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Author Topic: saving a 1980 KZ750 twin  (Read 67821 times)

Offline Tune-A-Fishİ

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Re: saving a 1980 KZ750 twin
« Reply #100 on: Apr 07, 2016, 17:47:24 »
I forgot I had these lol






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"I didn't come here and I ain't leavin"  Willie Nelson

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Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #101 on: Apr 07, 2016, 18:49:12 »
Those look nice.

Im planning out my header design and want to run over it here for my own clarity and to get the opinions of some knowledgeable folks here.
Its going to be a stock motor with the stock carbs and airbox. (for the time being)

The stock header ID is 1.28" Since i figure this is probably the optimal size for good velocity I didn't want to go bigger but the tube i have found comes in 1.5" with a .065 wall which puts me at 1.37" ID this is only 0.1" diameter increase so it shouldn't effect it much but will probably move the powerband up slightly in the RPM range.

From what I understand it is good to have a larger exhaust diameter than exhaust port to create a step to help prevent reversion. The exhaust port is 1.37". I don't want to go bigger because it would kill the exhaust velocity, so i have been scheming on ways to help prevent reversion. I put a internal chamfer on my spigots to mimic the factory header design where the two tubes are welded together. I figure a small step like this may help with reversion. 
I have also been reading about anti-reversion inserts and am contemplating adding them. Does anyone have any experience with them? i have read about them over at the XS650 forums and a guy that races one swears by them. Apparently they don't significantly increase power but help with throttle response and torque.
Im asking this because it will change how I design the exhaust flanges. If i do the anti-reversion inserts the exhaust collar will have to fit on from the head side and use a ring to hold the exhaust in place much like the factory. If i don't use the AR inserts the collars will simply slide on from the collector end. I drew up a cutaway real quick to show what I mean.

Thoughts?
« Last Edit: Apr 07, 2016, 18:56:02 by doc_rot »

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #102 on: Apr 16, 2016, 02:19:45 »
Got a start on the exhaust collars.

Offline JadusMotorcycleParts

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Re: saving a 1980 KZ750 twin
« Reply #103 on: Apr 16, 2016, 07:26:11 »
Man, cant believe you machined those exhaust flanges from billet stainless.  That shows extreme patience and dedication!  They look wicked.

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #104 on: Apr 16, 2016, 15:28:27 »
Man, cant believe you machined those exhaust flanges from billet stainless.  That shows extreme patience and dedication!  They look wicked.

You can't believe it because its actually aluminum. I might be stupid, but not crazy enough to do this in stainless.
« Last Edit: Apr 16, 2016, 16:03:50 by doc_rot »

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #105 on: Apr 17, 2016, 00:03:58 »
Got the retaining rings turnt

Offline Tune-A-Fishİ

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Re: saving a 1980 KZ750 twin
« Reply #106 on: Apr 17, 2016, 09:20:10 »
Nice detail Doc
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church

Offline JadusMotorcycleParts

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Re: saving a 1980 KZ750 twin
« Reply #107 on: Apr 19, 2016, 11:54:25 »
You can't believe it because its actually aluminum. I might be stupid, but not crazy enough to do this in stainless.

Aha, the spigots I meant.  Even so, dedication to the craft.

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #108 on: Apr 19, 2016, 13:47:55 »
thanks guys

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #109 on: Apr 23, 2016, 22:56:29 »
Exhaust flanges are nearly done. Had some fun on the rotary vise, also thinned them a bit and sank the retaining ring a bit deeper. No chamfer mills so I chamfered them with files. They still need a bit of polishing.