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Enthusiasts from around the world dedicated to the preservation and ritual flogging of the infamous Kawasaki 2-stroke Triples
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PostPosted: Mon Feb 05, 2018 9:36 pm 

Joined: Thu Jun 23, 2011 8:27 am
Posts: 170
Location: Danville, IL
Maybe the price will come down after all the "cool kids" buy them.


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PostPosted: Mon Feb 05, 2018 10:03 pm 
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Joined: Wed Jun 08, 2011 11:34 pm
Posts: 9826
Location: North Central NC
Or when someone sends a set to China. :lol:

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PostPosted: Tue Feb 06, 2018 6:43 am 
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Joined: Wed Jun 08, 2011 10:04 pm
Posts: 2223
Location: Just north of Toronto, Ontario
Im also not surprised on the price based on the machine time on those baby's likely require! They definitely could be made quicker if redesigned so that you could gang saw those ribs. It would mean doing something different than having those bridges, likely just rubber blocks would do.

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PostPosted: Tue Feb 06, 2018 9:12 am 
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Joined: Wed Jun 08, 2011 11:34 pm
Posts: 9826
Location: North Central NC
Or leave them unbridged and hear detonation better.

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PostPosted: Tue Feb 06, 2018 10:23 am 
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Joined: Wed Jun 08, 2011 10:04 pm
Posts: 2223
Location: Just north of Toronto, Ontario
I've heard somewhat poor reviews with DG fan style heads, was this because of the material used in extruded aluminum not remaining stable or just a poor combustion chamber shape?

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PostPosted: Tue Feb 06, 2018 10:57 am 
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Joined: Tue Jun 07, 2011 6:37 am
Posts: 10460
Location: Rio Rancho, New Mexico
I had read some where the fins actually cracked without the connectors, i guess it is possible. I believe there are upgreded repop cast heads out also. H2 heads are known to crack, I think that is more of bad prep and too much torque, personally. So I dont know why there are billet 500 ones, other than bling, which is fine. One interesting note, on a discussion on FB, Bo T stated the plug is far away from where it should be for best performance, which I agree, but i don't agree that the stock heads can't be reshaped to a much better performer, as i have been doing that for decades. I just wonder why all the trouble of billet and not a more modern chamber design.

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PostPosted: Tue Feb 06, 2018 5:51 pm 

Joined: Thu Jun 09, 2011 11:25 am
Posts: 3137
Walms mentioned DG heads, more problems than they were worth. Radial fins were OK, but, stone age chamber, squish designs really put the hurt on performance. Welding and recutting the chambers helped immensely.


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PostPosted: Tue Feb 06, 2018 8:01 pm 
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Joined: Wed Jun 08, 2011 10:28 pm
Posts: 1558
Location: Tampa Bay Florida
The DG heads were made to be used with ported engines and the chamber was smaller to regain lost compression. Many people who used them on stock engines "mysteriously" melted pistons... :think:

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PostPosted: Tue Feb 06, 2018 8:39 pm 

Joined: Thu Jun 09, 2011 11:25 am
Posts: 3137
The DG heads really didn't work well on modified engines, either.

As to John's thoughts on fins cracking without the metal bridge connectors between them, quite true, simple harmonic vibration causes a lot of failures in different areas. Another place was at the rear upper motor mount on the cases, ripped a part of the bolt boss right out of the upper case. That is why I never use an upper rear motor mount set.

It was also mentioned about spark plug positioning, and I said before that some of the Yamaha TZ heads used an offset chamber, with the spark plug aimed to the rear of the chamber. This brings me back to the development of the later h1R engines, before they went to the H1R-LC liquid cooled top ends. There were a few sets of testing heads made for those engines, and distributed all over the world to the teams. They were still air cooled designs, but, they had two spark plug holes in each head and a trench in the chamber. The trench and plug holes was symettrical, so, end heads could be swapped, end for end, and center simply rotated 180 degrees, so the testing would be symmetrical for the engines.

The testing revealed that when the plugs were in either spark plug hole, performance was nominally different, the engines ran the same with the plugs in either position. The glaring difference is, when the plugs were positioned in the rear holes, the engines started very easily, two serious steps, bump clutch, engine running. When the same plugs, plug wires were moved to the front positions, you literally had to tow the bike about 20 mph to get it to start. This is with NO other changes to anything, just actually moving the spark plug wire from the rear plug, to the front plug.

On some of the factory YZR Yamaha V4 500's, they had aftermarket heads, with pressure accumulators on them, like a shock oil reservoir. These reservoirs had a diaphragm in them, and a pressure valve in their ends, with a line going to the head right next to the plug holes. What the heads had were chambers that had head skulls in them that moved up and down a small distance in the head covers. When the engines were at higher rpm's, the chamber inserts moved upwards in the covers, lowering the compression, then, the pressure in the reservoir moved the inserts back down, for better acceleration.

They worked well for what they were, only one serious problem, mechanics had to use air impacts to set the spark plugs into the chambers, but, the plugs still came loose, and out of the plug holes after a short time, as there was nothing to stop the inserts from turning in the covers. Nice idea, no setting device for the chamber in the cover. I can't remember the name of these heads, someone from Europe might.

We did a lot of very strange testing 45+ years ago.


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PostPosted: Wed Feb 07, 2018 4:56 am 
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Joined: Thu Jun 09, 2011 3:06 am
Posts: 4364
Location: PARIS FRANCE
have Ralf Schipmann heads on one of my H2, no connectors and have done around 6000 kilometers with: no crak no issue better combustion.


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