you have spent to much time and invested a lot to accomplish what you have in the last 5 years BUT…Im going to ask anyway

What is the most important areas to not touch or what areas require the most attention when getting that good of numbers from porting?
Are there any generalities that you have found to be completely false in porting these machines.

I do hope all the great tuners of theses bikes are keeping good notes to pass on or there "secrets" will go to the grave with them

it's ok Joe.

Some basics:

Be aware of inlet duration when running piston port if you will have low end power. (reeds are another animal)

Be aware of compression after portwork if you wanna have low end power.

Be aware of transfer duration if you wanna have mid range power/powerband starting early.

Be aware of blowdown area if you wanna have power on top.

Be aware of exhaust duration to ensure a good power stroke (torque)

Be aware of flow. It's all about mass flow, getting as most fresh charge as possible up into combustion chamber.

Be aware of carb size. Even a 34 carb is small on a H2. Bigger carbs, more power at all revs except below 3000

Be aware of pipes. Good pipes produce more power then less good pipes. A thumb of rule: Aggressive pipes makes more power in powerband, but less power before power band (especially mid range) than more moderate pipes.

Be aware of ignition timing. Most advance in mid range to weaken exhaust pulse, thus returning wave.

Reeds makes a lot more power from down low, up to mid range start. (better piston pumping)

Have in mind your H2 is a piston pumping device prior to powerband. When in powerband, there are another rules. Your engine is not a pump anymore, but a resonator. (provided you have effective pipes)

So, a stroker is a completely different animal than a foulstroker.

Be aware of if you change one thing, you ALWAYS also change something else in your engine.

This is just something that come to mind in a hurry right now, there are a lot more to it than this info. And off course, this points are really up for discussions as it is hard to be very certain of all the aspects in our beloved strokers.

Squish is good for detonation issues, but does not necessarily makes a lot more power.

Stay tuned Joe, and keep them questions coming. I will try to answer them as best as I can. But off course, some secrets are, and stays, in my garage

..j.

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

Did some more testing today. 1 result as expected, the other result not expected at all.

Here are the expected result, stock pipes. Linear curve. Notice, peak power rpm very close to stock. "It's all in the flow", and as long as one port for torque to get power, not port for rpm to get power, a nice curve is shown.



The other result surprises me. Jollymoto about same peak power as SpecII. This must be a jetting and timing issue, no way the Jollymoto pipes can't do more than this. But yes, they produce more torque, and they also hit the powerband a lot sooner then specII, and no flat spot recorded.

Here it is, specII vs Jollymoto




..j.

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

That curve with the Jollys is very impressive it would leave the bike with the spec II for dead in a road race situation!

Probably.

But something is happening at about 6500 rpm. The torque starts to flatten out. That's too early. Peak torque rpm should be higher.

But I won't tune in the Jollymoto pipes, as its all about specII on this H2.
And believe me, a 77 rwhp at 7000 rpm H2 with stock pipes feels VERY strong. More like a early 80-ties 1000cc inline 4 foul stroke

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

Great results Jorgen! I'll bet the jolly's would reach 100+ rwhp if timing was retarded some. But i know this was just a test, without tuning them in..

Jorgen.......yes I am taking notes.........keep this good info coming........very fascinating.....never know, may have a version II top end one day

THX Phil

Great information Jorgen, are you still intending to test the dencos on this bike?

Hi guys and thank's for the inspiring words.

I planned making a dyno run using the dencoes, but ended up only with jolly and stock.

Dencoes have a very good mid range, no flat spots at all on every dyno sheet piston port h2 I have seen. So, an assumption could be the mid range power on this engine would turn up between the stock pipes and the Jollymoto.

Peak power somewhere in the 90-ties. Dencoes are just a very very good design for street use. I really hope Jim will make them again, and maybe also the upswept denco version, the Denco RR. I have pics and dyno sheets of them as well, as Ståle has them on his stock cylinders vm34 ufoed h2. 77-78 rwhp, linear curve. GREAT pipes.

You hear me Jim??

..j.

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison