Kawi2strokes.com Forum

Agreed, that would be great!
Jorgen, do you know how steep the return cone angle is on your jolly pipes? Mine are about 8 degrees and that shoulden't be to bad i think?

Hi.

I am @work out in Barents Sea 73 degrees north at the moment, but will come up with something when comong home.

All I can say is, in addition to ign. timing, the exhaust plays a major role regarding flat spots just before piston closes transfers. Usally at about 2/3 of max torque rpm.

I struggeled really bad with my ported cylinders regarding that dip, and zeel eliminated some of it. But not all, by far not unfortinalety. But improved quite a lot the power in that rpm area.

Then I swapped to the very forgiving higgspeed chambers that I have. Wow. Almost no flat spot at all!!!

If you look at the last cone of higgsy, you will see it is long, and since the belly diameter is quite "old school", the cone is not steep at all. Have not measured it though...

The Jollymoto cone is VERY steep. That gives you a punch like other, more streetable, chambers do not give, when coming into the powerband.

But downside is, the strong and very abrupt returning wave kind of disturb everything regarding flow up transfers and scavenging pattern before you are on pipe.

Upside is, when the jollys hits........wow!!! And since they also are fatties theyare able to such up more air/fuel from crankcase, in which leads to even more of the same stuffed back up in combustion chamber. That means more power!!!!! More peak power.

Jollys are really race pipes, suited for high ex duration h2's due to they havea tuned length almost as long as higgspeed. And much longer than Dencoes.
I have a set of Figarolies 3:3, they are short.About 4 inches shorter tuned length than the jollys!!!.

So, without a exhaust valve, using aggresive fatties like jollymotoes or similar, with raised exhaust port and transfers, the flat spot is hard to overcome. But if you use higgspeed, the problem is almost not present at all. But again, you loose peak power and also the insane kick when hitting the powerband.

I have 2 h2's, the one you see in this thread,and 1 more conservative H2b for touring. obvious, the touring runs higgspeed, the cafe runs jollymotos.

Anyway: Zeel helps, but the most important aspect of this flat spot issue is the pipe design as far as I have found out.

Jorgen

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

What pipes you running?

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

Oil rig??? You must be as Bad A** as the your custom H2!
I look forward to reading about all the testing you do on these bikes, it good reading and VERY informative.
Thanks

I have the same experience as you Jorgen, the current pipes on my bike were designed for John's race bike to rev to 11k and they have a flat spot but my torque pipe that has max power at 8.5k does not.
For a street pipe, one must be honest with themselves to make the tuned length realistic.
The interesting thing is the race pipe has a 11 deg angle where the torque pipe is 8.5 deg.
I plan to make some 9 deg cones for my race pipes, it will change the tuned length and drop the max hp by about 700 rpm while smoothing out the power curve. Maybe best of both worlds because the shallower angle also allows more over reving as well

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http://kawatriple.com/wtf/

well.. they are modified snowmobile pipes (yamaha srx 700 with115mm. od. Belly) joined them with the fbg taperd downpipes and they worked damned good with stock cylinders.

But with (heavy)porting it was a diff. story.. So now they are about 5" shorter (mostly at the belly) but the endcone is the same.. Really like them besides that damned flatspot, really great topend and pulls good at cruisingspeed.

So maybe i should try a milder endcone and a zeelbox to cure the flatspot?

Good idea.

You have any pictures of your pipes?
What is the length from cylinder to end of last cone? I mean, approximately. You may measure in pipe middle line if you can. I only ask to see if your pipes are average, long, or perhaps very short which is not very good if you have raised your ex a lot. You have a port map?

If you like, start a new thread about your bike, then others with more knowledge than me may step in.

Jorgen

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

Flatspot racing.. second pair out is me..

https://www.youtube.com/watch?v=DrIaiBE ... 1iuvPvoan1

Yep. Google Transocean Spitsbergen. That's my babe

And no, I am just mummys little boy

Hehe, I have an education as aircraft mechanic, now working as a well tech supervisor offshore. Love my job. Personal best: 24 meters waves

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

I will have to check my notes for length etc. Yes, will start a flatspot thread..